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Turkey Tenderness in Relation to Holding In and Rate of Passage Through Thawing Range of Temperature
Turkey Tenderness in Relation to Holding In and Rate of Passage Through Thawing Range of Temperature A. A.
K L O S E , A.
A.
CAMPBELL, M.
F.
POOL AND H.
L.
HANSON
Western Regional Research Laboratory,1 Albany, California (Received for publication February 17, 1961)
INTRODUCTION
I
1 \ laboratory of the Western Utilization Research and Development Division, Agriculture Research Service, U. S. Department of Agriculture.
EXPERIMENTAL WORK AND RESULTS
Evaluation oj Holding at 27°F. Experiment A. Beltsville turkey hens, 15 weeks old and 7 lbs. live weight, were starved overnight, shocked for 3-5 seconds, bled for 2 minutes with an outside neck cut, scalded at 140°F. for 30 seconds, picked with minimum force on a single drum picker, eviscerated immediately, placed in ice slush 35 minutes after slaughter and chilled for periods indicated in Table 1, removed from ice slush and drained for 10 minutes, packaged in evacuated, heat-shrunk plastic film bags, placed in a — 30°F., 1300 feet per
1 633
Downloaded from http://ps.oxfordjournals.org/ at Kainan University on May 8, 2015
N THE tenderization reactions that normally take place in poultry meat within 24 hours after slaughter, it has been well established that all reactions are essentially arrested at 0°F. and below, and that tenderization can proceed in the unfrozen state either before freezing or after thawing (Koonz et al., 1954; Klose et al., 19S9; Pool et al., 1959). These reports and others (Klose et al., 1960a; Dodge and Stadelman, 1960) have also demonstrated that 1-2 hours in ice slush, with or without mechanical agitation, does not provide adequate tenderization for small turkeys to be cooked from the frozen state. Slow tenderization has been shown to'occur in the 25-27°F. range, where only about 70 percent of the water in the muscle is frozen out (Klose et al., 1959; Pool et al., 1959), but in the initial experiments no determinations were made of the effect of holding for days at 25-27°F. on off-flavor development. Like other meats, poultry meat has also been found to exhibit "thaw rigor," in which muscle frozen pre-rigor exhibits a rapid onset of rigor generally accompanied by shortening when it is thawed. In experiments with paired, excised chicken breast muscles, de Fremery and Pool (1960) have shown that freezing and thawing the excised muscle before the normal onset of rigor produces, even when followed by an adequate aging period, a tougher muscle than one
frozen and thawed after passing through rigor. Previous tests with whole carcasses had not indicated appreciable differences in tenderization accomplished by holding before freezing compared to holding after thawing for the same time, but there was always an uncertainty introduced in evaluating the tenderization accomplished during the thawing period. If the order of sequence of freezing and aging, or the rate of thawing, were to have an important effect on ultimate tenderness, this would be of critical interest to processors who convert raw frozen poultry into precooked frozen products, and to any consumer who wishes to accomplish aging and tenderization after thawing instead of before freezing. This paper describes extended evaluations of tenderization and possible flavor changes induced by 25-27°F. holding, and also provides evaluations of the effect of rate of thawing (i.e., rate of passage through 2030°F. range) on ultimate tenderness.
1634
A. A. KLOSE, A. A. CAMPBELL, M. F. POOL AND H. L. HANSON
TABLE 1.—Effect of holding at 27° F. on shear force (Experiment A., six IS week Beltsville turkey hens per group) Holding Condition1
Shear Force, Pectoralis super., lbs.
Group 27°F. Air
Average2
Range
(hrs.) 0 243 2 2 2 1 1 1
(days) 0 0 3 7 14 3 7 14
20 10 13 11 11 13 14 13
14-26 8-12 10-15 9-13 9-14 11-17 12-16 10-17
1 Prior to cooking and shearing, all groups were held at 0°F. for 2\ months minus times held at 27°F 2 Based on a pooled error variance, the least significant difference between groups is estimated to be 3 at 5 percent level and 4 at 1 percent level of probability. 3 Ice slush allowed to drain freely after first 8 hours.
minute air blast freezer 20 minutes after removal from the chill tank, removed from the freezer after 5 hours, and held in 0°F. storage or a combination of 27°F. storage and 0°F. storage as indicated in Table 1, before roasting from the frozen state and determining shear force values. There were six turkeys per group. Birds were roasted from the frozen state in a 325°F. rotating electric oven to an internal breast temperature of 180°F. Shear tests using the Warner-Bratzler apparatus were made on 1 square inch cross section strips of the Pectoralis superficialis muscle from the left side. In order to determine if the longest (14 days) period of holding at 27°F. had any adverse effect on flavor, a taste panel of 11 judges made 6 replicate comparisons of flavor in Groups 2 and 5, using the breast and thigh muscles on the right side. Each judge ranked both light and dark meat, the group having the least off-flavor being ranked 1 and the other group, 2. The average panel ranks for groups 2 and 5 were 1.50 and 1.50 for the dark meat, and 1.59 and 1.41, respectively, for the light
Downloaded from http://ps.oxfordjournals.org/ at Kainan University on May 8, 2015
Ice Slush
meat. The difference indicated for the light meat was not significant. Shear force values as shown in Table 1 indicate that a combination of 1 hour ice chill and 3 days at 27°F. after freezing accomplished 70 percent as much tenderization as the completely adequate 24 hour ice chill. Increasing the 27°F. holding period from 3 days to 14 days did not have a significant effect. Increasing the time in ice chill from 1 to 2 hours for the two longer 27°F. holding periods had a small effect, significant at the 5 percent level. These results confirm previous findings and suggest that a high quality, adequately tenderized product can be achieved with a very rapid, short ice chilling procedure if the frozen birds are held at about 27°F. for several days. For very light (white) birds (e.g., immersion frozen turkeys), the 27°F. holding may cause a slight surface darkening due to formation of larger sized ice crystals (van den Berg and Lentz, 1958; Klose and Pool, 1956), but the eating quality should be unaffected. Experiment B. Two groups of six Bronze turkey hens each (16 lbs. average live weight) were processed and evaluated in the same manner as described above for experiment A, except for the chilling and holding conditions, which are listed in Table 2. The essentially equivalent mean shear force values and flavor ranks indicate that the combination of 1 hour in ice slush and 14 days at 27°F. is equivalent in tenderizing effect to 48 hours in ice slush, and that the 14 days at 27°F. had no significant effect on flavor. Evaluation of Effect of Thawing Rate on Tenderization. Uniform lots of Beltsville hen turkeys (15 weeks old for experiment C and 22 weeks old for experiment D) were shocked, bled for 2 minutes, scalded at 140°F. for 30 seconds, picked in a cyclic rubber fingered picker for 20 seconds, eviscerated immediately, chilled as indicated in Table 3, packaged in evacuated, heat-
TURKEY TENDERNESS AND THAWING
1635
TABLE 2.—Effect of holding at Z7°F. on shear force and flavor (Experiment B., six 20 week Bronze turkey hens per group) Holding Condition1
Mean Flavor Ranks 2
Shear Values, lbs.
Group
1 2
Ice Slush
27°F. Air
Average
Range
Light Meat
Dark Meat
hrs. 1 48
days 14 0
11 10
9-12 6-15
1.60 1.40
1.49 1.51
1
Prior to cooking and shearing, Group 1 held 2 months at 0°F. and Group 2 held 2 | months at 0°F. 2 The two groups were ranked for off-flavor, 1 being assigned to group sample having least off-flavor, 2 to other sample of pair. Differences, representing data from 12 judges and 6 replications are not significant at 5 percent level of probability.
ied, has no significant effect on the ultimate tenderness of turkeys held for a sufficiently long aging period. Since tap water thawing would probably be rapid enough for any commercial or domestic thawing operation, the data indicate that there need be no special concern over the possibility of toughening the meat of frozen whole turkey carcasses by too rapid thawing. SUMMARY Ready-to-cook turkey hens were subjected to variations in chilling and thawing procedures in order to determine the effect on ultimate tenderness and flavor of variations in the extent of holding at 27°F. and |
32
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«
/"MEAT
UJ
5 24 DC UJ Q. 2 UJ 1-
20 6
12
18
24
HOURS
FIG. 1. Temperature in packaged, ready-to-cook turkey in relation to programed increase in air temperature, with air velocity over turkey of about SO ft./min.
Downloaded from http://ps.oxfordjournals.org/ at Kainan University on May 8, 2015
shrunk plastic bags, and frozen rapidly on open shelves in a — 30°F., 1300 feet per minute, air blast freezer. The frozen carcasses were stored at — 10°F. for several weeks and until subjected to the thawing procedures described in Table 3. In the airthawing procedures, the carcass temperature naturally lagged behind the air temperature (by about 3°F. in first 24 hours for group 1 of experiment D) but the rate of temperature increase in the carcass over the thawing range (20°F. to 30°F.) was quite gradual, as shown for a pilot carcass in Figure 1. All thawed carcasses, and groups 1 and 2 of experiment C which were cooked from the frozen state, were roasted in a 325°F. rotating electric oven to an internal breast temperature of 180°F. Average shear force values for 1 square inch cross section strips of the Pectoralis superficialis, representing 42 to 60 values per group depending on size of the group, and the ranges between birds, are presented in Table 3. The extent of tenderization possible by holding in the unfrozen state either before or after freezing is indicated by the difference between the shear value, 26 lbs., for group 1 of experiment C and the shear value for groups 2 (9 lbs.) and 3 (10 lbs.) of the same experiment. However, there was no significant difference between groups 3and 4 of experiment C, or between groups 1 and 2 of experiment D, which shows that the rate of thawing, within the limits stud-
1636
A. A. KLOSE, A. A. CAMPBELL, M. F. POOL AND H. L. HANSON TABLTC 3.—Effect
Group
Number of Turkeys
Experiment C 1 2 3 4 Experiment D 1 2
of rate of thawing on ultimate tenderness
Chilling prior to freezing
Thawing and Holding
8 8 8 7
None 20 hrs. Ice Slush None None
None None Gradual, 1 4 days Sudden,2 4 days
9 10
None None
Gradual, 3 3 days Sudden,4 3 days
Shear Force Value, lbs. Ayerage
26 9 10 12
Range
11-39 5-15 5-13 7-17 8-12 6- 9
in the rate of temperature rise in the thawing (20°F. to 30°F.) region. Holding 1 hour ice chilled birds for as little as 3 days at 27°F. provided adequate tenderization, and no adverse flavor changes were noted after 14 days at 27°F. Increasing 27°F. holding time from 3 to 14 days had no significant effect on ultimate tenderness. For birds subsequently held at 27°F., increasing ice chilling time from 1 hour to 2 hours had a small and probably unimportant effect. Wide differences in rate of thawing of birds frozen pre-rigor had no adverse effect on ultimate tenderness achieved by holding after thawing. Holding frozen turkeys for a short period in the intermediate thawing range offers promise of providing tenderness in birds which, for reasons of economics or convenience, can neither be chilled long enough nor held long enough in the thawed condition to provide desired degrees of tenderness. REFERENCES de Fremery, D., and M. F. Pool, 1960. Biochemistry of chicken muscle as related to rigor mortis
and tenderization. Food Research, 25: 73-87. Dodge, J. W., and W. J. Stadelman, 1960. Relationships between pH, tenderness, and moisture levels during early post-mortem aging of turkey meat. Food Technology, 14: 43-46. Klose, A. A., M. F. Pool, M. B. Wide, H. L. Hanson and H. Lineweaver, 19S9. Poultry tenderness. I. Influence of processing on tenderness of turkeys. Food Technology, 13: 20-24. Klose, A. A., M. F. Pool, D. de Fremery, A. A. Campbell and H. L. Hanson, 1960a. Effect of laboratory scale agitated chilling of poultry on quality. Poultry Sci. 39: 1193-1198. Klose, A. A., A. A. Campbell, H. L. Hanson and H. Lineweaver, 1960b. Effect of duration and type of chilling and thawing on tenderness of frozen turkeys. Poultry Sci. 39: 1265. Klose, A. A., and M. F. Pool, 1956. Effect of freezing conditions on apearance of frozen turkeys. Food Technology, 10: 34-38. Koonz, C. H., M. I. Darrow and E. O. Essary, 1954. Factors influencing tenderness of principal muscles composing the poultry carcass. Food Technology, 8: 97-100. Pool, M. F., D. de Fremery, A. A. Campbell and A A. Klose, 1959. Poultry tenderness. II. Influence of processing on tenderness of chickens. Food Technology, 13 : 25-29. van den Berg, L., and C. P. Lentz, 1958. Liquid immersion and air blast freezing of poultry. American Egg and Poultry Review 20(8) : 6-8, 22-23.
Downloaded from http://ps.oxfordjournals.org/ at Kainan University on May 8, 2015
1 Carcasses at - 10°F. transferred to air at 10°F. for 8 hrs., 20°F. for next 15 hrs., 30°F. for next 24 hrs., and at 37° F. for rest of 4 day period. 2 Carcasses at — 10°F. transferred to 60°F. circulating water for 4 hrs., and in air at 37°F. for rest of 4 day period. 3 Carcasses transferred from — 10°F. to 0°F. to 10°F. to 20°F. air over 1 week period, then air temperature was raised from 20° F. to 34° F. gradually over a 24 hr. period, followed by a steady air temperature of 37°F. for the final 48 hrs. of 72 hr. thawing and holding period. 4 Carcasses transferred from — 10°F. to 0°F. to 10°F. to 20°F. air over 1 week period, then thawed rapidly in 60°F. circulating tap water for 2 hrs., and held in air at 37°F. for final 70 hrs. of 72 hr. thawing and holding period.
K L O S E , A.
A.
CAMPBELL, M.
F.
POOL AND H.
L.
HANSON
Western Regional Research Laboratory,1 Albany, California (Received for publication February 17, 1961)
INTRODUCTION
I
1 \ laboratory of the Western Utilization Research and Development Division, Agriculture Research Service, U. S. Department of Agriculture.
EXPERIMENTAL WORK AND RESULTS
Evaluation oj Holding at 27°F. Experiment A. Beltsville turkey hens, 15 weeks old and 7 lbs. live weight, were starved overnight, shocked for 3-5 seconds, bled for 2 minutes with an outside neck cut, scalded at 140°F. for 30 seconds, picked with minimum force on a single drum picker, eviscerated immediately, placed in ice slush 35 minutes after slaughter and chilled for periods indicated in Table 1, removed from ice slush and drained for 10 minutes, packaged in evacuated, heat-shrunk plastic film bags, placed in a — 30°F., 1300 feet per
1 633
Downloaded from http://ps.oxfordjournals.org/ at Kainan University on May 8, 2015
N THE tenderization reactions that normally take place in poultry meat within 24 hours after slaughter, it has been well established that all reactions are essentially arrested at 0°F. and below, and that tenderization can proceed in the unfrozen state either before freezing or after thawing (Koonz et al., 1954; Klose et al., 19S9; Pool et al., 1959). These reports and others (Klose et al., 1960a; Dodge and Stadelman, 1960) have also demonstrated that 1-2 hours in ice slush, with or without mechanical agitation, does not provide adequate tenderization for small turkeys to be cooked from the frozen state. Slow tenderization has been shown to'occur in the 25-27°F. range, where only about 70 percent of the water in the muscle is frozen out (Klose et al., 1959; Pool et al., 1959), but in the initial experiments no determinations were made of the effect of holding for days at 25-27°F. on off-flavor development. Like other meats, poultry meat has also been found to exhibit "thaw rigor," in which muscle frozen pre-rigor exhibits a rapid onset of rigor generally accompanied by shortening when it is thawed. In experiments with paired, excised chicken breast muscles, de Fremery and Pool (1960) have shown that freezing and thawing the excised muscle before the normal onset of rigor produces, even when followed by an adequate aging period, a tougher muscle than one
frozen and thawed after passing through rigor. Previous tests with whole carcasses had not indicated appreciable differences in tenderization accomplished by holding before freezing compared to holding after thawing for the same time, but there was always an uncertainty introduced in evaluating the tenderization accomplished during the thawing period. If the order of sequence of freezing and aging, or the rate of thawing, were to have an important effect on ultimate tenderness, this would be of critical interest to processors who convert raw frozen poultry into precooked frozen products, and to any consumer who wishes to accomplish aging and tenderization after thawing instead of before freezing. This paper describes extended evaluations of tenderization and possible flavor changes induced by 25-27°F. holding, and also provides evaluations of the effect of rate of thawing (i.e., rate of passage through 2030°F. range) on ultimate tenderness.
1634
A. A. KLOSE, A. A. CAMPBELL, M. F. POOL AND H. L. HANSON
TABLE 1.—Effect of holding at 27° F. on shear force (Experiment A., six IS week Beltsville turkey hens per group) Holding Condition1
Shear Force, Pectoralis super., lbs.
Group 27°F. Air
Average2
Range
(hrs.) 0 243 2 2 2 1 1 1
(days) 0 0 3 7 14 3 7 14
20 10 13 11 11 13 14 13
14-26 8-12 10-15 9-13 9-14 11-17 12-16 10-17
1 Prior to cooking and shearing, all groups were held at 0°F. for 2\ months minus times held at 27°F 2 Based on a pooled error variance, the least significant difference between groups is estimated to be 3 at 5 percent level and 4 at 1 percent level of probability. 3 Ice slush allowed to drain freely after first 8 hours.
minute air blast freezer 20 minutes after removal from the chill tank, removed from the freezer after 5 hours, and held in 0°F. storage or a combination of 27°F. storage and 0°F. storage as indicated in Table 1, before roasting from the frozen state and determining shear force values. There were six turkeys per group. Birds were roasted from the frozen state in a 325°F. rotating electric oven to an internal breast temperature of 180°F. Shear tests using the Warner-Bratzler apparatus were made on 1 square inch cross section strips of the Pectoralis superficialis muscle from the left side. In order to determine if the longest (14 days) period of holding at 27°F. had any adverse effect on flavor, a taste panel of 11 judges made 6 replicate comparisons of flavor in Groups 2 and 5, using the breast and thigh muscles on the right side. Each judge ranked both light and dark meat, the group having the least off-flavor being ranked 1 and the other group, 2. The average panel ranks for groups 2 and 5 were 1.50 and 1.50 for the dark meat, and 1.59 and 1.41, respectively, for the light
Downloaded from http://ps.oxfordjournals.org/ at Kainan University on May 8, 2015
Ice Slush
meat. The difference indicated for the light meat was not significant. Shear force values as shown in Table 1 indicate that a combination of 1 hour ice chill and 3 days at 27°F. after freezing accomplished 70 percent as much tenderization as the completely adequate 24 hour ice chill. Increasing the 27°F. holding period from 3 days to 14 days did not have a significant effect. Increasing the time in ice chill from 1 to 2 hours for the two longer 27°F. holding periods had a small effect, significant at the 5 percent level. These results confirm previous findings and suggest that a high quality, adequately tenderized product can be achieved with a very rapid, short ice chilling procedure if the frozen birds are held at about 27°F. for several days. For very light (white) birds (e.g., immersion frozen turkeys), the 27°F. holding may cause a slight surface darkening due to formation of larger sized ice crystals (van den Berg and Lentz, 1958; Klose and Pool, 1956), but the eating quality should be unaffected. Experiment B. Two groups of six Bronze turkey hens each (16 lbs. average live weight) were processed and evaluated in the same manner as described above for experiment A, except for the chilling and holding conditions, which are listed in Table 2. The essentially equivalent mean shear force values and flavor ranks indicate that the combination of 1 hour in ice slush and 14 days at 27°F. is equivalent in tenderizing effect to 48 hours in ice slush, and that the 14 days at 27°F. had no significant effect on flavor. Evaluation of Effect of Thawing Rate on Tenderization. Uniform lots of Beltsville hen turkeys (15 weeks old for experiment C and 22 weeks old for experiment D) were shocked, bled for 2 minutes, scalded at 140°F. for 30 seconds, picked in a cyclic rubber fingered picker for 20 seconds, eviscerated immediately, chilled as indicated in Table 3, packaged in evacuated, heat-
TURKEY TENDERNESS AND THAWING
1635
TABLE 2.—Effect of holding at Z7°F. on shear force and flavor (Experiment B., six 20 week Bronze turkey hens per group) Holding Condition1
Mean Flavor Ranks 2
Shear Values, lbs.
Group
1 2
Ice Slush
27°F. Air
Average
Range
Light Meat
Dark Meat
hrs. 1 48
days 14 0
11 10
9-12 6-15
1.60 1.40
1.49 1.51
1
Prior to cooking and shearing, Group 1 held 2 months at 0°F. and Group 2 held 2 | months at 0°F. 2 The two groups were ranked for off-flavor, 1 being assigned to group sample having least off-flavor, 2 to other sample of pair. Differences, representing data from 12 judges and 6 replications are not significant at 5 percent level of probability.
ied, has no significant effect on the ultimate tenderness of turkeys held for a sufficiently long aging period. Since tap water thawing would probably be rapid enough for any commercial or domestic thawing operation, the data indicate that there need be no special concern over the possibility of toughening the meat of frozen whole turkey carcasses by too rapid thawing. SUMMARY Ready-to-cook turkey hens were subjected to variations in chilling and thawing procedures in order to determine the effect on ultimate tenderness and flavor of variations in the extent of holding at 27°F. and |
32
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-28
«
/"MEAT
UJ
5 24 DC UJ Q. 2 UJ 1-
20 6
12
18
24
HOURS
FIG. 1. Temperature in packaged, ready-to-cook turkey in relation to programed increase in air temperature, with air velocity over turkey of about SO ft./min.
Downloaded from http://ps.oxfordjournals.org/ at Kainan University on May 8, 2015
shrunk plastic bags, and frozen rapidly on open shelves in a — 30°F., 1300 feet per minute, air blast freezer. The frozen carcasses were stored at — 10°F. for several weeks and until subjected to the thawing procedures described in Table 3. In the airthawing procedures, the carcass temperature naturally lagged behind the air temperature (by about 3°F. in first 24 hours for group 1 of experiment D) but the rate of temperature increase in the carcass over the thawing range (20°F. to 30°F.) was quite gradual, as shown for a pilot carcass in Figure 1. All thawed carcasses, and groups 1 and 2 of experiment C which were cooked from the frozen state, were roasted in a 325°F. rotating electric oven to an internal breast temperature of 180°F. Average shear force values for 1 square inch cross section strips of the Pectoralis superficialis, representing 42 to 60 values per group depending on size of the group, and the ranges between birds, are presented in Table 3. The extent of tenderization possible by holding in the unfrozen state either before or after freezing is indicated by the difference between the shear value, 26 lbs., for group 1 of experiment C and the shear value for groups 2 (9 lbs.) and 3 (10 lbs.) of the same experiment. However, there was no significant difference between groups 3and 4 of experiment C, or between groups 1 and 2 of experiment D, which shows that the rate of thawing, within the limits stud-
1636
A. A. KLOSE, A. A. CAMPBELL, M. F. POOL AND H. L. HANSON TABLTC 3.—Effect
Group
Number of Turkeys
Experiment C 1 2 3 4 Experiment D 1 2
of rate of thawing on ultimate tenderness
Chilling prior to freezing
Thawing and Holding
8 8 8 7
None 20 hrs. Ice Slush None None
None None Gradual, 1 4 days Sudden,2 4 days
9 10
None None
Gradual, 3 3 days Sudden,4 3 days
Shear Force Value, lbs. Ayerage
26 9 10 12
Range
11-39 5-15 5-13 7-17 8-12 6- 9
in the rate of temperature rise in the thawing (20°F. to 30°F.) region. Holding 1 hour ice chilled birds for as little as 3 days at 27°F. provided adequate tenderization, and no adverse flavor changes were noted after 14 days at 27°F. Increasing 27°F. holding time from 3 to 14 days had no significant effect on ultimate tenderness. For birds subsequently held at 27°F., increasing ice chilling time from 1 hour to 2 hours had a small and probably unimportant effect. Wide differences in rate of thawing of birds frozen pre-rigor had no adverse effect on ultimate tenderness achieved by holding after thawing. Holding frozen turkeys for a short period in the intermediate thawing range offers promise of providing tenderness in birds which, for reasons of economics or convenience, can neither be chilled long enough nor held long enough in the thawed condition to provide desired degrees of tenderness. REFERENCES de Fremery, D., and M. F. Pool, 1960. Biochemistry of chicken muscle as related to rigor mortis
and tenderization. Food Research, 25: 73-87. Dodge, J. W., and W. J. Stadelman, 1960. Relationships between pH, tenderness, and moisture levels during early post-mortem aging of turkey meat. Food Technology, 14: 43-46. Klose, A. A., M. F. Pool, M. B. Wide, H. L. Hanson and H. Lineweaver, 19S9. Poultry tenderness. I. Influence of processing on tenderness of turkeys. Food Technology, 13: 20-24. Klose, A. A., M. F. Pool, D. de Fremery, A. A. Campbell and H. L. Hanson, 1960a. Effect of laboratory scale agitated chilling of poultry on quality. Poultry Sci. 39: 1193-1198. Klose, A. A., A. A. Campbell, H. L. Hanson and H. Lineweaver, 1960b. Effect of duration and type of chilling and thawing on tenderness of frozen turkeys. Poultry Sci. 39: 1265. Klose, A. A., and M. F. Pool, 1956. Effect of freezing conditions on apearance of frozen turkeys. Food Technology, 10: 34-38. Koonz, C. H., M. I. Darrow and E. O. Essary, 1954. Factors influencing tenderness of principal muscles composing the poultry carcass. Food Technology, 8: 97-100. Pool, M. F., D. de Fremery, A. A. Campbell and A A. Klose, 1959. Poultry tenderness. II. Influence of processing on tenderness of chickens. Food Technology, 13 : 25-29. van den Berg, L., and C. P. Lentz, 1958. Liquid immersion and air blast freezing of poultry. American Egg and Poultry Review 20(8) : 6-8, 22-23.
Downloaded from http://ps.oxfordjournals.org/ at Kainan University on May 8, 2015
1 Carcasses at - 10°F. transferred to air at 10°F. for 8 hrs., 20°F. for next 15 hrs., 30°F. for next 24 hrs., and at 37° F. for rest of 4 day period. 2 Carcasses at — 10°F. transferred to 60°F. circulating water for 4 hrs., and in air at 37°F. for rest of 4 day period. 3 Carcasses transferred from — 10°F. to 0°F. to 10°F. to 20°F. air over 1 week period, then air temperature was raised from 20° F. to 34° F. gradually over a 24 hr. period, followed by a steady air temperature of 37°F. for the final 48 hrs. of 72 hr. thawing and holding period. 4 Carcasses transferred from — 10°F. to 0°F. to 10°F. to 20°F. air over 1 week period, then thawed rapidly in 60°F. circulating tap water for 2 hrs., and held in air at 37°F. for final 70 hrs. of 72 hr. thawing and holding period.