TH ESlS .1 C-A{Q.4..(.4,L t" CL“ (LOk - r-n.’ _ '35:}. H‘.‘ ”.1 .H'" .ash'udt- - .. .' — n-.. - -')V .- _ _=.3 _L_A~_.=L.__— A STUDY OF THE mm 0? HEATED AND mm CMIFUGE 03 m ACCURACY O! m 313006! me A am 0! m mm 01' HIITED AND UNHM'I'ED CMIFUGB O! m ACCURACY OF THE BABOOCK TET mun hapoctmll: taunted to the Graduate School or 113111.311 auto 0011.30 of Agriculture and Applied Science in part1“ fulfillment or the ”quits-onto for the «gr» of later of Balance. 3: Jon-pl lethal hhl 1958 LCKH’OHW i'he vriter eiehee to expreee hie einoere eppreoietion to P. 3. Leon, leeooiete Proteeeor or Deiry lennfecturee, for ‘ hie nneeeeing efforte in the direction of thie experiment end for hie eeeietenee end critioieee in the preperetion of thie nenneoript. he writer ie eleo greetly indebted to I. 1.. Anthony, Proreeeor of Deiry Bun’oendry, end to G. leloolm front, leeiet- ent Profeeeor of Deiry mum... for their help in neking thie work poeeible. he enthor viehee to expreee hie gretitude to L. O. hone, Profeeeor of lethemetioel atetietice, for hie eeeietence in the interpretetion of then dete, to c. D. Bell, leeooiete Protoeeor of chuietry. for hie helpful euggeetione, end to the men: othere whoee kindly eid ie Inch epprecieted. 98078 TABLE OF CONTENTS INTRODUCTION REVIEW OF LITERATURE A. B. The Derelomnent of Chemical Teete Previous Studies on the Bebcock Teet 1. studies on the Accurecy of the Bebcock Teet 2. Studies on Residual Pet PURPOSE 0? THE EXPERIMENT PBOCEUBE L. B. C. D. Procedure for the Bebcock Test 1. Oti’iciel lethod 2. Hethod Followed in this Study Procedure for the Chemicel (Mojonnier) Test Procedure for Residual ht Determinetion l. Preperetion of Bebcock Tests for the Determinet ion of Residuel Fat 2. htrection of the Reeiduel Fet 8. 'me Check on the Procedure The Method for Determining the Tempereture of the Teete mmnmmn. RESULTS 1. B. C. Oonperison of Bebcock and MoJonnier Results Results of Reeiduel ht Determinetions l. Preliminery Triels 2. Results of Residuel Put Determinations lti‘eot of Centrifuge Temperetures on the Test Tempereturee Page 11 11 19 22 25 23 23 25 27 2’7 2'7 28 29 29 31 51 56 59 SW CONCLUS IONS LITERATURE CITED 62 65 66 IITBODUCTIOH One of the lost noteble echievenents in.the edvencenent of dairy- ing’wes the develop-eat of the Bebccck test for the determinetion of fet in nilk end nilk products. It wee devised by the lete Dr. Stephen I. Bebcock, of the Iisconsin Agriculturel Inperilent Stetion, end wee first nede public in 1890. Dr. lebcock wee the first of new investi- getors neking studies st thet tine in the designing of e precticel test. His test hes proven reletively sinple, quick, scourete, end inr expensive. Inuprinoiple it consists ef the eetion.of one reegent, strong sul- furic hon, oh the nilk solids not fet end the seperetion of the fet brought ebout by centrifugel force supplied by e.eechenicel centrifuge. he eetien of the ecid is to breek down the protective fil- eround the fet globules, which the min: proteins form, by so-celled dissolving of the nilk solids not rut. The ecid, due to its greet efftnity for weter, on nixing with nilk generetes e considereble emount of heet which nelts the milk fet end eids in the seperetion. Since the ecid is such e heevy liquid, neerly twice es heevy es nilk, it increeses the difference in specific grevity between the milk fet end the liquid surrounding it thereby eiding in.the seperetion. The Bebcock test is now used to determine the velue of’neny nillion dollers worth of products. ‘Beceuee of its edeptebility it is used in Inn: lines of deirying end hes proven.elnost indispensible. Since the introduction of the test precticell: ell nilk is bought and sold on.e fet besis. It is either bought et e specified price per pound of fet or the nilk is bought et e specified price per hundred pounds of nilk eonteining e certein renge ef fet, ssy 8.8 to 8.5 per cent, end e de- duction of e few cents for every one-tenth of one per cent fet the nilk fells below this renge or e preniu edded of e few cents for every one-tenth ef one per cent the fet content exceeds this renge. Severel other nodified plens ere elso in use. he test hes been of greet help to butter end cheese esters in detecting ebnornel fet loes- . es during nenufecture. It hes been of greet essistsnce to the deiry fer-er in the culling of the unprofiteble cow. It hes done nuch towerd stopping the wetering end ski-hing of nilk which wee so couon before its invention. It hes elso nede possible s new field in deiry reseerch. ‘ he Bebcoek test hes long been eccepted ee the officiel test by the deiry industry end is so recognised in precticelly ell stetes. here hes been such investigetion in ettenpting to prove the reliebility of the test yet there ere e few questions concerning the cperetion of the test which heve not been definitely settled. the of such questions is thet perteining to the efficiency in the seperetion of fet in the tests when the centrifuges ere opereted et exceedingly low, roan, end high‘teepereturee. heee conditions ere known to exist in eeny deiry plents. Inere steen centrifuges ere used the te-pereture et which the nechines eperete is ebout 135° to 160' F4 if electric testers or hend testers ere ueed end no heet is supplied the te-peretures nay range from ebeut 70° to 100' 1.. while extreme conditions ney be encountered during the winter nonthe where testing is doneout of doors or in un- heeted roons end unheeted testers es night be the cese in some cow testing work where the tests ere node in hend teetere during the colder nonths. Recently producers and producers' organisetione heve interested themselves in this question, heving noticed the wide verietions in temeretures et which the centrifuges ere opereted in the testing of their products. In view of the feet thet no perticuler te-pereture is specified in the stenderd procedure for the Bebcock test e study releting to this question wee underteken. KEVIN Ol' LITERATURI he fet of nilk is generelly regerded es its noet velueble cen- etituent. leny nilk products ere sold with the price being determined by the velue ef the fet in the product. Stete end l'ederel etenderds heve been set up reguletiu the mini-u enount of fet to be conteined in the verieus products. let in nilk veries widely end edulteretion is reletively eesy. for these reesons nuch upheeis hes been put on nethode for detereining the per cent of fet in nilk end nilk products end chuiets heve been endeevoring to devise sinple end eccurete netheds for neking such deteninetions. hey were encoureged greetly by the greet strides node in the deiry industry during the letter helf of the ltth century. 0f greetest ilportence wes the pessege of the [etch Lot (1) in lmwhich nede possible the esteblishnent of etete experi- nent stetiene, end, since the need for e preeticeble fet test wee ee inperetive et thet perticuler period new investigetors etteched thet problen. IoJcneier end key (S) heve coepiled e list of the nethods which resulted fro. the efforts of these eerly workers. Cone of these eerly tests heve nerits end others ere entirely ilprecticel. d. Tests where chenicels ere not used: 1. Green deuges. 8. I'Jord'e Centrifugel creen test. S. neeren's pioscope. d. reser's lectoseope. I. he churn test. 6. the 011 churn tent. 3. i'ests where chenicels ere used with or without the essistence ef centrifugel force: 1. Soxlet's nethod. r. hort's eethod. 8. Persons' nethod. d. hilyer end Iillerd's nethod. 5. dochren's nethod. 6. ddens' Peper coil nethod. 1. he loese-Gottlieb nethod. S. leilson's Keolin method. 9. Lieber-enn-Ssekely's nethod. 1o. Ieibull's desiccetion nethod. ll. Bell's meretion nethod. n. lichnond's Xieselguhr nethod. 18. he Storeh nethod. ld. he Ierner~Schnid nethod. 15. he hittheusen eethod. 16. he Ienklyn nethod. 17. he be Level hectorite. 10. he he Level lutyroneter. 1!. he Lefihen end he- eethod. n. he Gerber nethcd. ll. he huesien Bebcock nethod. n. he Bebcoek nethod. fl. Sichler'e Bin-Acid Butyroneter test. 24. Lindstoe's Butyroneter test. 85. he loJonnier nethod. his list indicetes the i-ense amount of work done in the etteupts to secure setisfeetory nethods. he greeter pert of it see done during the decede 1880-1890. Berthel (8) else gives en interesting end couplets survey of the useful tests for the estinetion of the per cent of fet in milk end milk products. he clessifies the tests into scientific end precticel tests thereby shenging the ebove list sonewhet to neke the tests nore under- stendeble. Sue of the tests in the United Stetes nede possible by the funds supplied by the hetch Act (1) were the Short test (d) devised et the Vis- consin hperinent Stetion in 1888, the Cochren test (5) devised et the Penneylvenie hperinent Stetion in 1889, the Persone' test (6) devised et the lew hpshire Experiment Stetion in 1888, the Petrick test or 'Iowe Stetion Iilk i'est" devised et the lows Experiment Stetion in 1890, end the Peilyer end Iillerd's test (8) devised et the lenses herinsnt Stetion in 1888. Perrington (9) in smerising the procedure of these tests end neking triels with then concluded thet the Oochren end Petrick nethods were the sinpleet end eesiest to operete. Freer end Halter (10) in leking couperisons between the Short, Cochren, end grevinetric (the Bebcosk Asbestos) nethods found thet the Short nethod geve results evereg- ing 0.15 per cent higher end the Cochren 0.08 per cent lower then the grevinetric nethod. Iith this generel emery of the eerly tests e survey of the chuicel tests should be ettempted to show their development end to indicete the stetus of the test used in this experinent. he Development of Chuicel Tests. Probebly the first grevimetric test using e fet solvent for extrec- tion of the fet wee the Lane method (11) reported in hglend in 1885. By this method e known weight of milk wee deposited on e coil of white blotting peper, end, efter ellowing to dry, the peper wee treeted with enhydrous ethyl ether. he ethereel extrect wee rogerdod es e11 fet but it wee leter shown thet the peper conteined other ether soluble sub- etenoes. he procedure wee leter modified so thet e peper free from ether soluble substences wee used. his nothod wee long considered es the best of grevimetric determinetion methods. In 1888 Roses (1:) published the results of e method which he hed devised end which now beers his nemo. he method wee similer to thet of the ddeme' method but where the ddeme' method technique required e dry extrection of the milk the hoses meds use of e wot extrection method. he procedure for the loose method is es follows (13) 3 About 20 grems of the milk ere mixed with 2 c.c. of e-sonie, then 46 c.c. of elcohol end 180 c.e. of e mixture of equel perts of ether end light petroleum ere edded. he mixture is sheken in e etoppored burette of 250 c.c. cepecity. he volume of the ethereel by» is reed off, end 25 c.c. of it is sveporeted in e tered flesk, the fet being dried by eepireting dried eir thru the flesk for 10 minutes, while heeting in e glycerol beth et eo°c. he reeiduo is then cooled end weighed, end the percentage of fet is celculeted. in eddition of 0.016 per cent should be meds for fet remeining in the equoous loyer. In 1892 Bottlieb (1‘) modified the Roses method by reducing the veins of milk to 10 grems end reducing the value of elcohol to 10 c.c. he emount of oech other wee reduced to 25 c.c. else. he pronounced the method setiefectory end steted thet it campered fevorebly with other methods. he method wee speedier then the noose nethod end could be ' eppliod to other deiry products. Long (15) in 189: secured results with the Roose-Gottlieb method which compered fevorebly with other grevimetric methods. Ieibull (18) end Kuhn (1?) showed thet the loose-Gottlieb method geve more eccurete results then other methods used by than. Popp (18) working with Siegfeld obteined setiefectory results by the noose-Gottliob method on both whole end ski-ed milk. hey meds e series of tests on whole ud ski-ed milk letting the ether etehc in the milk for I}, 1, s, 8 end 6 hours. By ellowing this solution to stend for 6 hours they ob- teinod en increese of 0.07 per cent of fet for the whole milk end 8.02 per cent increese for the ski-ed milk. hey veried the strength of the .onie solution used but found thet this hed no offset. In 190‘ Pepp (19) eunounsed e revised method for the hoses-Oottlieb test es follows: Plece 10 c.c. of the milk in e 100 c.c. tube greduetod to 0.5 ea. In this order edd l c.c. of snonie of proper concentretion, 10 c.c. of ethyl elcohol, :5 c.c. of ethyl end 85 c.c. of petroleum ether. df'tsr sheking on oech eddition let stand for 1 hour. dfter lest eddi- tion, drew off the ethereel fet solution until 1.5 c.c. of it rneins in the tube. 'eeh the fet left in the tube with other end edd to the fet solution, oveporete the others, dry, end weigh the fet. lultiply the weight of fet found by 10 to give direct per cent. hohrig (80) simpli- fied the removing of the ethereel solution by devising e gredueted stopperod cylinder which hed e spigot on the side et the 85 c.c. merk. his spigot ellowed the drewing off of eliquot portions of the ethereel solution into weighed flesks- hensen (21) node tests with the Boeee-Gottlieb nethod by peptising the proteins in the nilk end then testing the nilk by the Booss-Gottlieb end Ldems' method. Both nethods geve setisfectory results elthough results were somewhet lower on the unpeptised milk with the ldems' moth- ed. Burr (88) curried on experiments to find the seponifying offset of the eucnie on the fet in the loose-dottlieb nethed. He found thet there wee no such effect. he theorized thet in the cese of milk the chencos for seponifieetion were much less es s ccnsidoreble portion of the e-onie is combined with the cesein. Gordon (88) verified the eccurecy of the loose-dottlieb method re- sults by using the Bohrig tube. Results obteined from severel samples of creem, milk, end ski-ed milk ccmpered fevorebly with other methods. he expleined thet the ethyl-petroleum other proportion is very importent in securing eccurete deterninetions. lhen 10 c.e. of ethyl other end 80 c.c. of petrolom other were used, results much too low were obteined. he retie ecoording to Gordon should be neerly thet rocc-ended in the stenderd procedure. he Roses-Gottliob method geined ccnsidoreble prominence in leter yeere. Biol-end (2d) mekee this stetuenti "0n the hole, the Gottliob method is the best, though those due to ldems, Storch, Ierner-Schmidt, end leel ere little, if et ell inferior in eccurecy.” hru the efforts of the lete G. I. fetrick, former heed of the Deiry Deboretary of the United Stetes Depertmont of Agriculture, the Boeee-Gottlieb method wee first brought to the ettention of hericen chemists. It is now used 10 quite extensively end is included as the official method by the Associa- tion of Official Agricultural Chemists end other organisations. Realising that the Hoooe-Gottlieb method required too much time to be of practical value in the dairy industry, J. J. lioJonnier (85) in 1915 wee successful in devising apparatus which materially shortened the time for manipulation of the test. By the use of the centrifuge, vacuum oven, water-cooled desiccator, etc., much time could be saved without sacri- fice of accuracy. loJonnier end Troy (25) report work on the accuracy of the method in comparison with the Adams end Babcock methods. hey found close agreement between the Adams end loJonnier methods when applied to fresh milk but considerable disagreement between thehebcock and the other two methods. he only literature that could be found dealing precisely with the comparison of the IoJonnier and Boese-Gottlieb methods was that which was reported by Dehlberg (27). from the averages of six samples tested in duplicate he secured an average of 4.59 per cent for the official Ioese-Oottlieb and 4.81 per cent for the modified Roese-Gottlieb or loJonnier. he IoJonnier is '5 modified Hoese-Gottlieb method and is so con- sidered by loJonnior and' Troy (28). Other writers seem to concede the some point when they make comparisons with the HoJonnier as the Bosse- Bottlieb method. Phillips (29) makes no explanation but cells the loJonnier method the Hoese-Gottlieb method. Hoyt (50) says: ”he loose-Gottlieb is an official method of the Association of Official Agricultural Chaists. It was run on the loJonnier apparatus." )‘isher 11 and Halts (51) make this statement: "he directions for carrying out the Roese-Gottlieb determinations using the lioJonnier apparatus were followed exactly as given by HoJonnier and tray in 'i'echnicel Control of Dairy Products (page 109)“. M10, Swaps, and Dean (32), Chase end King (53), and Bird and Sands'fld) use the loJonnier method as a standard of comparison in their work. he lojcnnier method, then, has been and is generally recognised as a standard ch-icel test for the determination of the per cent of fat in milk and milk products. Previous Studies _o_n_ .t_h_o_ Babcock 323; Studios 23 22'. Accuracy _o_r_ 331-... Bebcock 2331. Babcock (as) first described his test for the per cent of fat in milk and milk products in 1890 and again (58) in 1898. Ho checked the method against the Bebcock asbestos gravimetric method which at that time. was the official test of the Association of Official Agricultural Chemists. hirty somplos of milk were tested and practically exact agreement was found between the average values. I-ediately on the introduction of the Babcock method many experi- menters took up the task of proving its worthiness. ' In 1891 Sudor (37) on comparing the average results from 100 samples of milk found thet the gravimetric method was 0.016 per cent higher than the Babcoek method. Patterson (88) in 1891 ran a series of tests by the lebcook, Adams Paper Coil, Beimling, and Patrick methods. He states that the heimling and Patrick methods more nearly compare with the gravimetric method 12 while the labcock fell below. However, he attributed this as partially due to the slipping of the belt on the Babcock centrifuge. hits (59) in 1891 made a series of tests by the Babcock and the Adams Paper Coil methods, as well as a few others. It was noted on three analyses of whole milk by the Dabcock and Adams methods, operated accord- ing to directions, that difficulty was encountered in obtaining fat free from casein and the results varied widely from the results obtained by the Adams method. In 1891 some work was reported at the Connecticut Agricultural Ix- periment Station (40) showing that on 52 comparative tests the Debcock averaged 0.10 per cent above the "standard method used in chuicel laboratories.” I Bailey (41) has conveniently compiled a table of the results secured by some of the early workers and this is reported in fable A. hose results show close agreement between gravimetric method results. Iarthel (48) in reporting some of his own investigations, says that the labcoek method gives results 0.08 to 0.08 per cent lower than the Roses-dottlieb. hJonnier and froy (45) report 52 tests being made on whole milk ,by the labcoek and IoJonnier method. Two operators made the Debcock deter— minations. Out of the 104 tests compared with the Iojonnier results they state that 51.9 per cent of the tests were overread and 45.5 per cent were underroad. he some authors also report (44) the testing of 14 samples of milk by the habcock, Adana, and HeJonnior methods. hey no- ticed a close agreement between the lioJonnior and Adams methods on fresh milk but the lebcock tests showed considerable disagreement between these 13 henna ‘ 000.0“ 30.0 3 not?» anon 2.0.0“ . 30.0 00H ”unnernuvvounom 00.0 55.? 0.70...” hobo noun; u an: Men 0.: 0n nevnenes no.0: em £0253 03.0“ 000.0- 3 3.30m them «3.3 “2.? 8 sesusehem . 333m 3.0“ as». .502. h 3.9 3::- un ass-ahead 23385.8 house Send and? 3 e305»:— esem n36“ 2.0.0.. 3 Staten 3:33 Sash 806 we seer—2.3— .3.33 «00.0”... 30.0.. 3 use?» notepad 000.0.“ 30.0 on noeenem compo.- evd‘en L mean-oh enough-mice crave—arena 3.33.395 on» one 3.3353 Has no one no nepli 530534 5 use: cacao.— nooepen noeeaon there shoes shaves.» onennoepd eeoneueuuum no omens: noeopen Se «0 omens: 33m euo‘ :0 scenes! 3.35590 cue nooonem on» neeevon one-«hemlg .4 canny 14 other two methods. he difference was not constant in any direction. In 1917 Bailey (45) reported that on the average of 190 comparisons made by reading the Babcock milk test from the bottom of the lower menis- cue to the extreme top of the upper meniscus, results were obtained with the Babccok method averaging 0.050 per cent higher than the Hoese-Gottlieb method. Hartvet (45) in 1917 reports the work done by ten collaborators making similar comparisons. heir results show the average of the tests by the Babeock method to be 0.04 per cent lower than the average tests by the Hoese-Cottliob procedure. Again in 19” several investigators reported their work. Hoyt (47) tested s-ples of milk by the Babcock, Reese-Cottlieb (lioJonnior) , Admss, and Asbestos methods. he average readings of the Babcock tests, read- ing from the extras of one to the extreme of the other meniscus, was 0.079 per cent above the Roses-Gottlieb (Mojonnier) figures, 0.091 per cent above the Adams figures, and 0.175 per cent above the Asbestos figures. By using glymol to flatten the meniscus on the milk test re- sults were obtained with the Bebcock test figures being 0.058 per cent below those of the Basso-Cottlieb, 0.046 per cent below the Adams, and 0.055 per cent above the results of the Asbestos. Hoyt therefore favors ehenging the procedure for the reading of the Habcock test in order that the test will more nearly conform to the figures. obtained by the gravi- metric methods, but only if other investigators confirm his results. Phillips (48) reported that from the average of 50 comparative tests with the Babcock tests being read from the bottom of the lower meniscus to the extreme top of the upper meniscus, the Babcock method gave results averaging 0.0588 per cent higher than the Hoese-Gottlieb (HoJonnior) 15 method. he habcock test was higher in every case, the Iinill- variation being 0.005 per cent and the maximum variation 0.126 per cent. When he used glymol on the tests the Bebcock method gave results 0.087 per cent lower than the Basso-Cottlieb (laJonnier) method. hen 52 samples of milk were run by the Babcock and Reese-Cottlieb methods, Dehlberg (49) found that the average results by the Babcock method was 0.10 per cent higher than the Reese-Gottlieb method. he Bebeock tests were read in the usual manner. Pishor and Ialts (50) on comparing the results from 16 samples of milk run by the Bebcock, Gerber, and Roese-Gottlieb (Madonnior) methods found that for milk the average variation from the Roses-Gottlieb method was 30.157 per cent for the Babcock method and t0.122 per cent for the Gerber method. Dehlberg, Holm, and Troy (51) made 925 tests of milk and cream in conjunction with workers in three different research laboratories and four different dairy control laboratories. hey concluded that the Bebcock and Gerber methods were Just as accurate as the chemical test and that the Babcock test did not yield higher results than the hoses- 0ottlieb test. Hunsiker (52) showed the effect of adding glymol to milk tests before reading. 3y destroying the meniscus with glymol the results were uniformly 0.2 per cent too low showing that the meniscus must necessarily be included to compensate for the residual fat left in the bulb of the test bottle. Dean, fields, and hglend (55) made a study on cream tests and found that by the use of glymol the cream test by the Babcock method was 0.28 per cent higher than the chnical test. hen the Bebcock 16 tests were read from the bottom of the lower meniscus to the bottom of the upper meniscus the Babcock test was 0.52 per cent higher than the chuical test. hose results are similar to those presented by Hunsikor, et. al. (at) and confirmed by Spitser and spple (55). Ho part of the meniscus should be included in the reading of cresm tests. he use of glymol is strongly urged. Dehle, Swope, and Dean (56) in 1950 report a modified Babcock test for buttorfat in condensed and evaporated milk. In order for the Babcock test to conform to the results by the loJonnier method the test must be read fru the bottom of the lower meniscus to the bottom of the uper meniscus. mines and King (or) on making a comparison of the modified Babcock method for buttorfat in ice cream and the HoJcnnier method, concluded that the modified laboock tests geve results averaging 0.04 percent higher than the loJonnier tests. Some explanation as to why the results of the Hebcock tests are lower than the chemical or gravimetric tests migit be obtained from the work of hurston and Peterson (58), and others. hey studied the Babcock test for fat in buttermilk and also the Gerber, butyl alcohol, and liojonnior methods for fat in buttermilk. hey concluded that the Babcock test was the most accurate of the tests considered. hey based this conclusion on the fact that buttermilk has a lecithin content nearly as high as the fat content and when reagents are used for the extraction of the fat which also dissolve lecithin, such as other, butyl alcohol, etc., the fat content is greatly exaggerated. he Baboock test for fat in butter- milk yielde nearly true buttorfat while other extraction methods yield 17 both buttorfat and lecithin. Similarly, in the cases of other milk products the lecithin content might introduce an error when extraction methods are used. he lecithin content of various milk products are given by Chapman (59) and are included in fable 3. From this table an idea may be obtained of the probable inaccuracies occurring in methods which use reagents, in which lecithin is soluble, for the extraction of the fat. fable 3 Per Cent of Lecithin in Hilk Products. £2223. £15 _C_r_eam_ Ski-ed £i_l_k_ Butteimilk Stocklassa 0.1015 Burow 0.0555 Koch and Ioods 0.0797 lerking and Haensel 0.0529 Glikin 0.0755 m 0.0447 0.1981 0.0165 0.1502 Studies 22 M _agd Unheeted Centrig‘ge. lo detailed study has been made regarding the effect of heated or unheated centrifuges on the accuracy of the labcoek test. Bebcock in his first descriptions of the test did not specify whether the centrifuges should be maintained at any certain temperature. However, provision was made for a water Jacket on the testers, and this to be filled with hot water in order to keep the centrifuge warm'. hen the manufacturing companies began building steam turbine centrifuges it was noted by Fall (50) that due to their con- 18 struction some acquired it very high temperature. One type of turbine tester had an opening above the spindle which admitted cool air and re- duced the temperature in the tester to about 140°]. he other type was closed on top. lo cool air being drawn in, this centrifuge sometimes reached a temperature of about 200°P. Noll made tests in both types of centrifuges and compared them with tests made by the gravimetric method. he difference varied from 0.10 to 0.50 per cent, varying according to the richness of the milk. hen the tests were read direct from the tester at soo'r the reading was 0.15 per cent too high for e per cent milk and 0.11 per cent too hid: for 5 per cent milk. hen the tests were read from the centrifuge at 140°r. the results were comparable to the gravimetric test. his increase in value of fat may have been due to the temperature at which the tests were read and not necessarily to more efficient separation of the fat. hrrington (61) was able to increase the efficiency of the Babcoek test for ski-ed milk by adding an excess of acid and by whirling the tests longer and in a hot centrifuge (about 200%.). He secured no different readings in the skimmed milk tests whether read at 120%. or 200°]. Hence, the higher results were due to more efficient ruoval of the residual fat. Bailey (62) reported the results of 18 tests run inen unheated tester. He concluded that the effect of testing in am unheated tester depended on the temperature of the room, the length of time the tests are exposed to room temperature after mixing, particularly in a cold room, and possibly on the type of tester. At ordinary room temperature tests gave the some reading whether run in a heated factory tester or in a hand teeter if they were centrifuged directly after mixing and the 19 water added with a temperature above 180°]. Very little difference was noted between the results obtained in the heated turbine tester and the hand tester even when the room temperature was down to 50°]. It should be noted however that the temperature of the water added to the test was well above that reco-ended by standard technique. lelscn (55) made a study of the labccck test in 1926. He noticed that the temperature of the room in which the tests were read caused no appreciable changes. hat is, when the tests were read with the room temperature at 19°]. the resulting readings were 0.019 per cent lower than when read in a room at 84°]. hen the temperature of the contri- fuge was 100°]., 52 samples averaged 0.049 per cent higher than the IoJonnier results but when the temperature of the centrifuge was 150°]. the samples averaged 0.07 per cent higher than the IoJonnier results. Ira the literature reviewed it is readily seen that a variety of results and contradictory conclusions as to the accuracy of the Babcock test are available. Studies _o_n_ Hesiduel _]_h_t_; Search of the literature revealed but little work on residual fat determinations. Halvorson (54) devised a method for the determination of what he termed ”residual fat" but not residual fat as usually considered. His method was that of extracting the sugar solution discarded from a modified ice cream test to deter- mine the per cent of fat that would be lost thru such a procedure. Hunsikor, et a1. (55) made a rather complete study of the residual fat in cream tests. hey noticed two sources of residual fat, namely, that which adheres to the glass and that which is contained in the liquid below the fat colun. ha a series of 25 cream tests the re- sidual fat adhering to the glass amounted to 0.041 per cent, that in 20 the liquid portion amounted to 0.226 per cent, and for all tests the total residual fet amounted to 0.280 per cent. heir procedure was as follows: "Six test bottles were used for each determination. he necks of the bottles were resend by scratching with a file and breaking them off at their base. he contents of the bottles were transferred to 500 c.c. boakers. he empty bottles were rinsed with hot water and the rinsings added to the solution in.the boakers. This solution was then neutralisod with potassium hydroxide, care being taken to avoid excessive evolution of heat. he neutralisod solution was then Illdlfly acidified to hasten the filtration and also to convert any soluble soap that may have formed into insoluble acid. he liquid was filtered through a wotted fat-free filter paper and the residual fat washed with distilled water. he filter paper was dried, extracted with other and weighed in the usual way. he results multiplied by L253: represent the per cent residual fat in the liquid. "he test bottles after rinsing with hot water, were dried and rinsed with other. he rinsings were evaporated and the fat weighed. he re- sults multiplied by 10% yield the per cent residual fat adhering to the class." Bailey (55) reported residual fat tests made on milk. His procedure and co-ents are as follows: ”To determine the residual fat the necks of four bottles were broken off and the liquid below the fat column poured into a separatory funnel. his liquid was extracted with he portions of ethyl ether, first 150 c.c. end then 75 c.c. the ethereal extract washed twice with water, evaporated to dryness, the residue taken up with petrolem other (boiling point be- 81 low 60°C.) filtered, and the weight of the fat determined. A similar method has been used for the same purpose with ice cream tests (64). "his method for determining the residual fat was checked up by subjecting some skim milk to the Hebcock procedure and then determining all the fat as above. he fat was also determined by extracting the same amount of skim milk in a separatory funnel by the Hoese-Gottliob method in order to determine the actual amount present. On three com- parisons in duplicate the per cent recovered by the above method ranged from 90.5 to 98.8 with an average of 94.8. ”he residual fat found in 58 samples of milk varied from 0.065 per cent to 0.255 per cent calculated as reading on the bottle gradua- tion, and averaged 0.152 per cent. hile this variation is large, there are very few extreme values. The variation is probably due to a varia- tion in the sise of the fat globules." 28 PURPOSE OF THE mum Since there is such a variation in the procedure for the operation of the Babcock test with particular reference to the tmnperatures at which the tests should be centrifuged and, since there is quite a demand that this point be clarified, this experimental work was undertaken. he chief object was to ascertain whether there is any material difference in the results from milk tests when centrifuged at low temperatures (55°40°].). at media or room taperatures (709].), and at high temper- atures (155°-150°].). If a considerable difference be found in the efficiency of the fat separation in heated and unheated centrifuges, then the procedure for the Habcock test mould be altered and the requir-ent be made that centrifuges be maintained at a prescribed temperature. In further pursuit of the above purpose, chemical tests were made in conjunction with the Babcock tests in order to secure a recognised standard for comparison. . If a difference in the efficiency of separation of fat due to (whirling at various temperatures exists, this difference should be account- ed for in the smount of residual fat remaining in the body of the Babcock test bottle. Consequently, it was the obJoct of this experiment to de- termine the residual fat remaining in the tests when centrifuged at low, medium, and high temperatures. Lastly, it was thought to be of interest that the temperature re- sulting from the heat generated by the action of the sulfuric acid on the milk be roeorded and also the drop in temperature after whirling at the Various tuperatures be ascertained. PROCEDUHI Procedure for the Babcack “rest he procedure used in this experiment for the estimation of fat in milk by the Babcock method was similar to that outlined by the Association of Official Agricultural Chaists (57) and, the Anericen Dairy Science Association prepared by O. ]. Hunaiker and conittee (85) and (59). he procedure outlined by these two organisations differ but slightly. It is interesting to note that the former states that the centrifuge should be maintained at a temperature of at least 55°C. (151°P.) during the whirling period while the latter makes no such statement. Of course, the final word in the testing procedure which concerns the Dabcoek test operator in the dairy plant rests in the regulations and procedures set up by the individual states. hose state regulations vary too. In order that a clearer understanding might be had concern- ing a standard procedure the official procedure of the Association of Official Agricultural Chemists (57) is here given since it offers a more detailed description. Official Method. w. Sulfuric acid -- Specific gravity 1.52-1.85 at eoSc. ”Marat". he standard centrim, however driven, shall be constructed thruout and so mounted as to be capable, when filled to capac- 1ty, of rotating at the necessary speed with a minimu of vibration and without liability of causing injury or accident. It shall be heated, electrically or otherwise, to a temperature of at least 55°C during the Process of centrifugalising. It shall be provided with a speed indica- tor, permanently attached, if possible. he proper rate of rotation 84 may be ascertained by reference to the table below. By ”diameter of wheel“ is meant the distance between the inside bottoms of opposite cups measured thru the center of rotation of the centrifuge wheel while the cups are horisontally extended. Disaster of wheel, in inches: 10 l2 l4 15 18 20 22 24 lo. revolutions per minute: 1074 950 909 845 800 759 724 595 "he _wa_t_e_l; 2th for test bottles shall be provided with a thermome- ter and a device for maintaining a temperature of os°-so°c. “Determination. i'ransfor 18 p. of the sample, prepared as directed, to the milk-test battle by means of the pipet. Plow out the milk remain- ing in the pipot tip after free outflow has ceased. Add 17.5 c.c. of H.504, preferably not all at one time, pouring it down the side of the neck of the bottle in such a way as to wash any traces of the milk into the bulb. he temperature of the acid shall be about lo°-so°c. hake until all traces of curd have disappeared: then transfer the bottle to the centrifuge: counterbalance it; and, after the proper speed has been attained, whirl 5 minutes. Add soft ago at co', or above, until the bulb of the bottle is filled. hirl 2 minutes. Add hot H20 until the liquid colnn approaches the top graduation of the scale. Ihirl 1 minute longer at a temperature of 55°~50°C. lransfer the bottle to the warm water bath maintained at a temperature of 55°-50°C., i-erso it to the level of the top of the fat calm, and leave it there until the col-m is in equilibri. and the lower fat surface has assumed a final form. meets the bottle from the bath; wipe it; and, with the aid of dividers or calipers, measure the fat colt-n, in terms of percentage by weight, from its lower surface to the hiaest point of the upper meniscus. ”he fat column, at the time of measurement, should be translucent, of a golden yellow or amber color, and free from visible suspended 85 particles. Reject all tests in which the fat coll-n is milky or shows the presence of curd or of charred matter, or in which the reading is indistinct or uncertain." m followed in .t_h_i_s_ M am. Regular coemercial, unstendardisod sulfuric acid of speci- fic gravity 1.84 was used. On account of its strength only about 15 c.c. were used. Apia-runs. he 3:31 bottles were standard Babcock milk test bottles meeting the specifications of the State of Michigan (70), the Association of Official Agricultural Chuists (57), and the United States Bureau of Standards (71) . However, they were ro-chocked for accuracy by the mercury method and all bottles that did not exactly check were rejected. The pipettes used were standard pipettes meeting the specifications of the state of lichigen(70). he centrifuge used was an electric, twenty-four bottle tester having a diameter of 15 inches and running at a speed of 850 revolutions per minute. It was made portable by mounting on a concrete block of relatively light weight and was fastened to the concrete block by means of long, threaded bolts placed in the concrete, thereby simplifying leveling. he tester was equipped with an electric heater and a ther- mameter for registering its temperature. he _w_a_t_o_l_'_ _b_a_t_l_l_ for the test bottles was a thermostatically controlled water bath maintained at a temperature of 158°]. Determination. hirty samples of milk representing the patrons delivering milk to the college dairy were collected daily on various days until over five hundred samples were collected. hch sample was well 26 mixed by pouring back and forth from two containers six to eight times. lech sample was pipetted into six Babcock test bottles which previously had been re-checked for accuracy. he pipetted portions from the same sample were divided into three lots of two each to be whirled with the centrifuge operating at low, medium, and high temperatures, the tests for each temperature being run in duplicate. The tests to be centrifuged at a low temperature were placed in a twenty-four bottle shaker and about 15 c.c. of acid added to each. After complete shaking, the tests were immediately placed in the centrifuge which was located in the refrigerator at 55°to 40°]. and whirled for five, two, and one minute intervals. Hot, soft water was added to the tests in accordance with the procedure of the Official Method (67). he tests were i-ediately placed in a constant t-porature water bath and held at a temperature of 158°]. for readings at a later period. he same procedure was carried out with the remaining two lots of tests except for the location of the centrifuge and the temperature at which it was run. he second lot was whirled with the same centrifuge located in the laboratory with the temperature at the start at 70°]. but the t-perature should rise due to the heat from the tests. he third lot was whirled with the temperature of the tester at 135° to 150°]. this temperature being maintained by the use of an electric heating oluent. After completion of the centrifuging and after the tests had re- mainod in the water bath for at least three minutes they were removed singly from the water bath and readings made by two persons. he results were determined individually and tabulated on separate records. 27 Procedure for the Chemical (Hojonnier) Test he regular procedure for the Hojonnier fat determination in milk was used (72) except that the milk samples were accurately weighed in- stead of measured from a Hojonnier ten-gram pipette. his modification would render the procedure practically identical to that of the official Hoese-Gottliob Method. Because of the time involved in making duplicate tests of the milk, in a majority of cases one determination was made on each sample. How- ever, sixty samples were run in duplicate to check the accuracy of the operator. he average difference between the duplicate tests was 1.0.021 per cent with a variation of from 0.000 to 0.072 per cent. herofore, the single tests were considered very reliable. Procedure _f_¢_>_i; Hesiduel 1a; Determination Since there is no official procedure for the determination of that amount of fat which remains in the body of the Babcock test due to the minute sise of fat globule, the following procedure was devised and checked for accuracy: Preparation 55 Babcock Tests for the Determination 5! Residual l‘at. he Babcock milk test bottle was first balanced on an analytical balance after which 17.5 c.c. of a well mixed sample of milk was pipetted into it and the exact weight of the sample was determined to the fourth decimal. Twelve samples of milk were weighed in this manner until seventy-tn tests had been obtained. hose seventy-two tests were divided into three lots of twenty-four each and the tests completed with the centrifuge Operating at low, media, and hidl temperatures as in the case of the regular experimental procedure. After centrifuging, the fat was floated from the neck of the test bottles by means of boiling water and the tests whirled for another minute. Any traces of fat were again removed with boiling water. This method of eliminating the fat from the neck of the tests was thought to be just as efficient, and much more economical, as the method used by Bailey (55) where the necks of the bottles were broken off to eliminate the fat. thraction of the Residual Fat. hch test prepared in the above manner was emptied into 250 c.c. separatory funnels. The test bottle was refilled with water and rinsed into the separatory funnel thereby diluting the acid mixture. he test bottle was again rinsed with a small portion of ethyl ether to remove all traces of fat in the bottle and the contents emptied into the separatory funnel. hen 50 c.c. of ethyl ether was added to the acid mixture, the funnel stoppered tightly and the mixture shaken vigorously for 20 seconds. 50 c.c. of petroleum ether was then added and the mixture again shaken for 20 seconds after which 20 c.c. of ethyl alcohol was added and the mixture shaken for 50 seconds. he alcohol was necessary for the removal of the gelatinous mixture which collected at the interface between the acid mixture. and the other solu- tion. he test was allowed to stand for five minutes or until complete separation of the ethereal layer after which the acid mixture was drawn into a beaker for re-extraction. Isanwhile the remaining ethereal layer was washed twice with 100 c.c. portions of water and then filtered thru a fine, fat free filter into weighed aluminimi (Hojonnier) fat dishes. Per the re-extraction the acid mixture was treated with 25 c.c. of ethyl ether, 25 c.c. of petroleum ether, and 10 c.c. of ethyl alcohol and the mixture was shaken for 20 second intervals after the addition of each reagent. he acid mixture was again drawn off and discarded while the mining ethereal layer was washed twice with 100 c.c. portions of water and the ether-fat solution filtered into the fat dish. Care was exercised to insure that all the wash water which clung to the sides of the separatory funnel above the ethereal layer was shaken down into the water layer before the final separation was made in both extractions. )‘rom this point on the fat dishes were treated in the regular chcnnier technique (72). .52. _C__h_gg_k_ _o_n_ the grocedure. This method was checked for accuracy by determining the amount of fat that could be recovered when a weighed amount of pure butter oil was passed thru the sue procedure. Four tests were run with the fat being weighed into water while four other tests were run with the fat being weighed into sulfuric acid. Only 15 c.c. of acid were used for each test as in the regular Babcock tests. .721 12322332.! Determining the Temperature g_f_ _t_l_1_e_ m. Since the amount of heat generated by the action of sulfuric acid on milk, and the drop in temperature due to centrifuging at various t:mper~ atures was thought to be of interest, this simple procedure was followed and the expensive method of.the calorimeter was not used for obvious reasons. Twelve charges of 17.6 c.c. of milk were pipetted into each of twelve Babcock cream test bottles for the convenience of the larger neck. After the addition of the acid to the milk a thermometer was lowered into the bottom of the test bottle and the test shaken, the highest tempera- ture reached being recorded. After these twelve temperatures were de- termined thirty-six more portions of milk were pipetted into cream test bottles to be divided into lots of twelve each for the determination of the drop. in temperature when centrifuged at low, medium, and high temperatures. mess three lots were centrifuged in exactly the same manner as in the experimental procedure for the Babcock test for milk. 30 Hot soft water at a temperature of about 160°F. was used in.tilling the tests. After completion of the mirling, the test bottles were removed from.the tester one at a time and held over a container to catch the overflow while the thermometer was being lowered to the bottom cf’the test bottle. 'lhe highest temperature for the tests was again recorded. 51 EXPERIMENTAL RESULTS Comparison 52 Babcock and Mogonnier Results. It was the purpose of this experimental work to ascertain whether a significant difference in the efficiency of the fat separation existed when heated and unheated centrifuges were used in the operation of the Babcock test for the estimation of fat in milk. Further, a comparison between the Babcock test and a standard chmical test, such as the loJonnier method, was thought necessary if positive conclusions were to be drawn. Il‘he comparison was made to determine at which temperature of centrifuging, the results of the Babcock test would more nearly equal those of the MoJonnier test. Consequently, samples of milk representing the patrons delivering milk daily to the college dairy were collected until 515 samples were obtained. The samples were treated and tested according to the procedure previously given. lhe results are reported in detail in Tables I to XVIII inclusive. Bach sasmle of milk was tested in duplicate at each of the three temperatures of centrifuging, namely, 60° to cs°r., 95° to 100%., 135° to 150°r. ror each tempera- ture of centrifuging four readings were made of these duplicate tests due to their having been read by two readers. In this manner it was hoped to eliminate differences due to personal factors as much as possible. The average of these four readings at each temperature of centrifuging appear in a fifth colan under the three main headings of "Low, radium and High 'rsmperature". 'lhese averages are the figures that were considered in the interpretation of these data. he attempt was made to show differences due to individual readers as that was beyond the scope of this problu. However, others (41) have done this and found that an average variation as high as 0.15 per cent might exist. In order to facilitate the interpretation of these data a few mathe- matical calculations were necessary and the results are summarised in fuble XIX. It will be noted that the average or mean readings for the 513 samples when centrifuged at the various temperatures were as fellows: Ihen centrifuged at low temperatures (60°to 68°F.) the mean reading was 3.78 per cent: at medium temperatures (85° to 100°P.) the mean reading was 8.75 per cent; and, at high tanperatures (135° to 150%.), the mean\‘reading was 8.16 per cent. This would make a difference in the average reading;u. ef’0.04 per cent between the tests centrifuged at low and at high temper- atures, the greatest difference in.means that might be attributed to the differences in temperatures of’centrifugingt However, the last column of the table shows a probable error of”t0.0177 which is nearly half the difference. Therefore, one could not conclude that this difference in average readings is due to the variation in temperatures of’centrifugingt lhese differences in average readings resulting in the three lots of tests can be explained only in part. It indeed seems odd that the average readings would progress upward as they were centrifuged at higher temperatures, yet these differences are of no significance mathematically. Perhaps this variable factor had its influences but not sufficiently great to attribute the differences to it. Since these differences can not be due to variations in speed of centrifuging, length of time of centrifuging, length of time of’holding tests after mixing the acid and milk, inaccuracies in glassware, etc., all of which were held constant in this experiment, the differences might be due to variations in read- ings by the individual readers, slight errors in pipetting, and more ocelusion of water and sulfuric acid in the fat column in the case of some tests. It appeared in the case of the Babcock tests centrifuged at the low temperatures that the fat column receded in the neck due to the lower temperature while centrifuging and it is possible that some of the fat did not rise again when the tests were innersed in a water bath but clung to the glass near the bottom of the neck. Consequently it was not included in the reading and lower averages were obtained for the tests centrifuged at low temperatures. Even though water was added to the tests which was higher in temperature than is recoumended in standard procedures yet the coldness of the room brought the temper- ature of the fat colunn down during centrifuging to about the solidi- tying taperature of .111: fat tee“ to 95°“. the fat in the tests made in the cold room or low temperature centrifuge was usually near solidi- fication when the test bottles were removed from the centrifuge even though water at a temperature of 1580?. was added to the tests. I'able XXIII shows that the average tmperaturs of the tests after centrifuging in a tester at 60° to 68°F. to be 94.5%. or very near the solidifica- tion temperature of. milk fat. In order to insure that the tests would come from the cold centrifuge in a good condition the water added should be much higher than 158°). lines the Babcock test results were not materially altered due to temperatures of centrifuging, a mean of all the test was secured for comparison with the chemical test. Since the means were obtained from the same number of tests in the case of each temperature of whirling, an average of these means was secured to represent the mean of all Babcock tests made. he mean of all the Babcock tests was found to be 8.74 per cent while inspeetion of Table 111 shows the mean of the lojonnier tests to be 8.67 per cent. Apparantly the Babcock method yields results 0.07 per cent higher than the MoJonnier method. The last column of the same table shows a probable error in the means “10.0172 which would indi- cate that this difference is hiaily significant and under the same con- ditions of investigation similar differences should be obtained. An explanation as to why the Babcock method should produce higher results than the lioJonnier method can be obtained from the work of Bailey (41). The losses to the fat colmn studied by Bailey are: (a) residual fat which averaged 0.132 per cent, and (b) the amount of milk delivered by the pipette which was found to be 0.076 grams less than should have been delivered; while the gains to the fat colmn appeared as: (a) impurities in the fat in the neck of the bottle which was mostly acid and water amounting to about 0.78% of the total fat, (b) reading of tests at 130° 4450?. instead of 113°r. at which temper- ature fat has a specific gravity of 0.9, and (c) the inclusion of the upper meniscus in reading the test. The explanation as to why the Babcock method yielded higher results than the loJonnier method seems to be that the gains to the fat column greatly offset the losses. Patrons' lilk Samples 'l'ested January 25, 1983. Table I Chemical 'fest .11 um mum lledimEerature Low Sgerature fit2scccacxssccccxc2322cc ....................... 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Mum m 4 6: .8 Lo: .3ch nocdom Lo: noudom hog—om Lo: novdom nocaoml magnum 0.35m vomwFHagaoF undeauauew WE LA capauomeobpfiguox J5 ohfiuuoflfilfiw 62H .3. 8.3. not: .39...» an: .3823 :3" .25 Tabla XVIII Putronl' 111k 83ml” Tented Int-ch 25, 1938. 3333333333333333333333 33 3332:; I) '33333333333333333333333333as $83$$§3§¥$,,$€3338,83,.3838? 3 n 3333333 3333333333333 33 3 333§33333.333338333335333333 »»T» Tnnurfnn???» n:»»»» I an???» US 333333333333 3 .3333333333333 82$?8fl333332 H3333833 8: 83 OOOOOOOOOOOOOOOOOOOOOOOOOOOO OOOOOOOOOOOOOOOOOOOOOOOOOOOO 228°83333382 32288833388 88 °388 33 3333333°33.3333333 '3333 00000000000000000000000000000 33: ”83333"33 33 3388838838323 »»v»v»»¢¢»»»»»»»»»»»»v»»'0non 9 33333333333 H3 333333333333333 3n 'uthuifoSoS 'ffiéfiééééédfiééffiéffiffin »»¢»¢»»¢¢»»»»»»»»»»»nvnnvnvo»» F3 " 33333333333 33333333 333333333 D 3 333°3333333°3 H33333 323°3833 E3?3?3333333?3....$%§33??$3$¥3 55 3.20.0 no.0 33.0: c: 33.0 03. 00.0 30.0 a 2.» u 3: 20 0.838.08a 303 n: 9.3 3.593989 gadofi +l ssao.o 30.0 33.3: 3 300.0 3... 8.0 08.0 n 2.» *4 2.8.0 H 8.0 no.7; .3 30.3.0 «3. 8.0 08.0..." my.» a «a 2... 0.3930059 ion 3.- #0033 «20.0 N 00.0 «Eh: .3 2.8.0.». 00.0 $3.03 7: 2.8.0 .0 00.0 $3.33 3 003.3 3. 00.0 20.0% 2.» a H: 20 “38008. .800: no 53.0350on vane pom a.“ name ham 5 #25 new 3009 flap-ca gonna imam mo deaf-«hon 82326: Song a.“ no no 30.30; 902m 0330.5 0.30836 d3 £02.; omduo: 3.: ~35: 005.: r .3083 :3. “38000: 05 “.823 no ban-pm 3.3.330 Man 0.23.. Reeulte .93. Residual Fat Determinatione. Preliminagl Triale. Since there ie no etandard procedure for the determination of the fat that remains in the liquid portion below the fat colmn of the Babcock teet a procedure was devieed which wae de- ecrihed in the "Procedure" of thie manuecript. In order to check thie method, preliminary teete were run. About 0.1000 gram portione er hutter oil were weighed into eeparatory funnele and extracted according to thie procedure. he percentage recovery of the 8 teete run wae about 98.5 per cent. he detaile of theee preliminary triale are ehown in i'a‘ele n. Table xx Beeulte of Reeidual Fat friale. 55 weight of Ieight of weight Per Cent Loee 0r lixture fat taken fat recovered difference difference Gain 011 1n.water .1054 sue. .1052 gne. .0022 sue. 2.087 Lcee oil in water .1016 gas. .1002 gme. .0014 gne. 1.378 Loea oil in water .1052 gme. .1006 gne. .0026 gme. 2.519 Loee oil in water .0979 gme. .0972 sue. .0007 gme. 0.716 Loee Averafi 2.2.5 9:113 Difference M 011 in acid .0969 gme. .0956 gme. .0015 gme. 1.841 Loee oil in acid .0984 gme. .1008 gme. .0024 awe. 2.439 Gain oil in acid .1062 gme. .1046.gne. .0016 .ne. 1.606 Loee 011 in acid .093: gee. ' .0954. sale. .0001 go. 1.071 Gain dragggg Per Cent Difference 11:222. Ava-go 333; 0393 Difference £9; =1; 31 =l'_1__._e_1_1_ 66 Reaulte of Beeiduel rat Deteminationa. The detaile of the‘ teete made to determine the amount of reeidual fat contained in the Babcock teete when centrifuged at low, medium, and high temperaturee are ehown in ‘i‘able XII. The teete repreeent 12 eemplee of milk prepared accord- ing to the procedure outlined and teeted in duplicate for each tempera- ture of centrifuging. fable n11 givee the eunnary of the teete and it will be noticed that the average amount of reeidual fht contained in the teat at the low temperaturee of mirling was 0.1801 per cent; at the medium temperature it wae 0.1194 per cent; while at the high tuper- aturea it wae 0.0881 per cent. meee averagee would tend to indicate that the greateet amount of reeidual fat in preeent in the teete centri- fuged at low temperaturee while the leaet amount of fat ie preeent in the teete centrifuged at higher temperaturee. However, the teete vary ccneiderably from their averagee at the acne temperature of centrifuging, hence, theee averagee are leee significant. In the laet column of the table appeare the probable error of these averagee. Prom theee it ie noticed that there ie a great variation in the teete in the cane claee and coneequently there ie not enough difference in then averagee to conclude that there ie any appreciable difference in reeidual fat con- tent ef the Babcock milk teete ahen centrifuged at varioue temperaturee. Table 111 Per Cent Residual Pat in Babcock Milk Teete. "eup' ""‘1. “Po'rTonTt t 4' T‘r'o'r' lc'tent fit at $71- I—T—Cent t at lmuber Low Tmerature Medium Temperature gigh Tunperature 1 0.2082 0.1649 0.1210 14 0.1769 0.1176 0.1061 2 0.1626 0.1120 0.0667 26 0.1686 0.1191 0.0710 6 0.1666 0.1162 0.0794 ' 5a 0.1967 0.1102 0.0878 4 0.1661 0.1416 0.1092 44 0.1602 0.1664 0.0790 6 0.1668 0.1667 0.0866 5a 0.1646 0.1664 0.0770 6 0.1426 0.1002 0.0916 6a 0.1219 0.1680 0.0787 7 0.1727 0.1261 0.0761 74 0.1791 0.1001 0.0911 8 0.1692 0.1184 0.0826 80 0.2466 0.1096 0.1161 9 0.1126 0.1648 0.0646 94 0.1164 0.1202 0.0671 10 0.2620 0.1676 0.0921 104 0.2266 0.1216 0.0806 11 0.2276 0.0692 0.1267 11a 0.2690 0.1066 0.1210 12 0.0766 0.0667 124 0.0996 0.0726 58 $36 a. 28.6 a as n «a .3 86.6 6.36 $3.0 n 38.0 .. a: .. F E 306 2.6.6 386 n .386 .. ms .. H: 3 63.6 63.6 88.6 H 336 .. n: .8. $86 1... 3:5 .- «a «a 88.6.“ 32.6 a F a... end—«enemas flaw guinea-en. Inade— eugenenI-a a3 3...: 3036356069 cyan newt-«pen do «6 90.23% you.“ eapepoum gonna 0330.3 58332638 68m ”spasm .3 2888 983.383 anon hem canon. :69 nooepcm 5 no you ewauuvueo nee! .3355 no madness HHNH canon 59 Effect 91 Centrifugg Taggemturee an the Teet Tagoraturee. The temperaturee of the centrifuge at low, medium, and high tempera- ture were obeerved at varioue and irregular intervale to aecertain the range in temperature at which it Operated. The common range appeared to be for the low temperature, 60° to 68°F., for the media temperature, 66° to 100%., the for the high tauperature, 166° to 160%. A6 etated in the ”Procedure” the centrifuge wae placed in a refrigerator at 86°- 40°r. for the low temperature centrifuging, while the other teete were run in the laboratory which had a temperature of about 70°]. The temperaturee of the centrifuge ie markedly increaeed by the heat of the teete. The temperaturee of 12 eamplee of milk were obtained after mixing with acid and after centrifuging at the varioue temperaturee. he re- eulte are reported in Table 11111. On mixing the acid and milk in the teat bottle the average temperature wae about 219°P. After centrifuging in the heated teeter at 166° to 150°F., with the water added in .11 caeee at 168°l., the temperature of the teete dropped to an average of 1680!. After centrifuging at media temperature (86° ~100°l‘.) the average temper- ature of the teete dropped to about 131°F., while at low temperature (60° 48°F.) the average temperature of the teete dropped to 94.601'. hie etudy ie important in explaining many featuree of the Babcock teet. The heat from the teete raieee the temperature of the centrifuge fru 26 to 66 degreee, the final temperature of the centrifuge, of tour», depmding on the temperature of the room in inch it ie located. At ordinary room temperaturee the heat from the teete maintaine the tapera- ture of the teeter at about 100°r. which 1- a eatiefactory temperature and which indicatee that no heater ie required. Alec, the conditione that exiet at extreme low temperaturee of centrifuging are better ex- plained from thie data. Ihen the centrifuge ie running at a tempera- ture of about 65°F. we would expect to remove the teete after centri- fuging at about 94°F. which 18 near the eolidifying point of mint fat. Solidification of the fat 16 undeeirable. To improve thie condition water ehould be added to the teete at almoet boiling temperature. 61 Table XXIII Temperature of the Acid-Milk Mixturee in the Babcock Teet Bottle. Sample Degreee I. Degreee F. after centrifuging'at M at etart Low Taperature Medium Temperature Manure 1 214 106 166 166 2 221 109 162 162 6 221 106 129 167 4 217 104 166 172 6 216 ' 88 162 169 6 219 90 162 169 7 e 217 88 162 167 8 217 90 162 167 9 221 90 129 172 10 226 96 127 171 11 221 82 129 167 12 9.22 .92 12.2 1.69. lean 219.2 94.6 160.9 168.0 7 Temperature of the milk and acid on mixing 70°r. 7 Tnperature of Water .6066 to the teete 166°r. 62 SUMMARY Inaccurate technique in teeting milk and milk produete may cauee material 1066 both to the producer and to the manufacturer. The uee of centrifugee operating at varying temperaturee ie thought by ecme to be euch a practice. Coneequently, in thie expert-ant eamplee of milk repreeenting the patrone delivering’milk daily to the college dairy were collected until 616 eamplee were obtained. Each sample wae teeted for fat by the Hedonnier and Babcock methode. Single determinatione were made by the lojonnier method according to etandard procedure except that the eamplee were weighed inetead of measured. Sixty eamplee were run in duplicate to prove the reliability of the eingle teete. The average difference between the duplicatee wae toe per cent. For the Babcock determinatione each eample wae pipetted into re- checked and abeolutely accurate Babcock teat bottlee. Six teete were made on each eample, duplicatee being made according to etandard proce- dure with the eame centrifuge operating at low temperaturee (600 to 6803.), at medium temperaturee (86° to 100°r.), and at high tempere- turee ( 166° to 15003.). After centrifuging, the teete were immediately placed in a conetant temperature water bath at 168°F., held at leaet five minutee, and read by two readere. The average of the four readinge wae coneidered the reading of the teat for that particular centrifuging temperature. The reeulte of the M0jonnier determinatione ehowed an average of 6.67 d’ 0.017 per cent for the 616 determinatione. The meane of the 616 eamplee teeted by the Babcock method were ae followe: at low temperaturee 66 of centrifuging the mean was 6.72 * 0.018 per cent, at medium tempera- tures of centrifuging the mean was 6.75 1' 0.018 per cent, and at high temperatures of centrifuging the mean was 6.76 1' 0.018 per cent. This makes a difference in the means of 0.01 1' 0.0177 per cent for the med- ium end high temperatures of centrifuging, 0.04 1’ 0.0177 per cent for the low and high temperatures, and 0.06 3.0.0177 percent for the low and medium temperatures of centrifuging. These results indicate that there are no differences in readings due to the temperatures of centri- mains- On comparison of the Mojonnier and Babcock results, a marked dif- ference was noted. The mean of all Babcock tests (1569 in all) was 6.74 '1' 0.018 per cent and the mean of the MoJonnier tests was 6.67 1' 0.017 per cent. The difference in means was 0.07 11.0172 per cent. This figure is very significant and the conclusion could be drawn that the Babcock method yields higher results, by 0.07 30.0172 per cent, than the Mojonnier method. Residual fat determinations were made on 12 samples of milk run in duplicate at the above mentioned temperatures of centrifuging. At low temperatures of centrifuging an average of 0.1801 1" 0.0266 per cent of residual fat remained in the Babcock test, at medium tempera- tures 0.1194 1: 0.0161 per cent remained, while at high temperatures 0.0881 1'0.0151 per cent was present. The tests in each class varied widely from their means and consequently these differences in residual fat cannot be definitely attributed to the various temperatures of centrifuging. me temperature of the milk and acid mixture after mixing was ascertained as well as the dr0p in temperature after centrifuging at the various temperatures. It was found that the heat of the tests raised the temperature of the centrifuge from 25 to 66 degrees. How- ever, in the cold centrifuge the tests when removed after whirling were nearly at the solidifying temperature of milk fat. To overcome this condition , water should be added to the tests at near its boiling point. 66 CONCLUSIONS The results from this experimental work indicate the following conclusions: 1. Although there appears to be slight differences in the average tests by the Babcock method due to centrifuging at various temperatures, yet this difference is not significant. No appreciable variation in readings can be attributed to centrifuging at low or moderately high temperatures. 2. here is a significant difference between the results secured by the liojonnier and Babcock methods. he Babcock method yields re- sults averaging 0.07 1' 0.0172 per cent higher than the HoJonnier method. 6. me Babcock tests contain on an average of 0.129 per cent fat remaining in the liquid portion below the fat coltmn. No differences in the amounts can be attributed to temperatures of centrifuging as the tests varied widely from their means. 1. 2. 4. 6. 66 LITERATURE CITED 1888 The Hatch Act Pennsylvania Agr'l. Exp. Sta. Annual Reports (1889) pp. 7-9 MoJonnier, T., and Troy, 11. C. 1926 he Technical Control of Dairy Products Mojennier Bros. Co., Chicago, 111., 2nd ed., p. 66 Barthel, Dr. Chr. 1910 liilk and Dairy Products Translated by Goodwin, 9., Ph. D. McMillan and Company, low York., pp. 52-65 Short, 7. G. 1888 A New Method for Determining rat in Milk Iisconsin Agr'l. Exp. Sta. 6th Annual Report Cochran Pennsylvania Agr'l. Exp. Sta. Annual Reports (1889) p. 186 Parsons, C. Le 1886 A law Yoluetric lethod for the Estimation of Fat in lilk, Skinned Hilk, Buttermilk, and Cree. New Bampshire Agr'l. m. Sta. 1st Annual Report, 701. 1, p. 69 7e 10. 11. 12. 18. 67 P‘trick, Ge le 1890 The Iowa lilk Station Test Iowa Exp. Sta. Bul. 8 Failyer,‘ G. 11., and Villard, J. T. 1888 A New Method of Milk Analysis for the use of Dairymen Kansas Agr'l. lxp. Sta. Annual Reports (1888) p. 149 hrrmon, Be Be 1890 Investigations of lilk Tests Illinois Agr'l. Exp. Sta. m. 10 bur, lm., and Holter, 0. L. 1691 Simple Methods of Determining lilk Fat Pennsylvania Agr'l. m. Sta. 1st Annual Report, p. 172 Richmond, H. D. 1920 Dairy Chemistry Charles Griffin a. Co., Ltd., London, England, 6rd ed. rev., p. 115 Reese, Bruno 1888 Analysis of lilkt Fat Determinations Zeitschrift fur Angewandte Chemie., 701. 1, pp. 100-107 Abet. in Jour. Chan. 8001., Vol. 64, p. 1166 110506111015 Es, md Troy, Be Ce 1926 The Technical Control of Dairy Products loJonnier Bros. 00., Chicago, 111., 2nd ed., p. 67 14. 18. 16. 17. 18. 19. 801361 lob, E. 1893 Lang 1896 Estimation of the fat in Milk Ab.‘e 1n J°nre Chue 80¢1e, '01s 62, ppe 649-550 Chas O'Dtre, 'Ole 1, ’0 960 Abst. from Review by rieh.r, c. 11., and Walts, c. 0. (See 61) Is ibull 1898 Kuhn 1898 Milk ZtEe, 'Ole 27, Fe ‘06 Abst. from Review by Fisher, C. 1., and Salts, C. 0. (See 61) Milk Ztg., Vol. 27, p. 772 Abst. from Review by lojonnier, 9., and Troy, R. C. The Technical Control of Dairy Products, p. 68 Popp , It. 1905 Zeiteehrift fur Untersuchung der Nahrungsund Genussmit, Vol.7, p.772 Abst. from Review by Fisher, C. 3., and Islts, C. C. (869 51) PMs n' 1904 lilch-Ztg. , voi. 20 Abst. from Review by Fisher, 0. F., and Walts, C. 0. (See 61) 20. 21. 22. 23. 24. 69 Rohrig 1906 - --------- Amir. Zeit. Nahr. Genussn., Vol. 9, pp. 661-566 Abst. from Review by rieher, c. 7., and waite, c. 0. (See 61) Thomson 1905 -— Th. Sv. Landw. Tersuchsstat., 701. 62, pp. 687-699 Abst. from Review by Mojonnier, T., and Troy, R. C. The Technical Control of Dairy Products, p. 69 Burr, A. 1905 Saponification of rat by Amonia in the Roese-Gottlieb Method of Estimating Pat in Milk Milchw. Zentr., V01. 1, pp. 248-250 Abst. in Jour. Chem. Soci., Vol. 88, Part 2, pp. 559-660 Gordan, P. 1906 Experiments with Rohrig's Modification of the Gottlieb-Roese Apparatus Milchw. Zentr., Vol. 2, pp. 224-227 ‘b". in Jon-re Chm. 30°1e, 'Ole ’0, hrt 2, ppe 501-502 Richmond, R. D. 1914 Dairy Chemistry Charles Griffin 8: 00., Ltd., London, Mgland, 2nd ed. rev. pp. 118-119 26. 27. 28. 29. 80. 51. 7O Mojonnier, T., and Troy, H. 0. 1925 he Technical Control of Dairy Products Mojonnier Bros. 00., Chicago, 111., 2nd ed., p. 44 Mojonnier, T., and Troy, 11. 0. 1925 The Technical Control of Dairy Products Mojonnier Bros. 00., Chicago, I11., 2nd ed., p. 52 Dahlberg, A. 0. 1926 Comparison of the Roese-Cottlieb and Babcock Methods of Testing Jour. of Ass'n. of Off. Agr'l. Chem., Vol. 7, pp. 159-169 Mojonnier, T., and Troy, H. C. 1925 he Technical Control of Dairy Products Mojonnier Bros. 00., Chicago, 111., 2nd ed., p. 45 Phillips, 0. A. 1926 A Comparison of the Babcock and the Roese-Gottlieb (Mojonnier) Methods for Determination of Butterfat in Milk Journal of Dairy Science, Vol. 6, No. 6, p. 549 Hoyt, C. P. 1926 Reading the Fat Colun in the Babcock Tests for Milk Jour. of the Ass'n. of Off. Agr'l. Chem, Vol. 6, pp. 654-662 Pisher, R. 0., and Walts, C. 0. 1926 A Comparative Study of Methods for Determining the Per Cent of Pat in Dairy Products Connecticut (Storrs) Agr'l. Exp. Sta., Bul. 161 33. 65. 66. 67. 71 Dahle, C. D., Swope, I. D., and Dean, P. J. 1960 A Test for Butterfat in Condensed and Evaporated Milk Pennsylvania Agr'l. Exp. Sta. Bul. 258 Chfl.., ls Se, md Kine, F. Ge 1929 A Comparison of the Modified Babcock and the Mojonnier Methods for Butterfat in Ice Cream Journal of Dairy Science, 701. 12, No. 6, p. 476 Bird, 3. 9., and Sands, G. 0. 1960 The Effect of Lipins on the Fat Test of Buttemuilk Journal of Dairy Science, 701. 16, lo. 6, p. 456 Babcock, S. M. 1890 A New Method for the lstmtion of Pat in Milk, lspecially Adapted to Creameries and Cheese Factories Wisconsin Agr'l. Exp. Sta. Annual Reports, 701. 6 and 7, p. 98 Babcock, S. M. 1892 Notes on the Use of the Babcock Test and the Lactometer Wisconsin Agr'l. Exp. Sta. Dul. 61 Snyder, Barry 1891 Application of Dr. Babcock's Centrifugal Method to the Analysis of Milk, Ski-milk, Buttermilk, and Butter llew York (Cornell) Agr'l. Exp. Sta. Dul. 29 Patterson, 1.. 0. 1691 Comparative Tests of Machines and Methods for the Determination of Pat in Milk Mississippi Agr'l. Exp. Sta. Dul. 15, p. 6 41. 42. 72 Site, B. R. 1891 The Creamery Industry Vest Virginia Agr'l. Exp. Sta. 6rd Annual Report 1891 The Babcock Method of Determining ht in Milk Connecticut Agr'l. Exp. Sta. Annual Reports (1891) Bailey, D. B. 1919 Study of Babcock Test for Butterfat in Milk Journal of Dairy Science, 701. 2, So. 5, p. 661 Barthel, Dr. 0hr. 1910 Milk and Dairy Products Translated by Goodwin, 9., Ph. D. McMillan and Company, New York, p. 64 MoJonnier, T., and Troy, 2. C. 1926 The Technical Control of Dairy Products MoJonnier Bros. 00., Chicago, 111., 2nd ed., p. 60 MoJonnier, T., and Troy, R. C. 1925 he Technical Control of Dairy Products MoJonnier Bros. 00., Chicago, 111., 2nd ed., p. 61 Bailey, D. l. 1919 Study of Babcock Test for Butterfat in Milk Journal of Dairy Science, 701. 2, lo. 6, p. 661 4.6. 47. 49. 50. 51. 52. 75 Hortvet, Julius 1917 Report on Dairy Products (Adulteration) Jour. of lss'n. of Off. Agr'l. Chem, Vol. 8, pp. 868-267 Hoyt, C. P. 1926 Reading the rat Column in the Babcock Test for [ilk Jon:- 0: “I'ne Of Otto Agr'l. Cline, '010 6, ’Pe 3541-862 Phillips, 0. 1. 1926 A Comparison of the Babcock and the Boese-Gottlieb (HoJonnier) Hethods for Detennination of Buttertat in Iilk Journal of Dairy Science, Vol. 6, lo. 6, p. 649 “111.5038, 10 o. 1926 Couparison of the Boese-Gottlieb and Babcock Hethods of Testing Joure of “U'ne Of Offs m‘1e Ch-” '01s 7, Ppe 1.59-1" ’1'1101', Be 0., m "ltU, Ge Co 1966 A Cmparative Study of lethods for Detemining the Per Cent of ht in Dairy Products Connecticut (Storrs) Agr'l. hp. Sta. Bul. 161 Dehlberg, A. C., Hols, Geo. 1., and 'l'roy, H. C. 1926 L Coaparison of the Babcock, Gerber, and Roese-Gottlieh Methods for Determining the Percentage of Pat in Milk and Crea- Hev York (Genera) Agr'l. hp. Sta. Tech. Bul. 126 MInCr, as ’e 1916 Affect of Glynol Purdue lgr'l. hp. Sta. 25th Annual Report, p. ‘0 54. 55. 56. 57. 74 Doan, 1". J., Fields, J. D., and mgland, C. I. 1926 Comparison of Methods of Reading Cream Tests Journal of Dairy Science, Vol. 6, No. 6, p. 406 Hunziker, 0. 3., et a1. 1910 Testing Cream for Buttertat Purdue Agr'l. Exp. Sta., Bul. 145 ”it"t. 000e, ‘nd ”pl.’ '0 P0 1964 Reading the Pat in Cream Tests Journal of Dairy Science, Vol. 7, lo. 2, p. 161 Dahle, C. D., Svope, I. D., and Doan, P. J. 1960 A Test for Buttertat in Condensed and Evaporated Milk Pennsylvania Agr'l. Exp. Sta., Bul. 260 Chase, E. 8., and King, 1'. G. 1929 A Comparison of the Modified Babcock and the Mojonnier Methods for Butterfat in Ice Cream Journal of Dairy Science, Vol. 12, Ho. 6, p. 476 hurston, 1.. M., and Petersen, I. E. 1986 Dipins and Sterols as Sources of Error in the Estimation of Pat in Butter-ilk by Ether Extraction Methods Journal of Dairy Science, Vol. 11, lo. 4, p. 270 m, 0e 'e 1980 The Effect of Lecithin in Dairy Products upon Butterfat Determinations Journal of Dairy Science, Vol. 11, No. 6, p. 429 61. 62. 65. 66. 75 Ioll, P. I. 1900 Influence of the Babcock Test Wisconsin Agr'l. hp. Sta. 7th Annual Report, p. 76 hrrington, B. H. 1900 Influence of the Babcock Teet-II. Influence of Tuperature on Tests of Skinnilk by the Babcock Test Iisconsin Agr'l. hp. Sta. Ilth Annual Report, p. 81 Bailey, D. I. 1919 Study of Babcock Test for Dutterfat in Milk Journal of Dairy Science, Vol. g, No. 6, p. 661 I’lun, De 3. 1926 Babcock Test Studies California Agr'l. Exp. Sta. Annual Reports (1926) pp. 66-64 Balverson, J. 0. 1916 The Modified Babcock Test for Pat in Sweetened Dairy Products- Ice Cream Journal of Industrial and Engineering Chemistry, Vol. 6, p. 406 Hunsiker, 0. 1., et a1. 1910 Testing Cross: for Butterfat Purdue m'le he 3“., Me 145, p. 568 Bailey, D. I. 1919 am, of Babcock Test for Butterfat in Milk Journal of Dairy Science, Vol. 2, lo. 6, p. 660 67. 68. 69. 70. 71. 72. 1950 76 Official and Tentative methods of'Analysis of’the Association of Official Agricultural Chemists “I'll. of Otto ‘81-'10 Chme at WSShington, De Ce, 5rd Ode, pp. 217-219 Hunsikor, 0. F. 1918 Specifications and Directions for Testing Milk and Cream.f0r Butterfat JOurnal of Dairy Science, Vol. 1, No. 1, p. 68 Hunlik3r, Os Fe 1922 1929 Specifications and Directions fOr Testing Milk and Cream for Butterfat Journal of Dairy Science, Vol. 5, No. 2, p. 178 Act No. 280, Public Acts, 1907 Lass Relating to the Department of Agriculture (Michigan) Testing of Glass Volumetric Apparatus U. 8. Bureau of Standards Circular 9, 8th ed. Mbjonnier, T., and Troy, H. C. 1925 The Tbohnical Control of Dairy Products Mbjonnier Bros. Co., Chicago, 111., 2nd ed., pp. 108-109 no ‘ on .4 USE 0 am 3‘3?" ‘ d "J ”1 If! ‘7 2 1’37 HIGAN STATE UNIVERSITY LIBRAR IE ILL ILLLL ILL II