EVALUATION OF GMECTNE METHODS (13*? MEASURENG DIFFERENCES EN TEXTURE OF FREEZE-DRIED POULTRY MEAT Ti‘cesls for flu Devon of M. S. MICHIGAN STATE UNIVERSITY Linda. May Beie 1965 THESIS LIBRARY Michigan State University ROGM USE ONLY EVALUATION OF OBJECTIVE METHODS OF MEASURING DIFFERENCES IN TEXTURE OF FREEZE-DRIED POULTRY MEAT by Linda May Sale A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Foods and Nutrition I965 ABSTRACT EVALUATION OF OBJECTIVE METHODS OF MEASURING DIFFERENCES IN TEXTURE OF FREEZE-DRIED POULTRY MEAT by Linda May Bele Studies show mechanical devices are effective in measuring textural characteristic differences in chicken freeze dried after cooking, which are detectable by sensory evaluation. Freeze-dried chicken is readily distinguishable from a frozen comparison. Freezing method (-l00 and -320°F.) has little or no effect of practical importance on poultry meat to be freeze dried. Poultry meat cooked before freeze drying has less desirable textural characteristics than meat cooked after freeze drying. Breast meat is more adversely affected by freeze drying than thigh meat. ACKNOWLEDGMENTS The author wishes to express her sincere gratitude to Dr. Hans Lineweaver, Chief of Poultry Laboratory, for making this Opportunity to undertake thesis research at Western Regional Research Laboratory possible. The author wishes to express a special debt of gratitude to Dr. Helen Hanson Palmer for her understanding, guidance, and encouragement during the course of research for this degree and during the preparation of this thesis. Also thanks are extended to Alvin Klose, Robert Sayre and personneT of the Poultry Laboratory for their assistance, interest, and helpful suggestions. The author owes thanks to the Graduate Committee of the College of Home Economics for approving this opportunity to complete thesis researchat Western Regional Research Laboratory, to Dr. Theodore F. Irmiter, and to members of the guidance committee. TABLE VI. VII. VIII. XI. LIST OF TABLES Ability of Panel to Distinguish Freeze- Dried from Frozen Poultry Meat . Summary of Objective Measurement of Frozen and Freeze-Dried Meat. Summary of Significant Differences Between Frozen and Freeze-Dried Poultry Meat . Increase in Shear Values of Meat Frozen or Freeze Dried After Cooking . Yields of Chicken Meat Before and After Cooking. . . . . . . . . . . . Average Percent Moisture of Chicken Meat . Summary of Water- -Holding Capacity of Frozen and Freeze- Dried Meat. . . . Ability of Panel to Distinguish Freeze-Dried Poultry Meat Frozen at -IOF . and -320°F. Summary of Objective Measurement of Freeze- Dried Chicken Frozen at -l0°F. and -3200 F. Summary of Water-Holding Capacity of Frgeze- Dried Chicken Frozen at -IO°F. and -320F Summary of Objective Measurement of Breast and Thigh Meat Freeze Dried Before and After Cooking. . . . . . . . . . . . . Page 27 3O 32 3A 35 36 39 45 A6 48 SI EXHIBIT O\U‘I.PUJN LIST OF EXHIBITS Diagram of Experimental Design. Score Sheet - Triangle Test . Typical Shear Force Curves Instron Test Cell Percentage Rehydration Formula. Photomicrographs of Processed Chicken Breast Meat . Page IS 6] 62 6A 65 66 TABLE OF CONTENTS ACKNOWLEDGMENTS . LIST OF TABLES LIST OF EXHIBITST . . . . . . . ..... INTRODUCTION REVIEW OF LITERATURE Texture. Sensory Evaluation Mechanical Devices. Kramer Shear Press Instron . Succulometer Grau-Hamm Press Freeze Dehydration Freezing Methods PROCEDURE . Sample Processing Freeze Drying. Sample Preparation and Rehydration Sensory Evaluation . Objective Evaluation . wwmprwww N—d-u-l-d—l—l—l OCDVOU‘IU‘IUJG) TABLE OF CONTENTS CON"T. Page Kramer Shear Press. . . . . . . . . . . 20 Instron . . . . . . . . . . . . . . . . 22 Succulometer. . . . . . . . . . . . . . 23 Grau-Hamm Press . . . . . . . . . . . . 23 Moisture Determination . . . . . . . . 24 Photomicrographs . . . . . . . . . . . 24 Statistical Analysis . . . . . . . . . . . . 25 RESULTS AND DISCUSSION . . . . . . . . . . . . . 26 Correlation Between Taste Panel Judgments and Results of Objective Tests of Frozen and Freeze-Dried Meat. . . . . . 26 Panel Tests . . . . . . . . . . . . . . 26 Texture. . . . . . . . . . . . . . 28 Juiciness . . . . . . . . . . . . 28 Flavor . . . . . . . . . . . . . . 29 Shear Resistance. . . . . . . . . . . . 29 Yield . . . . . . . . . . . . . . . . . 33 Moisture Content. . . . . . . . . . . . 33 Water-Holding Capacity . . . . . . . . 37 Photomicrographs. . . . . . . . . . . . 40 Effect of Freezing Method on .Quality of Freeze- Dried Poultry. . . . . . . . 43 Panel Tests . . . . . . . . . . . . . . 43 TABLE OF CONTENTS CON'T. Shear Resistance Moisture Content Water-Holding Capacity. Effect of Freeze Drying on Breast and Thigh Meat. . . Panel Tests Shear Resistance Moisture Content. WaternHolding Capacity. SUMMARY AND CONCLUSIONS LITERATURE CITED. APPENDIX. Page 44 47 47 49 49 50 50 52 53 56 57 INTRODUCTION Freeze dehydration has established itself as a new method of food preservation. As a growing segment of the multi-billion dollar food industry, the value of freeze-dried products is expected to exceed one-half billion dollars by I970. Freeze-dried foods will replace certain frozen, canned or dried foods, when they fill a specific need or their unique qualities give them a particular advantage, but they will not affect the need for the other food processing methods. Even though freeze-dried foods are of higher quality than those dried by other methods, freeze-dried foods are seldom equal to fresh or frozen products in quality. For continued growth and deveIOpment, providing products of better functional and sensory qualities, and lowering costs and processing times, much research still needs to be undertaken. At the present, freeze-dried poultry meat Is not uniform in rehydration, juiciness, and flavor character- istics. To expidite the deveIOpment of improved freeze- dried poultry products, means are needed to measure the effect of processing variables on meat quality. In addition, the performance of taste panels in judging food characteristics is often inconsistent and testing foods by panels is usually time consuming and expensive. The purpose of this investigation was to determine (I) the relationship between objective and sensory methods of measuring texture, tenderness, and juiciness to find out whether objective methods for these determinations could be used in place of sensory methods to eliminate the inconsistencies, cost and time required for taste panel testing, and'(2) the effect of the method of preparation, cooking before and after freezing and freeze drying, and freezing temperatures, -l0°F. and ~3200F., on the quality of freeze-dried chicken breast and thigh meat. REVIEW OF LITERATURE Texture Sensory Evaluation Texture is one of the least well defined of the many sensory food attributes. Most of the study of texture has dealt with a specific textural character- istic in a specific food. Szczesniak (l963a) reviewed the definitions of texture and developed a system of nomenclature. Texture was considered as a composite of the structural elements of food and the way in which these elements react with physiological senses. Textural characteristics were classified into mechanical and geometrical qualities as well as those related to the moisture and fat content of the product. Mechanical characteristics, shown by reaction of food in the mouth, were divided into the primary parameters of hardness, cohesiveness, viscosity, elasticity, and adhesiveness, and into the secondary parameters of brittleness, chewiness, and gumminess. Geometrical characteristics, reflected mainly in appearance of food, were divided into two groups: those relating to size and shape of the particles, and those relating to shape and orientation of the particles. Moisture and fat content, with secondary parameters of oiliness and greasiness, are considered the mouthfeel qualities. This classification of textural characteristics has lent itself to use with both objective and subjective methods of texture characterization (Brandt t l., l963; Szczesniak t al., 1963). Mechanical Devices Numerous mechanical devices have been devel0ped to measure the textural characteristics of food. Szczesniak (l963b0 reviewed examples of typical devices for measuring texture. Kramer Shear Press Kramer 2; al., (l95l) deveIOped a multipurpose shear press for evaluation of the physical characteristics of foods. Improvements in the Kramer shear press (Kramer and Backinger, I959) and addition of an automatic recorder (Decker _£_§l., I957) extended the usefulness of the shear press. This instrument uses hydraulic pressure to force a series of metal blades through the food product held in a box (standard cell) having a number of slots which match the blades in size and spacing. Pressures resulting from the passage of the blades through the food product are transmitted through a proving ring and transducer to an automatic recording device, thereby producing a permanent record of force required to shear the product. From this graphic record it is possible to calculate the maximum force reading at one point, and a time-force curve (total work) for the entire stroke. Good correlation between the Kramer shear press and tenderness judgments of competent sensory evaluation panels have been established for poultry products. Cameron and Ryan (I955) reported a correlation coefficient of 0.975 when Kramer shear tenderness values of broiler meat were compared with sensory ratings. Shannon _£._I., (I957) reported a correlation of 0.86 between Kramer shear tenderness values and a sensory panel using the ”chew scoreII on cooked breast muscle of chicken. Sosebee ._E._l., (I964) stated there was little discrepancy between taste panel evaluations and Kramer shear press values for tenderness of ffeeze-dried chicken treated with various enzyme solutions. However, no data on correlation was included. Wells t al., (I962) indicated the shear press measure- ments have some limitations as an objective method of measuring the tenderness of freeze-dried poultry meat. Shear press measurements contradicted taste panel findings on tenderness of freeze-dried chicken breast meat as affected by age of hens and pre~slaughter feeding of several different ions. When cooked samples prepared from frozen chicken were evaluated by the taste panel and Kramer shear, agreement between the two methods of evaluation was close. 'Kamstra and Saffle (I959) reported results obtained from the Kramer shear were not as useful as those determined by a taste panel because of the wide variation between samples and the inherent limitations of the recorder attachment. Because of the particular range of the recorder selected (i.e. 300, l000, 3000) many samples fell below the base line (0) or gave readings above the maximum limit (l00) of the recorder. Instron The Instron incorporates a highly sensitive elec- tronic weighing system with load cells employing bonded- wire strain gages for detecting and recording the tensile or compression load applied to the sample under test. The moving crosshead, to which the plunger jaw is attached, is Operated by two vertical drive screws from a synchronous motor driving through a unique gear box that provides a considerable flexibility of control over the motion of this plunger. The chart of the recorder is driven synchronously at a wide variety of Speed ratios with respect to the crosshead, thus enabling measurements of sample extension to be made with a large choice of magnification factors. Recording of the puncturing and shearing force is similar to the Kramer shear and appro- prirate total force and work curve areas can be calculated. The Instron has not been used as a means of evaluating poultry texture. However, Kulwich 2; al., (I963) mounted a slice-tenderness evaluator for pork in an Instron and used it to make a continuous recording of the force curve for 0.2” thick slices of cooked pork. Succulometer The Kramer shear press can be equipped with a Succulometer cell, which facilitates measurement of the volume of liquid expressed from a known weight of material under specified conditions of pressure and time. The shear press with succulometer cell is Operated in the same manner as with the standard shear cell. Literature on the use of the Succulometer cell of the Kramer shear press is limited. Grau-Hamm Press Szczesniak et al., (I963) observed rehydrated freeze- dried beef releases most of its moisture quickly (on the first two chews). The ability of meat to hold its own or added water during application of any force (pressing, heating, grinding, chewing) has been called ”water- holding capacity” and must be defined in terms of the method of measurement. The water released is called I'Ioose water” and the water held by the tissues, llbound water.” Thus, ”water-holding capacity” of meat can be expressed as the amount of loose water related to the total content of moisture in muscle, or the amount of “bound water” related to muscle or muscle protein (Hamm, I960). A combination method of the press technique and filter paper technique has been deveIOped by Grau and Hamm and reported by Hamm (I960) for determining the ”water-holding capacity” of meat. Freeze Dehydration The basic principles and ramifications of freeze dehydration have been thoroughly discussed by Flosdorf (I949), Gane (I954), and Harper and Tappel (I957). Fundamentally, freeze dehydration (lyOphilization, drying by sublimation) involves the removal of moisture from a frozen product (raw or cooked) under conditions of high vacuum and controlled temperature. The water must sublime to get a satisfactory freeze-dried product (Bird, I964; Flosdorf, I949; Gane, I954; Ziemba, I960). Some of the advantages of freezing and dehydrating are combined in the freeze dehydration process. Freeze— dried foods are of higher quality than foods dried by other methods. They do not change appreciably in size, shape, or color; they retain nutrients and flavor; and they rehydrate more easily and quickly. Dehydrated products can be stored at room temperature, and the reduced weight will minimize shipping and handling costs. Freeze dehydration, however, has drawbacks. In comparison with canned and frozen foods, processing costs are high. Lengthy processing time and monitoring are required. The size of portion that can be freeze dried is limited to pieces not more than 3/4” thick. Undesirable prOperties that have been encountered include dry friable texture, toughness, and the appearance of the dry food may be unappetizing. Expensive packaging is needed to keep out light, moisture, and oxygen which would impair the storage life of the dried food. Seltzer (l96l) mentioned factors to consider for improved tenderness of chicken which is to be freeze dried. Selection of the poultry as to type of bird, age l0 and feeding and the effect of processing techniques such assnalding, plucking and chilling were discussed. The preparation of the food product to be freeze dried (both raw and cooked) is important as is the control of the processes of freezing and dehydrating. The food is quick-frozen, either by one of therecognized methods (air-blast, liquid immersion) or in the drier by evaporation under vacuum. After freezing, the loaded trays are placed in the freeze drier and the air is evacuated from the chamber. Products are dried in this chamber at very low pressure (below I mm mercury) by controlled input of heat. Processing is controlled to prevent the product from thawing. Drying time, usually l0-20 hours, depends on the type of product, its moisture content, its thickness, the type of dehydrating equipment and operating techniques used. It is imperative for the best keeping qualities in most foods that the moTSture content be reduced to low levels of 0.5 to 2.0%. After the food has been dried, the.heat is turned off and the chamber is back flushed with nitrogen to retard product oxidation. (The product is removed from the chamber and is ready for packaging under vacuum or in nitrogen (Flosdorf, I949; Gane, I954; Harper and Tappel, I957; Ziemba, I957). ll Wang 2331., (1954) and Yao_£__l_., (I956) Indicated freeze dehydration is the mildest method known for drying meats but even this process causes undesirable changes of meat quality. Research on preparation, prOperties, histological, histochemical, and chemical characteristics of freeze-dried meat have been reported by Auerback gt il:2 (I954), Doty _e_t_gl_., (I953), Tappel _£§L, (I955, I957). Van Arsdel and COpley (I964), and Wang gt _l., (I953, I954). The rehydration level of freeze-dried beef has generally been above 80% of the original water content. Auerbach ._£ _l,, (I954) found freeze-dried beef rehydrated-to 80-90%. Harper and Tappel (I957) stated freshly-prepared freeze-dried beef rehydrated to 80-l00%. Tappel gt 31., (I955) reported l-inch pieces of Biceps femoris of beef attained an 80-90% level of rehydration. Wang 2£.§lo: (I954) found the structural pattern of frozen dried muscle tissue to be a function of rate of freezing which is determined by the freezing temperature used. As freezing rate decreased with rising temperature, freezing changed from an intracellular to an intercellular pattern. However, all samples, regardless of the freezing temperature, re- hydrated to 85-90% of the original moisture content, and the muscle fibers returned to 89-98% of their original l2 diameter. Suden _£._l., (I964) reported freeze-dried pork rehydrated to 73.8%, a lower level than reported for beef. Tappel _£y_l., (I957) reported rehydration in 2l2°F. water at atmospheric pressure was poor. Rehydration levels for freeze-dried poultry have been low. Pre-cooked freeze-dried poultry rehydrated to 68% when held at atmospheric pressure for IS minutes and to 63% when held under vacuum for 2 minutes. Yao gt al., (I956) also reported lower rehydration levels of 57-74% for pre-cooked freeze-dried poultry. PrOperties, acceptability, and stability of freeze- dried meat have been studied. Tappel gt al., (I955) reported freeze dehydration appears to be the only practical method for production of high quality serving size pieces of meat (steaks, chops, stew meat), fish, and poultry. In sensory evaluations the freeze-dried food could usually be differentiated from the frozen control and usually had a drier texture. Yao _£,_l., (I956) rehydrated cooked, freeze-dried chicken meat satisfactorily; its sensory quality compared favorably with that of controls which had not been freeze dried. Brooks (I958), Harper and Tappel (I957), and Tappel et I., (I955) reported reconstituted freeze-dried meat was tougher and had a drier texture than frozen control meat. I3 I., (I959) reported that in freeze-dried meat, Hamdy g; the decrease of tenderness and juiciness Of the rehydrated samples apparently is caused by a loss of the water- holding capacity of the muscle proteins. Both Harper and Tappel (I957) and Hamdy E£.§l-: (I959) pointed out the dry texture and the decrease of meat hydration is one of the principal problems in freeze-dried meat. Freezing Methods Commercial use of cold-air blast and liquid immersion freezing (i.e. sodium chloride, liquid nitrogen, propylene- glycol) have made possible very rapid freezing of meat. Both methods are being used with poultry meat (Marion and Stadelman, I958). Deatherage and Hamm (I960) showed that quick freezing of muscle tissue does not decrease the hydration of muscle nor cause protein denaturation. They concluded the influence of freeze dehydration on the water-holding capacity of meat is not due to the freezing process but to the process of dehydration. Quick freezing (~550C.) caused a very small but significant increase of the water-holding capacity of meat, probably by a mechanical loosening of tissue structure due to the formation of tiny ice crystals l4 inside the cells. Slow freezing (-l50C.) caused a significantly small decrease of the water-holding capacity of meat, probably due to some destruction of protein structure by formation of large ice crystals between the cells. Marion and Stadelman (I958) found the method of freezing (liquid at I0°F.; plate at 00F., and moving air at -l5°F.) exerted no significant effect on percentage drip, percentage total cooking loss, and tenderness of breast muscle of turkey. Wang t I., (I954) found rehydration does not depend on the freezing temperature. PROCEDURE Sample Processing Breast.and thigh meat from nine-week-old fryer chickens, both male and female, and chilled 24 hours was obtained from a commercial source. The meat was divided into two lots, half deboned raw and the other half cooked in a steamer]; the breast meat was cooked l5 minutes and the thigh meat cooked 20 minutes and then deboned. All skin and subcutaneous fat was removed from the muscles. All deboned meat was held on trays overnight at 20°F. (-6.7°C.) to make it firm enough for dicing. The meat was diced into l/2” x l/2ll x 5/8“ pieces with a Urschell Dicer2 and weighed into polyetheylene bags. Half of each lot was rapidly frozen in liquid nitrogen at -320°F. (-I90.6°C.) and held at -30°F. (-34.4OC.); the remaining half was slowly frozen in an air-blast freezer at -l0°F. (-23.3OC.) and held ' at -l00F. Testing was completed within 2-l/2 months to keep storage deterioration at a minimum. l ”Steamcraft” steam cooker, Cleveland Range Co., Cleveland, Ohio, direct steam-two compartment model. 2 Model #F, Urschell Labs., Inc., Valparaiso, Ind. l5 Freeze Drying Half of the frozen breast and thigh meat needed each I during the 20-24 hours day was dried in a freeze drier immediately prior to use. Each freeze-dried sample was compared with a control sample held in frozen storage. Throughout the freeze drying operation the condenser was maintained at -60°F. (-5l.I°C.) the chamber pressure at 25-50 microns and the shelf heat was automatically shut off when the product temperature reached 50F. (-l5°C.). Because some of the diced meat stuck together and froze in large clumps (4ml/2”x 3-l/2” x 2-l/2” or smaller), some raw samples required longer than 24 hours to dry. Meat Breast or Thigh Debone ‘76:? Raw Debone, I Freeze -320°F. Freeze -l0°F. Freeze -I0°F. Freeze L3200F. Stfire -30fF.‘ Stqre -l09F. Store -l0°F. Store -30°F. l Freeze Store Freeze Store Freeze Store lFreeze Store Dry, Frozen Dry Frozen Dry Frozen Dry ' Frozen Exhibit I. Diagram of Experimental Design I RePP Sublimator, RePP Industries Incorporated, The VirTis Co., Gardiner, N.Y., model #ll-IS. I7 Sample Preparation and Rehydration The frozen meat was thawed and the thawed or dried meat was cooked or rehydrated according to the following plan: raw, thawed ................. cook cooked, thawed meat ......... heat raw, freeze—dried meat ...... rehydrate, cook cooked, freeze-dried meat...rehydrate Based on pilot studies varying rehydration time and temperature of water for rehydration, the freeze-dried samples were rehydrated in 6-l/3 parts by weight of distilled water for 20 minutes, with stirring at 5 minute intervals. The samples were drained, reweighed and rehydration ratios calculated. Rehydration ratios of freeze-dried meat were not affected by the length of time of reconstitution. The temperature of the water for rehydration was 77°F. (25°C.) for raw meat since it was found that higher temperatures resulted in ”case-hardening” and decreased water-absorbing ability. For cooked meat samples the temperature of the water for rehydration was 2I2°F. (l00°C.). The cooked, thawed meat was just covered with boiling water and held for 5 minutes, which was found adequate to bring the meat to serving temperature, before draining and reweighing. The raw rehydrated or thawed samples were cooked in the steamer l8 for 5 minutes, which was adequate to cook the raw samples. Following of the above mentioned conditions yielded the most complete and consistant rehydration and cooking of the samples. Samples for the panel were held in covered dishes in a water bath l26°F. (52°C.) for a half-hour to insure a uniform serving temperature. Sensory Evaluation Eight persons from the Poultry laboratory who had previous experience In judging texture and tenderness of poultry served as the panel. Panel members were blind- folded to eliminate visual identification of samples due to differences in color and size of particles after rehydrating and/or cooking. Each day two triangle tests were presented to the panel. The panelists removed the blindfold between the tests and indicated the odd sample on a score sheet (Exhibit 2, Appendix). They also indicated whether the selection was based on flavor, texture or juiciness. The triangle test, supplemented by a record of the basis for the judges' selections of odd samples, was selected because it best fulfilled the objectives of this l9 experiment. It was felt the side-by-side comparison used here was more sensitive in detecting small differences than in the single-sample test such as the hedonic or rating scale. For sensory evaluation, panel comparisons were made according to the following plan of processing variables: Frozen vs. Freeze-dried meat Breast Meat Raw, frozen at -l0°F. Raw, frozen at -320°F. Cooked, frozen at -l0°F. Cooked, frozen at -320°F. Thigh Meat Same as for Breast meat Freezing at -l0°F. vs. at -320°F. before freeze-drying Raw breast meat Cooked breast meat Raw thigh meat Cooked thigh meat Freeze-dried breast meat vs. Freeze-dried thigh meat Cooked, frozen at -l0°F. Cooked, frozen at -320°F. Each triangle test was randomized independently and replicated four times. 20 Objective Evaluation Kramer Shear Press I A recording Kramer shear press equipped with an automatic recorder2 was used for measuring shear resistance. Preliminary trials with sample weights of 30-65 grams and l00 grams gave shear forces which were high. As the sample size increased, the shear force decreased. It was found that samples of l20-l40 grams (wet weight) gave moSt consistant results, therefore sample weights in this range were used in the experiment. These results are in agree- ment with results of Cameron and Ryan (I955) that the sample size greatly influences the tenderness measurement with the Kramer shear press. The larger sample is more representative of the lot and shear force is more accurate in terms of the true value of the test lot. The faster the speed by which the blade descended through the sample, the higher was the peak reading. For example, two 66 gram samples, on 3,000 lb. recorder range, give shear force values of l4.8 lb./g. with a l5 second downstroke speed and l2.2 lb./g. with a 30 second down- stroke speed. Repeated shearings on the same sample give lower readings (i.e. first pass through: l2.l lb./g.; second IKSP, model SP-l2 Imp. Varian Strip Chart~Recorder, model G llA-Fl. 2l pass through: l0.5 lb./g.; and third pass through: 9.9 Ib./g.). Using an average of the successive pass throughs as the shear force value is not a true indication of the texture of the test sample. Wells _£‘§l., (I962) reported that each sample was sheared three times while other investigators report shearing the sample once. Samples were poured into the standard cell with random orientation of the meat fibers with respect to the slots of the shear press. In certain cases it may be necessary to orient the sample pieces in the test cell. Meat samples cut with or against the fiber grain will yield different values depending on orientation in the test cell. However, orientation of diced chicken is impractical, and this product did not tend to pack or form cavities. From this preliminary work using different recorder ranges and downstroke shear speeds on samples of l20-l40 grams a calibration of 3,000 lb. full range scale, a 3,000 lb. proving ring, and I5 second downstroke speed was maintained for all tests. The shear force was recorded and then divided by the weight of the sample to obtain the force per gram. This value was used as the mechanical index of shear resistance for the samples tested. Representative 22 curves of shear force for the different test samples are presented in the Appendix (Exhibit 3). The conditions used for this test were based on information supplied with the equipment (Anon.) and on the preliminary tests with diced chicken. Sample size was limited] however, for practical considerations. Use Of a weighed sample rather than a full cell improved The number of replications on some samples precision. was limited because losses in cooking and on rehydration were greater than anticipated. Instron A standard test cell for holding the meat and a plunger adapted from the Kramer shear test cell, were designed, constructed and mounted on an Instron]. This instrument makes a continuous recording of the force- penetnation curve. The plunger consisted of 20 uniformly spaced metal dowels which were forced down through the sample in a cell having holes Spaced to match the metal dowels (Exhibit 4, Appendix). 1 Model TM, Instron Engineering Corp., Canton, Mass. 23 Because of the small capacity of this cell, samples of IO grams wet weight were randomly placed in the cell and sheared. Initial studies indicated that a calibration of 200 lb. full scale, 5 lb. full load, and downstroke speed of 2 inches per second would be most suitable. Two samples of each variable were sheared once. Calculation of shear force was the same as for the Kramer shear press. Succulometer Expressible liquid was determined in the succulometer cell supplied with the Kramer shear press. A 70 gram sample, wet weight, was placed randomly in the cell. A standard calibration of 3,000 lb. full scale, 3,000 lb. proving ring, and downstrokespeed of 30 seconds was used. The full force was maintained on the sample for 30 seconds and liquid expressed through the spout in the cell was collected in a graduated cylinder. Expressible liquid was calculated as the percent of the weight of liquid expressed from a known weight of material, under established conditions of pressure and time. Grau-Hamm Press In the method of Grau and Hamm 300 mg of meat tissue was placed on a piece of filter paper and mounted between two plexiglass plates which were subjected to pressure. 24 The pressure on the plates was exerted by turning down two hand screws. The pressure was applied to the plates for five minutes. The meat tissue was pressed to a thin round film and the eXpressed juice was absorbed by the filter paper. The area of the ring of expressed juice absorbed by the filter paper is prOportional to the amount of loose water. Using a planimeter the areas of the inner meat disc and outer annular ring of moisture were determined. The |'water-holding capacity“ was expressed as a ratio of the area of the outer circle to that of the inner circle. Preliminary experiments indicated that best results were obtained in this work when 300 mg of meat tissues were pressed at l,000 lbs. for 5 minutes. These modified conditions were used for the remainder of this experiment. Moisture Determination The moisture content of the frozen, freeze dried, rehydrated and cooked meat samples was determined by the vacuum oven method (AOAC - 22.3). Samples were weighed into aluminum dishes and placed in a vacuum oven, maintained at l97.6°F. (92°C.) and l5-20 mm mercury for 5 hours. Photomicrographs Photomicrographs were made to see if any differences 25 in the structure of the meat were evident and if any differences noted might be related to observations on texture and/or water-holding capacity. Wang gt al., (I954) observed differences in the structure of freeze- dried meat processed at different temperatures. Longitudinal section views were made. To prepare specimens for photography the freeze-dried samples were first reconstituted. Both the control and freeze-dried samples were frozen in liquid nitrogen (-320°F.) and sliced on a microtome. The photomicrographs were made with a magnification of 500X. Statistical Analysis Data from the Kramer shear, Instron, SuccuTometer, and Grau-Hamm press were subject to analysis of variance (Guenther, I964) using a one-way classification. Corre- lations were calculated between the Kramer shear versus Instron for frozen breast, freeze-dried breast, frozen thigh, and freeze-dried thigh. RESULTS AND DISCUSSION Correlation Between Taste Panel Judgments and Results of Objective Tests of Frozen and Freeze-Dried Meat Panel Tests The taste panel was able to distinguish (Table I) between frozen and freeze-dried meat under all conditions tested (breast or thigh meat, frozen at -l0°F. or -320°F., frozen before and after cooking). Differences were very highly significant (pz:0.00l) for all comparisons, except for thigh meat frozen at -l0°F. before cooking, which was significant at the p<:0.0l level. The taste panel indicated the frozen samples had better sensory prOperties than the freeze-dried samples; texture and juiciness were Usually the basis for distinguishing between the frozen and freeze- dried meat. This is in agreement with results reported by Brooks (I958) and Tappel et al., (I955, I957) that reconstituted freeze-dried meat and poultry was tougher and had a drier texture than the control meat. In addition, a flavor difference was noted by 2/3 of the judges between frozen and freeze-dried thigh meat frozen at -320°F. before cooking. 26 27 Table I. Ability of Panel to Distinguish Freeze-Dried from Frozen Poultry Meat Type of Freezing Triangle Testa Meat Temp. b (0F.) No. of Correct Correct Judgments 'Judgments (%) Frozen and Freeze Dried Before Cooking Breast -l0° 29 9l*** -3ZO° 27 84*** Thigh -I0° I8 56** -320° 28 88*** Frozen and Freeze Dried After Cooking Breast -IO0 27 84*** -3200 27 84*** Thigh -l0° 32 l00*** -320° 31 97*** a 8 judges, 4 replications of each test b **, *** p<:0.0I and 0.00l, respectively 28 Texture: The texture of breast meat frozen before cooking was described by the panel as more cohesive, firm, tender, crumbly, and better than the texture of the meat freeze dried before cooking, which was generally described as hard and slightly more tough. Thigh meat frozen before cooking was generally described as tender, firm, and good or outstanding compared to the meat freeze dried before cooking, variously described as tough or tender, stringy, and slightly more rubbery. Texture of meat frozen after cooking was usually described as softer, more tender, and better than the texture of meat freeze dried after cooking, which was described as dry, grainy, stringy, rubbery, tough, and hard. Juiciness: Breast meat frozen before cooking was generally described as more juicy and having suStained moisture release during chewing compared with the meat freeze dried before cooking, described as having more rapid moisture release and being soggy, watery, mealy, wet or dry (a conflict probably based on the presence of loosely held water initially and its rapid release on chewing). Similar comments were made about the thigh meat frozen or freeze dried before cooking. 29 A similar difference in juiciness was found between the samples frozen or freeze dried after cooking. The frozen samples were generally described as more juicy and the freeze-dried samples are more dry and as having more rapid water release. Flavor: The flavor of the breast meat frozen before cooking was described as good to superior compared to the meat freeze dried before cooking, described as flavorless, flat, bland, off, stale, and watery. Thigh meat frozen before cooking had typical, desirable chicken flavor compared to the meat freeze dried before cooking, which was described as slightly off or rancid, cardboard, bland, and having less chicken flavor. However, since approximately equal numbers of favorable and adverse flavor comments were made on chicken meat frozen or freeze dried after cooking, it was apparent that factors other than flavor were primarily responsible for the ease with which frozen and freeze-dried samples were differentiated. Shear Resistance The shear resistance of the freeze-dried meat was consistently greater than that of the frozen meat (Table II). For all comparisons of meat frozen after cooking, the O 3 .>_O>_uomam6c ._oo.o new ._o.o .mo.ou.d eee .ee .e O_OEMm mo Encm LOO OOLOL mo .mp4 m 1.! kkkm.__ m kw.m_ m kkm.o_ m hkm.¢_ m po_co m.m a m.m_ : m.: m m.m m CONOLG oomm- poxoou «%%0.N_ m m.m_ m ¥%¥0.__ N «%¥0.m_ m U®_Lo N.m : o.N_ a 0.: : o.m : CONoLm oo_- poxooQ m.m m m.m_ m m.: N «km.m m vm_co m.m J N.N_ : m.m m m.o m CONOLD oonI 3mm km.m m «o.m_ m _.J m m.m m Um_co m.o : m.o_ J n.m : 0.x J cowocu 00—- 3mm em\e_a ea\e_v Am\e_v fld\e_c mm_aEmm mO_OEmm mo_aEmm mO_aEmm mOoLOm mo .02 mOOLOu mo .02 OOOLOm mo .02 mOoLou mo .02 em_ee emmdem em_ee emneem mc_>co co coLumc_ Loamcx oo_co A.uov mc_N66cu Lo .QEOP OLOLOm new: ucoencumc_ CONOLG mc_NmOLm ucoEumOch 6mm: pm_cm-mwomcu 6cm CONOLG mo ucoEOLJmmoz o>_uo0mpo mo >cmEE3m .__ p.6mp 3l difference between Kramer shear values of frozen and freeze- dried meat was significant at pz:0.0l or p<:0.00I level. Differences for meat frozen before cooking were not signi- ficant except for the breast meat frozen at -320°F. For all comparisons of meat frozen after cooking, the difference between Instron shear values of frozen-and freeze-dried meat was significant (p<:0.05 or £om po_co omxoou oeumcp>zom po_co p p p p p omxooo 3mm poxoou .m U a U .QEWW ummz UO_LQIONOOLm mcowoLm mc_NOOcu mo OO>H me_xoou tdaea een decade and: edxe_ea to ae_d_> .> d_ane 36 .00.J Ou m.~ .mm_aEmm J "mos_m> :0_£p O O a o .mm.N Ou _.N .mm_aEmm J “mo:_m> ;m_zh . .0 0.0 Ou 0.0 .mm_aEmm N. mucmmchOc m:_m> Lommfi “.00.0 Ou 0.0 .mm_QEmm J ucmmmcaOc mm:_m> ummOcmm mm.0 Op 0.0 .mm_aEmm N_I0_ mucOmOcamc O:_m> comm: 0_J~ Ou ~._ .mm_aEmm 0.1m. mucmm0cawc O:_m> sommm .00.0 0» 0.0 .mm_aEmm 0_-m mOCOmmLaOL O:_m> Lomm 00.0 On 0.J .mm_aEmm 0IJ ucmmmcamc mo:_m> ummOcmw q00._ ob J._ .mm_aEmm 0_Im mucmmOcamc m:_m> 50mm .m0.0 O» 0.0 .mO_aEmm 0_Im mucmmmcamc O:_m> Lommw mm.~ Op 0.. .mm_aEmm 0_-N— mucmmchOL O:_m> Lommn >czoLoE EE 0N-0_ .Umumc_ammicmum3 .mcso; 0 ..0ON0 um co>0m m._0 N.00 0.N 0.00 0.00 0.00 _._m _.N m._m oommI _.N0 0.50 m._ 0.00 0.00 m._0 0.0m 0.N 0.0m 00—- £m_;h n.00 0.0m _.m 0.00 _.MN m.n0 0.xm 0.0 0.0m oowm- m.me m.om m.~ m._m m.00 m.00 a.MN _.N _.mm 00.. emndtm Ax0 A00 “N0 “xv 1H&0 “xv AND A&0 Axv ahom_co .Owomcuv 00_L0 co_u _AcmNOLmV vm_c0 mmc_ mNOOLm OcmNOLL co_umc0 ovm_c0 0c_ -mcv>som . 0c_ummI mwomcm INOmcm U I>me oNOmcu INmmcm Lmuma cmum< cmum< cmumq mc_xooQ Lmum< 0000K- coum< cmuu< mc_xooo cmum< mc_xooU mLOWmm 00_c0 ONOOLL Lo CONOcu A.uov mmmmum mc_mmmooLm .QEOH ummz mc_~omcu mo 00>» mummz cmxo_;0 mo ecsum_oz “coucoa Ommco>< ._> 0.005 37 cooking than meat frozen and dehydrated after cooking (Table VI). This indicates that samples freeze dried before cooking absorb more of the rehydration liquid and have an increased water-holding capacity than samples freeze dried after cooking. The cooked meats do not absorb the water completely as the raw tissue and the water is not bound as strongly as in the raw tissue. On this basis the meat dried before cooking would have a sustained mois- ture release upon chewing, and be moist and juicy; whereas, the meat dried after cooking would have rapid moisture release upon chewing and tend to be dry and powdery. Comments by the taste panel with regard to the juiciness of the various meat samples support this. Barrie _£__l., (I964) reported dark raw meat had more moisture than light raw, but light cooked had more than dark cooked meat. In this experiment, raw thigh meat had less moisture than raw breast while cooked breast meat had more moisture than cooked thigh. Water-Holding Capacity In this study rehydration levels (see Exhibit 5, Appendix, for formula) of freeze-dried poultry ranged from 8l-97% for raw meats and 66-9l% for cooked meats, which corresponds with results of Auerback t I., (I954), 38 Tappel et al., (I955), and Wang t al., (I954) for raw beef. However, Tappel _£._l-: (I957) found precooked freeze- dried poultry to have relatively poor rehydration character- istics. Yao gt al., (I956) reported lower rehydration ratios of 57-74% for serving-size pieces (l-l/2‘I x 2” x 5/8”) of precooked poultry. - In tests with the Succulometer, more water could be pressed from the breast meat freeze dried than from the breast meat frozen. The difference was significant at p<0.0l for meat frozen at -l0°F. and at p<0.05 for the meat frozen at -320°F. Little or no measurable water could be pressed from either the frozen or freeze-dried thigh meat (Table VII). Much of the water abosrbed by the freeze- dried meat is not firmly held by the muscle structure. The water-holding capacity, as determined by the Grau- Hamm press (Table VII), of the thigh meat was lower and changed little due to the processing‘conditions (frozen at -I00F. and -3200F., frozen before and after cooking) which is in agreement with the results obtained with the Succulometer. The breast had an overall higher water- holding capacity and changed more due to the processing conditions. However, the individual effects of the processing conditions on the water-holding capacity do not agree with Succulometer results. 39 >_m>_uooam0c ._0.0 0cm 00.0va «a .3 m_oL_o cmcc_ mo mmcm Ou m_0c_o emuno mo mmcm mo o_umm n uzm_03 m_aEmm mo ucmOLOa m 0.0 0 0.J 0 0.0 m k0.m_ m vm_c0 e.m m e.m m 0.0 a m.m_ a eaNota oon- aaxaee _.m 0 N.m 0 0.0 0 «kw.mN 0 vo_c0 0.0 m 0.J m N.0 J _.N_ J CONoLu 00—- vmxoou J.m 0 0.J 0 J.0 N e...N._N N 02.5 J.0 m 0.0 m 0.0 m 0.__ m CONOLO O0Nm- 3mm J.m 0 0.0 0 0.0 N 440.0. N 0.075 0.0 m J.J m 0.0 N J.0 N CONOLL 00—- 3mm 1 I - I E 8. 0_:o_4 mm_aEmm U_:U_4 mmeEmm mu_:o_4 mm_QEmm m0_:o_4 mm_mEmm mmOLQXm mo .oz MmOLQXm 00 .oz mmoLQXm mo .oz mmOLQXu mo .oz £m_;h umwmcm ;m_zh ummmcm 0c_>c0 co mmmcm Emeismcu cmumEo_:oonm nm_c0 A.mov 0c_NmOLL co .QEOH OLOmOm 00m: mucmEscumc_ coNoLL 0c_Nomcm ucOEummcH “mo: vO_LQIONmOLu 0cm cmNoLm mo >u_omam0 0c_n_OI-Lmumz mo >LmEEDm .__> O_nmp 40 Photomicrographs A study of the photomicrographs (Exhibit 6, Appendix) indicates less damage to the muscle tissue when the poultry meat is processed uncooked than when the meat is cooked before processing. The uncooked breast meat frozen at -lO°F. (Photo A) serves as a control sample for purposes of comparison. There was very little damage to the muscle tissue in this sample. No distortion or alteration in the muscle fibers or interfibral spaces was evident. The uncooked breast meat frozen at -3200F. (Photo B) was damaged. The muscle appears to have shrunk slightly and the interfibral spaces appear to have Opened up slightly. A few latitudinal breaks in the fibers are also observed. This difference due to freezing temperature was also noted in Succulometer tests for water-holding capacity. More expressible liquid was obtained from the -320°F. sample than from the -l0°F. sample. For raw samples, quick-freezing brings about a decrease in water-holding capacity. The cooked breast meat frozen at -l00F. (Photo E) was similar to the uncooked meat frozen at -l0°F. (control) in structural organization. Shrinking of the muscle fibers 4l was noted but was minimal. Cross-striations of the muscle fibers were very pronounced in this cooked sample and in all cooked samples. There are more latitudinal breaks in the cooked meat fibers than in the uncooked meat fibers. The cooked breast meat frozen at -320°F. (Photo F) presents another distinct pattern. It it characterized by shrunken muscle fibers, emergence of a new space system between fibers, prominent cross-striations and fragmentation of the individual muscle fibers. The water-holding capacity of the cooked samples, as determined by the Succulometer, show that less expressible liquid was obtained from meat frozen at -320°F. than from that frozen at -l0°F. For cooked samples, quick-freezing (-320°F.) brings about a small increase in water-holding capacity. The uncooked breast frozen at -l0°F. and freeze dried (Photo C) presents yet another structural pattern. It is characterized by reduction in the diameter of muscle fibers and the emergence<fiia knge interfibral space system which no longer bears any resemblance to the spaces in the raw control sample either in size or in location. These shrunken muscle fibers are grouped together into small bundles and the fibers in the hxdles are packed together. This is 42 the result of slow but complete intercellular freezing. The uncooked breast frozen at -320°F. and freeze dried (Photo 0) showed an altered proportion of muscle fibers and interfibral Spaces, although the total tissue volume Showed less change. This change probably resulted from considerable shrinking by the muscle fibers. The fibers are irregularly shriveled longitudinally. Spaces appear inside these shriveled muscle fibers and fragmentation of the muscle fiber is evident. Again the water-holding capacity was similar to that of the raw frozen controls. More expressible liqu d was obtained from the quick-frozen (-320°F.) samples than from the slow-frozen (-l0°F.) samples. Quick-freezing brings about a decrease in water-holding capacity. I The cooked breast frozen at -l0°F. and freeze dried (Photo G) has an altered proportion of muscle fibers and interfibral spaces, which results from shrinkage by the muscle fibers. The fibers are irregularly shriveled longitudinally so that they are no longer of a uniform width. Thick sections Show that the continuity of the individual muscle fibers are not broken. This irregular pattern of the shriveling suggests that a mixed intra- and intercellular freezing has probably determined the structural pattern of the tissues. The shriveling and 43 absence of spaces inside these shriveled muscle fibers combined, indicate that freezing started out to be intra- cellular but became more and more intercellular. The cooked breast frozen at -320°F. and freeze dried (Photo H) again presents a distinct pattern. It is characterized by uni- form reduction in the diameter of the muscle fibers, a Space system between fibers and severe fragmentation across muscle fibers. The water-holding capacity of cooked freeze-dried samples, as determined by the Succulometer, Show more liquid was expressed from the slowly frozen (Pl0°F.) samples than from the quick-frozen (-320°F.) samples. Quick-freezing results in a small increase in water-holding capacity, while slow-freezing brings about a small decrease in water-honing capacity. The structure of the meat as Shown in the photo- micrographs offer a basis for explaining the differences noted in the water-holding capacity and texture of the samples subjected to the different processing treatments. Effect of Freezing Method on Quality of Freeze-Dried Poultry Panel Tests The taste panel detected no Significant difference between freeze-dried chicken meat frozen at -l00F. or 44 -320°F. before cooking (Table VIII). However, the freezing temperature did affect the sensory prOperties of the chicken meat frozen and dried after cooking. The panel detected this difference at p4:0.00l for the thigh meat and p<.0.0l for breast meat. Texture and juiciness were the characteristics mentioned by the panel to distinguish between samples frozen by the two methods. However, their comments were so comparable for samples frozen by the two different methods it was concluded there was no difference between the freezing methods. Shear Resistance The freezing temperatures used (-l0°F. and -320°F.) did not have a significant effect on the Shear resistance of meat freeze dried before cooking (Table IX). However, for meat freeze dried after cooking, samples frozen at -3200F. had lower Shear resistance than those frozen at -l0°F. The difference in cooked breast meat was signifi- cant at p<:0.0l for the Kramer shear and p<;0.05 for the Instron; the difference in thigh meat was not significant. Although no panel tests were performed on frozen chicken meat frozen at the two temgaratures, objective measurements show no Significant differences. This data is in agreement with that of Marion and Stadelman (I958) and Barrie t al., (I964). 45 Table VIII. Ability of Panel to Distinguish Freeze-Dried Poultry Meat Frozen at -l0 F. and -320°F. T ' l T a Type of rIang e est b Meat No. of Correct Correct Judgments Judgments (%) Frozen at -l0°F. and -3200F. Before Cooking Breast l3 4IN‘S' Thigh 10 31N-3- Frozen at -l0°F. and -320°F. After Cooking Breast I8 56** Thigh 22 69*** a 8 judges, 4 replications of each test b N.S., not significant; **, *** pAL0.0l and 0.00l, respectively N_a>_eddamdt ._oo.o ecn mo.o“va ate .4 m_aEmm mo Emcm cog OOLON mo .m04 m 46 0.__ N 0.N J 0.0. N 0.J m 00NmI. o.~_ N N.@ a o... N 0.: a oo_- ea_eN 0.0_ m 0.0_ J «krm.J_ N 0.0 m ooni N.m_ m 0.N_ J 0.0_ N 0.0 J 00—- ummmcm mc_xooo cmum< m.N m 0.0 J 0.J N 0.0 m ooni m.N m m.0 a _.a N N.m m 00.. em_eN N.m_ N N.N_ J 0.0 0 0.0 m OONMI e.m_ N m.e_ a N.@ e o.N a oo_N amaetm NaNm_0 NaNa_0 NaNa_0 NaNa_0 , mc_xooo mLOmmm mm_0Emm . mm_aEmm . mmflmEmm mm_mEmm mmoLoN 00 .oz mOOLON mo .02 mOOLOL mo .02 mmoLoN mo .02 oo_c0-mNOOcu cmNoLu UO_L0IONOOcm CONOLL cocumc_ LmEmLx wmmww ummz 00m: mHCOEJLumc_ mc_Nomcu mo OQNN «NOONmi ocm .mO0_I um CONOLN cmxo_50 UO_c0-mNomcu mo ucmEOcsmmmz O>_uomwno mo NLmEEsm .x. m_nmh 47 A relationship between the freezing methods and the order of freezing and cooking are indicated. When the muscle is cooked after processing, there is no Significant difference in shear resistance between the two freezing methods. However, meat cooked before processing and frozen at -320°F. had lower Shear values than that frozen at -l0°F. Moisture Content Final moisture content of breast meat freeze dried before and after cooking is 3 to 4% higher for samples frozen at -320°F. than at -l0°F. (Table VI). Only slight differences were found for thigh meat frozen at the two temperatures. Meats freeze dried before cooking had 4 to 6% higher moisture content than those freeze dried after cooking. Water-Holding Capacity Water-holding capacity of freeze-dried breast was significantly different (p210.05) for the two freezing methods according to Succulometer tests (Table X). Results indicate for the freeze-dried cooked samples, quick freezing increases water-holding capacity compared to slower freezing Since less liquid is pressed out of the muscle. Approximately equal amounts of rehydrating liquid are absorbed by the meats freeze dried before and after cooking. Muscles freeze dried 48 O_OL_O cocc_ 00.04vm « mo mocm Ou O_OL_O cmuso mo mmcm mo O_umm n u:0_03 O_aEmm mo ucmome m 0.0 0 0.0 m 0.0 0 0.0 J 00Nmi _.m e 0.m m m.o 0 a._ a 00.- em_ee 0.J 0 0.0 m k0.m_ w 0.0_ J 00Nm- N.m 0 0.J m 0.0N 0 _.N_ J oo_i ummmcm 0c_xooo cOum< J.0 0 J.0 m J.0 N 0.0 J OONm- J.0 0 0.0 m 0.0 N 0.0 J 00—- ;0_;N 0.J 0 0.0 m «N._N N 0.__ m O0Nm- m.m 0 J.J m 0.0. N J.0 N oo_- ummmtm 1 . NNU NNp mc_xooo OLONOm ;U_:o_4 mmmmEmm U_:o_4 mO_QEmm U_:U_4 mmemamm U_:m_4 mm_QEmm wmmcaxM mo .02 @moLaxM mo .02 mmoLaxM 00 .oz MmmcaxM mo .02 vmfitQIONOmcm CONOLN 00_L0ION00LN cmNocm mmOcm EEmIismco LOuOEo_:oo:m A.mov .QEON ummz new: muc0E3Lumc_ 0c_NOmcu mo oQNH .Noon- 0cm .0 cmNoLN cmxo_;0 Uo_coiowoocm No >u_omam0 0c_U_OIILOum3 00 m 0.- um cmEEzm .x ®_nmN 49 before cooking, in contrast, lost more liquid from the quick frozen samples than from the slow frozen samples. No Significant differences were found in the water-holding capacities of frozen chicken related to freezing tempera- ture (Table X). Water-holding capacity is also affected by the order of freezing and cooking for breast meat showing the same trend as the shear press results. The freeze-dried thigh meat had a slightly lower water- holding capacity (not statistically Significant) than the freeze-dried breast meat, based on Grau-Hamm press results (Table X) and results are in agreement with those of the Succulometer, except for breast meat frozen-after cooking at the two different temperatures. Effect of Freeze Drying on Breast and Thigh Meat Panel Tests The panel distinguished (at p<:0.00l level of Signifi- cance) between breast and thigh meat freeze dried after cooking, frozen at either temperature. Correct panel judgments for distinguishing between cooked freeze-dried breast and thigh meat were 84% and 8l% for meats frozen at -l0°F. and -320°F., respectively. 50 Detection of the difference between freeze-dried breast and thigh meat was primarily based on differences in texture and juiciness. The freeze-dried thigh meat, regardless of freezing method, was more desirable than the breast meat. Although adverse comments were made about the texture and juiciness of both samples, the breast meat was generally considered to be more dry, powdery, stringy, hard, and tough and to have more rapid moisture release than the thigh meat. No panel evaluations were obtained for the breast and thigh meat freeze dried before cooking. Shear Resistance Freeze-dried thigh meat had lower Shear resistance than breast meat freeze dried before and after cooking (Table XI). The shear values were Significantly different at p<:0.00l for all comparisons with both the Kramer shear and the Instron. Moisture Content Breast meat, freeze dried before cooking, had a higher moisture content after cooking than thigh meat, whether frozen at -l0°F. or -3200F. (Table VI). Similarly, breast meat, freeze dried after cooking, had a higher moisture content after rehydration than thigh meat. 5l O_OL_O cmcc_ .00.0.Va «a...» mo mmcm Ou m_OL_o c0030 00 mmcm mo o_umm o u:m_03 O_aEmm mo ucmOcmm n O_aEmm mo Emcm Lea ooLOm mo .mpJ m J.0 0 araJ.0 0 «**0.N 0 *340.J N cm_;h 0.: a N._N N N.m_ N. m.m e amadtm aeNm- a.m e aaao.o m «ram.N m ree_.a N em_eN a.m a a.e_ .N e.m_ N N.@ a aaadtm 00.- 0c_xooo OLOmmm 0.0 0 *«k0.0 0. «%R0.__ 0 *k«0.0_ N ;m_LN 0.J 0 0.0_ 0 0.0_ m 0.J_ N ummmcm OONm- _.m 0 «RN0.0 0 «««O.N_ w «r40.__ N ;0_£N N.m 0 0.0N 0 N.0_ 0 0.0_ N ummwcm oo_- NNO NaNmeo NaNa_0 0c_x000 cmum< OU_30_4 mO_QEmm U_:U_4 mO_QEmm mm_aEmm I. mo_aEmm mmmcaxu 00 .Oz MmmcaxM mo .02 mOoLou mo .02 m00com 00 .oz . A.mov mmmcd EEmIiamcu cmuoEO_:oo:m cOLumc_ LOEmcx ummz .aEmN mo OQNN mc_~00cm 00m: muc0E3Lumc_ mc_xoou cmum< 0cm OLONOm om_L0 memLu ummz £m_£H Ucm ummmLm m0 ucmEmLDmmmz ®>_uommno m0 >LmEEJm ._x 0.3mh 52 Water-Hélding Capacity The Succulometer pressed little or no water from the thigh meat compared with that pressed from the breast meat, indicating that the liquid absorbed by the thigh was held more firmly by the muscle cell structure (Table XI). The difference in water-holding capacity of breast and thigh meat was significant (p<;0.00l) for the meat freeze dried before or after cooking. The Grau-Hamm press expressed less water from the freeze-dried thigh frozen at the two different temperatures than from the freeze-dried breast meat, which agrees with Succulometer results (Table XI). SUMMARY AND CONCLUSIONS Objective methods of measuring texture and juiciness differences in frozen and freeze-dried chicken meat were evaluated. The effect of the freezing method (-IO°F. and -320°F.) on the quality of freeze-dried poultry meat and the effect of freeze drying on cooked breast and thigh meat were also studied. The following conclusions were drawn: l. Freeze-dried poultry meat was readily distinguished from frozen meat by the taste panel under all conditions tested. The frozen samples had better sensory prOperties than the freeze-dried samples, with texture and juiciness as the distinguishing characteristics. 2. The taste panel detected no Significant difference between freeze-dried chicken meat frozen at the two temperatures before cooking; whereas, the sensory prOperties of chicken meat freeze dried afte: cooking were affected by the freezing temperature. 3. The taste panel distinguished between breast and thigh meat freeze-dried after cooking, with texture and juiciness as the distinguishing characteristics, the 53 54 thigh meat being more desirable than the breast meat. 4. Objective methods for measuring textural character- Istics can substitute for more time-consuming and expensive panel tests in a research project designed to improve the texture of freeze-dried chicken. 5. The Kramer shear and Instron measurements showed differences in the texture of frozen and freeze-dried poultry. These objective results were not as consistent with the taste panel on meat frozen or freeze dried before cooking as were the results from meat frozen or freeze dried afteg cooking. The Kramer Shear is Slightly more sensitive than the Instron in measuring textural differences. 6. High correlation coefficients were obtained between the shear values from the Kramer and Instron tests. 7. The Succulometer and Grau-Hamm press showed differences in the water-holding capacity of chicken meat. The water absorbed by the freeze-dried meat was not held as firmly by the muscle structure as in the frozen samples. Breast meat had a lower water-holding capacity than thigh meat. The water-holding capacity was affected by the order of freezing and cooking of the chicken meat. The Succulometer appeared to be more suitable than the Grau-Hamm press. 55 8. Photomicrographs showed marked differences in the structure of the chicken meat (frozen or freeze dried) as affected by the order of cooking and the temperature of freezing. These differences in structure helped to explain differences noted in the water-holding capacity and textural characteristics of the samples. 9. The textural characteristics of the frozen and freeze-dried chicken breast and thigh meat were affected by the order of cooking and the two freezing temperatures. LITERATURE CITED Anonymous. I'DeveIOping Standards of Quality on the Basis of Allo-Kramer Shear-Press Values.’l Allo Precision Metals Engineering, Inc. ROckville, Maryland. Laboratory Paper ASP-4. AOAC. I950. Official methods of analysis. 7th ed. Association of Official Agricultural Chemists. Washington, D.C. p. 343. Auerbach, E., H. 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Powers. I962. Taste-panel and Shear-press evaluation of tenderness of freeze- dried chicken as affected by age and pre-Slaughter feeding of ions- Food Technol. 16, I37. Yao, A., A.|. Nelson, and M.P. Steinberg. I956. Factors affecting the rate of chicken meat dehydration under vacuum. Food Technol. 10, I45. Ziemba, J.W. I960. Freeze-drying. Food Engin. 32, 57. APPENDIX Exhibit 2. Score Sheet - TRIANGLE TEST Each set of samples will contain 2 like and l odd sample Check Od' Please indicate basis for Sample Sample selection of odd sample Flavor Juiciness Texture Comments (dry, juicy, (soft,hard; rapid moisture stringy, release) rubbery; tender,tough, friable) A B C D E F 6l 62 Exhibit 3. Typical Shear Force Curves >Force Time é—— Tender Tough Meat Meat Kramer Shear 63 Exhibit 3, Con't. ——9 Force Time é——- Tender Tough Meat Meat Instron 64 Exhibit 4. Instron Test Cell Photo B - Assembled 65 Exhibit 5. Percentage Rehydration calculated according to the formulaa: WR/WL X IOO where WR - grams moisture regained in rehydration WL grams moisture lost in freeze dehydration Example: Uncooked breast frozen at -320°F. and dried Weight before freeze drying Weight after freeze drying Loss (WL) Weight after rehydration Gain (WR) _4l3-ll0 450 grams ll0 340 4l3 303 303/340 x l00 : 89.ll% a Suden t 1., (1964) (D 0) 66 Exhibit 6. Photomicrographs of Processed Chicken . Breast Meat ~I0°F. (Frozen Control) (A) Uncooked Before Freezing '————* -3zu*r; r Uncooked Before Freezing 67 Exhibit 6. Con't. -l0°F. Freeze Dried (C) Uncooked Before Freeze Drying ' ‘————‘¥r -320°F. Freeze'Driéd‘T Uncooked Before Freeze Drying 68 Exhibit 6. Con't. g-IOOF. Frozen (E) Cooked Before Freezing u'v - . IIULCII \I'I' Cooked Before Freezing fr, 69 Exhibit 6. Con't. -l0°F. Freeze Dried (G) Cooked Before Freeze Drying -320°F. Freeze Dried (H) Cooked Before Freeze Drying