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Cryogenic and Conventional Freezing of Chicken1
317
TURKEY MEAT STABILITY
Salmon, R. E., and J. B. O'Neil, 1971. The effect of the level and source of dietary fat on the growth, feed efficiency, grade and carcass composition of turkeys. Poultry Sci. SO: 1456-1467. Salmon, R. E., and J. B. O'Neil, 1973. The effect of the level and source and of a change of source of dietary fat on the fatty acid composition of the depot fat and the thigh and breast meat of turkeys as related to age. Poultry Sci. 52:302-314. Tarladgis, B. G., B. M. Watts and M. T. Younathon, 1960. A distillation method for the quantitative determination of malonaldehyde in rancid foods, J. Amer. Oil Chem. Soc. 37: 44-48.
Cryogenic and Conventional Freezing of Chicken1 E. M. STREETER2 AND J. V. SPENCER Department of Animal Sciences, Washington State University, Pullman, Washington 99163 (Received for publication May 6, 1972)
ABSTRACT Air blast, "Freon," "Nitreon" and liquid nitrogen spray processes were employed in the freezing of chicken fryer halves. Drip loss, cooking loss, shear force, visual bone darkening measurements and sensory evaluations were made on halves after cooking. The pectoralis major muscle was used for shear measurement with a Warner-Bratzler tenderometer. Degree of bone darkening was scored by a sensory panel. Liquid nitrogen frozen halves had the least drip loss. Average cooking loss was highest for air blast frozen halves and lowest for non-frozen halves. Non-frozen halves showed lowest cooking loss, shear force values and bone darkening scores. Only minor differences between freezing methods were noted in shear values and bone darkening. POULTEY SCIENCE 52:
INTRODUCTION
R
ATE of freezing, temperature and duration of storage, type of packaging material along with method of handling during and after thawing have been reported to affect those properties that contribute to the quality of frozen foods. It is generally accepted that faster freezing rates produce higher quality products than do slower rates of freezing, yet findings of experimental studies disagree. Du1 Scientific Paper No. 3500, College of Agriculture, Washington State University, Pullman. Project No. 1515. 2 Deceased.
317-325,
1973
bois et al. (1942) reported that poultry rapidly frozen at — 40°C. possessed better all-around quality, including palatability, when compared with carcasses conventionally frozen at — 12°C. Eklund et al. (1957) stated that, on the basis of appearance, turkey carcasses frozen at — 29°C. and — 40°C. in air blast were "superior" to those frozen at — 17.8°C. Novak and Rao (1966) reported that poultry parts frozen in liquid nitrogen spray had a smoother texture and a more normal flesh color, in both the frozen and thawed state, than did parts which were frozen in air blast. They also reported that chicken parts frozen in
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toxidation of turkey lipids. J. Food Sci. 29: S30-S34. Moran, E. T. Jr., and J. Somers, 1971. Live performance and depot fatty acid analysis of large white turkeys fed full-fat soybean rations. Proc. Guelph Nutrition Conf. for Feed Manufacturers, 73-79. Osborn, W. E., R. E. Moreng and T. E. Hartung, 1969. Turkey lipid characteristics: Influence of sex, age and estradiol-17 beta-monpalmitate. Poultry Sci. 48: 274-283. Palmer, A. Z., D. E. Brady, H. D. Naumann and L. N. Tucker, 1952. Deterioration in frozen pork as related to fat composition, storage temperature, length of storage period and packaging treatment. Missouri Agr. Exp. Sta. Bull. 492.
318
E. M. STEEETEE AND J. V. SPENCEE
extent of bleeding and varying processing conditions had no effect on bone darkening. These conflicting reports suggested the need for further study in these areas especially where newer methods of freezing are employed. The purpose of this study, therefore, was to compare the more recently developed methods of freezing, i.e. by immersion in "Freon" 1 food freezant, the "Nitreon"2 process, and liquid nitrogen spray with the more conventional air blast method of freezing. Drip loss, cooking loss, shear force value and sensory panel score were used as criteria for evaluating frozen and thawed chicken halves, along with visual scoring of the degree of bone darkening. METHODS AND MATERIALS
Three replications were made using 50 Hubbard-White Mountain chicken broilers nine weeks of age per trial. All birds were slaughtered and processed in a manner similar to that of commercial operations and chilled in ice and water for four hours. Paired halves were used in this study. The left half was used as a non-frozen control and the right half was subjected to one of the four freezing methods. The frozen halves were stored one week at — 17.8°C. and the non-frozen halves were stored the same period at 1.1 °C. Cold air blast freezing was carried out in a cell operating at — 29°C. Air velocity, as measured by a velometer, was 100 f.p.m. as it flowed over the product being frozen. Temperature of the chicken halves and the chamber were measured and recorded using copper-constantan thermocouples connected to a recording potentiometer. A laboratory-size drum freezer was employed for immersion freezing using "Freon 1
"Freon" is the E. I. DuPont de Nemours Company name for dichlorodifluoromethane. 2 Patented freezing process of Nitreon, Inc., Spokane, Washington.
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liquid nitrogen spray showed less bone darkening. However, Pickett and Miller (1967) reported liquid nitrogen immersion freezing of turkeys yielded a product which was comparable with that produced by the conventional freezing method. Khan and van den Berg (1967) reported there was less drip loss from carcasses rapidly frozen in a methanol dry ice mixture (—80°C.) than from carcasses frozen in air ( - 1 7 . 8 ° C ) . Li et al. (1969) reported chicken thighs frozen by liquid nitrogen spray had higher initial color and appearance scores, less drip loss and lower shearpress values when compared with sharp frozen ( —29°C.) meat. In addition, when compared with sharp frozen thighs, liquid nitrogen frozen thighs showed a marked decrease in bone and meat darkening. In the same study, these workers reported that after cooking chicken thighs frozen by liquid nitrogen spray ( — 195.8° C.) or sharp freezing ( —29°C), the resulting sensory scores did not differ significantly in color, appearance, aroma, flavor, texture and tenderness. All researchers do not agree upon the reported advantages of rapid freezing. Stewart et al. (1945) froze broiler quarters at -67.8°C. for 10 minutes and at -20.6°C. for 5 hours and found that neither aging, which was accomplished by placing in a cooler at 1.1°C. for 18 hours before freezing, nor freezing rate produced any detectable differences in palatability scores. Marion and Stadelman (1958) reported that the rate of freezing poultry meat did not have a significant influence on the percent of drip loss, percent cooking loss or tenderness of broilers frozen at certain temperatures between - 1 2 ° C . and -26.2°C. Rate of freezing did not, when considered as a main effect, have a significant influence on tenderness according to Miller and May (1965). Brant and Stewart (1950) reported that genetic background,
319
FREEZING OF C H I C K E N
Food Freezant 12" (dichlorodifluoromethane). A mixture of "Freon 11" and dry ice was used as a cooling medium to condense the "Freon" food freezant gas as it was charged into the freezing chamber. For optimum freezing conditions (the freezant boiling at the product surface), the temperature of the liquid was maintained at - 3 0 ° C . (Fig. 1).
The liquid nitrogen spray freezing apparatus consisted of an insulated box constructed of a double thickness of 2-inch polystyrene foam. Insulated f-inch copper tubing carried the liquid nitrogen from the tank to the freezing chamber. Threeeighths inch hard drawn copper tubing, perforated every six inches with j^-inch diameter holes, was used as a spray header
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Freezing Chamber
Copper Tubing
Outer Jacket
ff 20" Freezer Basket \
FIG. 1. DuPont laboratory freezer.
E. M. STREETER AND J. V. SPENCER
Polystyrene Foam
Foil
Freezer
/,S
,S
Chamber
SS
/ 7 / V Vr
£
rS
,S ZZ-
/ / /
42" Tray FIG. 2. Liquid nitrogen freezer.
for the liquid nitrogen. A removable wire mesh tray was located ten inches below the copper header. The liquid nitrogen was held under pressure in a 100 liter tank. Liquid nitrogen was metered into the freezing chamber at SO p.s.i. for 30 seconds to pre-cool the chamber prior to freezing. Chicken halves were then introduced and liquid nitrogen was sprayed directly on the carcasses (Fig. 2). The "Nitreon" process can be described as a combination of a mechanical air blast freezer system and a liquid nitrogen spray system. The system used in this study con-
sisted of two freezing cells each equipped with 30 horsepower compressors for the mechanical refrigeration system. A copper tubing header, through which liquid nitrogen under pressure was sprayed into an air stream, was located six feet above the chamber floor on the wall opposite the evaporators. The velocity of this stream of air was 750 f.p.m. as measured by a velometer. The liquid nitrogen spray forced into the air stream did not come in contact with the product being frozen but vaporized in the air stream thus lowering the air temperature and creating an inert atmosphere in
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Mumlnum
FREEZING OF CHICKEN
3
Annie temperature analyzer, Model A-8, manufactured by Mechanical Refrigerator Enterprises, North Hollywood, California.
indicated the highest degree of preference and one indicated the lowest degree of preference.) Force required to shear the meat was measured with the Warner-Bratzler shear apparatus. Five shear measurements were recorded for each one cm.2 by four cm. long sample of the pectoralis major muscle. After samples had been obtained for taste panel use and for determination of shear force, all halves were deboned. The femur and tibia of each frozen half were fastened together for comparison with the same bones from the corresponding unfrozen half. An experienced panel of four judges, employing a scoring system of one to five (one indicated no bone darkening and five indicated severe darkening of the bone), evaluated the degree of bone darkening. Duncan's new multiple range procedure was used for statistical analysis of data (Steel and Torrie, 1960). RESULTS AND DISCUSSION
Freezing rates and chamber temperatures employed in this study are shown in Figures 3 and 4. Air blast freezing at —29° C. required 110-120 minutes for halves to reach — 10°C. Three different temperature stages are apparent in the cooling curve: 1—sensible heat; 2—latent heat; and 3— sensible heat. The "Freon" food freezant, "Nitreon" and liquid nitrogen spray frozen halves showed no such definite freezing stages. This observation probably can be attributed to the rapid rate of freezing obtained with these three methods. "Freon" food freezant frozen halves required 10 to 12 minutes to be frozen to — 10°C. while halves frozen by the "Nitreon" process and liquid nitrogen spray required 18 to 20 minutes to reach — 10°C. internally. Temperatures in the freezing chamber for air blast, "Freon" food freezant and liquid nitrogen spray were constant at — 29°C,
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the cell. The chamber temperature was lowered to — 53.8°C. in 8 to 10 minutes. When the temperature rose above — 53.8°C, a solenoid valve was actuated and additional liquid nitrogen was sprayed into the cell to maintain the desired temperature. An Annie3 temperature analyzer probe was inserted in one carcass half to measure internal temperature. The probe and other themocouples used in temperature measurement were placed in the broiler half approximately one inch proximally from the femoral-pelvic joint. All halves were frozen unpackaged to an internal temperature of — 10°C. After freezing, all halves were packaged individually in polyethylene bags and placed in a — 17.8°C. freezer. After one week's storage at — 17.8°C, all frozen halves were removed from the freezer, unpackaged, weighed, repackaged and transferred to a 1.1°C. cooler and allowed to thaw for 16 hours. The thawed halves were then drained five minutes, reweighed to determine drip loss and packaged in aluminum foil for cooking, using a "drug store" wrap. They were then placed in an oven preheated to 162.8°C; and after an internal temperature of 80°C. was reached, all halves were removed. Non-frozen control halves were cooked in the same manner at the same time. The juices that accumulated during cooking were drained and all halves were reweighed to determine cooking loss. Sensory panels, using experienced personnel, evaluated the cooked meat for color, juiciness, tenderness, texture, flavor and general acceptability. For taste panel evaluation, a portion of the biceps Jemoris was removed from one cooked half relegated to each freezing treatment and the corresponding non-frozen control half for rating on a one to ten Hedonic scale. (Ten
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E. M. STKEETER AND J. V. SPENCER
Chicken Flesh
40
30
20
§ 10
15
30
45
60
75
90
105
120
Time in Minutes FIG. 3. Characteristic temperature change of chicken flesh during air blast freezing at —20°F. (—29°C).
Freezing
Chambers
» "Nitreon" o "Freon Food Freezant 12" x Liquid Nitrogen Spray 10 Time in Minutes
FIG. 4. Temperature changes in representative chicken half during freezing by "Freon," "Nitreon," and liquid nitrogen spray.
- 3 0 ° C . and < - 100°C, respectively. The "Nitreon" process took 8 to 10 minutes to reach — 53.8°C. and maintained this temperature throughout the process with only minor fluctuations. Table 1 shows mean scores obtained for the quality factors evaluated. The halves frozen by "Freon" food freezant had the lowest mean drip loss but this was not statistically significantly lower than the drip loss from halves frozen with liquid nitrogen spray or the "Nitreon" process. Drip loss from air blast frozen halves was not significantly different from that of liquid nitrogen and "Nitreon" process frozen halves, but was significantly greater (P < 0.0S) than the loss from "Freon" frozen halves. The non-frozen halves had the lowest mean cooking loss and this was statistically significantly different from the cooking loss of those halves subjected to freezing by the "Nitreon" process, liquid nitrogen and
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Air Blast Cell
-20
323
FREEZING OF CHICKEN TABLE 1.—Duncan's new multiple range comparison of sensory panel score means for all consumer acceptability characteristics of chicken halves frozen, thawed and cooked Treatments 1
Taste panel Drip loss (%) Cooking loss (%) Shear force2 (lbs./cm. ) Bone darkening
7.65
DDM
AB
NF s2
—
22.9" 5.38" 2.05"
7.26* 2.84 b 29.5°
b
7.54" 1.92* 26.S b
6.45"* 2.58 b
6.72 b 2.42»b
NIT
LN
s;
b
7.59» 2.22** 25.8 b
6.93 2.02»b 25.9 b
+0.16 + 0.25 + 1.05
5.6*>b 2.71 b
6.58 ab 2.43 b
+ 0.43 + 0.13
1 Treatment codes: NF, non-frozen; AB, air blast; DDM, dichlorodifluoromethane; NIT, Nitreon; LN, liquid nitrogen spray; sj, standard error of the mean. 2 Any two means within a characteristic with a common superscript are not significantly different at the 5% level of probability.
zant immersion and air blast system were scored slightly lower. Liquid nitrogen spray frozen halves were rated significantly lower than the non-frozen halves, "Nitreon" process, and "Freon" food freezant immersion frozen halves, but not significantly lower than air blast frozen halves. These results can be attributed in part to the lower scores liquid nitrogen spray frozen halves received for juiciness and tenderness (Table 2). As shown in Table 1, the Warner-Bratzler shear values obtained indicated that there were no significant differences between the halves frozen by the various freezing methods. All freezing methods resulted in the production of higher shear force values for frozen halves than for nonfrozen halves. Only "Freon" food freezant TABLE 2.—Sensory panel mean scores1 for different consumer acceptability characteristics of chicken halves after freezing, thawing and cooking Treatments2 Characteristic Color Juiciness Tenderness Texture Flavor General acceptability
NF
AB
DDM
NIT
LN
7.90 7.50 7.92 7.82 7.42 7.50
7.47 7.22 7.55 7.32 6.80 6.90
7.45 7.35 7.80 7.52 7.10 7.35
7.87 7.25 7.62 7.65 7.35 7.62
7.52 6.65 6.62 6.72 6.97 6.90
1 Mean taste panel ratings using a Hedonic (ten indicated the highest degree of preference the2 lowest degree of preference). Treatment codes: NF, non-frozen; AB, dichlorodifluoromethane; NIT, Nitreon; LN,
scale of one to ten and one indicated air blast; DDM, liquid nitrogen.
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"Freon" process. The more rapidly frozen halves showed greater amounts of cooking loss than non-frozen halves but did not differ significantly from each other. Air blast frozen halves yielded the largest cooking loss. This loss varied significantly from the cooking loss observed in all other groups used in the study. These findings probably can be accounted for by the influence of freezing rate on ice crystal size. It can be assumed that smaller ice crystals were formed in halves frozen with "Freon" food freezant, "Nitreon" process and liquid nitrogen than with the air blast systems; consequently, less cell disruption should have been experienced which resulted in smaller amounts of drip and cooking loss. The results reported here concur with those of Koonz and Ramsbottom (1939) and Li et al. (1969) who reported that by employing faster rates of freezing, smaller amounts of drip loss would result. This effect is not supported by Pearson and Miller (1950) or Marion and Stadelman (1958) who reported that the rate of freezing did not influence the percentage of drip loss under the conditions of their experiments. Taste panels gave the highest scores for the over-all quality of cooked meat from non-frozen halves. Those halves frozen by the "Nitreon" process, "Freon" food free-
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E. M. STREETER AND J. V. SPENCER
nitrogen freezing completely eliminated bone darkening. What appear to be discrepancies in results among different studies of freezing methods can probably be attributed to differences in birds and classes of poultry used, specific freezing techniques, and methods of measuring effects attributable to freezing. ACKNOWLEDGMENT
The writers wish to thank Miss Lydia J. Tryhnew and Mr. John A. Verstrate for assistance in the conduct of this research and preparation of this manuscript. REFERENCES Brant, A. W., and G. F. Stewart, 1950. Bone darkening in frozen poultry. Food Technol. 4 : 168-174. Carlin, F., B. Lowe and G. F. Stewart, 1949. The effect of aging versus aging, freezing and thawing on the palatability of eviscerated poultry. Food Technol. 3 : 156-159. Dubois, C. W., D. K. Tressler and F. Fenton, 1942. The effect of rate of freezing and temperature of storage on the quality of frozen poultry. Refrig. Eng. 44: 93-99, 122. Eklund, M. W., W. E. Matson and J. V. Spencer, 1957. Freezing characteristics of eviscerated poultry using liquid immersion and air blast systems. Poultry Sci. 36: 1115. Ellis, C , and J. G. Woodroof, 1959. Prevention of bone darkening. Food Technol. 13: 533538. Khan, A. W., and L. van den Berg, 1967. Biochemical and quality changes occurring during freezing of poultry meat. J. Food Sci. 32: 148-150. Koonz, C. H., and J. M. Ramsbottom, 1939. Susceptibility of frozen cell waste of poultry meat to drip. Food Res. 4 : 485-492. Koonz, C. H., and J. M. Ramsbottom, 1947. Influence of freezing on color of bones and adjacent tissues. Food Res. 12: 393-399. Li, K. C , E. K. Heaton and J. E. Marion, 1969. Freezing chicken thighs by liquid nitrogen and sharp freezing process. Food Technol. 23 : 241-243. Marion, W. W., and W. J. Stadelman, 1958. Effects of various freezing methods on qual-
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immersion frozen halves varied significantly in shear force values from the nonfrozen halves. They were not significantly different from the halves frozen by other freezing methods. Taste panel results reported here tend to confirm the results of Carlin et al. (1949), Miller and May (1965) and Stewart et al. (1945) who reported that the rate of freezing did not have a significant influence on tenderness and palatability scores of chicken. However, none of the above studies employed liquid nitrogen freezing of chicken meat. Li et al. (1969) reported that sensory scores for cooked chicken thighs frozen by liquid nitrogen spray or sharp freezing did not differ significantly. Their results are substantiated by the findings reported here. Lower Warner-Bratzler shear values, however, for liquid nitrogen frozen poultry than for those frozen by conventional air blast freezing system were reported by Pickett and Miller (1967) and Li et al. (1969). Different rates of freezing and varying storage conditions could account in part for conflicting results. On the basis of bone darkening, there were no significant differences between the various methods of freezing used in this study (Table 1). In general, all bones from carcasses that had been frozen were darker than non-frozen bones. "Freon" food freezant immersion freezing resulted in bones which were not significantly darker than the non-frozen controls while liquid nitrogen spray, "Nitreon" process and air blast frozen bones were all statistically significantly darker than the non-frozen controls. These results agree with those of Woodroof and Shelor (1948), Ellis and Woodroof 1959) and Koonz and Ramsbottom (1947) who reported that freezing young chicken resulted in bone darkening when the chicken was thawed and cooked. However, Li et al. (1969) reported that liquid
FREEZING OF CHICKEN ity of poultry meats. Food Technol. 12: 367369. Miller, W. O., and K. N. May, 196S. Tenderness of chicken as affected by rate of freezing, storage time and temperature, and freeze drying. Food Technol. 19: 1171-1174. Novak, A., and R. Rao, 1966. Efficient freezing with liquid nitrogen. Food Eng. 38: 53-56. Pearson, A. M., and J. I. Miller, 19S0. The influence of rate of freezing and length of freezer storage upon the quality of beef of known origin. J. Anim. Sci. 9: 13-19. Pickett, L. D., and B. F. Miller, 1967. The effect
325
of liquid nitrogen on the taste, tenderness and keeping quality of dressed turkey. Poultry Sci. 46: 1148-1153. Steel, R. G., and J. H. Torrie, 1960. Principles and Procedures of Statistics. McGraw-Hill, N. Y. pp. 106-108. Stewa t, G. F., H. L. Hanson, B. Lowe and J. J. Austin, 1945. Effects of aging, freezing rate, and storage period on palatability of broilers. Food Res. 10: 16-27. Woodroof, J. G., and E. Shelor, 1948. Prevention of bone darkening in frozen-packed chickens. Food Inds. 20: 48-52.
NEWS AND NOTES Hatchery in Parsonburg. He joined Chick Master in 1944. Bob McCarty has been appointed Eastern Sales Manager. He has been Assistant Installation and Service Manager for Chick Master. HUNGARIAN W.P.S.A. BRANCH The Hungarian members of the World's Poultry Science Association formed a Branch of the Association—the 33rd—in August, 1972. The officers are: President—Dr. Domokos Dersi, Director of the Veterinary Medical Research Institute of the Hungarian Academy of Science; Vice President— Prof. Dr. Istvan Kantor, Head of the Poultry Section of the High-School for Animal Husbandry; and Secretary—Dr. Laszlo Szentirmai, Mezogazdasagi es Elelmezesugyi Miniszterium (Ministry of Agriculture), Kossuth ter 11, Budapest V.
ifestly owes its existence at this time to Mr. May who gave up other activities to ensure the survival of the WPSA.-"-. Mr. May has been a member of the Association for about 40 years. He served with the British Army during World War I, joining at its outbreak in 1914. At the end of hostilities, he began a career in journalism, and soon became Sub-Editor of Poultry World. He was appointed Editor in 1933, and continued in that position until his retirement in 1962. He was created a Member of the Most Excellent Order of the British Empire in 1963, and was the recipient of the B.O.C.M. Poultry Award in 1959, the Goodchild Trophy of the British Turkey Federation in 1960, and a Distinguished Service to the Industry Award of the British Poultry and Egg Producers Association in 1961.
MACDOUGALL MEDAL George May, M.B.E., is the 1972 recipient of the Macdougall Medal of the World's Poultry Science Association. He is the third member to receive the Award. Major Macdougall was the first to receive the Medal in 1962. Dr. Heuser, Honorary Past Secretary, was the second recipient in 1966. Mr. May is Production Manager of the World's Poultry Science Journal, being appointed in 1964. The citation read: "Mr. May came to the 'rescue' of the Association at the time of Macdougall's sudden death by at once taking over the secretarial duties and maintaining the WPSA Office in operation. One of the major claims advanced on behalf of Mr. May for the award is that the WPSA man-
RALSTON PURINA NOTES John R. Pedersen, Poultry Economist with the Ralston Purina Company for the past three years, has joined the staff of United Egg Producers, to head the Department of Marketing and Statistical Analysis. JAY L. LUSH HONORED Jay L. Lush, Charles F. Curtiss Distinguished Professor in Agriculture at Iowa State University, was honored at a special symposium and banquet sponsored by the American Dairy Science Association, the American Society of Animal Science, and the Poultry Science Association, held July 20, 1972, between the annual meetings of the former two societies at Virginia Polytechnic Institute and State ;University.
(Continued on page 331)
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(Continued from page 295)
TURKEY MEAT STABILITY
Salmon, R. E., and J. B. O'Neil, 1971. The effect of the level and source of dietary fat on the growth, feed efficiency, grade and carcass composition of turkeys. Poultry Sci. SO: 1456-1467. Salmon, R. E., and J. B. O'Neil, 1973. The effect of the level and source and of a change of source of dietary fat on the fatty acid composition of the depot fat and the thigh and breast meat of turkeys as related to age. Poultry Sci. 52:302-314. Tarladgis, B. G., B. M. Watts and M. T. Younathon, 1960. A distillation method for the quantitative determination of malonaldehyde in rancid foods, J. Amer. Oil Chem. Soc. 37: 44-48.
Cryogenic and Conventional Freezing of Chicken1 E. M. STREETER2 AND J. V. SPENCER Department of Animal Sciences, Washington State University, Pullman, Washington 99163 (Received for publication May 6, 1972)
ABSTRACT Air blast, "Freon," "Nitreon" and liquid nitrogen spray processes were employed in the freezing of chicken fryer halves. Drip loss, cooking loss, shear force, visual bone darkening measurements and sensory evaluations were made on halves after cooking. The pectoralis major muscle was used for shear measurement with a Warner-Bratzler tenderometer. Degree of bone darkening was scored by a sensory panel. Liquid nitrogen frozen halves had the least drip loss. Average cooking loss was highest for air blast frozen halves and lowest for non-frozen halves. Non-frozen halves showed lowest cooking loss, shear force values and bone darkening scores. Only minor differences between freezing methods were noted in shear values and bone darkening. POULTEY SCIENCE 52:
INTRODUCTION
R
ATE of freezing, temperature and duration of storage, type of packaging material along with method of handling during and after thawing have been reported to affect those properties that contribute to the quality of frozen foods. It is generally accepted that faster freezing rates produce higher quality products than do slower rates of freezing, yet findings of experimental studies disagree. Du1 Scientific Paper No. 3500, College of Agriculture, Washington State University, Pullman. Project No. 1515. 2 Deceased.
317-325,
1973
bois et al. (1942) reported that poultry rapidly frozen at — 40°C. possessed better all-around quality, including palatability, when compared with carcasses conventionally frozen at — 12°C. Eklund et al. (1957) stated that, on the basis of appearance, turkey carcasses frozen at — 29°C. and — 40°C. in air blast were "superior" to those frozen at — 17.8°C. Novak and Rao (1966) reported that poultry parts frozen in liquid nitrogen spray had a smoother texture and a more normal flesh color, in both the frozen and thawed state, than did parts which were frozen in air blast. They also reported that chicken parts frozen in
Downloaded from http://ps.oxfordjournals.org/ by guest on April 7, 2015
toxidation of turkey lipids. J. Food Sci. 29: S30-S34. Moran, E. T. Jr., and J. Somers, 1971. Live performance and depot fatty acid analysis of large white turkeys fed full-fat soybean rations. Proc. Guelph Nutrition Conf. for Feed Manufacturers, 73-79. Osborn, W. E., R. E. Moreng and T. E. Hartung, 1969. Turkey lipid characteristics: Influence of sex, age and estradiol-17 beta-monpalmitate. Poultry Sci. 48: 274-283. Palmer, A. Z., D. E. Brady, H. D. Naumann and L. N. Tucker, 1952. Deterioration in frozen pork as related to fat composition, storage temperature, length of storage period and packaging treatment. Missouri Agr. Exp. Sta. Bull. 492.
318
E. M. STEEETEE AND J. V. SPENCEE
extent of bleeding and varying processing conditions had no effect on bone darkening. These conflicting reports suggested the need for further study in these areas especially where newer methods of freezing are employed. The purpose of this study, therefore, was to compare the more recently developed methods of freezing, i.e. by immersion in "Freon" 1 food freezant, the "Nitreon"2 process, and liquid nitrogen spray with the more conventional air blast method of freezing. Drip loss, cooking loss, shear force value and sensory panel score were used as criteria for evaluating frozen and thawed chicken halves, along with visual scoring of the degree of bone darkening. METHODS AND MATERIALS
Three replications were made using 50 Hubbard-White Mountain chicken broilers nine weeks of age per trial. All birds were slaughtered and processed in a manner similar to that of commercial operations and chilled in ice and water for four hours. Paired halves were used in this study. The left half was used as a non-frozen control and the right half was subjected to one of the four freezing methods. The frozen halves were stored one week at — 17.8°C. and the non-frozen halves were stored the same period at 1.1 °C. Cold air blast freezing was carried out in a cell operating at — 29°C. Air velocity, as measured by a velometer, was 100 f.p.m. as it flowed over the product being frozen. Temperature of the chicken halves and the chamber were measured and recorded using copper-constantan thermocouples connected to a recording potentiometer. A laboratory-size drum freezer was employed for immersion freezing using "Freon 1
"Freon" is the E. I. DuPont de Nemours Company name for dichlorodifluoromethane. 2 Patented freezing process of Nitreon, Inc., Spokane, Washington.
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liquid nitrogen spray showed less bone darkening. However, Pickett and Miller (1967) reported liquid nitrogen immersion freezing of turkeys yielded a product which was comparable with that produced by the conventional freezing method. Khan and van den Berg (1967) reported there was less drip loss from carcasses rapidly frozen in a methanol dry ice mixture (—80°C.) than from carcasses frozen in air ( - 1 7 . 8 ° C ) . Li et al. (1969) reported chicken thighs frozen by liquid nitrogen spray had higher initial color and appearance scores, less drip loss and lower shearpress values when compared with sharp frozen ( —29°C.) meat. In addition, when compared with sharp frozen thighs, liquid nitrogen frozen thighs showed a marked decrease in bone and meat darkening. In the same study, these workers reported that after cooking chicken thighs frozen by liquid nitrogen spray ( — 195.8° C.) or sharp freezing ( —29°C), the resulting sensory scores did not differ significantly in color, appearance, aroma, flavor, texture and tenderness. All researchers do not agree upon the reported advantages of rapid freezing. Stewart et al. (1945) froze broiler quarters at -67.8°C. for 10 minutes and at -20.6°C. for 5 hours and found that neither aging, which was accomplished by placing in a cooler at 1.1°C. for 18 hours before freezing, nor freezing rate produced any detectable differences in palatability scores. Marion and Stadelman (1958) reported that the rate of freezing poultry meat did not have a significant influence on the percent of drip loss, percent cooking loss or tenderness of broilers frozen at certain temperatures between - 1 2 ° C . and -26.2°C. Rate of freezing did not, when considered as a main effect, have a significant influence on tenderness according to Miller and May (1965). Brant and Stewart (1950) reported that genetic background,
319
FREEZING OF C H I C K E N
Food Freezant 12" (dichlorodifluoromethane). A mixture of "Freon 11" and dry ice was used as a cooling medium to condense the "Freon" food freezant gas as it was charged into the freezing chamber. For optimum freezing conditions (the freezant boiling at the product surface), the temperature of the liquid was maintained at - 3 0 ° C . (Fig. 1).
The liquid nitrogen spray freezing apparatus consisted of an insulated box constructed of a double thickness of 2-inch polystyrene foam. Insulated f-inch copper tubing carried the liquid nitrogen from the tank to the freezing chamber. Threeeighths inch hard drawn copper tubing, perforated every six inches with j^-inch diameter holes, was used as a spray header
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Freezing Chamber
Copper Tubing
Outer Jacket
ff 20" Freezer Basket \
FIG. 1. DuPont laboratory freezer.
E. M. STREETER AND J. V. SPENCER
Polystyrene Foam
Foil
Freezer
/,S
,S
Chamber
SS
/ 7 / V Vr
£
rS
,S ZZ-
/ / /
42" Tray FIG. 2. Liquid nitrogen freezer.
for the liquid nitrogen. A removable wire mesh tray was located ten inches below the copper header. The liquid nitrogen was held under pressure in a 100 liter tank. Liquid nitrogen was metered into the freezing chamber at SO p.s.i. for 30 seconds to pre-cool the chamber prior to freezing. Chicken halves were then introduced and liquid nitrogen was sprayed directly on the carcasses (Fig. 2). The "Nitreon" process can be described as a combination of a mechanical air blast freezer system and a liquid nitrogen spray system. The system used in this study con-
sisted of two freezing cells each equipped with 30 horsepower compressors for the mechanical refrigeration system. A copper tubing header, through which liquid nitrogen under pressure was sprayed into an air stream, was located six feet above the chamber floor on the wall opposite the evaporators. The velocity of this stream of air was 750 f.p.m. as measured by a velometer. The liquid nitrogen spray forced into the air stream did not come in contact with the product being frozen but vaporized in the air stream thus lowering the air temperature and creating an inert atmosphere in
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Mumlnum
FREEZING OF CHICKEN
3
Annie temperature analyzer, Model A-8, manufactured by Mechanical Refrigerator Enterprises, North Hollywood, California.
indicated the highest degree of preference and one indicated the lowest degree of preference.) Force required to shear the meat was measured with the Warner-Bratzler shear apparatus. Five shear measurements were recorded for each one cm.2 by four cm. long sample of the pectoralis major muscle. After samples had been obtained for taste panel use and for determination of shear force, all halves were deboned. The femur and tibia of each frozen half were fastened together for comparison with the same bones from the corresponding unfrozen half. An experienced panel of four judges, employing a scoring system of one to five (one indicated no bone darkening and five indicated severe darkening of the bone), evaluated the degree of bone darkening. Duncan's new multiple range procedure was used for statistical analysis of data (Steel and Torrie, 1960). RESULTS AND DISCUSSION
Freezing rates and chamber temperatures employed in this study are shown in Figures 3 and 4. Air blast freezing at —29° C. required 110-120 minutes for halves to reach — 10°C. Three different temperature stages are apparent in the cooling curve: 1—sensible heat; 2—latent heat; and 3— sensible heat. The "Freon" food freezant, "Nitreon" and liquid nitrogen spray frozen halves showed no such definite freezing stages. This observation probably can be attributed to the rapid rate of freezing obtained with these three methods. "Freon" food freezant frozen halves required 10 to 12 minutes to be frozen to — 10°C. while halves frozen by the "Nitreon" process and liquid nitrogen spray required 18 to 20 minutes to reach — 10°C. internally. Temperatures in the freezing chamber for air blast, "Freon" food freezant and liquid nitrogen spray were constant at — 29°C,
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the cell. The chamber temperature was lowered to — 53.8°C. in 8 to 10 minutes. When the temperature rose above — 53.8°C, a solenoid valve was actuated and additional liquid nitrogen was sprayed into the cell to maintain the desired temperature. An Annie3 temperature analyzer probe was inserted in one carcass half to measure internal temperature. The probe and other themocouples used in temperature measurement were placed in the broiler half approximately one inch proximally from the femoral-pelvic joint. All halves were frozen unpackaged to an internal temperature of — 10°C. After freezing, all halves were packaged individually in polyethylene bags and placed in a — 17.8°C. freezer. After one week's storage at — 17.8°C, all frozen halves were removed from the freezer, unpackaged, weighed, repackaged and transferred to a 1.1°C. cooler and allowed to thaw for 16 hours. The thawed halves were then drained five minutes, reweighed to determine drip loss and packaged in aluminum foil for cooking, using a "drug store" wrap. They were then placed in an oven preheated to 162.8°C; and after an internal temperature of 80°C. was reached, all halves were removed. Non-frozen control halves were cooked in the same manner at the same time. The juices that accumulated during cooking were drained and all halves were reweighed to determine cooking loss. Sensory panels, using experienced personnel, evaluated the cooked meat for color, juiciness, tenderness, texture, flavor and general acceptability. For taste panel evaluation, a portion of the biceps Jemoris was removed from one cooked half relegated to each freezing treatment and the corresponding non-frozen control half for rating on a one to ten Hedonic scale. (Ten
321
322
E. M. STKEETER AND J. V. SPENCER
Chicken Flesh
40
30
20
§ 10
15
30
45
60
75
90
105
120
Time in Minutes FIG. 3. Characteristic temperature change of chicken flesh during air blast freezing at —20°F. (—29°C).
Freezing
Chambers
» "Nitreon" o "Freon Food Freezant 12" x Liquid Nitrogen Spray 10 Time in Minutes
FIG. 4. Temperature changes in representative chicken half during freezing by "Freon," "Nitreon," and liquid nitrogen spray.
- 3 0 ° C . and < - 100°C, respectively. The "Nitreon" process took 8 to 10 minutes to reach — 53.8°C. and maintained this temperature throughout the process with only minor fluctuations. Table 1 shows mean scores obtained for the quality factors evaluated. The halves frozen by "Freon" food freezant had the lowest mean drip loss but this was not statistically significantly lower than the drip loss from halves frozen with liquid nitrogen spray or the "Nitreon" process. Drip loss from air blast frozen halves was not significantly different from that of liquid nitrogen and "Nitreon" process frozen halves, but was significantly greater (P < 0.0S) than the loss from "Freon" frozen halves. The non-frozen halves had the lowest mean cooking loss and this was statistically significantly different from the cooking loss of those halves subjected to freezing by the "Nitreon" process, liquid nitrogen and
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Air Blast Cell
-20
323
FREEZING OF CHICKEN TABLE 1.—Duncan's new multiple range comparison of sensory panel score means for all consumer acceptability characteristics of chicken halves frozen, thawed and cooked Treatments 1
Taste panel Drip loss (%) Cooking loss (%) Shear force2 (lbs./cm. ) Bone darkening
7.65
DDM
AB
NF s2
—
22.9" 5.38" 2.05"
7.26* 2.84 b 29.5°
b
7.54" 1.92* 26.S b
6.45"* 2.58 b
6.72 b 2.42»b
NIT
LN
s;
b
7.59» 2.22** 25.8 b
6.93 2.02»b 25.9 b
+0.16 + 0.25 + 1.05
5.6*>b 2.71 b
6.58 ab 2.43 b
+ 0.43 + 0.13
1 Treatment codes: NF, non-frozen; AB, air blast; DDM, dichlorodifluoromethane; NIT, Nitreon; LN, liquid nitrogen spray; sj, standard error of the mean. 2 Any two means within a characteristic with a common superscript are not significantly different at the 5% level of probability.
zant immersion and air blast system were scored slightly lower. Liquid nitrogen spray frozen halves were rated significantly lower than the non-frozen halves, "Nitreon" process, and "Freon" food freezant immersion frozen halves, but not significantly lower than air blast frozen halves. These results can be attributed in part to the lower scores liquid nitrogen spray frozen halves received for juiciness and tenderness (Table 2). As shown in Table 1, the Warner-Bratzler shear values obtained indicated that there were no significant differences between the halves frozen by the various freezing methods. All freezing methods resulted in the production of higher shear force values for frozen halves than for nonfrozen halves. Only "Freon" food freezant TABLE 2.—Sensory panel mean scores1 for different consumer acceptability characteristics of chicken halves after freezing, thawing and cooking Treatments2 Characteristic Color Juiciness Tenderness Texture Flavor General acceptability
NF
AB
DDM
NIT
LN
7.90 7.50 7.92 7.82 7.42 7.50
7.47 7.22 7.55 7.32 6.80 6.90
7.45 7.35 7.80 7.52 7.10 7.35
7.87 7.25 7.62 7.65 7.35 7.62
7.52 6.65 6.62 6.72 6.97 6.90
1 Mean taste panel ratings using a Hedonic (ten indicated the highest degree of preference the2 lowest degree of preference). Treatment codes: NF, non-frozen; AB, dichlorodifluoromethane; NIT, Nitreon; LN,
scale of one to ten and one indicated air blast; DDM, liquid nitrogen.
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"Freon" process. The more rapidly frozen halves showed greater amounts of cooking loss than non-frozen halves but did not differ significantly from each other. Air blast frozen halves yielded the largest cooking loss. This loss varied significantly from the cooking loss observed in all other groups used in the study. These findings probably can be accounted for by the influence of freezing rate on ice crystal size. It can be assumed that smaller ice crystals were formed in halves frozen with "Freon" food freezant, "Nitreon" process and liquid nitrogen than with the air blast systems; consequently, less cell disruption should have been experienced which resulted in smaller amounts of drip and cooking loss. The results reported here concur with those of Koonz and Ramsbottom (1939) and Li et al. (1969) who reported that by employing faster rates of freezing, smaller amounts of drip loss would result. This effect is not supported by Pearson and Miller (1950) or Marion and Stadelman (1958) who reported that the rate of freezing did not influence the percentage of drip loss under the conditions of their experiments. Taste panels gave the highest scores for the over-all quality of cooked meat from non-frozen halves. Those halves frozen by the "Nitreon" process, "Freon" food free-
324
E. M. STREETER AND J. V. SPENCER
nitrogen freezing completely eliminated bone darkening. What appear to be discrepancies in results among different studies of freezing methods can probably be attributed to differences in birds and classes of poultry used, specific freezing techniques, and methods of measuring effects attributable to freezing. ACKNOWLEDGMENT
The writers wish to thank Miss Lydia J. Tryhnew and Mr. John A. Verstrate for assistance in the conduct of this research and preparation of this manuscript. REFERENCES Brant, A. W., and G. F. Stewart, 1950. Bone darkening in frozen poultry. Food Technol. 4 : 168-174. Carlin, F., B. Lowe and G. F. Stewart, 1949. The effect of aging versus aging, freezing and thawing on the palatability of eviscerated poultry. Food Technol. 3 : 156-159. Dubois, C. W., D. K. Tressler and F. Fenton, 1942. The effect of rate of freezing and temperature of storage on the quality of frozen poultry. Refrig. Eng. 44: 93-99, 122. Eklund, M. W., W. E. Matson and J. V. Spencer, 1957. Freezing characteristics of eviscerated poultry using liquid immersion and air blast systems. Poultry Sci. 36: 1115. Ellis, C , and J. G. Woodroof, 1959. Prevention of bone darkening. Food Technol. 13: 533538. Khan, A. W., and L. van den Berg, 1967. Biochemical and quality changes occurring during freezing of poultry meat. J. Food Sci. 32: 148-150. Koonz, C. H., and J. M. Ramsbottom, 1939. Susceptibility of frozen cell waste of poultry meat to drip. Food Res. 4 : 485-492. Koonz, C. H., and J. M. Ramsbottom, 1947. Influence of freezing on color of bones and adjacent tissues. Food Res. 12: 393-399. Li, K. C , E. K. Heaton and J. E. Marion, 1969. Freezing chicken thighs by liquid nitrogen and sharp freezing process. Food Technol. 23 : 241-243. Marion, W. W., and W. J. Stadelman, 1958. Effects of various freezing methods on qual-
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immersion frozen halves varied significantly in shear force values from the nonfrozen halves. They were not significantly different from the halves frozen by other freezing methods. Taste panel results reported here tend to confirm the results of Carlin et al. (1949), Miller and May (1965) and Stewart et al. (1945) who reported that the rate of freezing did not have a significant influence on tenderness and palatability scores of chicken. However, none of the above studies employed liquid nitrogen freezing of chicken meat. Li et al. (1969) reported that sensory scores for cooked chicken thighs frozen by liquid nitrogen spray or sharp freezing did not differ significantly. Their results are substantiated by the findings reported here. Lower Warner-Bratzler shear values, however, for liquid nitrogen frozen poultry than for those frozen by conventional air blast freezing system were reported by Pickett and Miller (1967) and Li et al. (1969). Different rates of freezing and varying storage conditions could account in part for conflicting results. On the basis of bone darkening, there were no significant differences between the various methods of freezing used in this study (Table 1). In general, all bones from carcasses that had been frozen were darker than non-frozen bones. "Freon" food freezant immersion freezing resulted in bones which were not significantly darker than the non-frozen controls while liquid nitrogen spray, "Nitreon" process and air blast frozen bones were all statistically significantly darker than the non-frozen controls. These results agree with those of Woodroof and Shelor (1948), Ellis and Woodroof 1959) and Koonz and Ramsbottom (1947) who reported that freezing young chicken resulted in bone darkening when the chicken was thawed and cooked. However, Li et al. (1969) reported that liquid
FREEZING OF CHICKEN ity of poultry meats. Food Technol. 12: 367369. Miller, W. O., and K. N. May, 196S. Tenderness of chicken as affected by rate of freezing, storage time and temperature, and freeze drying. Food Technol. 19: 1171-1174. Novak, A., and R. Rao, 1966. Efficient freezing with liquid nitrogen. Food Eng. 38: 53-56. Pearson, A. M., and J. I. Miller, 19S0. The influence of rate of freezing and length of freezer storage upon the quality of beef of known origin. J. Anim. Sci. 9: 13-19. Pickett, L. D., and B. F. Miller, 1967. The effect
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of liquid nitrogen on the taste, tenderness and keeping quality of dressed turkey. Poultry Sci. 46: 1148-1153. Steel, R. G., and J. H. Torrie, 1960. Principles and Procedures of Statistics. McGraw-Hill, N. Y. pp. 106-108. Stewa t, G. F., H. L. Hanson, B. Lowe and J. J. Austin, 1945. Effects of aging, freezing rate, and storage period on palatability of broilers. Food Res. 10: 16-27. Woodroof, J. G., and E. Shelor, 1948. Prevention of bone darkening in frozen-packed chickens. Food Inds. 20: 48-52.
NEWS AND NOTES Hatchery in Parsonburg. He joined Chick Master in 1944. Bob McCarty has been appointed Eastern Sales Manager. He has been Assistant Installation and Service Manager for Chick Master. HUNGARIAN W.P.S.A. BRANCH The Hungarian members of the World's Poultry Science Association formed a Branch of the Association—the 33rd—in August, 1972. The officers are: President—Dr. Domokos Dersi, Director of the Veterinary Medical Research Institute of the Hungarian Academy of Science; Vice President— Prof. Dr. Istvan Kantor, Head of the Poultry Section of the High-School for Animal Husbandry; and Secretary—Dr. Laszlo Szentirmai, Mezogazdasagi es Elelmezesugyi Miniszterium (Ministry of Agriculture), Kossuth ter 11, Budapest V.
ifestly owes its existence at this time to Mr. May who gave up other activities to ensure the survival of the WPSA.-"-. Mr. May has been a member of the Association for about 40 years. He served with the British Army during World War I, joining at its outbreak in 1914. At the end of hostilities, he began a career in journalism, and soon became Sub-Editor of Poultry World. He was appointed Editor in 1933, and continued in that position until his retirement in 1962. He was created a Member of the Most Excellent Order of the British Empire in 1963, and was the recipient of the B.O.C.M. Poultry Award in 1959, the Goodchild Trophy of the British Turkey Federation in 1960, and a Distinguished Service to the Industry Award of the British Poultry and Egg Producers Association in 1961.
MACDOUGALL MEDAL George May, M.B.E., is the 1972 recipient of the Macdougall Medal of the World's Poultry Science Association. He is the third member to receive the Award. Major Macdougall was the first to receive the Medal in 1962. Dr. Heuser, Honorary Past Secretary, was the second recipient in 1966. Mr. May is Production Manager of the World's Poultry Science Journal, being appointed in 1964. The citation read: "Mr. May came to the 'rescue' of the Association at the time of Macdougall's sudden death by at once taking over the secretarial duties and maintaining the WPSA Office in operation. One of the major claims advanced on behalf of Mr. May for the award is that the WPSA man-
RALSTON PURINA NOTES John R. Pedersen, Poultry Economist with the Ralston Purina Company for the past three years, has joined the staff of United Egg Producers, to head the Department of Marketing and Statistical Analysis. JAY L. LUSH HONORED Jay L. Lush, Charles F. Curtiss Distinguished Professor in Agriculture at Iowa State University, was honored at a special symposium and banquet sponsored by the American Dairy Science Association, the American Society of Animal Science, and the Poultry Science Association, held July 20, 1972, between the annual meetings of the former two societies at Virginia Polytechnic Institute and State ;University.
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