Factors Affecting the Drying, Stability, and Rehydration of Freeze-Dried Chicken Meat1

Factors Affecting the Drying, Stability, and Rehydration of Freeze-Dried Chicken Meat1 A. J. MATJRER 2 , R. C. B A K E R AND D . V. V A D E H R A

Department of Poultry Science, Cornell University, Ithaca, New York 14850 (Received for publication July 31, 1972) ABSTRACT Breasts, legs, and thighs of broilers and light fowl were cooked, freezedried, and rehydrated to determine the effect of several raw materials, storage, and processing variables on the tenderness, juiciness, and flavor of the end product. Sex of broilers had no significant effect on freeze-dried, rehydrated product quality. Except for a tenderness advantage in favor of meat samples from broilers fed on a low energy ration, there were no noticeable product differences due to carcass fat content. Frozen storage of raw meat materials which were subsequently freeze-dried did not allow much deterioration until half a year of storage had expired. Storage of freeze-dried samples caused a significant decline in quality after half a year and again at the end of the year of study. Freeze-dried, rehydrated light meat and broiler carcasses were nearly always of better quality than dark meat and light fowl respectively. Correlation coefficients of r = 0.88 for tenderness and r = — 0.77 for juiciness were obtained when subjective and objective methods of evaluation were compared. POUITRY SCIENCE 52: 784-792, 1973

INTRODUCTION

P

O U L T R Y processing consisted of merely killing and dressing operations until recently when the changing food picture began requiring further processed products. Various forms of dehydrated poultry meat are now being used in b a b y foods, military and camping meals, and space program menus. Among the dehydration methods applicable to foods, freeze-drying is an ideal method for the maintenance of the desirable functional and palatability characteristics (Harper a n d T a p p e l , 1957). T h e principle of freezedrying involves the removal of water from a food b y sublimation (Bird, 1964), thus providing a high quality rehydrated product. Nevertheless, there are still problems remaining in the preparation of freezedried poultry meat. Goodwin et al. (1969) indicated t h a t a 1

This research was conducted in the Philippines under the Ford Foundation sponsored University of the Philippines—Cornell Graduate Education Program. 2 Present address: Department of Poultry Science, University of Wisconsin, Madison, Wisconsin 53706.

tenderness difference existed between sexes in eight-week-old broilers which had been frozen and stored until evaluated. T h e males exhibited lower shear values t h a n the females for both the breast and the thigh. No research h a d been conducted to show whether this slight difference would show u p after freeze-drying. According to Saravacos and Moyer (1966), lipid compounds found in foods m a y have an effect on the retention of flavor compounds during freeze-drying since most of these compounds are fat soluble. Seltzer (1961) suggested t h a t poultry suitable for dehydration should contain some fat, but not excessive amounts which could possibly be very susceptible to rancidity. Freezer storage of meat can result in a gradual decrease in odor and flavor acceptability. However, Sawyer et al. (1960) reported t h a t well packaged turkeys and cut-up chicken stored at — 18°C. will remain in good condition for one year, when stored at — 12°C. will remain in good condition only six m o n t h s and when held at — 7°C. only three months. Odor and flavor changes occur mainly in the fatty con-

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stituents of meat. Findings by Miller and May (1965) indicated that shorter times and lower storage temperatures resulted in more tender meat with both freezedried and non-freeze-dried chicken samples. If the relative rate of deterioration at different storage temperatures is known, better raw material selection and storage should allow better freeze-dried products. Freeze-dried foods offer excellent stability and long shelf life without requiring refrigeration (American Meat Institute Foundation, 1962). Mountney (1966) reported that freeze-dried chicken meat had good storage stability for six months at 38°C. and below. The most prominent types of deterioration of freeze-dried meats are fat rancidity, non-enzymatic browning, and protein denaturation (American Meat Institute Foundation, 1960). According to Burke andDecareau (1964), freeze-dried foods have shorter shelf lives at higher storage temperatures. The advantages of freeze-dried meat can be lost in a few days if the dried product is exposed to oxygen (Seltzer, 1961). Correlations cannot be found in the literature between sensory juiciness scores and rehydration ratio values for freezedried chicken meat. However, Wells and Dawson (1966) did report that the percentage of water uptake during rehydration was directly related to juiciness as measured by a taste panel. MATERIALS AND METHODS

Preparation of Meat Materials. General. The meat materials used consisted of a combination of legs and thighs (dark meat) and breasts (light meat) of either eight-week-old broilers or light fowl (Leghorns—-nine or 15 months of lay) as stated in the results. Poultry was obtained from the Poultry Division at the University of the Philippines, College of Agriculture

785

(UPCA), or from a nearby commercial poultryman. The birds were suspended in funnels and slaughtered by cutting their throats. Feathers were removed following subscalding of the birds in 60 + 2°C. water for approximately one minute. After handplucking, eviscerating, cutting the carcasses into parts, and chilling for five hours in ice water, the meat was frozen at — 20°C. for later analysis. Influence of sex. In an attempt to determine whether sex of broilers had any effect on the resulting freeze-dried product, male and female broilers were packaged separately after slaughtering and compared after the freeze-drying process. Effect of carcass fat. Broilers were raised on two rations of different energy levels (2300 and 2700 Kcal. M.E./kg. of feed). The respective carcasses were analyzed and compared to investigate the influence of fat content on end-product tenderness, juiciness, and flavor. Raw Storage. Both broiler and light fowl carcasses were prepared as described earlier. Samples of each class of chicken were analyzed at zero time (i.e. they were not placed in the freezer for storage). The remainder of the carcass parts were frozen at - 2 0 ° C . After 24 hours at - 2 0 ° C , half of the carcass samples were transferred to a — 10°C. freezer for storage studies. In addition to the samples analyzed after zero storage, carcass parts were analyzed after 1,4, 26 and 52 weeks of raw storage at the two different temperatures to investigate the effect of storage of raw ingredients on the final freeze-dried product. All samples were analyzed immediately after freeze-dehydration and rehydration. Freeze-Dried Storage. Broiler and light fowl samples were freeze-dried immedi-

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A. J. MAURER, R. C. BAKER AND D. V. VADEHRA

ately after slaughter and cooking and were stored in the dehydrated form at the three temperatures of 10°C, 21°C, and ambient temperature (20-38°C.) for five storage periods (0, 1, 4, 26 and52 weeks). Storage at 10°C. was in a household type refrigerator, storage at 21°C. was in an air-conditioned laboratory and ambient storage was in an office. The zero storage samples were analyzed immediately after the freeze-drying process. Correlation Studies. All freeze-dried samples were used in correlating objective and subjective results to obtain an indication of the reliability of objective measurements as substitutes for sensory evaluations by a taste panel. Cooking Procedures. The meat was thawed in a 21°C. air-conditioned room (60% relative humidity) for six hours prior to cooking. The carcass parts were cooked in water to an internal temperature of 88°C. After cooling for 10 minutes in running tap water (approximately 33°C), the skin was discarded and the meat was trimmed from the bones into chunks about four cm. long and two cm. wide. These samples were then placed on an enamel tray and frozen at — 20°C. for subsequent dehydration. Freeze-Drying. Samples were dehydrated in a model 10-010 Virtis automatic freezedryer. A combination bulk dryer and heat rack (Virtis 10-010 BDI) was used for providing thermostatically controlled 32°C. heat to trays on which the samples were placed. A thermocouple vacuum gauge registered the vacuum attained by a 75 liters/minute Precision vacuum pump. The pump was equipped with a gas ballast for prevention of contaminant vapor condensation within the pump. Samples being dehydrated were placed into the bulk dryer and subjected to a

vacuum of 100 microns for a few minutes before the heat rack cord was plugged into the electrical circuit. Faster sublimation resulted with the use of the heat rack, but the freeze-dryer had to establish its own equilibrium before heat was added to the system. The vacuum maintained during dehydration was approximately 60 microns. The one-liter capacity of the condensing coil and the space on the trays allowed dehydration of the breasts, thighs and legs of two chickens at a time. After 20 hours of dehydration, the samples were removed from the bulk dryer and analyzed immediately or placed into plastic bags inside jars to allow additional sample preparation or storage studies prior to analysis. Atmospheric oxygen was excluded by orally sucking the air from the plastic bags. The residual moisture content of the meat after freeze-drving was 21-4%. Rehydration. All meat samples were rehydrated by placing them into shallow pans containing two liters of water for every 40 gm. of meat. A standard rehydration temperature of 25°C. was maintained with the aid of a water bath. Meat samples were rehydrated for 15 minutes. At all times the water was deep enough for complete submersion. Halfway through the procedure the water was stirred for a few seconds with a spatula to facilitate rehydration. After the 15 minutes in water, the samples were removed and placed on double thickness Tan Kraft paper towels for one minute. Weighing of the samples followed and a rehydration ratio was calculated by dividing the sample weight before rehydration into the sample weight after rehydration. Subjective Analyses. A trained taste panel of eight judges was used to evaluate all

FEEEZE-DEIED MEAT

the meat samples. Four men and four women tasted four samples in duplicate and scored the rehydrated meat for tenderness, juiciness, and flavor based on a nine point hedonic scale (the closer the value to one, the greater the degree of excellence). All samples were tasted in duplicate and unless specified otherwise in the results, each reported value is the average of 16 taste tests. Two chickens were used for each treatment. The four samples tasted in duplicate at a sitting were light and dark meat from the same class of chickens from two different treatments. The samples from different storage times were tasted as the respective storage time expired.

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found for samples in several portions of the research by placing the meat on an Ohaus moisture determination balance. Heat was supplied from an infra-red lamp at a distance of one inch from the sample. The heater control setting was at 140 watts for one hour. Fat content. A Goldfisch apparatus was used for analyzing the fat content of the meat. Two gm. of sample were wrapped in filter paper and placed inside a thimble which was then attached to the extraction apparatus. Forty ml. of chloroformmethanol (2:1) were poured into a weighed beaker and placed under the thimble containing the sample. After extraction for 10 hours the solvent was evaporated from the beaker and a final weight was recorded. Objective Measurements. All samples were Percent crude fat was calculated by dianalyzed using both subjective and objec- viding the weight of the fat extract by the tive methods whenever appropriate. Un- original sample weight and multiplying like the taste panel used for subjective by 100. evaluations, a variety of methods was emData analysis. All data were analyzed ployed for determining the respective ob- by factorial analysis of variance using an jective analyses. IBM 360-75 computer. Tukey's w-proWarner-Bratzler. Tenderness measure- cedure was used for making comparisons ments were assessed using a Warner- among treatment means (Steel and Torrie, Bratzler meat shear. Two runs of eight 1960). In addition, correlation coefficients meat samples per treatment were sheared were determined for the experiment comacross the grain. The pounds of force re- paring subjective and objective methods quired during shearing registered on the of evaluations. scale dial. Immediately after shearing the RESULTS AND DISCUSSION cut surface of the meat was blotted on a paper towel to provide a cross sectional Influence of Sex. According to the data in measurement of the sheared area. A pen Table 1, both male and female broilers was used to outline the blot for later trac- gave similar f reeze-dried, rehydrated pieces ing with a Keuffel and Esser planimeter. of meat. The only significant difference Thus, the shear force was ultimately ex- was found when comparing the rehydrapressed in gm. of force required to shear tion ratios of the two sexes; female careach square mm. of cross sectional meat cass parts had slightly higher rehydration area (gm./mm. 2 ). ratios than the males. It is known that dark meat of chicken Rehydration ratio. Juiciness of all rehydrated samples was assessed by calcula- has more interstitial fat and connective tion of the rehydration ratio as defined tissue than is found in light meat. Since poultry fat is said to contribute to aroma earlier. Percent moisture. Percent moisture was and flavor, it is possible that dark meat

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A. J. MATJRER, R. C. B A K E R AND D . V.

VADEHRA

T A B L E 1.—Effect of sex and carcass pari of chicken on the tenderness, juiciness, and flavor of freeze-dried, rehydrated broiler meat

Objective results Subjective scores'ib

Carcass part

Sex

Tenderness

Juiciness

Warner-Bratzler a gm./mm. 2

Flavor

Rehydration ratio" wt. after rehyd. wt. before rehyd.

Male

Light meat Dark meat

2.88 2.62

3.06 2.94

3.62 2.06

25.39 23.58

3.26 2.74

Female

Light meat Dark meat

2.50 2.31

3.19 3.06

3.19 2.25

29.40 24.32

3.34 2.80

a Subjective scores were based on a nine point hedonic scale; the closer the value to one, the greater the degree of excellence. b Two runs of eight evaluations each have been averaged for the taste panel and shear values. 0 Rehydration ratio results are averages of two replications.

will often be considered more flavorful when compared with light meat (Table 1). T h e rehydration ratio observations were probably a function of the composition of the meat. Unless connective tissue is softened during cooking or at high rehydration water temperatures, it is relatively slow to pick u p water as indicated in the rehydration ratios. Since there were no consistent or highly significant differences in tenderness, juiciness, or flavor of freeze-dried broiler meat due to sex, it was considered a sufficient reason for using straight-run broilers for future studies involving birds of this age. Effect of Carcass Fat. Broilers were fed rations of either high or low energy to provide carcasses with different fat contents. T A B L E 2.—Effect

Ration

Table 2 lists the fat levels which were subsequently used for the carcass fat investigation. Meat samples from broilers fed the low energy ration (2300 kcal. M.E./kg.) were found to be more tender t h a n the high energy ration samples by the taste panel. T h e Warner-Bratzler shear values were not significantly different, b u t an interaction between fat content and carcass part resulted due to the higher shear values obtained for low energy ration dark meat. Carcass p a r t tenderness differences were not significant. Carcass fat content exerted little influence on juiciness as perceived by the taste panel. As can be seen in Table 2, the values for the samples high in fat and those low in fat were similar. However,

of carcass fat content on the tenderness, juiciness,

Subjective scores*

Kcal. M.E./kg.

Fat content

2700

2.62 4.42

Light meat Dark meat

3.06 3.06

2300

1.99 3.97

Light meat Dark meat

2.25 2.31

%

broiler meat

Objective results

Carcass sample Part

and flavor of freeze-dried

Rehyd. ratio c wt. after rehyd.

Flavor

b Warner-Bratzler gm./mm.2

3.81 3.81

3.44 2.50

39.66 34.33

3.06 2.75

3.81 3.44

3.25 2.44

24.85 42.86

3.21 2.71

Tenderness Juiciness

*b The closer the value to one, the greater the degree of excellence. Results are averages of 16 evaluations. c Results are averages of two replications.

wt. before rehyd.

FREEZE-DRIED MEAT

789

weeks. However, the Warner-Bratzler shear values indicated that the zero sample was the most tender. Light meat was significantly more tender than dark meat, and broilers were significantly more tender than light fowl (P<0.01). A significant interaction (P<0.01) between carcass part and class of chicken revealed that the tenderness differences between broiler and light fowl varied with carcass part. The decrease in light fowl tenderness was of a larger magnitude than that found in broiler meat. Light fowl dark meat was quite a bit less Effect of Storage of Raw Material. Broilers tender than that of the light meat; broiler and light fowl (15 months of lay) were light and dark meat showed smaller tencooked and freeze-dried after 0, 1, 4, 26 derness differences. The Warner-Bratzler and 52 weeks of frozen storage at either meat shear also showed a tenderness inter—10 or — 20°C. The sensory scores result- action including storage time indicating ing from storage of raw material are sum- different amounts of toughening at the five storage periods. marized in Table 3.

there was a highly significant difference between the juiciness values for light and dark meat as measured by the rehydration ratio; light meat was juicier than dark meat. The flavor scores of the high and low carcass fat samples were not significantly different (Table 2) even though there was a trend towards more flavor in the leaner meat. Again, carcass part was the factor where variation existed. Dark meat was significantly more flavorful than light meat at the 1% level of probability.

Both the taste panel scores and the Warner-Bratzler meat shear values showed significant changes (P<0.01) in tenderness of freeze-dried meat due to length of frozen storage of the raw carcasses. According to the sensory scores, the most tender meat was attained after four weeks of storage and the least tender after 52 TABLE 3.—Significant effects of frozen storage of raw meat materials on the tenderness, juiciness, and flavor of freeze-dried chicken meat Subjective scores a b Factor

Level Tenderness Juiciness

Flavor

0 1 4 26 52

4.12/3 b 3.91a/S 3.44a 3.45a 4.21/3

3.78/Sy 3.91T) 3.34a/3 3.06a 4.36S

3.06a 3.45a/3 3.34a 3.23a 3.84/3

Carcass partf1

Light meat D a r k meat

3.20a 4.48/3

3.19a 4.19/3

3.30a 3.47a

Class of chicken d

Broiler Light fowl

2.49a 5.180

2.84a 4.54/3

2.81a 3.96/3

~10°C. -20°C.

3.78a 3.89a

3.62a 3.76a

3.32a 3.46a

Weeks of storage 0

Temperature of storage"

a The closer the value to one, the greater the degree of excellence. b Values with the same subscript are not statistically significant from each other (P <0.01). 0 Results are averages of 128 evaluations. d Results are averages of 320 evaluations.

Temperature of storage of raw meat had no significant effect on the tenderness of the freeze-dried product; the results were quite similar for —10 and — 20°C. within storage times, carcass parts, and class of chickens. Subjective and objective tests showed that the 26-week samples from frozen storage were the most juicy. However, only the taste panel detected a significant difference (P<0.01). Both carcass part and class of chicken produced significant differences in juiciness (P<0.01). Light meat and broilers were consistently juicier than their counterparts (Table 3). Wells et al. (1962) also reported that younger birds rehydrated to a significantly greater extent than older birds. Freezer temperature had no significant effect on the juiciness of the freeze-dried chicken meat. The samples stored at — 10°C. were slightly better than the — 20°C. samples. A highly significant flavor difference existed among the freeze-dried samples that were stored in raw form for the five

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A. J. MAURER, R. C. BAKER AND D. V. VADEHRA

T A B L E 4.—Significant effects of storage offreezedried chicken met t o/i the tenderness, juiciness, and flavor of the rehydrated samples Factor

Level

Subjective scoresab Tenderness Juiciness

Flavor

0 1 4 26 52

3.86a b 3.94a 3.80a 4.603 5.25 7

3.45a 3.68a 3.66a 4.223 4.78y

3.20a 3.41a 3.54a 4.793 5.58 T

Carcass part d

Light meat Dark meat

3.80a 4.783

3.43a 4.483

4.15a 4.053

Class of chickend

Broiler Light fowl

2.89a 5.693

3.14a 4.773

3.44a 4.773

Temperature of storagee

10°C. 21°C. Ambient

4.00a 4.413 4.463

3.72a 4.003 4.153

3.66a 4.283 4.383

Weeks of storage0

a The closer the value to one, the greater the degree of excellence. b Values with the same subscript are not statistically significant from each other (P <0.01). c Results are averages of 192 evaluations. d Results are averages of 480 evaluations. 6 Results are averages of 320 evaluations.

storage periods. The 52-week sample was least flavorful, while the 0- and 26-week samples had the most flavor. There was no significant flavor difference between light and dark meat, but the dark meat of broilers tended to be more flavorful than the light meat; the reverse was true of light fowl. Broilers were significantly preferred to light fowl (P<0.01). Storage temperature had no marked effect on flavor content of the freeze-dried samples (Table 3). Trends and results due to temperature of storage were consistent within storage times, carcass parts, and class of chickens. Generally, the carcasses which were in storage for up to half a year experienced no great amount of deterioration in terms of tenderness, juiciness, or flavor. Variations were present, but only samples stored for one year were consistently of lower quality. Storage may have allowed additional aging to occur which subsequently improved meat quality. However, after a year in frozen storage, the cycling of the freezer's defrost unit possibly caused crystal structure changes, migration of soluble solids, and a subsequent decline in quality of the meat.

Effect of Storage of Freeze-Dried Meat. Table 4 depicts the changes in tenderness, juiciness, and flavor of freeze-dried broiler and light fowl (15 months of lay) meats which were stored up to one year at three different temperatures. Highly significant declines in tenderness occurred at the end of a year of storage. Both the taste panel and the Warner-Bratzler meat shear detected the greatest toughening of the freeze-dried meat between the four-week and the 26-week storage periods. This tenderness change was largely due to light meat toughening in both classes of chickens at the 21°C. and ambient storage treatments. Bele et al. (1966) also found that breast meat can be more adversely affected than thigh. Significant additional toughening (P<0.01) also occurred between the 26-week and 52-week storage times as found by the taste panel. Carcass part and class of chicken each exhibited highly significant differences in tenderness. However, light meat was more tender than dark meat most noticeably in light fowl and broilers were more tender than light fowl to a greater degree at the beginning of the storage study. The 10°C. storage temperature resulted in significantly (P<0.01) greater tenderness than the two higher temperatures. Most of this significance occurred toward the end of the experiment as the warmer storage temperatures allowed deterioration at a faster rate. Juiciness decline followed the same pattern as the changes in tenderness. Flavor changes were slight during the first four weeks of storage. Highly significant losses of flavor occurred, however, after 26 and 52 weeks of storage. The flavor loss was observed to a greater extent in light fowl dark meat. The taste panel did not detect any significant flavor differences between light meat and dark meat, although dark meat flavor was

791

FREEZE-DRIED MEAT

slightly better than light meat flavor in the early part of the storage study. Broilers were significantly more flavorful than light fowl (P<0.01). The 10°C. storage treatment afforded best conditions for flavor retention; samples stored at 21°C. and ambient temperature were significantly different (P<0.01) from the 10°C. sample, but not significantly different from each other. An increasing rate of flavor loss was noted after 26 weeks of storage at 21°C. and ambient conditions. As expected and in agreement with other researchers, the quality of freeze-dried chicken declined as temperature and time of storage increased. Although there were few visible changes in the freeze-dried samples, rancidity, browning, and protein denaturation probably occurred. Freezedried chicken seemed to be of good quality up to half a year, but after that, the samples were not as acceptable, especially the samples stored under ambient conditions. Subjective and Objective Measurement

Cor-

relations. Table 5 presents the correlation coefficients comparing subjective and objective measurements of tenderness, juiciness, and flavor of freeze-dried chicken meat. All correlation coefficients were highly significant at the 1% level of probability. As can be seen, the correlation coeffi-

cient of r = 0.88 for taste panel tenderness and Warner-Bratzler shear force was quite high indicating that similar parameters were being measured. Since these two methods of tenderness measurements are functionally related, the square of the correlation coefficient was computed to assess the value of the objective methods as an index of sensory tenderness (Szczesniak, 1968). After squaring the correlation coefficient (r) of 0.88, the coefficient of determination (r2 = 0.77) was found indicating that the Warner-Bratzler meat shear detected 77% of the variation in sensory tenderness. A correlation coefficient of r = — 0.77 was obtained relating taste panel juiciness to rehydration ratio values. The negative coefficient indicated that as sensory juiciness improved (hedonic values decreased), rehydration ratio calculations increased (i.e. the two methods of determining juiciness were in agreement). Approximately 60% of the variation in juiciness was detected by the rehydration ratio. According to Table 5, tenderness and juiciness are closely associated with each other as evidenced by a correlation coefficient of r =. 0.86. Flavor is not as closely associated with objective tenderness and juiciness measurements. Based on the significant correlation coefficients obtained, it seems that tenderness and juiciness of freeze-dried chicken can be evaluated by

TABLE 5.—Correlation coefficients comparing subjective and objective measurements of tenderness, juiciness, andflavorof freeze-dried chicken meat Subjective scoresab Tenderness Tenderness Juiciness Flavor Warner-Bratzler Rehydration ratio a b

1.00 0.86 0.72 0.88 -0.62

Juiciness 1.00 0.62 0.80 -0.77

Objective results ab Flavor

1.00 0.58 -0.33

Warner-Bratzler

1.00 -0.68

Correlation coefficients were based on 180 observations per variable. All correlation coefficients were significant at the one percent level of probability.

Rehyd. ratio

1.00

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A. J. M A U R E R , R.

C. B A K E R A N D D .

o b j e c t i v e m e t h o d s if a t a s t e p a n e l is n o t available. REFERENCES American Meat Institute Foundation, 1960. The Science of Meat and Meat Products. W. H. Freeman and Company, San Francisco. American Meat Institute Foundation, 1962. Freezedrying of meat products. Technical Session. 57th Annual Meeting of the American Meat Institute, Palmer House, Chicago. Bele, L. M., H. H. Palmer, A. A. Klose and T. F. Irmiter, 1966. Evaluation of objective methods of measuring differences in texture of freezedried chicken meat. J. Food Sci. 31: 791-800. Bird, K., 1964. Freeze-dried foods and tomorrow's consumer. Presented to home economists. Savannah State College, Savannah, Georgia. Burke, R. F., and R. V. Decareau, 1964. Recent advances in the freeze-drying of food products. Adv. Food Res. 13:1-88. Goodwin, T. L., L. D. Andrews and J. E. Webb, 1969. The influence of age, sex and energy level on the tenderness of broilers. Poultry Sci. 48: 548-552. Harper, J. C , and A. L. Tappel, 1957. Freeze-drying of food products. Adv. Food Res. 7: 171-234. Miller, W. O., and K. N. May, 1965. Tenderness of chicken affected by rate of freezing, storage time and temperature and freeze-drying. Food Technol. 19: 147-150. Mountney, G. J., 1966. Poultry Products Technol-

V.

VADEHRA

ogy. The Avi Publishing Company, Inc., Westport, Connecticut. Saravacos, G. D., and J. C. Mover, 1966. Volatility of some flavor compounds during freeze-drying of foods. New York State Agricultural Experiment Station Journal Paper No. 1533. Sawyer, F., T. Midura and R. M. Vondell, 1960. Handling and merchandising frozen food. Coop. Ext. Serv., University of Massachusetts, Amherst, Massachusetts. Seltzer, E., 1961. Importance of selection and processing method for successful freeze-drying of chicken. Food Technol. 15: 18-22. Steel, R. G. D., and J. H. Torrie, 1960. Principles and Procedures of Statistics. McGraw-Hill Book Company, Inc., New York. Szczesniak, A. S., 1968. Correlations between objective and sensory texture measurements. Food Technol. 22: 981-985. Tarladgis, B. G., B. M. Watts and M. T. Younathan, 1960. A distillation method for the quantitative determination of malonaldehyde in rancid foods. J. Am. Oil Chem. Soc. 37: 44-48. Wells, G. H., and L. E. Dawson, 1966. Tenderness and juiciness of freeze-dried chicken meat as related to maturity of birds. Poultry Sci. 45: 1004-1008. Wells, G. H., K. N. May and J. J. Powers, 1962. 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: 137-139.

NEWS AND

NOTES

(Continued from page 760) the Wharton School, University of Pennsylvania, and received a doctorate at New York University Law School. He is a member of the American Institute of Biological Sciences, the American Association for the Advancement of Science, the Council of Biology Editors, the New Jersey Academy of Science, Pennsylvania Academy of Science, the Newcomen Society of North America, and the Holland Society of New York. DANISH BRANCH—W.P.S.A. At the annual meeting of the Danish Branch of the World's Poultry Science Association, Vagn E. Petersen, National Animal Research Institute (Poultry Department), Rolighedsvej 25, 1958 K0penhavn V., was elected Chairman, and L.

Yding Sorensen, Landsudvalget for Fjerkraevlen, Roskidevej 272A, 2610 Rodovre, was elected Secretary. THOMPSON-HAYWARD NOTES Dr. R. L. Arnold has joined Thompson-Hayward Chemical Company as a Nutritionist for the Feed Chemicals Division. MANITOBA NOTES Dr. Peter A. Kondra, Professor of Poultry Genetics, Animal Science Department, University of Manitoba, Winnipeg, Manitoba, Canada, has accepted a two-month volunteer assignment from Canadian Executive Service Overseas. He will serve as a Consultant on a poultry project in Sao Paulo, Brazil.

(Continued on page 798)