THE INFLUENCE OF CERTAIN FACTORS ON THE STORAGEOF FROZEN SWEET CREAM Thesis for the Degree of M. S. MICHIGAN STATE COLLEGE Martin Van Scheid I942 fik‘hixfilfi {If ‘I I I4 THE INELULNCE OF CERTAIN FACTORS ON THE STORAGE OF FROZEN SWEET CREAM THE INELUENCE OF CERTAIN TACTORS ON THE STORAGE OF BROZEN SWEET CREAM by Martin Van Scheid eewun- / A Thesis Submitted to the Graduate School of Michigan State College of Agriculture and Applied Science in partial fulfillment of the requirements for the degree of MASTER OB SCILNCE Department of Dairy Husbandry 1942 ACKNOWLEDGMENTS The writer wishes to express his sincere appreciation to Doctor G. M. Trout for his kindness in planning and directing this investiga- tion and for his careful guidance in the preparation of this manuscript. The writer also expresses his appreciation to Doctor I. A. Gould and Professor P. S. Lucas for their valued COOperation in certain phases of the study, and to Doctor Earl Weaver, Head of the Dairy Department for making this study possible. TABLE OF CONTENTS Page INTROHJCTION .OIOOOOOO0.0.0.0...0.00.00.00.00.0000IOOOOOOOOOOOO 1 REVIEV‘ OF ”mm 0.00.00.00.000.9.0.000...OOOOOOOOOOOOOOOOO 8 Importance of initial quality of cream.intended for frozen Storage 0..0.0.0.0...OOOOOOOOOOOOOOOOO0.00...OOOOOOOOOOOOOOO 3 Influence of pasteurization procedure on keeping preperties or cream OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO000...... 3 Effect of homogenization on chemical and physical properties or frozen cream 0..OOOOOOOOOOOOOOOOOOOOOOOI0.000000000000000 4 Influence of the use of sugar on certain preperties of cream 6 ‘Use of various types of containers for cream.storage ....... 7 Effect of rate of freezing on stability of fat emulsion of fmzen cream 0.00.00...COO...0.0...00.0000...OOOOOOOIOOOOOOO 8 Influence of fat content of the cream upon the homogeneity Of fre921n8 0.0.0.00000.0.00...0.0.0.0.0...OOOOOOOOOOOOOOOOO 9 The temperature and length of period that cream.may be stored fmzen OOOOOOOOOOOOOOOOOO0.0.0.0.0.0...OOOOOOOOOOOOOOOOOOOOO 10 .Methods used in defrosting cream ........................... 11 Use of the oxidation-reduction potential in predicting keep- ing quality Of cream 0.00.00.00.00.0...OOOOOOOOOOOOOOOOOO... 12 The relation of the hydrogen-ion concentration to length of Storage period or cream OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO. 13 Effect of carotene on oxidized flavor develOpment of milk and cream OOIOOOOOOOOOOOOOO0.0.0.000...OOOOOOOOOOOOOOOO000...... 14 The uses or frozen cream OOOOOOOIOOOOOOOOOO.0000...000......a 15 Problems encountered in storing frozen cream................ 16 1. Development of oxidized flavor ...................... 16 2. Destabilization of the fat emulsion ................. 18 mSE 0F mm'r .00....0.0.0.000000000COOOOOO0.0.0.00.0... SCOPE OF. MHG‘ATION .0OCOOIOOOOOOOOOOOOOOO.0...OOOOOOOOOOOOOOO WWW OCOOOOOOOOOOOOO0.0.0.000...OOOOOOOOOOOOOOOOOOOOOCOO mTS CCOOOOOCOOOOOOOOOOOOOOOOOOOOOOOO0.0.0.000...00.0.0000... Part I. Factors affecting flavor and fat emulsion stability or fmzeg Greg 000......OOOOOOOOOOOOOOOOOOOC..00... A The influence of several factors on the keeping quality or frozen cream OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. The effect of capper contamination on oxidized flavor development of frozen cream .............. The influence of homogenization on flavor of fmzen cream 00.0.0000...OOOOOOOOOOOOOOOOOOOOOOOO Type of container used for cream storage ........ Influence of pasteurization exposure on develOp- ment of the oxidized flavor in frozen cream...... page 22 23 25 31 31 31 31 33 35 34 Effect of season of the year on keeping quality of frozen cream O....000.0.0.0...OOODOOOOOOOOOOOOOOO 35 The influence of storage period on flavor of frozen cream .00.0.CO...COO....0...OOOOOOOOOOOOOOOOOOOOC Effect of carotene content of cream.on oxidized flavor develoment 0000......OOOOOOOOOOOOOOOOOOOO Influence of initial titratable acidity on oxi- dized flavor development in frozen cream ........ The use of hydrOgen-ion concentration determina- tions in fresh and frozen cream ................. The oxidation-reduction potential of fresh and stored cream O0......OOOOOOOOOOOOOOOOOO...0...... B The influence of several factors upon stability of fat meion .OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOCOOOCOO... 1. 2. Influence of homogenization on the free fat separation OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO... Effect of sugar on free fat separation of de- frOSted Cream 0.000000000000000000000000000..0... 35 36 36 37 37 79 P389 3. Effect of fat content on stability of fat emulsion of defrosted cream ..................... 80 4. Influence of length of storage period of cream.on stability of the fat emulsion of defrosted cream 80 5. Effect of pasteurization eXposure on free fat separation of defrosted cream ................... 81 6. Effect of speed of freezing on stability of fat emulsion of defrosted cream...................... 81 Part II. Utilization 2;_frozen cream in the ice cream mix... 87 1. Influence of sugar in frozen cream upon whipping ability and flavor of frozen cream.ice cream .... 87 2. Influence of dried egg yolk upon whipping ability of frozen-cream.mixes ........................... 88 8. The influence of dried egg yolk upon flavor of fNZQfl'CI‘BBm ice‘cream oecoococec0000000000000... 88 4. Influence of length of frozen-cream storage on Whipping ability Of mixes ......OOOOOOOOOOOOOOOO 89 5. Flavor of frozen-cream.ice cream.upon storage ... 89 6. Bacteria count of frozen-cream ice cream......... 90 DISCUSSION ..................................................... 100 SUMMARY 109 11mm CITED 0.0.0..........OOOOOOOOOOOOO......OOOOOOOOOOOOO 111 INTRODUCTION The demand for dairy products, which in most cases is comparative- ly uniform throughout the year, does not exactly coincide with butterfat production which usually reaches a peak during the late Spring and early summer’months. Consequently, problems arise in times of surplus as to satisfactory storage of dairy products in such form that they may be used when a shortage occurs.i As a result of research in processing and as well as through the deve10pment of modern machinery, the quality of butter, cheese, and dry milk solids has been improved so that longer periods of storage may be used without an appreciable loss in quality. Despite much research in ice cream, resulting in improved quality, production factors present a Special problem. Not only must it be made from fresh clean-flavored milk products, but the demand for those products of manufacture is greatest at that period of the year when production of butterfat is beginning to decrease. In other words, butterfat production is usually at a peak ahead of its demand for use in the manufacture of ice cream mix. The problem, then, has been that of a satisfactory method of storage of surplus butterfat which might be utilized later when the de- mand for ice cream.was greatest. In storing butterfat, either as cream.or a form.of butter, for future use in ice cream.manufacture, care should be taken that the initial flavor is excellent, that the biological and chemical prOperties are con- trolled, and, that the physical preperties will not be materially altered. Previous investigations have shown that the storage of butterfat in the form of frozen highrtesting cream had possibilities as a practical method of preserving the fat for future use in ice cream.mix. This method, however, presented certain limitations. The problems of devel- opment of off-flavors in the stored frozen cream and the effect of the freezing process upon the stability of the fat emulsion indicated need of further research in this field. With these in mind, the investiga- tion presented herein was undertaken. REV’IET’J OF LITERATURE _22_.....Im rtance 2.1; _.L___in tial 292.131 .92. sagas $222222; :2: £22.92 £22352. Ap- parently, only cream of the highest quality having low initial acidity and free from objectionable off-flavors and odors should be preserved by freezing. Ellenberger and White (1929) indicated only high quality cream should be stored frozen. Newlander and Ellenberger (1929) noted average quality cream did not keep well. Mack (1930-b) contended the quality of the frozen cream depended largely on the quality of the cream before freezing. ‘Morris and Sommer (1932) and Sommer (1937) stressed the importance of using cream.with.low initial acidity, while Dahle and Josephson (1939) pointed out the importance of selecting a cream.for freezing that had a low initial acidity and was free from cOpper contamination. They added that exceptional quality was desired in cream to be frozen. Dahle (1927, 1938) pointed out the advisability of using cream.with a low initial acid- ity as did Pederson (l941-a) and Parker (1941). Influence g; pasteurization W 9;; keepigg W of cream. Pasteurization has long been recognized as an essential process in assur- ing the keeping quality of frozen cream. IMost workers advised a high- temperature pasteurization exposure. Gould and Sommer (1939) showed that high-temperature pasteurization produced certain sulfhydryl reducing substances which were very effective in inhibiting oxidation. Mack (1939) suggested a pasteurization temperature of 160°F. and Combs (1939) stated that most plants favored highrtemperature pasteuriza- tion of cream intended for freezing and that sometimes it was deemed ad- visable to pasteurize at 175°F. for thirty minutes. However, Dahle and Josephson (1939) considered a pasteurization procedure of 1700 F. for fif- teen minutes to be adequate, but Lawhorn (1939) and Dahle and associates (1940) recommended temperatures as high as 190°F. flash. They admitted cooked flavors resulted from that exposure but stated that mix made from such frozen cream did not retain the cooked flavor. McFarland and Burgwald (1940) advocated the use of a pasteurization temperature of 172°F. for five minutes, indicating that this exposure seemed sufficient to inhibit develOpment of the oxidized flavor. Hewever, this exposure resulted in a cooked flavor which disappeared after one month of storage. Pederson (1941-a) suggested 1750 F. for fifteen to thirty minutes as sufficient for pasteurizating cream for frozen storage. Lawhorn (1939) concluded, ”When cream is heated to a temperature sufficiently high to produce sulfhydryl compounds, a greater degree of oxidative stability is imparted to the butterfat, as indicated by the in- creasing time of the induction period.” Effect 9;,homogenization pg.chemical and phyglga;,pr02erties g§_frozen creamt (Many investigators have homogenized cream prior to cooling in at- tempts to improve its qualities for frozen cream. Generally, pressures of 2500 to 3000 pounds were used. However, considerable controversy exists among the workers concerning the advisability of homogenizing cream for freezing. Inasmuch as homogenization has proven effective in preventing copper-induced oxidation in milk, it seemed quite logical to assume that such treatment might be applicable to cream also. Mack (1930-b) in a relatively early publication on the use of the homogenizer on cream for freezing, maintained homogenization of the cream did not prevent oiling off of the frozen cream upon defrosting and indi- cated that he did not consider homogenization advisable. Webb and Hall (1935) pointed out, ”Homogenization of low fat cream slightly retarded fat separation of the frozen cream.and that the fat clumps formed in cream.by homogenization were destroyed by freezing, while the heat stability destroyed by homogenization was restored by freezing.” Dahle and Josephson (1936) claimed homogenization before freezing produced a cream which oiled off to a much greater degree than did plain frozen cream.and added, ”Hemogenizing cream before freezing was found to be more detrimental to whipping than Just freezing alone.” Tracy (1936) presented data to show homogenization of milk prior to freezing materially reduced the tendency of the milk to "cream? upon de- frosting. He stated that when milk was properly homogenized, most of the fat remained as a stable emulsion after the milk had been frozen and thawed. Trout,(1941) on the other hand, showed that "A marked settling of the fat and the solids-not-fat of milk was noted when homogenized milk was frozen and then thawed.” 6 Tracy, Ramsey, and Ruehe (1933) showed that homogenization retarded cOpper-induced tallowiness in milk, while Thurston and associates (1936) indicated homogenization reduced or eliminated the susceptibility for the develOpment of the oxidized flavor in frozen milk. Larsen, Gould, and Trout (1941) pointed out that homogenization of milk tended to stabilize the milk against oxidation. Sommer (1937) suggested homogenization of the cream prior to freez— ing might be very beneficial in preventing tallowy flavor deveIOpment. Mc- Farland and Burgwald (1940) found homagenization to be effective in pre- venting the deveIOpment of the oxidized flavor in cream for 21 weeks even in the presence of considerable amounts of capper. ‘Lawhorn (1939) found homagenization caused considerable increase in the Eh of cream and claimed that homogenization improved the keeping qual- ity. Pederson (194l-a, 1941-b) advised homogenization of the cream.as did Parker (1941) also. Influence 9; the use 91 sygar an certain pmperties o_f cream. The incor- poration of sugar in the cream, either before or after pasteurization and prior to placing in the final container for freezing, has been said to ime prove both body and flavor of the cream. Price (193l-a) found ice cream from which all milk fat was supplied by frozen sweetened cream.possessed better whipping properties than mix wherein unsweetened frozen cream was used. 'He concluded after extensive studies that either sucrose or invert sugar could be used in frozen cream.with equal success. Bis data showing the effect of sweetened and non-sweetened frozen cream on the development of swell in ice cream is as follows: Treatment 'Kinds Ratio of Storage Number Time to Maximum of cream of sugar sugar to period of of get 90% swell cream. cream. trial§L_swell obtainab1e* Hours Minutes Per cent Not frozen none 48 4 8 96 Frozen none 48 4 9 94 Frozen sucrose 1-10 48 4 8 99 Frozen invert l-33:1O 48 4 8 101 Days Frozen none 14 3 9 95 Frozen sucrose .5:10 14 3 7 100 Frozen invert 14 3 7 102 Frozen sucrose 4:6 14 3 7 100 *Maximum swell obtainable with prOper consistency for drawing from freezer. Webb and Hall (1935) pointed out that increasing the solids-not-fat of the cream with additions of cane sugar, lessened the effect of the slow freezing process in the destruction of the fat emulsion. Doan and Baldwin (1936-b) agreed that the addition of sugar to the cream greatly reduced the per cent of fat de-emulsification upon defrosting. Tracy (1937) maintained that the poor whipping quality of frozen cream mix could be overcome to a great extent by the addition of 10 to 12 per cent sugar to the cream before storage. Mack (1930-b) contended the addition of 10 per cent sugar prior to freezing was a satisfactory method of preserving surplus cream.which was later used in the manufacture of ice cream.mix. Lawhorn (1939) showed sugar did not improve the keeping quality of frozen cream. Dahle, Lawhorn, and Barnhart (1940) presented data to show that the addition of 10 to 15 per cent sugar aided materially in the prevention of oiling off of frozen cream upon defrosting, but concluded that sugar did not improve the flavor of the cream.after six months storage. They stated that the flavor of the unsweetened frozen cream was preferable to that to which sugar had been added. Crowe and Winn (1941) stated, ”In the case of frozen cream to which sugar has been added, the point where viscosity limits the destabilizing effect of freezing is reached early and aggregation of the colloidal parti- cles is reduced.” gse Qghyarious typeg'gf containers for cream storag . Several different types of containers have been used for the storage of frozen cream. These include tin cans, paper cans, milk and ice cream metal cans, and even wood- en barrels. Ellenberger and White (1929) after extensive study, suggested cream containers should be free from here or corroded Spots of iron or c0pper, and although tinned receptacles are suitable containers, best re- sults were obtained by employing the use of lacquer, granite, or agate coatings to the cans. Grayson (1931) suggested lacquered tin cans. Tracy (1937) was quite exacting in his recommendations, advising the use of parchment paper beneath the lid to help in the exclusion of air from the cream. He added that only new, unscratched tin cans should be used. Combs (1939) pointed out the typical container was a straight-sided, fortybpound lard tin. Dahle and Josephson (1939) recommended the use of tin cans also. Dahle (1941) stated cream was most often stored in single service cans of five to six gallon capacity, although some used the type of paper cans commonly employed for dispensing ice cream. Pederson (l941-a) suggested the use of well-tinned receptacles for the storage of frozen cream. Effect o_f rate 2; freezing pg stability 9; fat emulsion o_f: $292.93 91m. The rate of freezing of a food product is important in that it controls quite largely the size of the ice crystals formed. That fast freezing is essential in securing the finest quality in the frozen food upon defrost- ing is no longer questioned. Price (1931-c) advocated the use of a Miller ice cream freezer for the fast freezing of cream and suggested a method whereby the process could be made continuous. GraySOn (1935) found, "Deaerating and freezing of milk or cream under high vacuum and hardening under extremely low temperature, is a suc- cessful way to store high quality cream for consumption as the fluid prod- uct." Webb and Hall (1935) showed a gradual precipitation of the casei- nate system and an immediate destruction of the fat emulsion due to the slow freezing of milk and cream. They also found that slow freezing caused excessive free fat separation or oiling—off during thawing. Lind- quist (1938) pointed out that application of fast freezing conditions to cream partially prevented oiling off. Roush (1939) designed a fast freezing method which was used quite successfully by Roadhouse and Henderson (1940). Carlton (1941) described several quick freezing methods used for various frozen foods. Possibly some of them might be applicable for cream although he made no statement to that effect. Influence 2§_2at contentlgf the cream upon thg homogeneitylgf freezing. There is some difference of Opinion among the investigators as to whether. or not cream freezes homogeneously. Most of them agreed, however, that there was little fat diffusion in cream containing forty per cent butter- fat or more. Trelogan and Combs (1936) demonstrated the relation of the per cent butterfat and the extent of fat diffusion as follows: _Type of Per cent butterfat in: cream Side Botton Center Top Low fat 18.75 19.25 18.50 25.50 Medium fat 29.00 29.50 29.50 30.50 fligh fat 39.12 39.25 39.00 39.25 Baldwin and Doan (1935) summarized most of the Opinions on the sub- ject in stating, "Increasing fat concentrations of milk constituents in both milk and cream retarded the diffusion or concentration of milk con- stituents into the unfrozen portion of the freezing product. When the fat concentration reached 25 per cent, diffusion was practically prevented and the cream froze homogeneously, Diffusion was probably inhibted by the in- 10 creased viscosity of the increased fat content, and also because of the more effective sealing of the interstices between deve10ping ice crystals by the increased fat content, and in the form of solidified globules.” Doan and Baldwin (1936-a) stated that homogenization of the cream.caused homogeneous freezing at a lower fat content than in nonhomogenized cream. Apparently, fat diffusion prior to freezing is of little importance commercially because too much storage space would be required for the stor- ing of any appreciable amount of fat if it were in the form of low fat cream. 19241131.th t Elm—£18.16 thsfnsmmimmaxw 212.232.. The length of time that cream.may be stored at a certain temperature and yet retain its original quality is of utmost importance. Newlander and Ellen- berger (1929) indicated that good quality frozen cream kept well at 00 F. for four to six months. Hack (1931) found that a room of ~50 F. kept a sample of cream for six months as well as a room of 10° F. kept the same sample for four months. He recommended holding periods of less than six months at -18° F. Lindquist (1955) used 00 to -1o° F., Dahle and Josephson (1939) suggested storing cream at -10° F., while Pederson (1941) advised storing below0°F. Generally, the above investigators have shown that a temperature of above 0° F. is not desirable from the standpoint of frozen cream storage and the temperature of the cold-room.should be 0° F. or below with the Cp- timum temperature well below 0° F. The temperature of the ordinary ice cream hardening room, therefore, would, in most cases be applicable for cream.storage. However, due to the expense involved in the building and refrigerating a hardening room, few commercial ice cream plants have suf- ficient space in their hardening rooms for the storage of any appreciable ll amount of frozen cream. Many plants have followed the practice of freez- ing cream in their hardening room with the aid of blower fans and than stor- with a commercial cold storage firm. Methods used in defrosting cream. Careful defrosting of the cream is essential in prevention of excessive oiling off of the butterfat and even under the most Optimum conditions, some oiling~off may still occur. ‘Mack (1931) stated that slow defrosting was advisable in that it resulted in better whipping qualities in the resulting ice cream.mix. Lindquiet (1935) found that when the cream was thawed slowly by immersion of the cans in water below 90° F., oiling—off was not prevented when the cream was later pasteurized. Gockley (1936-a) suggested cream.ahould be defrosted either by setting in the handling room overnight or by immersion of the cream cans in warm water, possibly in the cheese vat. The temperature could be more carefully controlled by the latter method, but the possibility of leaky cans might inhibit its use, as the freezing process often caused the ex- panding cream to burst the can, so the former method was probably the more practical. Pederson (1941-a, 1941-b) advised slow thawing of the cream. He suggested allowing the cream to set for two days in the handling room until all ice crystals disappeared. Gockley (l936-b) also reported using a "Creavy ice crusher” which was an ice crusher with the teeth having been removed. This method con- sisted of putting the can of cream in the crusher, having the frozen cream pressed out of it and into a hopper. The frozen mass could then be added directly to the pasteurizer. The advantages claimed for this procedure were that it conserved both time and Space and was equally as sanitary as other defrosting methods due to the fact that the ”crusher" was easily cleaned and sanitized. 12 Hewever, it destroyed the container, but on the other hand, most frozen cream containers are of the single service type, anyway. se pf_the oxidation-reduction potential 1p_predicting keeping guality‘pf m. Oxidation is quite commonly referred to as the loss of electrons and reduction is known as the gain of electrons. The measurement in elec- tric current of the preportion of oxidants to reductants in a solution is known as the oxidation-reduction potential. This is often expressed as Eh which is an intensity measure of the oxidation-reduction balance as ex- pressed in volts of electric current. Numerous workers have reported on the use of Eh as a means of pre- dicting the oxidative tendencies of cream after a period of frozen stor- age, but they do not all agree upon the reliability of such determinations in forecasting the keeping quality of cream during a period of frozen storage. Tracy, Ramsey and Ruehe (1933) found that cepper contamination in cream has the same general effects on the oxidation-reduction measurements as it did in milk. This indicates that they found that cOpper caused a definite rise in the Eh of cream. Lawhorn (1939) found considerable increase in Eh due to homogeniza- tion but concluded that homogenization tended to bmprove the keeping qual- ity of the cream. However, Tracy, Ramsey, and Ruehe (1933) and later Larsen, Gould and Trout (1941) concluded that homogenization had little or no effect upon the Eh of milk and contended that while homogenization retarded deveIOpment of the oxidized flavor, the explanation of that action did not appear to be associated with Eh. Lawhorn (1939) did considerable work on the use of Eh in frozen 13 cream.atudies and concluded that the oxidation-reduction potential was not a reliable criterion of the keeping quality of cream. Dahle, Lawhorn and.Barnhart (1940) made a very extensive study of Eh and the oxidized flavor of frozen cream and cited some very interest- ing observations. They found that the Eh of the cream increased during the first month of frozen storage and then decreased up to the end of the eightdmonth period during which time the flavor might have become oxidized. They also found that high temperature pasteurization decreased and c0pper increased the Eh. They did conclude, however, ”The initial Eh reading of the pasteurized cream before storage is a fair index of the keeping quality though not entirely reliable. It was found that cream with added copper having an initial Eh of above 0.30 volts usually deve10ped an oxidized flavor during storage of 6 to 8 months, while those below 0.30 volts seldom did. There were a few exceptions, however.” From the above, as well as other findings, it would appear that the reliability of the use of Eh in predicting the susceptibility of cream toward oxidized flavor development is as yet questionable. The relptipn.pf_the hydrogen ion-concentration‘pp length.pz spprage.pgzipn g£_cream. Although.much has been done relative to the per cent titratable acidity of cream prior to freezing, little attention has been given to the hydrogen—ion concentration to that cream as measured in terms of pH. Dahle, Lawhorn, and Barnhart (1940) found that the pH of cream de- creased upon frozen storage, indicating a greater intensity of hydrogen ions. They also found that titratable acidity of heated samples decreased I whereas if unheated cream.were stored, the acidity increased. It is in- teresting to note that while in one case (unheated cream) there was a rise 14 in titratable acidity as compared to a lowering in the other (heated), in both instances there was an increase in the hydrogen ion concentration. Effect gf_carotene pp,oxidized flaxor gaveIOpment pf,milk and ppeam. Anderson (1936) cited carotene as an inhibitor of oxidized flavor develop- ment in.market milk. Sommer (1938) suggested that carotene might be used as an anti—oxidant. Brown and others (1939) stated, ”Carotene fed at the rate of 350 mg. per day greatly reduced the tendency for metal-induced oxidized flavor to develop and resulted in an increased amount of carotene in the milk." However, Brown and co-workers (1940) later found a decreased caro- tens content of milk did not result in an increase in the intensity of oxidized flavor and concluded that the amount of carotene in the butterfat might not be the substance reaponsible for the reduction of milk suscepti- bility toward oxidized flavor development. They suggested that possibly some substance associated with the carotene rather than the carotene itself was reaponsible for the oxidative inhibitory action heretofore attributed to carotene. The intensity of yellow color has been frequently used as a means of securing a comparative estimate of the carotene content of milk or cream. Sommer (1938), however, showed that assumption to be erroneous and stated that the color of milk may not be regarded as a true index of the relative carotene content due to the difference in ability of dairy breeds to assimilate carotene. He stated that feed was more important than breed as an influence on carotene content of the milk. Consequently, under normal conditions, season of year would be the predominant factor. That carotene is quite stable in frozen milk products was demon- strated by Olson and co-workers (1939) who state, ”Milk can be stored 15 for considerable periods without affecting the carotene or Vitamin A content.” LI'_h_g pp_e_s_ pf fpozen m. The major part of frozen cream is used in the preparation of ice cream mix and it was with that in mind that the work of most investigators was undertaken. However, Roadhouse and Henderson (1940) described frozen cream which might later be used as table cream or in a reconstituted form. Some controversy exists among the investigators relative to the preportion of the fat from frozen cream that may be used safely in ice cream mix. Mack (1930-a) contended that an ice cream of desirable flavor was made only when not more than one-third of the total fat of the mix came from frozen cream. Gockley (1936-a) used up to 60 per cent of the total fat from frozen cream; Dahle and Josephson (1939) suggested frmm 30 to 50 per cent of the total fat from frozen cream; but Dahle, Lawhorn and Barnhart (1940) have indicated that frozen cream.may supply all of the fat of the mix. Parker (1941), however, cautioned against using over 25 per cent of the total cream of the mix from frozen cream. Apparently while the investigators differ considerably in opinion as to the percentage of the total fat of the mix which should come from frozen cream, they all agree that the percentage of the total fat which may be constituted by the frozen cream is directly preportional to the quality of that frozen cream. Therefore, one seems justified in assuming that when cream of such quality has been produced, the whole of the fat of the mix may be supplied by frozen cream. 16 Problems encountered';g.storipg frozen.ppppp. The difficulties encountered in the preserving of cream by freezing and low temperature storing are both chemical and physical in nature. The tendency of the cream toward deve10p- ment of oxidized flavor, and the occurrence of oilingwoff upon defrosting and pasteurizing in the mix have resulted in considerable investigation. 1. DevelOpment pf the oxidized glgyor. Even under the most ideal condi- tions, cream often exhibits susceptibility toward the develOpment of an oxidized flavor upon frozen storage as shown by Reid (1926). Sampey (1939) stated that when the dissolved oxygen was removed by heat and vacuum, the action of copper in accelerating the oxidation of ascorbic acid and the subsequent deveIOpment of the oxidized flavor was eliminated. Cream thus treated would then have to be filled under vacuum or in the presence of an inert gas such as nitrogen before storage. Lawhorn (1939) stated the replacement of oxygen with nitrogen in a vacuum sealed container seemed to improve the keeping quality of the cream. Roadhouse and Henderson (1940) used vacuum.sealed cans and reported no oxi- dative changes within six weeks. Most observers now believe that oxidized flavor is due to the oxi- dation of the phospholipids surrounding the fat globule rather than to the oxidation of the unsaturated fatty acids. Price (1932) was of the opinion that the addition of sugar to the cream.before freezing protected the lecithin from oxidation. Thurston and associates (1936) indicated lecithin rather than butterfat was affected in the development of the oxidized flavor and concluded that when the ab- sorbed lecithin was removed from the fat globule surface, there could be no oxidation taking place. 17 Swanson and Sommer (1940) concluded that cepper-induced oxidation of milk fat was due to oxidation of the phospholipids, lecithin and ceph- alin. Sommer (1936) decided lecithin was probably the mother substance of the oxidized flavor and suggested that homogenization of the cream prior to freezing might be very beneficial in preventing tallowy flavor deve10p- ment. Barnhart (1940) concluded, 'Butterfat is not the source of the oxi- dized flavor in frozen cream. The theory of phOSpholipid oxidation seems to be the more logical conclusion.” McFarland and Burgwald (1940) contended homogenization was effec- tive in preventing the develOpment of the oxidized flavor and also stated that pasteurization of the cream.at 175° F. for five minutes seemed to prevent develOpment of oxidation in the cream. Cepper contamination of the cream during processing is possibly the most common cause of oxidized flavor in frozen cream. With the advent of stainless steel equipment, however, and its rapidly increasing use, this source of contamination is diminishing in importance although there is yet much dairy equipment used from which metallic contamination is of vital concern. The use of anti-oxidants has been found to be beneficial in the prevention of the development of the oxidized flavor, and of these, Avenex, an oat flour product, is the most widely used. Dahle and Josephson (1939) pointed out the addition of one to two per cent of oat flour (Avenex) to the cream before freezing, enhanced the keeping quality of the cream before freezing, and that it was especially beneficial when used in conjunction with high temperature pasteurization. Meach and Tracy (1939) maintained oat flour was beneficial when used as an anti-oxidant in frozen cream. They suggested adding it as a gruel to the cream. of the weight of the fat. Barnhart (1940) used effectively both oat flour and a corn flour concentrate. 18 Lawhorn (1939) added oat flour at the rate of two per cent Dahle and associates (1940) presented data to show the effect of oat flour on the flavor of stored frozen cream as follows: Months in storage 0 1 3 6 Heating Izpppment ofpcreppgtemperature Flavor Flavor Flavor Flavor 150°F. 30 good good good good Control 170°F. flash cooked cooked cooked cooked 190°F. flashfcooked cooked cooked cooked Contr014-1 150°F. so good 00 0000 0000 p.p.m. cepper 170°F. flash cooked sl.cook sl.cook 0 190°F. flash*cooked o 00 000 Control+'1 150°F. so good o 0000 0000 p.p.m. copper 170°F. flash cooked good fair good -r2% oat flour 190°F. flashfcooked good good good *The 190° F. flash temperatures were heated to 140° F., then to 1900 F. with live steam directly injected into the cream. 2. Destabilization pfupngggp emulsion. Frozen cream, when defrosted and heated as in pasteurizating the mix, seems to have a general tendency toward oiling—off. Apparently the freezing process causes all cream to oil—off to some extent. However, various control measures reduce the amount of oiling—off to a minimum. Price (1939-c) suggested fast freezing as a preventive measure against oiling—off. Lindquist (1935) upon examination of cream.of four months stor- age, indicated that when the cream.was subjected to fast freezing conditions, oiling—off was partially prevented. Grayson (1935) and Roadhouse and Henderson (1940) have suggested meth- ods of fast freezing cream which indicated that they were fully aware of the destabilizing effect of the freezing and thawing processes which affect both 19 the protein and the fat to a much greater extent in a slow than in a fast- frozen product. Many workers have tried various ingredients added to the cream in an attempt to combat the destabilizing effect of the freezing process. Lindquist (1938) noted that the addition of sodium alginate (cocoloid) to cream.reduced the tendency toward oiling—off. In another investigation, however, Lindquist (1939) indicated no beneficial results were obtained up- on the addition of small amounts of sodium citrate and disodium phosphate to the cream prior to freezing. The addition to the cream of 10 to 15 per cent sugar has been the most successful method, other than fast freezing, of increasing the sta- bility of the fat emulsion upon thawing. Price (193l-b), Mack (1931), Webb and Hall (1935) and Dahle and Josephson (1939) all used sugar with varying degrees of success in preventing oiling+off as compared to that not containing sugar. Dahle and associates (1940) also used sugar in an attempt to lessen the tendency toward oiling—off and reported favorable results. The follow- ing data of Dahle and associates indicate the beneficial effect of using sugar: Per cent Trial Treatment "oilinggoff" Control frozen cream 90-100 1 Control+~10% sugar 40-45 Control*'10% sugar 35-40 Control frozen cream. 90-100 2 Control+-lO% sugar 45-50 Control+—l§% sugar 25-35 gee 9; frozen cream.ip;ice cream.mix. [Little has been done on the effect of frozen cream.on the flavor in finished ice cream after an appreciable period of storage. However, it has been found that if the flavor of the frozen cream were good, that of the ice cream was equally good. In some cases, the off-flavors in the frozen cream will not be discernible in the finished ice cream, for example, a cooked flavor in the frozen cream.may not appear in the final product. The flavor of the ice cream would as a rule be as good as that of the frozen cream.used in its manufacture. H0w- ever, the use of slightly off-flavor frozen cream in ice cream.mix might be possible if only a small per cent of the total fat was furnished by frozen cream. The chief objection, apparently to the use of frozen cream as the sole source of fat in a mix, was the poor whipping ability of the mix caused by the partial destabilization of the fat and protein of the fat and protein of the cream by the freezing process. As previously shown, the addition of sugar to the mix was bene- ficial in partially restoring the whipping ability of a mix. However, its stabilizing effect was not sufficient that the mix compared favorably in whipping ability to that made of fresh cream. In view of this condition, various attempts with reasonable suc- cess have been done to improve the whipping ability of mixes made with frozen cream, Most workers have agreed that the poor whipping ability of frozen cream mixes was due to the fact that the freezing process has re- moved the lecithin from the outer wall of the fat globule. Dahle, Lawhorn and Barnhart (1940) demonstrated that the neutraliz- ation of the acidity of the mixes to or even below normal, restored the whipping ability. They advised care in the selection of a neutralizer in order not to impart an off-flavor to the cream. They found that magnesium oxide proved very satisfactory as shown by the following table: 21 Trial Initial Final Final Time to reach No. acggity acidity pH 90h_overrun 1 0023 0018 6044 9'-30" 0.10 7.25 '7'-17“ 2 0.24 0.18 6.24 9'-10” 0.10 7.23 7'-35" 3 0.22 0.18 6.42 9'-25” 0.10 7.24 7'-10” Control (fresh cream) 0.22 0.18 7.45 7'-30" The addition of egg yolk, either frozen or dried, partially re- stored the whipping ability of frozen cream mix. Woodroof (1941) stated the whipping preperties of a mix may be restored by adding 0.2 to 0.4 per cent good quality egg yolk to the mix. 22 PURPOSE OF EXPERIMENT Previous investigations have shown that the freezing of cream for future use in ice cream.mix seems to have very definite possibilities. Indeed, several millions of pounds of frozen fresh sweet cream are now being stored annually for future use in ice cream manufacture. The pur- pose of this investigation, then is: 1. 2. 3. 4. To do further research on methods and processes intended to lessen the tendency toward the susceptibility of the frozen cream to the development of the oxidized flavor. To add to that which already has been done toward stabiliz- ing the fat emulsion and in turn make experimental studies toward methods which.may lessen the effect of the freezing process in causing destruction of the fat emulsion. To determine, according to the conditions set up in this experiment, the length of time that frozen cream.may be stored without serious deterioration of body and flavor. To ascertain, by use of cream preserved by frozen storage, what per cent of the total fat of the mix may be supplied by frozen cream.and the relationship of the quality of the frozen cream used therein to the quality of the finished ice cream. 23 SCOPE OF INVESTIGATION Although the main problems of frozen cream are largely two in number, namely, oiling—off and oxidation of the fats or fat-like sub- stances, the factors affecting these defects are quite numerous. Con- sequently, a number of those factors were included in this study. Data were secured on the following phases of this investigation: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. ll. 12. Influence of seasonal storage on flavor of frozen cream. Effect of copper contamination on flavor. Effect of sugar on the stability of fat emulsion and flavor. Effect of the pasteurization exposure on the keeping quality of the cream. Effect of various pressures of homogenization on stability of fat emulsion and flavor. Influence of type of container used for storage upon the flavor. Relation of initial titratable acidity to the keeping quality of the frozen cream. Use of the Eh and pH in forecasting the keeping quality of the cream. Relation of the carotene content of the cream to the keeping quality of the cream. Effect of rate of freezing on the stability of the fat emulsion. Relation of initial flavor of the cream to the final flavor after various periods of storage. Length of time that cream may be stored, according to the con— ditions of this experiment, without serious deterioration of flavor. 13. 14. 15. 16. 24 The effect of the use of frozen cream as the sole source of fat on the amount and ease of obtaining overrun when the mix is frozen. The effect of added egg yolk and/or sugar upon the whipping ability of frozen cream mixes. The effect of storage upon the flavor of frozen cream ice cream. The bacteria count of frozen cream ice cream. 25 EXPERIMENTAL The cream used in this experiment, secured from the separation of fresh, raw, mixed milk either from the College Creamery or from a local dairy company, had a fat content averaging slightly above 50 per cent. The milk was separated at about 100° F. after which the cream was cooled immediately to 60° F. Pasteurization followed at once. The cream was divided into three lots of which one was heated to 150° F. and held for thirty minutes; a second was heated to 1650 F. and held for fifteen minutes; and the third was heated to 185° F. for five minutes. In handling and processing the cream, precautions were taken against c0pper contamination throughout, the pasteurization being accom- plished in a stainless steel vat which was commonly used for the manu- facture of cottage cheese. Each lot was then subdivided into three lots which were homogenized at 0, 1500 and 3000 pounds pressure reapectively, using a Union Steam Pump 200-gallon viscolizer. The cream, frequently stirred, was cooled to 50° F. in ice water. Each lot thus pasteurized and homogenized was then subdivided into four lots, one serving as a control; a second lot having 1 part per mill- ion added cOpper in the form of an anhydrous cepper sulfate solution; a third lot had ten or fifteen per cent sugar added; and the fourth lot con- tained both sugar and cOpper added at the rates previous mentioned. Immediately following cooling and treatment, sufficient portions of the samples for study were put into three different types of containers, namely, glass, paper and tin. The glass container was an eightoounce may- onnaise-type jar with a water-proof inner lining screw cover; the paper 26 container was a pint Sealright carton and the tin container was a number two, ”C”-enamel, tin can, the lid of which was applied by an automatic, hand can sealer. When a lot was packaged, the packages were taken at once to a -10° F. room for freezing. In this room the samples remained as the ex- periment dictated. The accompanying data sheet(page 30) furnishes an out- line of the experiment insofar as preparations of the samples is concerned. Flavor examinations were made by two experienced judges on the cream.when fresh and after 3-, 6- and lZ—months storage. The intensity of the oxidized flavor was designated as follows: 7 : doubtful oxidized flavor +'= slight ” " ‘f +'= pronounced ” ” +'+'+‘: very pronounced ” ” For practical purposes in making tables and graphs these designations were given a numerical rating of 1, 2, 3 and 4, reapectively. The off-flavor recorded in the frozen cream samples was in every case the oxidized flavor. In the case of the presence of the cooked flavor which often occurred when pasteurization exposure exceeded 1600 F., it was not considered to be an off-flavor, inasmuch as the cooked flavor in the frozen cream did not re-appear in the ice cream mix or in the frozen ice cream. Fat content of the cream not containing sugar was determined by the Babcock method, whereas, that containing sugar was tested for fat accord- ing to the Minnesota method. The oxidation-reduction potential was determined on the nonhomogen- ized samples at 0, 180 and 360 days according to the Leeds and Northrup 27 potentiometer employing the use of the calomel half-cell and platinum electrodes. The quinhydrone electrode was used for the pH.determination. Titratable acidity was determined by the use of N/10 sodium hy- droxide using phenolthalein as the indicator. The initial acidity of the controls and of the nonhomogenized samples was taken immediately after cooling the cream. Fat emulsion stability was measured according to a method which was quite similar to that used by Webb and Hall (1935). It consisted of weighing nine grams of fresh unfrozen cream into regulation 9-gram 50-per cent cream.test bottles, freezing by different methods and holding for various periods of time. The bottles were then filled to the 50 per cent mark with 100° F. water. The samples were then centrifuged at 800 r.p.m. in an ordinary centrifuge commonly used for making the Babcock test of milk and cream. The centrifuge was warmed by the heat coil for fifteen minutes prior to and during the centrifuging period. The samples were then held 24 hours at 40° F. after which they were warmed for fifteen minutes in 100° F. water, prior to re-centrifuging for thirty minutes as before. After tempering the fat columns for three minutes in a 135° F. water bath, glymol was added to the tOp of the fat after which the fat columns were read immediately. Tests were made of the unfrozen cream.and that stored frozen for l, 90, 180 and 360 days. The carotene content of the cream in this experiment was determined under the direction of Dr. L. A. Moore, formerly of Michigan State College, according to the method devised by him. The procedure followed in making the carotene analysis of cream was as follows: A ten-gram sample of cream was weighed into a test tube and warmed to about 70° to 800 F. and to this, 28 ten ml. of ethyl alcohol was added and the sample well shaken. Ten ml. of benzin which was distilled over at 68° to 70° C. was added and again the sample was well shaken. After shaking, the sample was set into cool water, care being taken to avoid cooling sufficiently to cause fat solidi- fication. During a setting period of ten minutes that followed, the sam- ples were shaken three times for one minute each. After centrifuging at 1900 r.p.m. in a high speed centrifuge for four minutes, 1 ml. of the t0p (fat) portion was pipetted into a cell of a photo-electric colorimeter and read through a number 440 filter. The carotene content, derived by calcu- lation, was expressed as gammas or micrograms per gram.of fat in the cream. As a second part of the experiment, five-gallon lots of cream were frozen and stored for future use in ice cream manufacture. This cream was secured as before from the College Creamery and was pasteurized at 165° F. for 15 minutes, after which it was cooled to 55° F. To one lot of cream, 10 per cent sugar was added, while a second lot was stored without sugar. The cream, in lard-type tin containers, was placed in a cold room and frozen in still air at -10° F. Laboratory analysis of these samples in- cluded fat, flavor and titratable acidity. ‘ Mixes containing 12 per cent fat, 10 per cent serum.solids, 15 per cent sugar, and 0.35 per cent gelatin of 275 Bloom were made from.fresh control cream and from cream which had been stored frozen for 6, 3 and 1 month. Defrosting was brought about in the heating of the mix. Pas- teurization of the mix at 1500 F. for thirty'minutes was followed by homOgenization at 3000 pounds pressure in a single-stage, 200-gallon viscolizer. 29 The mixes were cooled to 500 F. and aged for 18 hours before freez- ing. Freezing was done in a 50-quart, direct-expansion, batch freezer equipped with a Drawrite indicator. A batch of regular mix was frozen and the freezer rinsed with one gallon of regular mix before freezing the mixes of the experiment. The rinsing procedure between batches was fol- lowed throughout the freezing trials. The time required to secure 90 per cent overrun was indicated by a stop watch. Samples of the ice cream.were taken at 90 per cent over- run for future scoring. The maximum overrun obtainable was also recorded. There was no regular sequence of freezing the mixes. In fact, they were chosen at random, inasmuch as rinsing of the freezer between batches would make similar freezing conditions for each of the batches of mix. I Scoring of the finished ice cream was done each week for the first two months, separate samples having been secured for each scoring, and thereafter at three and six months by two experienced Judges. Examina- tions for flavor, body and melting quality were done ”blind”. In addi- tion, the mixes were tested for flavor, acidity and oiling-off as pre- viously indicated. Another group of mixes similar to the first was made, frozen and Judged as before, excepting that 0.35 per cent dried egg yolk was added to the mix. sea \\L no em _ . madam .mon pm messes NH eupm< .oHE m 0 neH I.home 3 nommm mmmao .mqo we messes w sepm< sea women mmsao .mon pa menace NH popw¢ .ofie ma sea .amomwa .omee nomom .poem madam moon Ion...” .mno as mspnos m pepm< see .>an panda .Uwod macaw use .han we enemas NH n.9m4 .oea on "mpmm sflaw .ahooma III noose 3503-03 as macaw popsnemomv :«m .mOo as wepeos m w.pu< omouosm omouosm omouosm + omoeoom so + muchosm so , + omoposm so a“ possesses sense no MMH Egg H Hopunoo so MMH Ema H Houpsoo so MmH Ema H Honpnoo emoqum poem Hmeflwfiuo *7 on . floowa mo pooapoohe u wosasdxo open 1 voavspm nopedh odmsdm semno pmoim mo oweuopm one mnwnoohh 4253 deHEHfiua 31 RESULTS PART I FACTORS AFFECTING FLAVOR AND FAT EMULSION STABILITY OF FROZEN CREAM A. 21.13 Influence pf Several Factors pp 3113 Keeping Qpalipy pf Frozen Cream, Cream secured each.month throughout the year was treated by vari- ous methods as outlined in the procedure and stored frozen at 0° to -10° F. for 12 months during which time the samples were examined at 3, 6 and 12 month intervals for flavor. 1. The effect of c0pper contamination on oxidized flavor develOpment of frozen cream. As cOpper contamination is a very common cause of the de- ve10pment of oxidized flavor in dairy products, it was considered advis- able to ascertain just what effect the addition of cepper to the cream after pasteurization and prior to freezing might have on the flavor of the resulting frozen cream. ‘ Consequently, 1 part per million capper was added to the cream which was then well mixed and put immediately into containers for freezing. The data in tables 1 to 4, inclusive, show the effect of the added cepper on the flavor of the frozen cream after the various periods of storage. An analysis of the data reveals that when cOpper was present in the strength of 1 part per million, none of the conditions used in this experiment would render the cream entirely free from the development of the oxidized flavor. When similar samples were processed with no added c0pper and with very little capper, if any, due to contamination, the development of old, stale, oxidized flavors depended upon other factors, such as the pasteuriza- tion exposure. 32 Data in tables 1 to 4 indicate the flavor of all glass samples throughout the twelve-month period. Tables 5 to 16, inclusive, give the flavor data of the entire group of samples after 6 and 12 months storage. Figure 1 shows the comparison of the various treatments on the flavor of the cream. Data in tables 1 and 3 show quite clearly that cream may be pre- served frozen for at least one year with no detrimental effect on flavor if the prOper pasteurization exposure is followed and the cream.is kept free of cOpper. When the cream was held for 12 months, in no case was there any indication of the presence of the oxidized flavor in the samples pasteurized at 185° F. for 5 minutes, and that of 324 examinations made, only 4 were oxidized when the pasteurization exposure was 165° F. for 15 minutes. However, samples were frequently oxidized when pasteurized at 150° F. for :50 minutes. When 10 per cent sugar and 1 part per million cOpper were added to the samples, a slight advantage in flavor for the samples containing sugar was noted. However, sugar did not improve the flavor sufficiently to be of commercial significance when 1 part per million cOpper was present, as shown in table 4. The data in table 3 show little improvement in flavor as a result of additions of sugar without cepper contamination. Hewever, as both series of samples examined were largely without flavor criticism, it would be nat- ural to assume that flavor improvement, if any, could only be very slight. While in this series of samples, there was no significant difference in the number of samples having off—flavors, it also appeared that the flavor of the sugared samples was equally as clean and fresh as those of the con- trol lot. 33 The chief advantages of sugar additions, therefore, seem to be associated with its effect on the body of the cream. This will be dis- cussed later in greater detail. 2. The influence of homogenization on flavor of frozen cream. To ascer- tain the influence of homOgenization upon inhibition of development of the oxidized flavor in normal and cepper contaminated cream, batches of cream were passed through the viscolizer at 0, 1500 and 3000 pounds pressure, respectively. The data on the effect of homogenization upon flavor de- velopment are in tables 1 to 16, inclusive. An analysis of these data reveals that there was very slight in- hibitory effect on oxidation due to homogenization. Hewever, it should be emphasized that inasmuch as the oxidative inhibitory action is so very slight even in the samples containing 1 part per million copper (Figure 2), and due to the fact that if the cream had been properly processed it would likely have been excellent quality anyway (Figure 3), it is very doubtful whether homogenization of the cream prior to freezing would be of commercial significance. 0n the other hand, it must be borne in mind that homogenization was slightly beneficial. In plants wherein the quality of the cream was such that oxidized flavors were prone to develOp very slightly upon prolonged storage, homogenization might prove of slight value. 3. Type of container used for cream storageg. All the cream samples in these studies were stored in glass, paper and tin to ascertain the effect upon flavor. Data secured are presented in tables 17 to 24, inclusive. A study of these data shows no material difference in flavor char- acteristics of any specific type of container. However, the paper as a group appeared to be the least desirable, from the flavor standpoint, as 34 old, stale, flavors were sometimes noted in the cream which were not noticed when the other two types of container were used. 4. Igfluence of pasteurization exposure on development of the oxidized flavor in frozen cream. The pasteurization exposures used in this ex- periment are outlined on the data sheet and were 1500 F. for 30 minutes, 165° F. for 15 minutes and 1850 F. for 5 minutes. Data in tables 1 to 4 show the effect of these exposures upon the flavor of the cream after vari- ous storage periods. That pasteurization is absolutely essential in any type of cream designated for frozen storage was well illustrated by the examination of the raw control samples which were stored each.month in a glass container. The common defects of these samples were: very strong rancid, putrid, cheesy and bitter. In view of the condition of these samples even on the short three-month storage period, it was not considered necessary to include tables and graphs in this discussion. In no case was the raw sample in such condition that it might have any value as a human food product. Pasteurization at 150° F. for 30 minutes was easily the poorest of the lot so far as stabilizing the flavor was concerned. Even so, under certain conditions the cream treated in this manner was of good quality as shown by figure 4. Between the processes of 165° F. for 15 minutes and 1850 F. for 5 minutes, there was little to choose. Both were very effective in prevent- ing the appearance of the oxidized flavor. 0f the two, the process of 185) F. for 5 minutes was the most effective in preventing oxidation, but im- parted a slightly more cooked flavor to the cream which did not disappear even in one year of frozen storage. Figure 5 graphically points out the inability of any pasteurization 35 procedure to render a desirable flavored cream in the presence of 1 part per million copper. 5. Effect of season of the year on keeping_guality of frozen cream. Inas- much as fats and carotenoids of cream vary seasonally due to change in feeds, samples of cream were processed and stored each.month throughout the year to determine what effect, if any, normal seasonal changes would have upon the stability of flavor. The data included in tables 1 to 4 show that seasonal variation had very little effect on the flavor of the frozen cream. As seasonal variation also included such variations as feed and stage of lactation, this finding was especially interesting. Apparently one can store cream at any season of the year under identical conditions that might be used at any other period with equal success. The existence of this condition greatly facilitates matters in that it makes much simpler the recommended procedure of treat- ment of the cream inasmuch as it can be handled alike at any time of year. 6. The influence of storage period on flavor of frozen cream. In an ef- fort to determine the length of time that cream can be held by frozen stor- age, this portion of the experiment was set up for a long-time holding period, with regular intervals for flavor examination. Data in tables 1 to 4 show the effect of the storage periods of 3, 6 and 12 months on the resulting flavor of the frozen cream. Obviously, the flavor of the cream, regardless of treatment, is inversely preportional to the length of the storage period. Under any condition, one should use the frozen cream as soon as possible. Hewever, these data show that cream can be kept in excellent condition for a period of one year if prOperly processed, and other trials are now in progress in which samples will be removed and examined at two years. 36 7. Effect of carotene content of cream on oxidized flavor deveIOpment. Carotene analysis were made on the nonhomogenized samples when fresh and after 6 and 12 months storage according to the method outlined under ”Ex- perimental”. Table 25 and figure 6 show the relationship between the amount of carotene in the cream and the presence of the oxidized flavor. Analysis of these data shows no correlation existing between in- tensity of oxidized flavor and content of carotene in the sample. Indeed, even in samples containing cOpper, there was no significant difference between its carotene content and that of the control sample al- though there was a marked difference in the flavor of the two. 8. Influence of initial titratable acidity on oxidized flavor development in frozen cream. Titratable acidity determinations were made on the fresh nonhomogenized samples. The titratable acidity of all groups of samples stored is presented in table 26. As titratable acidity determinations were not made on any of the samples after a period of storage, no comparison can be made between it and the flavor after storage. Since the initial acidity of cream intended for storage is always of great importance, such determinations were made only on the fresh unfrozen cream. There did not appear to be any signifi- cant difference between the titratable acidity of the fresh samples due to the additions of cOpper, sugar or to the type of processing. There appeared to be a correlation between the titratable acidity and intensity of off flavors, eSpecially in those samples pasteurized at 150° F. for 30 minutes, upon storage (Table 26 and Figure 7). Apparently, this pasteurization exposure was not as effective as the other methods in preserving the cream when the initial acidity was unusually high. Undoubtedly, sweet cream of quite high initial acidity may be stored 3? frozen if the prOper processing methods are used (Table 26 and Figure 8). However, for best results, a cream having a low initial acidity is highly recommended. 9. The use of hydrogen—ion concentration determinations in fresh and frozen cream. Hydrogen-ion concentration determinations were made on the non- homogenized glass samples when fresh, and at 6 and 12 months according to the method outlined under ”Experimental". The pH of the samples pasteurized at 1650 F. for 15 minutes and the influence of time of storage upon the hydrogen-ion concentration of a frozen, high testing cream are shown in table 27. The pH did not appear to be materially altered by the addition of either COpper, sugar, or cOpper and sugar, either when the cream was fresh or after a period of storage. Several discrepancies in pH were noted as shown in table 28. These are largely unaccounted for and possibly may be due to some extent to ex- perimental error. Hewever, it should be borne in mind that the average fat test of the cream used was slightly over 50 per cent and even went as high as 60 per cent in one case, so it is considered that the presence of free fat in the defrosted cream due to the destabilized fat emulsion to- gether with the low percentage of the serum may have been responsible for some of these inconsistencies. As a rule, there was a slight lowering of the pH, or a gradual in- crease in the hydrogen-ion concentration, as the period of storage in- creased (Figure 9). 10. The oxidation-reduction_potentia1 of fresh and stored cream. The oxidation-reduction potential was determined on the nonhomogenized glass samples at O, 6. and 12 months. The Eh of all samples examined taken when fresh are shown in table 29; the arithmetic mean of all samples over the 12 month period being shown in table 30. Data in these tables show that the Eh of fresh cream is affected by a number of factors, mainly, capper, and pasteurization exposure. A comparison of the effect of cOpper to the control sample at each of the pasteurization exposures used is shown in figure 10. The addition of 1 part per million cepper to the cream quite ma- terially increased the Eh of the sample. This shows quite clearly that the presence of a strong oxidant will noticeably affect the Eh of a high fat cream. Conversely, the high temperature pasteurization exposure (Figure 10) materially lowered the Eh due probably to the liberation of the sulf- hydryls, glutathione and cysteine. 0f eSpecial interest, however,was the observation that under the conditions of the eXperiment, the pasteuriza- tion exposure had no effect upon the Eh of the cream when the cream was contaminated with 1 part per million cOpper. The seasons appeared to have an effect upon the Eh of the fresh cream. As this experiment included cream of each of the 12 months, it is interesting to note that the Eh was higher in the late fall and winter months and lower in the middle summer.months. Indeed, the Eh appears to coincide quite closely with the temperature of the season. Hewever, it 'must be borne in mind that only one 30-gallon lot of cream was processed and stored each.month.and this condition could have very easily been due, at least in part, to individual variations of the various lots of cream and might not be considered as conclusive evidence of the Eh of cream for that season. Also as seasons vary with geographical location, conditions found in this experiment might differ with the findings for the same month of another location. 59 Table l. The flavor of control samples of cream in glass containers at various periods of storage. : : Oxidized flavor of cream stored :Homoge- : 5 months when : 6 months when : 12 months when :nization: pasteurized at : pasteurized at : pasteurized at :pressurezl500F. 165°F. 18505.:1500F. 165°F. 185°F.:l50°F. 165°F. 185°F. Month: jlbs.lg; 50" 15" 5” : 50” 15” 5” : 50" 15” 53__ 0 a - - c - - ? - - 1500 at - - — - - - - - March 5000 - - - - - - - - -4__ O o - - o - - c - - 1500 - - - e - - - - - April 5000 - - - - - - - - ~ 0 - - - - ? - ? - - 1500 - — - - _ 9 - - - - ng 5000 - - - ? ? - - - - __ 0 - - - - - - 0t ? - 1500 - - - - - - o - - June 5000 - - - - - - c - - 0 - - - cc - - coo - - 1500 - - - - - - 9 - - luly 5000 - - — - - - o - - 0 - - - .- - - ? - - 1500 - - - - - - ? - - August 5000 - - - - ~ - c - - 0 ? - - - - - - - - 1500 ? - - 9f - - - - - Sept. 5000 - - - - - - - - -___ 0 - - - c — - ct - - 1500 - - - o - — - - - Oct. 5000 - - - — - - - - - ___ 0 - - - ? - - ? - - . 1500 - - - - - - - - - Nov. 5000 - - - - - - - - - __ 0 - - - - - ~ 0 ~ - 1500 - - - - -' - - - Dec. 5000 - ‘ - — - - - — - - ___ O - - - ? - - O - - 1500 - - - - - - c - - Jan. 5000 - *_, - - - - - - - ___ 0 - - - ? - - f - - 1500 - - - - - - - - - Fab. 5000 - - — - — - 40 Table 2. The flavor of copper treated cream samples in glass containers at various periods of storage. : : Oxidized flavor of cream stored :Homoge- : 5 months when : 6 months when : 12 months when :nization: pasteurized at : pasteurized at : pasteurized at :pressure:150°F. 165°F. 185°F.:l50°F. 165°F. 185°F.:150°F. 165°F. 185°“. Month: Ilbs.) : 50" 15" 5” : 50" 15" 5" : 50” 15" 5t_ 0 99 9 - 999 999 99 999 99 99 1500 99 9 ? 99 99 99 99 lost 9 March 5000 9 99 9 999 99 9 99 9 9 0 999 999 99 99 99 99 999 999 999 1500 999 99 99 99 99 99 999 99 99 Aggil 5000 999 99 99 99 99 99 999 999 99 0 999 9 9 9 99 99 999 999 99 1500 99 999 999 9 99 99 999 999 9 May 5000 999 99 99 99 99 99 999 99 9 0 99 99 99 999 99 99 999 99 99 1500 99 99 99 99 99 99 999 9 9 June 5000 99 99 99 99 99 99 999 9 9 0 99 99 99 999 99 99 999 999 999 1500 99 99 99 99 99 99 999 999 999 July 5000 99 99 99 99 99 99 999 999 999 0 999 999 99 999 999 99 999 999 999 1500 999 999 999 999 999 9 999 999 999 August 5000 999 99 99 999 999 9 999 999 999 0 999 99 99 999 99 9 999 99 99 1500 999 99 99 999 99 99 999 99 99 §§pt. 5000 99 99 99 999 99 99 999 99 99‘_ 0 999 99 9 999 99 99 999 999 99 1500 99 99 ? 999 99 99 999 999 99 October 5000 99 999 9 999 99 99 999 999 99 0 ? - - 99 99 99 999 99 9V 1500 ? - - 99 99 +9 99 9 9 Nov. 5000 ? - - 999 99 9 99 99 9 0 99 ? ? 99 99 9 999 99 99 1500 9 ? ? 99 99 9 999 99 99 Dec. 5000 9 ? ? 99 99 9 999 9 99 0 999 99 9 999 999 99 999 999 9 1500 999 999 9 999 99 99 999 99 9 Jan. 5000 99 99 9 999 9 9 999 99 9‘_ 0 999 999 9 999 99 99 999 999 999 1500 999 99 9 999 99 99 999 99 99 Feb. 5000 99 99 9 999 99 99 999 999 99 41 Table 5. The flavor of sugared cream samples in glass containers at various periods of storage. : Oxidized flavor of cream stored HomOge- : 5 months when ° 6 months when . : 12 months when :nization: pasteurized at : pasteurized at : pasteurized at ;pressure:150°F. 165°F. l85°F.:l50°F. 165°F. 185°F.:l50°F. 165°F. 185°F. Month:_L1bs.) : 50” 15” 5” : 50” 15" 5" : 50" 15" 5” 0 ? - - - - - - - - 1500 9 - - - - - - - - March 5000 - - - - - - - — - O 9 - - ? - - - - - 1500 - - - 9 - - - - - April 5000 - - - - - - - -‘g_ 0 - - - - - ? - - 1500 - - - - ? ? - - - may; 5000 - ~ - - 9 ? - - -_g_ 0 - - - - - - 9 - - ~ 1500 - - - - - - 9 - - June 5000 - - - - - ~ 9 - - O - - - - - - 9 - - 1500 - - - 9 - - ? - - July 5000 - - - - - - ? - - o - - - - - - - - - 1500 - - - - - - - - - August 5000 - - - - - - - - - ‘_ o - - - - - - - - - 1500 - - - - - - - - - Sept. 5000 - - - - - - - - -,g_ 0 - - — ? - - 9 - - 1500 - - - - - - - - - Oct. 5000 - - - - - - - - - ‘_ o - - - - - - - - 1500 - - - - - - - - - Nov. 5000 - - - - - - - - - ‘_ O - - - - - - 9 - - 1500 - - - - - — ? - - Dec. 5000 - - - - - - ? - - 4_ 0 - - - - - - ? - - 1500 - - - - - - - - - Jan. 5000 - - - - - - - - - O - - - - - - ? - - 1500 - - - - - - - - - Feb. 5000 — - - - - - - - - 42 Table 4. The flavor of sugared and cooper treated cream samples in glass containers at various periods of storage. : Oxidized flavor of cream stored .Homoge- : 5 months when : 6 months when : 12 months when :nization: pasteurized at : pasteurized at : pasteurized at :pressure:l5OOF. 165°F. 185°F.:150°F. 165°F. 185°F.:150°F. 165°F. 185°F. Month: (1bs.) : 50" 15" 5" : 50” 15” 5" : 50" 15" 5" O 99 99 - 99 99 99 99 '9 99 1500 9 9 ? 999 9 ? 99 9 9 March 5000 9 9 9 99 99 99 9 ? ? O 999. 99 9 999 9 99 999 99 99 1500 999 99 99 99 9 9 99 9 9 April 5000 99 9 - 99 9 9 99 99 9 O 99 ? - 9 99 9 99 99 99 1500 99 99 . 99 9 9 99 99 9 9 May, 5000 9 99 ? 9 99 9- 999 9 - 0 999 99 99 999 9 99 999 99 9 1500 99 9 99 99 9 9 9 9 9 June 5000 9 99 99 99 9 9 9 9 9 O 99 99— 99 999 9 9 999 999 99 1500 99 99 99 99 9 9 999 999 99 July 5000 99 99 99 99 9 9 999 999 99 O 9 99 99 999 99 9 999 999 99 1500 99 999 99 999 99 9 999 99 99 August 5000 99 99 99 999 99 9 999 lost 99 O 99 9- 9 999 99 9 999 9 9 1500 99 99 9« 99 99 9 99 9 9 Sept. 5000 99 99 9 99 99 9 99 9 9 0 99 99 9 999 99 9 999 99 9— 1500 99 99 9 999 99 99 9 99 99 October 5000 9 9 9 999 99 9 9 99 9 0 ? - - 99 99 9 99 9 9 1500 - - - 99 99 9 9 9 9 Nov. 5000 - - - 99 99 9 99 99 9 0 ? ? - 99 99 9 999 99 99 1500 ? ? ? 9 9 9 999 99 99 Dec. 5000 ? ? ? - 9 9 999 99 99 4_ 0 99 ,,, 9 99 99~ 9 999 99 - 1500 9 9 9 99 9 9 99 99 9 Jan. 5000 9 9 9 99 9 9 999 99 9_4_ O 99 9 ? 99 9 9 999 99 99 1500 9 9 ? 99 9 9 99 9 9 Feb. 5000 9 9 ? 99 9 9 99 99 9 ozlomlm Hobdam deuaduno Mo madame» m s m a an a “a p ovoeh smoke pemzm Ho omenopm use mnfinomuh eHe ++ 9 99+ 9 9+ I 99+ 99 9+ I 999 +9 spasm .eHon +9 I 999 I 99 I 99+ I +++ I 9+9 9 mmeHo IIHflamWIIpem ...Ha he 2385 NH 9 as .55 on "new 99 + +9 I = 9+ I 9+ + +9 I ++ 9 :HB .amoOmH III 99 I 99 + = +9 9 +99 9 9+ 9 99+ 99 spasm. A.moowwI00H 9 I 99 99 + +9 9 99 p 99 + mmeHo pmaeaemmmv = 3mm #00 as messes m as: 80.33 emoaosm $0.33 + mmosoem so + ,mmouosm so + emonosm so I cw pamsuwmaa sumac so MMH can H Honpcoo :0 EH can H Hospaoo H6 mH Ema H Hoannoo ommnopm poem HmaHMHno 3 o... I 983 +0 escapeona HzImHI: . S. .5: 8&5: openluagflqqsflglefiefiu Seawallllommalfllfluqilloafim sumac spasm mo pushovm use mnnnoehm .o 0.3.8 -.I IIIIEIEsgg, ,i I IIIIII |- IL I I 99 I I I 99 I 9 I 99 :HH I I 9 I I I 9 I N I 99 um um I I 9 I 9 I 9 I 99 I 99 mmch .mon pm mgpsoe NH NWNMH .nHE m w 9 N 9 I 9 N 9 I 99 N 99 5% .I ,momwH + N 9 I 99 N +9 I + N 9 .8 am 9 N 99 I 99 N 99 I 9 N 99 mmaHo .mao pm mnpnos w nupm¢ :HH 9 I 99 I = 9 I 99 I 99 I 999 9 I 99 I = 9 I 99 I 9 I 999 Amman 9 I 99 I = 9 I 999 I 99 I 999 mmmHo .mon pm mnpnue NH NVNMH .nHE mH 99 N 99 N = 99 N 99 N 9 I +9 :HH I.mome omHN 99 N 99 I = 9 N 99 N 9 I +9 Momma .Noam mmme mnmn .mno pm mgppos o papm< . 99 I 99 I 99 I 999 I 999 I 999 :He >mHh 99 I 999 I 99 I 999 I 999 I 999 nmadm .uHod 9.1. I 999 I 99 I .19 I 99 N 999 $30 fil as .m: pa mnvqus NH umpw4 .mHE om "mpmm + I I k = ... I + w + I + a | .mOOmH II 9 I 9 N = 9 I 9 N 9 I 9 .893. A . NooHNHMIooH 9 I 99 N = 9 I 9 I 9 I 9 N38 cmamflmmmmv .hoo pa mappoe m .AHH mmouosm mmouosm mmouosm 9 mmoposw so + ,mmonosm so . 9 ,mmohosm do :H pqospwwpa Edmno no MMH sun H Houpnoo so RMH Egg H Hoppnoo do MMH Ema H Houpnoo wmduopm pdwm HmnHmHno on *oowH *0 newspamua HHINHIm c.1511. @3285 33 J33 333% 933m '43 035m 6895 pmoxm Ho ounnovm «and wnwnomhh .P OHAGB II I, II IrIIIbILHM—Hwfifia. IIIII'II IIIIII I I L. oxImINH UmsHdem owwn n o o pHun¢de cmHvSNm hopodh Edmno pmmsm mo denopm wad wanmwhh €840 AdBZWEHmmmxw om OHBUB GHH 9 I 9 I 9 I 99 I 9 I 99 I pm am 9 I 9 N + I 99 I 9 I 99 I 9 I 9 I 9 I 9 I 9 I 99 I mmNHo .moh pm mgpsoe NH NNNMH .cHe m % 9 I 99 I 9 I 99 I 99 I 99 I :HN I.mommH 9 I 9 I 9 I 99 I 9 I 99 I pmawm mmeo 9 I 99 I 9 I 99 I 99 I 99 I .mno pm mgpzoa m pwpm< :HH 9 I 9 I 9 I 999 9 99 I 999 9 hmawm 9 I 9 N 9 I 999 9 99 I 999 9 9 I 9 I 9 I 9 I 99 I 99 N mmeo .mon pm mzpcus NH NWHNH .sHE mH 99 I 99 I 9 I 99 I 9 I 99 I :HB I.momoH omHN + l ++ I + l 9.... I + I .1..- l hmawnm .993 9 I 99 I 9 I 99 I 9 I 99 I wmmHo mcmH Ichmn .mao pm mzppoe m NapNH nHH .>an 9 9 +99 99 99 9 999 9+ 99 9 999 999 9 9 999 99 99 9 999 99 +99 9 999 99 hwawm .uHod 9 9 999 9 99 9 999 9 +99 9 999 99 mmeo o.mm Nam .man pm mnpzue NH NNPHH .cHE on "mpmm 99 I 99 I 99 I 999 9 999 I 999 9 QHH I.moomH III gnaw . I 9 I 999 I 99 I 999 I 999 I 99 9 m A mooww OOH mmm m whamo 99 I 99 I 99 I 99 I 999 I 999 I Ho c p3mHn 99 N 999 9 999 I 999 99 999 N , 99+ 99 pmndm .UHod 999 N 999 9 999 N 999 9 999 9 999 +99 mmmHo No.w: Nam .man Nu usages NH NWPNH .dHE om ”mdmm 999 I 999 I 999 I 999 9 9+9 I +99 +9 zHH I.m00mH III know . I 99 I 99 I +9 I +9 9 999 I ..99 99 m N boom. 00H wmw m whamm +9 I 99 I 99 I 99 I 999 I 999 99 Ho o dzdm mo .moo pm mzppoe o p.pm< machodm mmouodm mmopodm 9 mmogodm do 9 mmouodm do 9 mmonodm do dH pamEpmmpB Edwdo do MMH Ema H Hoppdoo do mmH Emu H Hoppdoo do mMH Ema H Hoppdoo wmwnopm paw: HadHMHno wooom moowH *0 pdmspdmya HzIoHIN IIIIIIIIIIIHmnmmuwI.vwdHdem mama uo>UHu douHoHNo no pHndnde umHodpm nopoah ozmH .NH thh oHQEwm Edmuo pumam mo mmmfiopm mam manmwhm .o 0.33.. mHn pmadm .wHod 999 I 999 9 999 I 999 N 999 I 999 N mmeo wo.Hm Nah .man pm mnpdue NH NQNNH .:HE om ”mpmm dHH IuMOOmH III pmawm A.m00HHIOOH pm 19 I 99... I 19 I 999 I 9+9 I 33 I 330 UBHMQNB .moo pa wnpdoe m n.pm< mopodm mmouodm mmogodm 9 mmONUdm do 9 mwopodm do 9 mmopodm do :H pdepmmpB Edwpo do MMH 5mm H Hoppdoo do mmw Ema H Hoppnoo do IMMH Ema H Hoppcoo mmwuopm pmmm Hdemeo no on moowH *0 F pdmapdmna Hal mlw HdINHIN umnHEaxm ovum o>dHM douHcHHo no pHadounH vaUdpm nowadh Edopo pmmzm mo mMMNOpm wad manomnh .OH OHAoB me 9 I 99 I 99 I 99 I 99 I 999 I 9 I 99 I 99 I 99 I 99 I 999 I pmadm .oHoN I I I - I - 1+ - +1 - 1 I £3 '33 E. .mon pa m£pdoe NH u NNH .dHE on "mumm 99 I 999 I 999 I I... I 999 I 91. I :2 I @003 ll 99 I 999 I 999 I .799 I 999 I 999 I .893. A . moowonoH and m wpwam 99 I 999 I 99 I 999 99 999 I 999 I Ho 6 o3¢m my .mOo pm mnphoe o u.pm< mmONOdm mmouodm wmouodw 9 mmopodm do 9 mwopodm do 9 mmouodm do dH pdepmmpa Edwho do mH Ema H Hoppdoo do mmH Ema H Houpdoo do ImmH Ema H Honpaoo wmanopm pwwm HdemHuo *0 0m *00wH *0 pdmspdmps 34% a HiIONIM ©®QHEMXQ Gamma .HOdeH UONHddHO HO hHHQQO¢NH flmflfisvm hopOdh gmfl .NH hmpfiwaBWDm ”H 5.5% Edwuo pmmim mo deuopm cam manomnh mHN 99 I 99 N 9 I 99 I 99 N 999 +9 madam .oHoH +9 I #9 .... 9 I .I. I 99 N +99 N 303 flag. . d m anus NH p.9H4 .dHE on "mamm +9 I 99 I ++mdn p m 99 I 99 I 99 I dHH InhoomH III +9 I ..9 I 99 I 99 I +9 I 9.. I 393 H .NoommISH 99 I .19 I 9.. I ..9 I +9 I 99 N 398 932252 :«m .mOo pm map as m u.um< mmouod mmouodw mmowodm machodm do 9 w mmopodm do . 9 mmonodm do dH pdwevwmne Edmuo do MMH sum H Hoppsoo do IMMH emu H Hoppdoo do mH Ema H Houpdoo,mmwnopm pwmm HdanHpo on $00“ *0 Newsamvha [41-43anwa 33 morgue had-:35" c033» 33am 02$ .8. hoe-open 395m .a H:Immlm Edoho vomim Ho owdhovm was deuoohh .nH OHAJB IIL + IIIIIIIIIIIIIIIII +93 fifinahm +9 I . +9 I = +9 I 99 I 99 I I 99 I :2. 99 I 99 I = +9 I 9+ I +9 I 99 I “mum“: +9 I +9 I = +9 I 9+ I 99 I 99 I mmaau 9 .Non pa mnpnoe NH pwpm¢ .sde m m 9 I 9 I = N I 9 I 9 I 9 I :2. IsmommH 9 I 9 I __ N I 9 I 9 I 9 I “mmam 9 .I 9 I = 9 I 9 I 9 I 9 I 330 + .Nqo pm mnpaos m I +99 +9 I 99 I 9 I 99 I = +9 I 9.9 I fie +9 I 99 I 99 I .I. I = +9 I 99 I 39mm .1. I 9 I 99 I 99 I = +9 I +9 I 330 .NON Na mgpzus NH “+999 .sHe ma N I 99 I 9 I +9 I 99 I 99 I :NN .Imomma .omHN 9 I 99 I 9 I 99 I 99 I 99 I do mm .podm 9 I 99 I 9 I 99 I 99 I +9 I 358 Iwmwm .mno #9 mgphos m papm< +9 I .....9 I +9 I 1.9 I ..99 9 999 9 a2. 43?. +1. I +99 I +99 N ...I. 9 +99 9 999 9 33m .33 .19 N 9.1. I 1.9 N 9+9 N 999 9 9+9 9 $30 0.2m $9.. .Nan pa mgpzue NH u 9H9 .:NE on "mpmm 9 I 99 I 99 I 99 I 99 I 999 I fie LINoomH I +9 I 99 I 9 I 99 I 99 I 9.9 N .393. A . moOHHIOOH ad - wude‘ m “Adam I I .T? I ... I .To. I Ar... I .TT I U H3mHN 99 I 999 N 99 I 999 9 99+ 9 99+ 99 pmawm .oNud +99 +9 999 I 99 I 999 9 999 N .99+ 9 mmmHo Nam .Nan Na wspsus NH N NNH .:NE on "mpmm 99 I 999 I 99 I +++ I 99 N 999 N :HN .umoomH III +9 I 999 I 99 I 999 N 99 I 999 9+ Nmawm A.NOOHHIOOH pm 99 I 999 I 99 I 999 I 99 I 999 N nmeo uopmpmammv 3¢m .Noo Na mnphoe m N.+N< mehODW mmOhOdm mmOhodm 9 mmouodw do 9 mmONOdm do 9 mmonodm do :H pamENMmNa Edmpo I do MMH Ema H Hogwdoo do xxflmH Ema H HOdioo do MMH and H Hoppdoo wmwNONm pumm HausHdo *0 on MoowH *0 pdmsvdopa WHHMIH HfllOHIN vaHEde deQ HDPGHM doudddko Ho hvduflovdH Umwvflpw hapOdh HJmH .wH hhflfiqufi mHQEdm Edouo pmmsm no mmMNONm odd MdHummuh wHN 99 I +++ N 99 I 999 I 999 N +99 9 pandm .UHod 99 I 999 I 99 I 999 I 999 N 999 9 mmmHo .IlmqmmII.NwN .Nan Na mspsus NH N NNH .cHe on "mpmm +9 I 999 I = 99 I 999 I 99 I 999 N nHa .umoomH III 99 I 999 I = 99 I 999. I 99 I 999 N Nmawmv A.NooMHIOOH .0 I I I I I mndHo ompmummmmv 99 999 __ 99 +99 99 +99 N 39m .Noo Nu mnNLoEIw N.NNH mmONOdm mmouodm mmopodm + mmogodw do + ,wwONOdm do 9 mmonodm do dH pdevwwNB Edmpo do MMH emu H Hedpdoo do mMH an“ H Hoypdoo do MMH Ema H Hodpdoo,mmup0pm puwm HudeHuo *0 on . *OOuH *0 odeadwna ImwnmIN EIHHIN 98238 33 85H». 8:38 No kflaofiug 833m 33$ ES .3 53%.— 32am It'll I‘II II? . Edouo pmmsm No omuuopm can MdHNmem .oH oHnuE Table 17. The flavor of control cream samples in various containers when stored 6 months. 55 Month March April May June July fie tin or paper) August September October November December January February; :Hbmoge- : :nization:150°F. - so" and :pressure: :_L1bs.) O 1500 3000 O 1500 3000 O 1500 5000 0 1500 3000 0 1500 3000 0 1500 3000 0 1500 3000 0 1500 3000 O 1500 3000 O 1500 3000 0 1500 3000 0 1500 3000 I. I'I'QII Oxidized flavor of cream when_pasteurized at :1850F. - 5" and stored in If N IO'OI :glass paper tin :1650F. - 15" and O O O 0 glass peper tin stored in I'PO‘fI'I O O stored in {glass paper tin Table 18. tainers when stored 6 months. The flavor of cepper treated cream samples in various con- 56 :Hbmoge- Oxidized flavor of creem when pasteurized at :nization:l50°F. - so" and :155“?. - 15" and :lBSUF. - 5" and :pressure: stored in : stored in : stored in Month ;_les,) {glass paper tin {glass paper tin {glass paper tin O 999 999 999 999 99 99 +9 99 99 1500 +9 99 +9 99 9 99 99 9+ 99 Mgrch 3000 999 99 999 99 99 99 9 99 9 O 99 9+ 99 99 99 99 9 9 9 1500 99 +99 99 99 99 99 9+ 99 99 April 3000 99 99 9+ 99 99 9 9+ 99 99 O 9 9 9 9+ 9+ 99 99 9 99 1500 9 9 9 99 99 99 99 99 9 May 3000 99 9- 9+ 99 99 99 +9 9 9 O 999 99 99+ 99 99 99 99 99 99 1500 99 999 999 99 99 99 99 99 99 June 3000 99 99 99 9+ 99 99 99 9 99 0 999 999 999 +9 99 +9 99 9+ 99 1500 +9 99 999 99 99 99 99 99 99 {ply 3000 99 99 99+ 99 99 99 99 +9 99 (No tin or 0 lost 999 99 paper) 1500 999 999 9 August 3000 99+ 99 9 0 999 999 +99 99 +9 99 9 99 99- 1500 99+ 999 999 99 99 99 99 9 9 September 3000 99+ 999 999 99 +9 99 99 9+ 99 O 999 999 999 99 99 99 99 99 99 1500 999 999 999 +9 99 99 99 +9 99 October 3000 +99 999 999 9+ 9+ 9+ 99 99 99 O 99 99 99 99 99 +9 99 9+ 99 1500 99 99 +9 99 +9 99 9 9 9 November 3000 999 99 99 99 99 99 9 9 9 O 99 999 999 9+ 9+ 99 9 9 9 1500 99 9+ 9+ 99 99 99 9 9 9 December 3000 99 9+ 99 99 99 99 9 9 9 O 999 999 999 999 999 999 99 +9 99 1500 999 +99 999 9+ 99 99 99 99 99 January 3000 999 999 999 9 99 99 9 9 9 O 999 999 999 99 99 99 9+ 99 99 1500 "999 999 999 99 99 99 99 99 99 Februarxp 3000 999 999 999 9+ 99 99 9+ 99 99 57 Table 19. The flavor of sugared cream samples in various containers when stored 6 months. :Homoge- : Oxidized flavor of cream when pasteurized at :nization:l§O°F. - so" and :165UF. - 15" and :IBSUF. - 5" and :pressure: stored in : stored in : stored in Month : (lbs.) : lass paper tin :glassppaper tin :glass paper tin March April May June July (No tin or Paper) August Sgptember October November December January, February 0 1500 3000 0 1500 3000 0 1500 3000 O 1500 3000 O 1500 3000 O 1500 3000 O 1500 3000 0 1500 3000 O 1500 3000 0 1500 3000 O 1500 3000 0 1500 3000 ff ! 9 9 9 ' 006's)! I O 9 9 9 | I 58 Table 20. The flavor of sugared and c0pper treated cream samples in various containers when stored 6 months. :Homoge- : Oxidized flavor of cream when_pasteurized at :nization:150°F. - 30” and :165OF. - 15" and :1850F. - 5" and :pressure: stored in : stored in : stored in Month : les.) :glass paper tin :glassppaper tin :glass paper tin O 99 99 999 99 9 99 99 99 9 1500 999 99 99 9 99 999 - 99 99 March 3000 99 9 99 99 99 99 99 99 99 O 99 99 99 9 9 99 99 9 9 1500 99 99 99 9 9 9 9 - 99 April 3000 9 99 99 9 99 9 9 9 9 0 9 9 9 99 9 9 9 __ 9 99 1500 9 9 9 9 9 99 99 99 9 M31; 3000 9 9 9 99 9 99 9 9 9 O 999 999 999 9 9 9 99 9 99 1500 99 99 99 9 9 9 9 9 9 June 3000 99 9 9 9 9 99 9 9 9 O 999 999 999 9 99 99 9 9 9 1500 99 99 999 9 99- 99 9 9 9 {ply 3000 99 99 99 9 99 99 9 99 9 (No tin or 0 999 99 9 paper) 1500 999 99 9 August 3000 999 99' 9 O 999 999 999 99 99 9 9 9 9 1500 99 999 99 99 99 9 9 9 9 September 8000 99 99 99 99 99 9 9 9 9— O 999 99 999 99 9 99 9 9 9 1500 999 99 999 99 9 99 99 9 99 October 3000 999 99 99 99 9 99 9 9 99_ O 99 99 99 99 9 9 9 9 9 1500 99 99 99 99 9 9 9 9 9 November 3000 99 99 99 9 9 99 9 49 9 0 99 99 99 99 99 99 9 9 9 1500 9‘ 9 99 9 9 9 9 ? ? December 3000 - 99 9 9 9 ? 9 9 9 0 99 99 99 99 99 99 9 9 9 1500 99 99 99 9 lost lost 9 9 9 Jaguarx_ 3000 99 99 99 9 9 9 9 9‘ 9 0 99- 99 99 9 9 9 9 9 9 1500 99 99 99 9 9 9 9 9 9 February 3000 99- 99 99 9 9 9 9 9 9 59 Table 21. The flavor of control cream samples in various containers when stored 12 months. :Homoge- : Oxidized flavor of cream whenppasteurized at :nization:lSO°F. - so" and :leboF. - 15" and :1850F. - 5" and :pressure: stored in : stored in : stored in Month : (lbs.)_;glass paper tin iglass paper tin :glass paper tin O ? - - ? - - - - - 1500 - - - - - - - - - March 3000 - - - - - - - - - 0 - 99 9 - - - - — - 1500 - 9 - - ? - - - - april 3090 - 9 - - — - - - - O - - - - - - - - - 1500 - - - - - - - - - May 3000 - - - - - - - - - 0 99 99 999 ? 9 9 - - - 1500 9 99 99 - 9 9 - - - lune 3000 9 99 99 - ? - - ? - 0 999 99 99 - - - - - - 1500 9 99 99 - - - - - - July 3000 9 9 99 o. - - - - - (No tin or O - — - paper) 1500 - - - August 3000 - - - o - - - - - - - - - 1500 - - - - - - - - - §gptember 3000 - - - - - - - - ‘- 0 99 99 99 - - — - - - 1500 - - - - — - - - - October 3000 - - - - - - - - - O ? 99 99 - - - - - - 1500 - - - — - - - - - November 3000 - - - - - - - - - O 9 9 9 - - - - - - 1500 ? 9 - - - - - - - December 3000 - - - - - - - - - O 9 99 9 - ? - - - - 1500 9 9 9 - - - - - - January 3000 - ? 9 - - - - - - O 9 9 9 - - - - - - 1500 - - - - - - - - - February 3000 - ? - - ? - - - - 60 Table 22. The flavor of couper treated cream samples in various containers when stored 12 months. :Homoge- : Oxidized flavor of cream when;p§§teurized at :nizationzisociu - so" and :1650F. - 15" and :1850F. - 5" and :pressure: stored in : stored in : stored in Month : (lbs.) :gless_p§per tin :glass paper tin ;g_ass_p§per tin O 999 99 999 99 99 99 99 99 99 1500 99 99 99 lost 9 9 9 9 9 March 3000 99 99 99 9 9 9 9 ? 9 O 999 999 999 999 999 999 999 99 99 1500 999 999 999 99 99 999 99 99 99 April 3000 999 999 999 999 99 99 99 99 99 0 999 999 999 999 999 999 99 99 99 1500 999 999 999_ 999 99 99 9 9 99 Mey_ 3000 999 999 99' 99 99 99 9 9 99 O 999 999 999 99 999 999 99 99 99 1500 999 999 999 9 999 999 9 99 99 June 3000 .999 999 999 9 9 9 9 '9 9;_ O 999 999 999 999 999 999 999 999 999 1500 999 999 999 999 999 999 999 999 99 July 3000 999 999 999 999 999 999 999 999 99, (No tin or 0 999 999 999 paper) 1500 999 999 999 August 3000 999 999 999 0 999 999 999 99 99 99 99 9 99 1500 999 99 99 99 99 99 99 9 9 §§ptember 3000 999 99 99_r 99 99 99 #99 9. 9 0 999 999 999 999 999 999 99 99 99 1500 999 999~ 999 999 999 999 99 99 99 Octoberpr 3000 999 999 999 999 999 999 99. 99_ 99_.l_ O 999 999 999 99 9 9 9 9 9 1500 99 99 99 9 9 9 9 9 9 November 3000 99 99 99 99 9 9 .9 9 9 O 999 999 999 99 99 99 99 99 99 1500 999 999 999 99 99 99 99 99 99 December 3000 999 999 999‘ 9 99 99 99 99 99 O 999 999 999 999 999 999 9 99 99 1500 999 999 999 99 999 99 9 9 9 Januaryp 3000 999 999 999 99 999 99 9 9 9 O 999 999 999. 999 999 99 999 lost 99 1500 999 999 99 99 99 99 99 99 9 Feb may 3000 99+ *9? CW ’99 99* *0 if 0" 1' Table 23. The flavor of sugared cream samples in various containers when stored 12 months. 61 Mghth June July be tin or paper) August September October November December January February :Homoge- : :nization:150°F. - 30” and :pressure: : jlbs.) :glass paper tin 0 1500 3000 0 1500 3000 0 1500 3000 O 1500 3000 0 1500 3000 0 1500 3000 O 1500 3000 0 1500 3000 O 1500 3000 0 1500 3000 O 1500 3000 0 1500 3000 Oxidized flavor of cream when_pasteurized at up OI~OWI°¢°0nfifil|°OOI*IIIIII'~3|*L¢QIIIISIIII stored in ll'fi'Dl 0‘? 0‘) O’l‘Ofi. 90 p 9 9 9 9 9 9. IN”! :1650F. - 15” and :glass paper tin stored in :1850F. - 5" and C O stored in :glass paper tin lost Table 24. 62 The flavor of sugared and COpper treated cream samples in various containers when stored 12 months. :Hbmoge- : :nization:l50°F. - SO" and Oxidized flavor of cream when_pasteurized at :1650 F. - 15" andleSOF. - 5" and :pressure: stored in 2 stored in : stored in Mppth : jlbs.) :glass paper tin : lass paper tin :glass_paper tin O 99 99 99 9 9 9 99 9 9 1500 99 9 9 9 9 9 9 9 9 March 3000 9. ? A9 ? ? ? ? ? ? 0 999 99 999 99 99 99 99 9 9 1500 .99 99 99 9 9 9 9 9 - April 3000 99 99 99 99 9 l9 9 9 9 0 99 999 999 99 9 99 99 ? 9 1500 99 99 99 9 9 9 9 - - Mex, 3000 999 ‘99 99 9 9 9 - - - O 999 999 99 99 99 99 9 9 9 1500 99 99 99 9 9 9 9 9 9 June 3000 9 9 9 9 9 9 9r 9 9 O 999 999 999 999 99 999 99 99 99 1500 999 999 999 999 99 99 99 99 9 July 3000 999 99 999 999 99 999 99 .l99 9. (No tin or O 999 999 99 paper) 1500 999 99 99 August 3000 999 lost 99 0 999 99 99 9 9 9 9 9 9 1500 99 99 99 9 9 9 9 9 9 geptember 3000 99 9 9 9 9 9 9 9 9 0 999 999 999 99 99 99 9 9 9 ' 1500 9 9 9 99 99 99 99 99 99 _ptober 3000 9 99 99 99 99 99 9 9 9 O 99 99 99 9 9 9 9x 9 9 1500 9 9 9 9 9 9 9 9 9 November 3000 99 99 99 99 9 9 9 9 9 O 999 999 999 99 99 99 99 99 99 1500 999 999 99 99 99 99 99 99 99 December 3000 999 999 99 ' 99 99 99 99 99 99 0 999 999 999 99 99 99 - 99 99 1500 99 99 99 99 99 99 9 9 9' January 5000 99 99 99 99 99 99 9 9 9 O 999 99 99 99 99 99 99 99 9 1500 99 99 99 9 9 9 9 9 9 February 5000 99 99 99 99 lost 9 9 9 9~ . x - . i . r 9 1 . ‘ 9 9 , , . g . 1 . v 9 7 , . . , . . a 9 - u . . Table 25. A comparison of the carotene content and the intensity of oxidized flavor in the nonhomogenized samples over a 12 month period when pasteurized by three different exposures and stored for 6 months. 63 :The oxidized flavor and carotene content of creamgpasteurized at :15003} - 30" treated:165°F. - 15” treated:185° F. - 5" treated : with : with : with4__ : 00pper : COpper : c0pper :con- cop- sug- and :con- c0p- sug- and :con— cop- sug- and Month :trol per ar sugar :trol per er sugar :trol per ar sugar 9* 999 - 99 e 999 - 99 - 99 - 99 Mar. 3.2**3.2 3.5 .31 3.5 3.5 3.3 3.21 2.9 3.5 3.. 3.16 9 99 ? 999 - 99 r 9 ' 99 - 99 52;. 2.6 2.8 3.0 2.92 3.0 3.0 3.0 2.99 3.0 2.9 3.0 2.91 - . - . ? 99 - 99 - 99 ? 9 Max. 8.8 8.4 9.1 8.11 9.2 7.7 8.9 8.78 8.8 7.8 9.3 8.08 - :999 - 999 - 99 - 9 - 99 - 99 1229 11.8 11.6 11.3 10.71 12.3 11.7 11.5 10.94 11.5 11.2 11.4 11.09 99 999 - 999 - 99 - 9 - 99 - 9 IB}Y 11.9 10.9 9.3 10.02 11.4‘ 9.2 11.0 9.95 11.2 10.3 10.7 9.81, - 999 - 999 - 999 - 99 - 99 r 9 August 9.8 9.6 11.0 11.3 10.9 9.5 10.1 10.50 10.1 10.1 9.7 9.82 - 999 - 999 - 99 - 99 - 9 - 9 Sept. 11.3 11.0 11.3 10.86‘ 11.1 10.7 11.4 10.84 11.2 11.3 11.0 10.71 9 999 ? 999 - 99 - 99 - 99 r 9 Oct. 12.0 11.4;1;.9 11.24 12.6 11.8:12.5 11.83 11.8 11.9 12.0 12.13L_. 7 99 - 99 - 99 - 99 - 99 - 9 Nov. 8.2 9.1 8.5 9.33 9.1 9.1 8.8 8.92 9.9 8.9 9.1 8.80 - 99 - 99 - 99 - 99 - 9 - 9 Dec. 5.9 5.4 5.7 5.57 5.9 5.41 5.7 5.62 5.8 5.7 5.5 5.66__ ? 999 - 99 - 999 - 99 - 99 ' 9 Jan. 4.1 4.0 3.6 3.55 3.9 4.1 3.9 4.08 4.1 3.9 3.7 4.08 7 999 - 99 - 99 - 9 ‘ 99 ' 9 Feb. 3.4 3.1 3.3 3.30 3.1 3.1 3.3 3.30 3.4 3.4 3.3 3.30 *Intensity of Oxidized flavor **Carotene content, gamma per gm. of fat 64 Table 26. The influence of the initial titratable acidity on the deve10p— ment of the oxidized flavor after 12 months' storage in the nonhomogenized glass container samples when pasteurized at three different exposures. : Pasteurized at : 1500!. - 30” treated: 165°F. - 15" treated: 185°F. - 5” treated : with : with : with : cOpper : capper : COpper :con- cop- sug- and :con- cOp- sug- and :con- c0p- sug- and Month :trol per ar sugar :trol_per ar sugar :trol per ar sugar 9* 999 - 99 - 99 - 9 - 99 - 99 Mar. .13** .12 .11 .11 .13 .13 .11 .11 .13 .13 .11 .105 9 999 - 999 - 999 - 99 - 999 - 99 April .12 .12 .10 .10 .12 .11 .10 .10 .12 .12 .10 .105 ? 999 ? 99 - 999 - 99 - 99 - 99 Max_ .13 .13 .12 .12 .13 .13 .12 .115 .12 .13 .11 .11 99 999 9 999 ? 99 - 99 - 99 - 9 June .17 .17 .16 .165 .15 .18 .155 .17 .16 .16 .15 .155 999 999 9 999 - 999 - 999 9 999 - 99 July .18 .18 .18 .17 .18 .18 .17 .17 .18 .18 .18 .17 ? 999 - 999 - 999 - 999 - 999 - 99 August .11 .10 .10 .10 .11 .ll .09 .09 .11 .ll .10 .09 - 999 - 999 - 99 - 9 - 99 - 9 Sept. .12 .11 .10 .10 .11 .11 .10 .10 .12 .11 .10 .10 99 999 9 999 - 999 - 99 - 99 - 9 Oct. .13 .13 .13 .12 .13 .13 .12 .13 .13 .13 .12 .12 - 999 ? 99 - 99 - 9 - 9 - 9 Nov. .12 .12 .11 .10 .12 .11 .11 .11 .12 .12 .ll .11 - 999 9 999 - 99 - 99 - 99 - 99 Dec. .13 .13 .12 .12 .13 .13 .13 .13 .13 .13 .12 .13 9 999 ? 999 1 - 999 - 99 - 9 - - Jan. .12 .12 .12 .11 .12 .12 .11 .11 .12 .12 .11 .11 9 999 ? 999 - 999 - 99 - 999 ~ 99 Feb. .11 .11 .10 .10 .11 .11 .10 .10 .11 .11 .10 .105 *Intensity of oxidized flavor **Per cent titratable acidity Table 65 27. The influence of various methods of treatment and length of storage period on the hydrogen-ion concentration of the glass container samples when nonhomogenized and pasteurized at 165° F. for 15 minutes. Month The pH of cream when : Fresh and : Fresh and . Fresh and : treated with : treated with : treated with : 00pper: COpper: c0pper :con- cepe sug~ and :con- cope sug- and :con- cep- sug- and :trol per ar sugfr :trol per ar sugar :trol per ar sugar Mar. 6.50 6.51 6.51 6.40 6.60 6.95 6.73 6.95 6.05 6.05 5.65 5.60 Apr. 6.70 6.74 6.70 6.70 6.60 6.60 6.50 6.40 6.60 6.45 6.20 6.20 May 6.57 6.62 6.52 6.50 6.80 6.60 6.60 6.60 6.75 6.60 6.66 6.60 June 6.27 6.34 6.24 6.25 6.40 6.40 6.25‘ 6.20 6.10 6.10 6.10 6.10 July 6.10 6.10 6.10 6.00 6.00 6.00 6.00 5.90 5.95 5.75 6.00 5.95 August 6.65 6.85 6.65 6.80 6.30 6.42 6.30 6.05 6.50 6.60 6.§8w“§,§gfl___ Sept. 6.66 6.66 6.60 6.60 6.15 6,l§h§.15 6.15 6.66 6.65 6.66 6.50 Oct. 6.55 6.43 6.25 6.25 6.40 6.30 6.25 6.20 6.18 6.16 6.16 6.10 Nov. 6.66 6.60 6.45 6.43 6.75 6.75 6.66 6.66 6.35 6.35 6.50 6.50 Dec. 6.55 6.50 6.35 6.43 6.20 6.35 6.15 6.25 6.35 6.16 6.25 6.16 Jan. 6.50 6.50 6.45 6.40 6.55 6.50 6.40 6.50 6.43 6.43 6.35 6.16 Feb. 6.25 6.25 6.25 6.35 6.40 6.50 6.40 6.60 6.25 6.25 6.55 6.55 66 Table 28. The influence of various pasteurization exposures and length of storage period on the hydrogen-ion concentration of the glass container samples when nonhomogenized. : The_pH of cream when : Fresh after t Stored 6 mos. after : Stored 12 mos. after : pasteurization at tgpasteurization at :4pasteurization at : 150°F. 165°F. 185°F.: 150°F. 16505. 18503.: ISOOF. 16561. lBSOF. Month 307 15" 5" : 307 15" 5" : 30" 157 5" Mar. lost 6.50 6.50 6.73 6.50 6.50 6.05 6.05 5.75 Apr. 6.70 6.70 6.70 6.55 6.60 6.60 6.45 6.60 6.50 May 6.60 6.57 6.62 6.70 6.60 6.70 6.50 6.75 6.66 June 6.35 6.27 6.32 6.30 6.40 6.20 ‘6.00 6.10 6.10 July 6.15 6.10 6.15 5.70 6.00 @105 5.65 5.95 5.90 August 6.65 6.65 6.65 6.30 6.30 6.15 6.26 6.50 6.40 Sept. 6.66 6.66 6.60 6.15 6.15 6.16 6.60 6.66 6.60 Oct. 6.45 6.55 6.20 6.35 6.40 6.20 6.25 6.16 6.10 Nov. 6.60 6.66 6.60 6.75 6.75 6.75 6.60 6.35 6.43 Dec. 6.43 6.55 6.55 6.20 6.20 6.25 6.25 6.35 6.43 Jan. 6.40 6.50 6.45 6.50 6.55 6.50 6.16 6.43 6.50 Feb. 6.25 6.25 6.25 6.20 6.40 6.60 6.25 6.25 6.25 67 Table 29. The influence of method of treatment, pasteurization exposure and season of year upon the oxidation-reduction potential of nonhomogenized fresh cream. Treatment : The Eh (volts) of fresh cream in of samples:Mar. Apr. May June July_6ug. Sept. Oct. mov. Dec. Jan. heb. Pasteurized at 1500 F. 30 min. Control .29 .29 .24 .3~ .23 .29 .33 .33 .41 .38 .34 .37 Sugar .31 .30 .2 .31 .30 .29 .35 .40 .42 .42 .39 .44 Copper .29 .29 .23 .28 .26 .27 .34 .34 .41 .40 .36 .38 COpper and Suggr .31 .32 .27 .29 .30 .29 .35 .35 .44 .42 .42 .43 Pasteruized at 165° F. 15 min. Control .16 .24 .16 .22 .23 .2 .29 .34 .44 .39 .31 .38 COpper .29 .38 .22 .26 .31 .31 .33 .40 .45 .42 .36 .44 Sugar .17 .25 .15 .20 .27 .28 .24 .33 .43 .38 .32 .37 Copper ‘ and Sugar» .24 .34 .22 .26 .31 .31 .34 .38 .44 .42 .37 .42 Pasteurized at 185° F. 5 min. Control .16 .24 .13 .19 .30 .27 .27 .32 .42 .35 .32 .36 COpper .28 .34 .23 .26 .36 .29 .34 .43 .44 .42 .40 .43 Sugar .20 .27 .15 .16 .26 .26 .28 .35 ..43 .36 .35 .40 Cepper and sugar .29 .36 .23 .27 .31 032 .34 038 .41 0‘41 .38 .45 Raw Control .16 .35 .22 .27 .10 lost .27 lost lost .40 .33 .38 68 Table 30. Oxidation-reduction potential (Eh) of homogenized cream samples when stored in glass for 12 months. (Average data from the 12 monthly samples). ' The Eh of stored cream when Treatment Pasteurized at : Pasteurized at : Pasteurized at of 150° F. for 30 min. : 165° F. for 30 min. : 185° F. for 30 min. sample copper: copper: c0pper con- cOp- sug- and :con- 00p- sug- and :con- cOp- sug- and trol per ar sugar :troljer ar sugar :trolper ar sugar 0. O. .0 O. O. C. Eh (volts) .33 .35 .32 .35 .29 .35 .28 .34 .28 .35 .29 .35 ——- COPPER- mam 9 /0 9’0 SUGAR -—-COPP£R-/PPM. «---mfl79b SLML4R q-I-IICCNVTVWDL OXID/ZED FL A VCR IN TENS! T Y MAMJJASO/VDJF MONTH big. 1. The influence of various treatments on the development of.the oxidized flavor during 6-months storage when nonhomogenized cream was pasteurized at 165° F. for 15 minutes. (fiverege of data from glass, paper and tin containers). 69 ‘L V~ ‘L fi~ fl~ '-—- CWDINDEY?-\‘Q§U T ‘ ‘\\ \l _1 58°F °F I85 °F MIN 6MIN. 5 MIN. PAS TE URIZ A TION EXPOSURE Fig. 10. The influence of cepper trettment on the oxidation-redaction potential of fresh nonhomoge- nized crerm when p“q?fiur12ed at different exposures. (Average dvtr from 15 monthly samples). 79 PART I. B. The Influence gf_Severg; Eactors upon Stabilitzlgf,Fat Emulsion. Nine-gram lots of each of the samples of cream stored during the months of December, January and February were weighed out into regulation 9-grem, 50 per cent cream.test bottles and tested for stability of fat emulsion according to the method outlined in the ”Emperimental”. The tests on each sample were made when fresh, and after having been frozen in a -10° F. hardening room and held 1, 90, 130 and 360 days. The data se- cured sre presented in tables 31 and 32. 1. Influence of homogenization on the free fat separation of cream, The ability of the homogenizer to stabilize the fat emulsion in a nonfrozen product is well recognized. In view of this fact, the effects of homogenization on the stability of the fat emulsion in both frozen and nonfrozen cream were especially interesting. The data show that homogenization had a very definite stabilizing effect upon the fat emulsion of the fresh, nonfrozen cream. In fact, the oiling-off in the nonfrozen product was practically eliminated in fresh cream upon the use of either 1500 or 3000 pounds pressure, but without homogenization a 50 per cent cream.yielded about 20 per cent free fat by the.method of testing employed. On the other hand, the data show that freezing almost entirely destroyed the effects of homogenization on the fat emulsion stability. Analysis of these data reveals that nothing is gained by homogenization insofar as fat emulsion stability is concerned if the cream is to be frozen. 2. Effect of gugar on free fat separation of:gefrosted frozen cream. Sugar has been used with varying degrees of success by previous workers as an aid in stabilizing the fat emulsion of the defrosted cream, and as this 80 experiment included samples containing ten per cent sugar, analyses were made on these samples at the same intervals of storage as those just pre- viously mentioned. Data in table 51 show that the addition of sugar to nonhomogenized nonfrozen cream caused only a slight decrease in the per cent oiling-off. This decrease was no greater than the amount of fat diSplaced by the addi- tion of the sugar. Sugar partially stabilized the fat emulsion against the effects of freezing when held frozen only 24 hours. The combination of homogenization and sugar seemed to be more beneficial than either pro- cess when used singly in preventing oiling-off, regardless of length of storage. As the length of frozen storage extended, the influence of sugar in stabilizing the fat emulsion was lessened. At the 3 and 12 month stor- age periods, sugar had no appreciable effect on the stability of the fat emulsion according to the method used in this experiment. 3. Effect of fat content on stability of fat emulsion of defrosted frozen cream. A.study was made of the relationship between the fat content of the cream and its susceptibility to oiling-off upon freezing and defrost- ing. The data secured are presented in table 32. The amount of fat destabilized was found to increase as the per cent fat in the cream increased. The data showed also that as the fat content was increased, the percentage of the total fat which was destabilized was greater. 4. Influence of length of storage period of cream on stability of the fat emulsion of defrosted frozen cream. Fresh cream not frozen was found to be more stable than that which had been frozen. However, according to the rigorous method of testing employed there was considerable oiling-off even in the fresh, nonfrozen cream. 81 The cream.frozen only 24 hours showed less fat destabilization than did that which had been frozen for either 3, 6 or 12 months (Tables 31 and 32). In this reSpect there was no appreciable difference in the samples stored frozen either at 3, 6 or 12 months, the three-months period seeming to be more than sufficient to complete destructive effects to the fat emulsion by the freezing process. 5. Effect of pasteurization exposure on free fat separation of_ggfrostgg zzgzen cgggg. Data showing the effect of the pasteurization exposure upon the destabilization of the fat emulsion in the nonhomogenized cream after six months are presented in table 32. Apparently, no significant differ- ences occur in oiling-off of fat as a result of the particular pasteuriza- tion exposures with the possible exception that the 165° F.-15 minute ex- posure seemed to be slightly less severe than the other two exposures. Data on a larger number of samples held various periods of time, and presented in table 31, show largely the same trend. ‘Undoubtedly, the more stable emulsion of the 165° F. pasteurization temperature may be ac- counted for by the lessened agitation than that of the 150°F. and the less heat than at the 185° F. exposure. On the other hand a slight increase in oiling-off as the tempera- ture of pasteurization was increased was noted in the nonfrozen group. 6. Effect of speed of freezinggon stab;;itygof fat emulsion of defrosted frozen cream. Samples of cream containing over 50 per cent fat were weighed out into regulation 9-grem test bottles and were frozen by various methods in order to ascertain the effect of the speed of freezing upon the destabilization of the fat emulsion. The data are presented in table 33 and shown graphically in figure 11. Despite the fact that fast freezing partially prevented destabilization of the fat, there was not the differ- 82 once in per cent oiling-off between fast and slow freezing as might be expected in view of the great difference in freezing time of the samples. However, there appeared to be a significant difference in the stability of the fat emulsion between each of the four respective rates of freezing. 83 Table 31. The influence of sugar, homogenization, pasteurization, freez- ing process and length of storage period on stability of fat emulsion. Figures represent fat column readings. (Average data of three trials; cream averaging 50% fat). The per cent free fat in cream when homogenized at {lbs.[ Pasteur-3 0 and treated with :1500 and treated with:3000 and treated with izntion 3 capper: capper: capper exposurozcon- cep- sug- and :con- cop- sug- and :con- cop— sug- and itro e a a :trol er er sugar :trol: per ar gggar 150° 30. 165° 15” 185° 5” Av. 1500 30a 155° 15'! 185° 50 Av. 150° 30:! 155° 15' 185° 51' Av. 150° 165° 15" 135° 5' Av. F. 18.2 F. 20.0 F. 24.0 20.7 F. 43.0 F. 33.0 F. 37.0 38.0 F. 46.0 F. 42.0 F. 46.0 45.0 41.0 F. 39.0 F. 43.0 41.0 18.0 17.0 29.0 21.3 31.5 33.0 35.0 38.0 46.0 40.0 46.0 44.0 42.0 37.0 41.0 40.0 18.0 17.0 18.0 18.0 41.0 38.0 42.0 40.0 39.0 37.0 41.0 39.0 16.8 18.8 18.0 18.0 29.5 25.0 33.0 29.0 41.0 37.0 41.0 40.0 40.0 35.0 41.0 39.0 Unfrozen 5.0 1.0 2.5 1.2 1.2 1.8 2.3 1.0 2.0 2.8 1.1 2.1 2.5 2.2 1.0 2.2 Frozen 24 hours 35.8 25.0 15.8 15.8 33.0 22.0 7.0 14.0 33.0 27.0 13.5 14.5 33.6 25.0 12.1 14.4 Frozen 3 months 43.0 45.0 37.0 41.0 42.0 35.0 39.0 39.0 33.0 41.0 42.0 35.0 38.0 33.0 31.0 34.0 Frozen.12 months 42.0 42.0 38.0 39.0 39.0 33.0 39.0 41.0 36.0 40.0 41.0 36.0 35.0 36.0 37.0 36.0 2.0 1.0 2.2 1.7 33.0 35.0 32.0 33.3 42.0 41.0 37.0 40.0 41.0 39.0 35.0 38.0 0.5 0.5 2.0 1.0 15.5 17.0 14.5 16.0 41.0 38.0 38.0 39.0 37.0 39.0 37.0 38.0 2.5 1.3 2.8 2.2 13.8 10.0 9.0 10.9 35.0 34.0 36.0 35.0 36.0 36.0 37.0 36.0 2.0 1.0 0.7 1.2 14.5 13.0 11.5 13.3 34.0 30.0 34.0 33.0 32.0 37.0 33.0 34.0 84 Table 32. The' influence of fat content on stability of fat emulsion in nonhomogenized cream stored for 6 months. Figures represent fat column readings. The per cent 01f_free fat in cream testing 1% butterfat) 0.. O. Pasteur- 45 and treated with : 50 and treated with : 54 and treated with izetion . capper: capper: capper exposure:con- cep- sug- and :con- cop- sug- and :con— cep- sug- and :tro a s a :t er ar sugar :trol per ar sugar 150° F. 30" 41 40.5 35 35 46 45 42 ' 40 50 49 48.5 48 165° F. 15" 32 33.5 28 25 44 38 39 38 50 50 46.0 47 185° F. 5" 40 41.0 38 37.5 47 45.541 41 49.550 49.0 47 Av. 38 38 34 33 46 43 41 40 50 50 48 47 85 Table 33. Influence of speed of freezing on the stability of the fat emulsion. Figures represent fat column readings. 3 zer cent fzee fat in cream at 3 months storage when frozen in 3 3Jiffy 3 3 3 3Jiffy Tria13 Dry’Ice3 3 3 Bag 3Dry Ice3 3 3Bag : and :Dry Ice3-10° F.3in -1oor.3 and 3Dry Ice 3-100 F.3in -10° F. mkfld: 3mm 3mm nuwm: 3mm 3mm 3 13:) 3115”) 3 (20') 3 (180") 3 13'1311581 3 (20") 3 1180”] 3 Series I - 5 cream. 3 Serieswgg - 53§_creem 47.5 50.0 52.0 51.0 44.0 49.0 51.0 52.0 47.0 50.0 50.5 51.0 43.0 49.0 52.0 52.0 46.0 49.0 51.0 51.0 44.0 48.0 51.0 52.0 46.0 48.0 50.0 51.0 45.0 50.0 50.0 53.0 47.5 50.0 49.5 51.5 44.0 50.0 51.0 53.0 47.5 49.5 50.. 51.0 43.0 49.0 5l.0 53.0 46.5 49.0 50.5 51.0 44.0 49.0 51.0 53.0 46.0 49.5 50.0 51.0 44.0 50.0 51.0 52.0 47.5 49.5 50.0 50.0 45.0 49.0 51.0 52.0 45.0 49.5 50.0 51.0 44.0 49.0 51.0 53.0 46.6 49.4 50.45 51.05 44.00 49.2 51.0 52.5 a: f.“ 3.. / 3 / :: Z“ %— : 6 20* I80 T/ME IN Ml/VU TE 5 Fig. 11. The effect of the Speed of freezing on stability of the fat emulsion. (Average 10 trials, 53—per cent, November cream). 86 87 PART II. UTILIZATION OF FROZEN CREAM IN THE ICE CREAM MIX 13: Impence 91 gag-tag Factors Ln the Whipping agility 9; Ezgn Cream use: and £22 Ears; 9.3. and W 1.0.6. 23.92. Duplicate lots of fresh. sweet cream were stored in forty-pound, lard-type tin containers 6, 3 and 1 month previous to the freezing trials. Ten per cent sucrose was added to one lot of the cream prior to freezing. Dried egg yolk was added to mixes made from both sugared and nonsugared frozen cream, the whipping ability of which was compared with that of like mix containing no added egg yolk. Fresh cream mixes were frozen as controls. Flavor determinations were made at regular intervals on representa- tive samples of all ice cream frozen. 1. nf uence of 8 er in frozen cream 11 on WM 1 abilit and flavo of frozen-cream ice creams Sugar was added to the cream prior to freezing to ascertain the effect of sugar on the pmperties of the mix made from that cream. Ten per cent sugar was added to the cream and the remainder added in the manufacture of the ice cream mix. Data secured on the freez- ing trials are included in table 34 and presented graphically in figures l2, l3 and 16. Sugar incorporation into the cream prior to freezing not only hastened freezing but also increased the maximum overrun obeainable . when compared to that of the cream stored without the previous sugar addi- tion. However, there was no significant flavor difference observed in the ice cream made from the sugared or nonsugared frozen cream mixes either when fresh or after lB-weeks storage. Similarly, no material body differ- ences in the ice cream from the two mixes were noted. 88 2. ;gglgence o_ftdgied egg yolk upon whippingability of frozen cream m_ix__g_s_. To another series of mixes similar to those Just previously dis- cussed but from another lot of cream, 0.35 per cent egg yolk was added both to the previously sugared and to the nonsugared frozen cream mixes to ascertain the effect of dried egg yolk addition to the whipping prop- erties of the mixes. The data secured are presented in table 35 and figures 14, 15 and 16. These data show a marked improvement both in the speed of obtain- ing and in the maximum overrun obtained as a result of the addition of egg yolk to frozen cream mixes. 0f especial interest was the fact that while the incorporation of 10 per cent sugar to the frozen cream consid- erably improved the whipping characteristics of that mix, (Table 34) , the same did not hold true of the mix wherein the egg yolk was added (Table 35). Figure 16 graphically shows that the addition of egg yolk to the ice cream mix resulted in uproved whipping ability to the mix when com- pared to both the plain and the sugared mixes. However, it will be noted also that the egg yolk addition did not restore the whipping preperties of the mix so that it compared favorably with the fresh cream mix (Figure 16). 3. The influence of egg y_o_lk upon flgvor of frozen-cream ice cream. A sufficient supply of the ice cream samples previously discussed under "Influence of dried egg yolk upon whipping ability of frozen cream mixes" was secured that individual samples might be examined at definite intervals for 18 weeks. The data are presented in tables 36 and 3'7. The data showed no material difference in the flavor of the fresh- cream ice cream. However, comparing the flavor data of the ice cream with- 89 out egg (Table 36) with those of egg ice cream (Table 3'?) the flavor of the egg samples was more desirable than that of the nonegg samples. While it must be remembered that these do not represent the same original batch of cream, at least one can conclude that the addition of egg does not prove a flavor deterrent in the case of frozen cream. 4. Influence of length of frozen cream: storage on whipping ability of mixes. The cream samples used in these mix freezing trials were 6-, 3- and l-month stored frozen and a fresh control. The data presented in tables 34 and 35 show no significant difference in the whipping ability of the mix due to the length of the storage period of the frozen cream, when the fat of the mix was supplied by frozen cream. Figure 13 points out graphically the comparative whipping ability of the frozen cream mixes from cream stored for the various periods of time. Obviously from these trials, the freezing process rather than the length of storage period of the cream is the factor responsible for the inferior whipping ability of a frozen cream mix. 5. Flavor of frozen-cream ice cream umn storagea In order that a flavor study might be made from these mixes, regular vanilla ice cream was made and sufficient samples were saved to flavor each week for 8 consecutive weeks as well as at 12 and 18 weeks storage. The samples were scored ”blind" by two experienced Judges, who were designated as A and B. Judge A indicated the intensity of any oxidized flavor present as in the Judging of the cream while Judge B gave a numerical score to the flavor of the ice cream. Body scores were given numerical ratings in both cases. The data included in table 56 show little difference between the flavor or body scores of the fresh-cream or frozen-cream ice cream either 90 when fresh or at the end of the lB-week holding period. Apparently, therefore, there could be no obJection to using frozen cream of good quality in ice cream from the standpoint of body and flavor criticism. Likewise, data presented in table 3'? from cream which had dried egg yolk added to all but the fresh sample, showed no significant differ- ence between the flavor of the fresh and the frozen-cream ice cream. However, as a rule, the egg samples were slightly more desirable in both body and flavor than the group of samples containing no egg (Table 36). This condition is not considered to be of significance, however, inasmuch as the initial cream was not the same, although it was very similar. Data in tables 36 and 37 show that the storage period of the cream up to six months did not affect the body or flavor of the resulting ice cream. 6. aacteria count of frozen-cream ice cream, The bacteria plate count of ice cream samples was made at lB-weeks storage. Analyses were made accord- ing to standard procedure. The data included in table 38 (show the bacteria plate count of the two groups of saples to be extranely low. Although the October (egg) series had a slightly higher plate count there seemed to be no material difference in any single sample of either group. These very low bacterial counts of the frozen-cream ice cream indi- cate that the use of frozen cream in mix might not raise the bacteria count of the resultant ice cream if the original cream were of good quality. Since low bacteria count in milk is often associated with oxidized flavor it is not improbable that such might be the case in ice cream. At any rate, it is considered worthy of mention that had the bacteria count been normal, some of the old, stale, flavors particularly in the September (nonegg) series might not have appeared. 91 Table 34. The influence of the addition of 10 per cent sugar to cream prior to freezing on the whipping preperties of the result- ing mixes. (Average data from 2 trials). The whipping preperties of high-testinggcream frozen in ‘March and 3 June and 3 August and Whipping stored 6 mos.3 stored 3 mos,3stored 1 mo. 3 ___ preperties without with :without with 3without With 3 September gpgar sugar:sugar spgar :sugar sugar :Apfresh Freezing time (min.) 12:22 11:50 13:26 10:17 13:17 10:18 8:14 Naximum.over- run obtainable 113 113 98 105 98 110 125 Table 35. The influence of the addition of 0.35 per cent egg yolk to the whipping preperties of plain and sugared cream mixes. (Aver- age data from.2 trials). The whippipg preperties of highptestipg cream frozen in April and 3 July and 3 September and3 Whipping stored 6 mos.- storeg_3pmos.3 stored 1 mo. 3 preperties without with 3without with 3without with 3 October spgpg___§pgar :sugar sugar :sugar sugar : fresh Freezing time (min.) 8:44 9:00 9:10 9:18 8:30 8:20 8:20 Maximum over- run obtain- able 120 120 119 120 118 120 125 92 Table 36. Body and flavor scores of ice cream.after various periods of storage. The bodLand flavor of ice cream after 1 week : 4 weekp : 8 weeks : 12 weeks : 18 weeks BodygFlavor: Body: FlavorLBody: Flavor: Bo d1: Flavor: Bofidy: Flavgg 1‘ Cream used 0. O. .0 Jud e A March (6 mos.) 1‘ ** J Without sugar 23.5 - 24 - 23 - 23 - 22.5 - Mb sugar 23.5 - 23.5 - 23.5 - 23 - 22.5 «- June (3 mos.) Without sugar 23.5 ? 23.5 e 22 23 22.5 t With sugar 23.5 ? 24 - 22 - 23 - 22.5 - August (1 mo.) Without sugar 23.0 - 23.5 o 22.5 - 23 - 22.5 - With gugar 23.5 - 23,5, - 22.5 f 23 - 22.5 - September Fresh 23.5 c 23.5 e 22 1 23 gig, 22.5 Judge B March (6 mos.) a Without sugar 23.5 44.5 22.5 43 23.5 44 23.5 43 22.5 42 With sugar 23 <_44.5 22.5_fi2§.5 23.54_é3 22.5 #43 23 43 June (3 mos.) Without sugar 23 43.5 22.5 44 23.5 44.5 22 43 21.5 43 may” 23 43.5 22.5 455.5 23.5 44.5 22.5 43 21.5 43 August (1 mo.) Without sugar 23 44 22.5 43 23.5 42 22.5 43 22.5 43 With 2288? 22.5 44 22.5 44 23.5 44.5 22.5 43 21.5 42 September Egan 23 44 22.5 43.5 23.5 22.5 22.5 4;. 21.5 42 *Based upon former ice cream score card - body 25 points; flavor 50 points. ”Intensity of oxidized flavor. 93 Table 37. Body and flavor scores of ice cream after various periods of storage. ThgbodLmd flavor of _ice cream after 1 week : 4 weeks : 8 weeks : 12 weeks : 18 weeks Cream used body: F1avor:BodL: Flavor:Body: Flavor:Bodz: FlavOp:Bodp:Flavo; Judge A April (6 mos.) ; 3* Without sugar 24 - 23 - 23 - 23 - 23 - With sugar 24 - 23 - 23 - 23 - 23 - July (3 mos.) Without sugar 24 - 23 - 23 - 23 - 23 - With s_pgar 23 ? 23 - 23 - 23 - 23 - Sept. (1 m0.) Without sugar 23 e 23 - 23 e 23 - 23 - Eith age; 23.5 - 23.5 - 23 - 23 - 23 - October Zpesh 23 - 2g - 23 e 23 - 23 - ledse .13 April (6 mos.) 3? Without sugar 23 45 22.5 43.5 22.5 44 22.5 44 23 , 43.5 With spgar 23 45 22.5 43.5 22.5 44 22.5 543: 23 43.5 July (3 mos.) Without sugar 23 45 22.5 43.5 23 44 23 43.5 23 43.5 flith agar 22.5 it; 22.5 43 5 22.5 23 44 22.5 . Sept. (1 “00) Without sugar 23 45 22.5 43.5 23 44 22.5 44 23 43.5 flith agar 23 4_4L 22.5 43.5 23 44 22.5 4; 23 4_3,,§___ October Ezesh 23 45 22,5 43.5 22 54,4, 22.5 A132 22 43.5 *Based upon former ice cream score card - body 25 points; flavor 50 points. “Intensity of oxidized flavor. 94 Table 38. The bacterial quality of l8-weeks old ice cream made from fresh and from frozen cream held for various storage periods. :Standard plate count of ice cream made from fresh and frozen :cream after lggweeks storage when Ice :Stored 6 mos, :Stored 3 mgs. 3 Stored 1 mo, 3 cream. :Without:With :Without:With :Without:With : :gpgar :gpgar : _g§r :sugar :sugar :sugar Fresh Without egg 800 900 500 300 450 1,000 1,000 With egg 3,000 2,500 1,200 1,500 3,400 2,400 1,300 95 63 7/], Pl. A/N - SUGAR R IE 3 m 0) k N 3. MA R JUNE A U G. 6 M05. 3 M05. / M0. SOURCE OF SAMPLE Fig. 12. The effect of the addition of 10 per cent sugar to cream prior to freezing on the speed of the ice cream mix made therefrom. (Aver-«go data from 2 trials). TIME Ctr/NJ T0 55611125 9096 OVERRUN f Q [4‘ g FRESH ”/5 SUGAR - Pl. A m 7 R. S V m TIME IN MINUTES Ch T '1” f Ullllllllllllllllllllllllllllllllllllllllllll FRESH 6 M05. .3 M05. / M0. A GE 0F CREAM Fig. 13. A comparison of the speed of freezing of mixes mide from sugared and nansugared frozen cream and from fresh cream. (Average data from 2 trials). 96 I4 PLA/N E 566 VOLK - FRESH CREAM CCWV77?CM If: 00 E 03 k WWIIIIIIIIIIIIIHIIHIIIIIIIIIIIII TIME IN M/NU TE 5 (\3 / 2 EXPERIMENT Fig. 14. The influence of the addition of 0.35 per cent cried egg yolk to frozen cream mix on maximum overrun obtainable. (leverage data from 6 trials in frozen cream mixes). 97 R Q PL AW @506 your FRESH CREAM CONTROL C. Q R Q 5 OVERRUN 0%) B Q (O Q I 2 EXPERIMENT Fig. 15. The influence of the addition of 0.35 per cent dried egg yolk to frozen cream mix on the maximum overrun obtainable. (Av- erage data from 6 trials in frozen cream mixes). 98 99 .\\\.U~ ‘I.’ \ ' MIMI.) Iza- ’1 “"5 mm FLA/N E SUGAR ZZZ] EGG [24 - FRESH I20 3? \. I6 2 / c? Q; //2 '41 h. 0 me E /04L 2 mo mm : ICE CREAM MIX Fig. 16. A comparison of the maximum overrun ob~ tained in mixes made from various lots of cream. 100 DISCUSSION COpper contamination had long been recognized as the predominant cause of oxidized flavor development of fresh cream. There has been, how- ever, a great variety of preventive methods that would retard oxidized flavor development after the capper has already been absorbed by the cream. Copper in the strength of 1 part per million gave a very definite off-flavor at three months storage which aging only intensified. Of course, it'was recognized that it was very unlikely for any cream to be contami- nated to that extent with capper in normal plant Operations, but on the other hand if by some processing method, the oxidized flavor could be in- hibited in cream containing that amount of capp‘er, certainly the method would be of considerable value to creamerymen. The addition of sugar to cream prior to freezing had been advocated by numerous workers but the findings of this experiment were not fully in agreement with than. Particularily was this true concerning flavor. While it was shown that the flavor of the cream containing sugar and no cepper was equally as good as that of the control, no maJor benefit was derived by the addition of the sugar to the capper sample in an attempt to "mask“ the oxidized flavor which might have deveIOped. McFarland and Burgwald (1940) showed that homogenization at 2300 to 2500 pounds pressure prevented the development of oxidized flavor in cream containing 3 parts per million capper, after 26 weeks storage. The results presented herein were quite contradictory to that finding. In fact, these findings revealed that homogenization had only a very slight detri- mental effect on the develOpment of the oxidized flavor even in cream con- 101 taining 1 part per million copper, and by no means inhibited the oxidized flavor develOpment entirely. Of the three types of containers used, glass, paper and tin, each had its advantages. The glass container was probably the most desirable from the standpoint of flavor alone. The tin showed good flavor and han- dled easily while the paper container was the most easily removed from the frozen cream, but in some cases seemed to give a slight off-flavor to the control sammes. However, the glass was obviously not desirable from the standpoint of breakage as well as cost so it appeared that either the paper or the lacquered tin container would have in most cases, proven satisfactory. Nevertheless, it was conceivable that a glass-lined receptacle would prove ideal for cream storage. Gould and Sommer (1939) showed the effect of high temperature pas- teurization in sulfhydryl production and the consequent reduction in tend- ency toward oxidation of fats or fat-like substances. McFarland and Burg- wald (1940) showed that pasteurization at 172° F. for 5 minutes prevented development of oxidized flavor in frozen cream after 26 weeks storage even in the presence of 2.5 parts per million c0pper. These findings were in partial agreement with the previous experi- ment but neither 165° F. for 15 minutes nor 185° F. for 5 minutes showed such inhibitory action as that cited by McFarland and Burgwald (1940). In fact, these tanperatures showed much improvement over 150° F. for 30 min- utes yet neither inhibited the oxidation in cream which contained 1 part per million cepper even in the short three-month storage period. Unques- tionably, however, high temperature pasteurization was very essential for cream designed for frozen storage. 102 The season of year in which most cream would be stored was of course during the flush season, or in the early spring and summer months. However, if one wished to store cream at any other period of year, it would keep equally well, as it apparently made very little difference whether winter or summer cream was stored. Ordinarily it was considered that frozen cream would be used after only a few months of storage. The logical assumption was that cream would be stored in the early summer surplus period and used later when the pas- tures are drier and production was not so great. However, in view of the fact that all of the stored cream might not be used or perhaps with the idea that it might be put up regularily for much longer storage periods, the cream was held in this experiment up to one year and in another ex- periment for two years. Upon the completion of the one year storage period, it was concluded that cream could be held that length of time without an appreciable loss of quality providing the initial quality was good and the processing meth- ods optimum. Various workers such as Newlander and Ellenberger (1929) and Mack (1931) indicated that cream would keep well up to six months, but hesitated to recommend a storage period of a full year. Dahle (1941) agreed that cream could be stored as long as one year and perhaps 18 months. Carotene content of cream apparently had very little effect upon the flavor of frozen cream either with or without copper contamination. Carotene had been cited as an oxidative inhibitory agent in numerous in- stances but while that condition existed in milk, it obviously did not ap- ply to cream when subjected to the conditions of this experiment. The carotene content of cream varied quite materially with the season of the year yet in no case was there correlation between the amount 103 of carotene due to season of the year and the presence or absence of the oxidized flavor. The best cream.for frozen storage was that with a low initial acidity. However, in view of the findings of this experiment, it appeared that most workers have over-stressed the quality angle from the titratable acidity standpoint. Dahle and Josephson (1939) contended that exceptional quality was desired in cream which was to be frozen. While a low initial acidity was desired in all fresh cream to be frozen, it did not follow that cream of higher acidity, yet sweet, and free from off odors and flavb ors could not be successfully held as frozen cream. These findings showed that relatively high initial acidity might be particularily detrimental to flavor if pasteurized at low temperatures, but no necessarily so when high temperature pasteurization was used. In view of that fact, it appeared that while low acidity was desirable, one should not refrain from storing cream merely on the basis that the initial acidity was slightly higher than normal. The use of pH as an indicator of quality of high testing cream de- signed for frozen storage appeared to be of no special value. While an idea of the initial quality could be obtained, there were other tests which were much simpler and more inexpensive than a measurement of the hydrOgen-ion concentration by the potentiometer. The fact that after Gemonths storage, the hydrogen-ion concentra- tion of the cream increased or the pH decreased was in agreement with the findings of other workers. Dahle, Lawhorn and Barnhart (1940) showed that aging of cream caused a decrease in titratable acidity which was particu- larily interesting in view of the fact that they also found a slight de- crease in pH over the same aging period. 104 As Em.measurements showed quite readily the effect of copper addi- tions to fresh cream, it appeared that the Eh value might have been bene- ficial in predicting the keeping quality of fresh cream, when considering the fact that the production of sulfhydryls or antieoxidants of the cream produced an Opposite effect on the Eh value. However, there were certain limitations to the use of Eh, and work- ers hesitated to recommend it as a conclusive test for cream quality prior to or during frozen storage. The fact that Eh varied greatly with the season of the year as well as certain unexplainable actions in the rela- tionship of the oxidants to reductants was quite largely reaponsible for the failure of Eh to be used commercially as a method of predicting the keeping quality of cream. As homogenization stabilized the fat emulsion of nonfrozen dairy products, it was only natural to assume that it might have like effect upon frozen cream. However, such was not the case. In fact, Dahle and Josephson (1936) pointed out that homogenization was not beneficial in preventing oiling-off of cream.and even caused greater oiling-off than in the case of nonhomogenized cream. These findings agreed with the previous work in that homogenization did not prevent oiling-off of the defrosted frozen cream, however, homogenization did not appear to facilitate the free fat separation. Webb and.Hall (1935) noted that homogenization of low-fat cream reduced fat separation. However, they also showed that increasing milk solids-not-fat decreased the per cent fat separation so perhaps the lessened fat separation of the lowaat cream.might have been in part due to the larger portion of milk solids as well as the homogenization pro- cedure. 105 These findings agreed with other workers in that the addition of sugar reduced somewhat the amount of free fat separation. However, these results showed less benefits to be derived frmm sugar additions than did other workers, but in heating the mixes there was decidedly less oiling- off observed in the sugared than in the nonsugared frozen cream.mixes. Probably less difference in these experiments in oiling-off as a result of the addition of sugar than that noted by other workers was due to the extremely rigorous testing method used. Certainly the greater whipping ability of the sugared frozen cream.mixes was further proof that the sugaring of cream.prior to freezing markedly reduced the per cent of free fat separation. While it was not economical to store low fat cream.by freezing it would have been better from the standpoint of the stability of the fat emulsion of the defrosted cream. These findings are in agreement with Webb and Hall (1935) who showed less oiling-off in low than in high fat cream. This condition was considered to be due to greater solids-not-fat in the low testing cream as well as the greater fat content in the high testing cream, both of which had inverse relationships toward stability of the fat emulsion. The findings in these studies did not agree with Webb and Hall (1935) that the fat was destabilized at once by the freezing process. A comparison of the samples of this experiment showed that while there was no greater fat emulsion destabilization either at 6 or 12 months than at 3 months, still there was greater free fat separation at 3 months than at 24 hours. ‘While it was agreed that the fat emulsion destabilization was brought about shortly, it was considered that the destruction of the fat emulsion was not accomplished immediately by the freezing process, but 106 rather requires a few days although not nearly so long as the precipita- tion of proteins in a frozen milk product. The temperature of pasteurization of the cream was of no material concern in the freezing of cream insofar as the effect that it had on the stability of the fat enmlsion. However, there was slightly less free fat separation in this experiment due to the 165° F. for 15 minute heat treat- ment than to either 150° F. for 30 minutes or 185° F. for 5 minutes, due perhaps to the greater holding and agitation time of the fomer and greater heat of the latter exposure. Numerous workers had shown that the speed of freezing affected the degree of free fat separation of defrosted cream. These findings agreed that faster freezing was beneficial in preventing oiling-off of the cream. The fact that samples frozen in three minutes showed greater difference in fat separation between it and the six and one-half minute cream than did the six and one-half to the one-hundred and eighty minute sample, appeared to be significant. One could readily deduct from these findings that the speed of freezing should be as near instantaneous as possible inasmuch as each successive longer freezing time gave greater free fat separation of the defrosted cream. Addition of ten per cent sugar to cream prior to freezing proved beneficial both to speed of whipping and to maximum overrun obtainable, but did not prove beneficial from the standpoint of flavor of the resulting ice cream as had been indicated by previous workers. Neither was there any significant difference in the body scores of the ice cream from sugared and nonsugared frozen cream. The addition of dried egg yolk to the mixes made from sugared and non- sugared frozen cream showed that sugar had no beneficial effect on speed of 107 whipping and maximum overnm obtainable when 0.35 per cent egg yolk was used. Experiments with the use of egg yolk by other workers also showed that egg yolk was beneficial in restoring whipping ability of frozen cream mixes. However, these findings showed that egg yolk did not restore the whipping ability of frozen cream mixes to such an extent that they would comPare favorably with the mix of fresh cream. Nevertheless, it was be— lieved that the whipping ability of frozen cream mixes was sufficiently restored by egg yolk additions to meet all practical purposes of comer- cial dairy plants. That the egg yolk was not a deterrent to flavor and body in ice cream either fresh or after 18 weeks storage was further proof that egg yolk was a very practical method of restoring the whipping ability of frozen cream mixes. Periods of storage of cream up to six months were not more detri- mental than one month from the standpoint of whipping or of flavor of the resulting ice cream. Therefore, it seemed logical that one might use cream which had been stored for one year with equal success as that stored for one month providing the processing had been such that the flavor was not affected by the longer period of storage. Obviously, the freezing process rather than the length of frozen storage was responsible for the loss of the whipping preperties of frozen cream. The flavor of frozen-cream ice cream both with and without egg yolk proved to be as good as that of the fresh product when fresh and after 18 weeks storage. The fact that very little work was on record of other ex- periments on the keeping quality of frozen-cream ice cream prevents a com- parison having been made of these and other findings on the flavor of frozen-cream ice cream after an appreciable period of storage. At any rate, there can be no objection to the use of frozen cream mixes on the basis of 108 flavor deterioration of the resulting ice cream due to prolonged storage, if one observed the processing precautions as outlined in this experiment. The bacteria count of the ice cream made from frozen cream showed no material difference to that of the fresh-cream ice cream. However, there was a slightly higher count in the ice cream containing the egg yolk but bacteriologically speaking, it was of no significance. The fact that all frozen-cream ice cream showed a very low bacteria plate count after 18 weeks of frozen storage demonstrated from the bacteriological standpoint that frozen cream might be used in the ice cream mix. 109 SUMMARY Samples of high—testing cream, averaging throughout the year 52.5 per cent fat, were processed, frozen and stored at -lO° F. and were ex- amined at 3, 6 and 12 months to note the development of the oxidized flavor. A.pasteurization exposure of 150° F. for 30 minutes was found inp adequate to protect the cream against the develOpment of off-flavors. Ex- posures of either 165° F. for 15 minutes or 185° F. for 5 minutes were sufficient to inhibit staling of cOpper-free cream.upon prolonged frozen storage. However, the higher pasteurization exposure was slightly more beneficial than the exposure of 165° F. for 15 minutes. The presence of 1 part per million cOpper added to the cream after pasteurization resulted in the development of a very undesirable oxidized flavor in all samples upon storage regardless of the method of processing. The addition of 10 per cent sugar to the cream aided in stabiliz- ing the fat emulsion but did not necessarily prove beneficial to flavor.- Homogenization.was slightly beneficial in inhibiting the develOp~ ment of the oxidized flavor, but did not stabilize the fat emulsion against free fat separation upon defrosting. However, fast freezing although not a complete preventive of oiling-off was beneficial in stabilizing the fat emulsion of frozen cream. Cream could be stored equally well in glass, paper or tin contain- ers insofar as development of off-flavors was concerned. However, the lacquered tin container seemed to be the most practical from a commercial standpoint as a container for cream.atorage although paper was believed to be quite satisfactory. 110 Cream might be stored equally well at any season of the year and might remain stored for a year or more with no apparent loss of quality to the cream if the prOper processing methods were used. Carotene had no inhibitory effect on the develOpment of cOpper- induced oxidized flavor in high testing cream. The initial titratable acidity should be low in cream intended for frozen storage. The hydrogen-ion concentration of fresh, sweet cream furnished lit- tle information of practical value in predicting the keeping quality of the cream. While oxidation-reduction measurements increased with cOpper con- tamination and decreased with high-temperature pasteurization, they were not conclusive indicators of the future keeping quality of the cream. Sugar additions to cream prior to freezing were beneficial to Whipping ability of the resulting ice cream mixes. Egg yolk was found to aid greatly in restoring the whipping prep- erties of frozen cream mixes. Neither sugar nor egg yolk greatly affected the flavor of ice cream upon storage. Bacteria counts of the frozen cream mixes were quite low. 111 LITERATURE CITED (1) Anderson, J. A. 1936. Off-flavored milk - a problem of animal nutrition. The Milk Dealer. 26(1):60. (2) Baldwin, F. B. and Doan, F. J. 1935. Observations on freezing of milk and cream. Jour. Dairy Sci. 18:629. (3) Barnhart, J. L. 1940. Factors affecting the stability of butterfat in frozen cream. Doctor's Thesis, Graduate School, Pa. State College, State College, Pa. ' (4) Brown, W. Carson, Vanlandingham, A. H. and Weakley, Chas. E. 1939. Oxidized flavor in milk. VII. Studies of the effect of carotene and ascorbic acid in the feed of the cow on the susceptibility of the milk to metal-induced oxidized flavor. Jour. Dairy Sci. 22:345. (5) , Vanlandingham, A. H. and Weakley, Chas. E. 1941. Oxidized flavor in.milk. II. The effect of the quality of hay and early stage of lactation on the carotene content of butterfat and on the ascorbic acid content of the milk and their relationship to the deve10pment of metal-induced oxidized flavor. Jour. Dairy Sci. 24:925. (6) Carlton, Harry. 1941. The frozen food industry. ‘University of Tennessee Press, Knoxville, Tennessee. 187 pp. (7) Combs, W. B. 1939. Personal comments. Ice Cream Field 34 (l):21. (8) Crows, L. K. and Winn, H. H. 1941. A.study of skimmilk for ice cream. Ice Cream Field 38(2):40. (9) Dahle, C. D. 1927. Frozen cream as a source of fat in ice cream. 40th.Ann. Rpt. Pa. Agr. Expt. Sta. Bul. 213, p.21. (10) 1958. An anti-oxidant for dairy products. Nat'l. Butter and Cheese Jour. 29(24):8. (11) 1941. Frozen cream - a review. Iour. Dairy Sci. 24:245. (12) (13) (14) (15) (16) (17) (18) (19) {20) (21) (22) (23) 112 and Josephson, D. V. 1936. The importance of the fat globule membrane in the freez- ing of ice cream. Proc. 36th Ann. Conv. Internal. Assoc. Ice Cream Mfrs. II, p. 100. and Josephson, D. V. 1939. Frozen cream-institute survey analyzed. Ice Cream Field 34(1):21. , Lawhorn, R. K. and Barnhart, .T. L. 1940. The effect of certain factors on the keeping quality of frozen cream. Proc. 40th Ann. Conv. Internal. Assoc. Ice Cream Mfrs. II, p. '7. Doan, 1“. J’. and Baldwin, F. B. 1936a. Freezing milk and cream. 48th Ann. Rpt. Pa. Agr. Expt. Sta. Bul. 320, p.22. and Baldwin, F. B. 1936b. Observations on the freezing of milk and cream. II. The destruction of the fat emulsion in frozen cream. J’our. Dairy Sci. 19:279. Ellenberger, H. B. and White, H. L. 1929. The keeping quality of stored dairy products. I. Metallic flavor in frozen cream. Vt. Agr. Expt. Sta. Bul. 299, p. 3. Gockley, R. R. 1936a. Frozen cream - the best method of handling and use. Ice Cream Review 20(5):40. 1936b. Frozen cream - the best method of handling and use. Proc. 36th Ann. Conv. Internal. Assoc. Ice Cream Mfrs. II, p. 68. Gould, I. A. Jr. and Sommer, H. H. 1939. Effect of heat on milk' with special reference to the OOOkGd flavor. Mich. Agr. mt. Sta. Tech. B111. 1640 Grayson, R. V. 1931. The freezing of milk as a relief to the dairy industry. Ice and Refrigeration 81:245. 1935. Freezing cream, ice cream mix for use in ice cream. Ice Cream Rev. 18(10):48. Larsen, P. B., Gould, I. A. Jr. and Trout, G. M. 1941. Oxidation-reduction potentials and the oxidized flavor in homogenized milk. J'our. Dairy Sci. 24: 789. (24) (25) (25) (27) (28) (29) (30) (31,) (32) (35) (34) (35) 113 Lawhorn, R. K. 1939. Factors affecting keeping quality of frozen cream.. - Master's Thesis, Pa. State College, State College, Pa. Lindquist, H. G. 1935. A study in the changes that occur in the storage of frozen sweet cream. Ann. Rpt. Mass. Agr. Expt. Sta. Bul. 315, p. 37. 1938. A study of the changes that occur in the storage of frozen sweet cream. Ann. Rpt. Mass. Agr. Expt. Sta. Bul. 347, p. 510 1939. Changes that occur in the storage of frozen sweet cream. Ann. Rpt. Mass. Agr. Expt. Sta. Bul. 355, p. 49. leach, A. C. and Tracy, P. H. 1939. Controlling oxidized flavors. Ice Cream Trade J'our. 35(3):32. Mack, M. J. 1930a. A study of frozen sweet cream for use in ice cream. Ann. Rpt. M888. Agr. Expt. Sta. Bul. 260, p. 3470 1930b. Frozen cream as an ingredient of ice cream. Mass. Agr. Expt. Sta. Bul. 268. 1931. Frozen sweet cream as an ingredient of ice cream. Proc. 3lst Ann. Conv. Internal. Assoc. Ice Cream Mfrs. II, p. '7. 1939. Personal cements. Ice Cream Field. 34(1):22. McFarland, G. C. and Burgwald, J'. H. 1940. Prevention of oxidized flavor in frozen cream by homoge- nization and high temperature pasteurization. Abst. Jour. Dairy Sci. 23:494. Morris, A. I. and Sommer, H. H. ' 1932. Minerals and acidity injure quality of cream in storage. Ann. Rpt. W18. Agr. Ente S1380 B111. 421, P0 1520 Newlander, J'. R. and Ellenberger, H. B. 1929. The keeping quality of stored dairy products. II. Com- parative keeping quality of cream, butter, and butter oil. Vt. Agr. Expt. Sta. Bul. 299, p. 10. (36) (37) (58) (39) (4o) (41) (42) (43) (44) (45) (46) (47) (4s) (49) 114 Olson, F. R., Hegsted, D. M. and Peterson, W. H. 1939. Determination of carotene and vitamin A in milk. Jour. Dairy Sci. 22:63. Parker, M. E. 1941. Review of progress of refrigeration of butter and cream. Reprint from Proc. Ann. Meeting American Inst. Refrig. May 12-13. Washington, D. C. Pederson, M. G. 1941a. The freezing and storing of cream for use in ice cream making. Ice Cream Rev. 24(9):40. 1941b. Personal correspondence. Letter 9-15—41. Price, W. v. 1931a. The influence of sweetened, frozen cream on the develop- ment of swell in ice cream. Jour. Dairy Sci. 14:221. 1931b. The effect of using frozen cream as an ingredient of mix. Ice Cream Trade Jour. 27(11):37. 1931c. Use of frozen cream in ice cream. Proc. 31st Ann. Conv. Internal. Assoc. Ice Cream Mfrs. II, p. 17. 1932. Sugar improves keeping quality of frozen cream. Ann. Rpt. Wis. Agr. Expt. Sta. Bul. 421, p. 131. Reid, W. H. E. 1926. The effect of freezing on the market ability of milk and cream. Milk Plant Monthly 15(6) :46. Roadhouse, C. L. and Henderson, J. L. 1940. How quick freezing affects keeping quality of milk and cream. Food Industries 12(6) :54. Roush, J. M. 1939. Quick frozen foods in cans. Food Industries 11(1):lO. sampey’ J. J. 1939. Storage of cream for ice cream. Ice Cream Trade Jour. 35(3):40. Sommer, H. H. 1936. Eliminating tallowy flavor defects in stored frozen cream. Ice Cream Rev. 19(11):36. 1937. Development of oxidized fat flavors in stored frozen cream and ice cream. Ice Cream Rev. 20(7)362. (50) (51) (52) (53) (54) (55) (56) (57) (58) (59) 115 1938. Market milk and related products. Madison, Wisconsin. Swanson, A. M. and Sommer, H. H. 1940. Effect of the developnent of oxidized flavor on the iodine number of the phospholipid fraction of milk. I our. Dairy Sci. 23:201. Thurston, L. 11., Brown, W. C. and Dustman, R. B. 1936. Oxidized flavor in milk. Jour. Dairy Sci. 19:671. Tracy, P. 3., Ramsey, R. J'. and Ruehe, H. A. 1933. Certain biological factors related to tallowiness in milk and cream. Ill. Agra Expt. Sta. B1110 3890 1936.1 Certain problems relating to the marketing of homogenized milk. Milk Dealer 25(5):60. 1937. Milk products in the mix. Ice Cream Trade .T our. 23(5):27. Trelogan, H. C. and Combs, W. B. 1936. Distribution of butterfat in frozen cream. Milk Dealer 25(3):44. Trout, G. M. 1941. The freezing and thawing of milk homogenized at various pressures. Jour. Dairy Sci. 24:277. Webb, B. H. and Hall, 8. A. 1935. Some physical effects of freezing upon milk and cream. J'our. Dairy Sci. 18:275. Woodroof, I. G. 1941. Foods suitable for freezing preservation. Freezing locker plants. 68. Agr. Expt. Ste. 3111. 212, p. 20. u .. ., t . J . .. a .1 . 4 . . . . \n I - l .\ .1. .. .a,| .I.- r\ n pl. . ...l‘ n n «rue-Hounwhu. \Ehuflhr..1.. .I.. ...l-. ...llilllutipllufiq... ...NHIIWTI...‘ Hutu-linkr‘lm All: n.- ~J .Iv. .H .21 . '1} ll.l...:.,..2 : . : . .:: u. .. 1.. ..v‘fi‘..llllllll¢li.! . ......Li. ......1: v . .. . .. ... Room USE om UIHHIIIIHHIIIIH 6 5 0 4 9 6 3 o 3 9 2 1 3