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Factors Affecting Turkey Meat Color1
Factors Affecting Turkey Meat Color1 D. J. MUGLER, J. D. MITCHELL 2 AND A. W. ADAMS Department of Dairy and Poultry Science, Kansas State University, Manhattan, Kansas 66502 (Received for publication May 8, 1970) INTRODUCTION
C
1
Contribution No. 783, Dept. of Dairy and Poultry Science, Kansas Agricultural Experiment Station, Manhattan 66502. 2 Present address: Director, Product Planning, John Labatt Ltd., London 10, Ontario, Canada.
p.p.m. from 14 weeks; they then processed the birds, packaged them and froze them until ready for color evaluation. Dietary nitrate and nitrite significantly increased visual scores of both cooked and uncooked meat samples and Gardner aL values of uncooked white meat. In this study we investigated several other parameters involving Gardner color difference values. The data reported here describes the effects of nitrate nitrogen in drinking water, age of bird, nitrate-nitrogen in chill water, cooking under hermetic conditions and grinding on turkey meat color. MATERIALS AND METHODS
Duplicate groups of Kimber Broad Breasted Bronze poults were brooded and reared in a naturally ventilated brooding and rearing house. In experiment 1, each group consisted of 40 sexed poults (20 males and 20 females). In experiment 2, 38 straight-run poults were used. Samples of cooked meat from experiment 1 were ground in experiment 3 to determine how grinding cooked meat affected Gardner color values. In experiment 1 poults from day old to date of processing drank well water containing levels of sodium nitrate equivalent to 0, 75, 150, 300, and 450 p.p.m. nitratenitrogen. Two turkeys were randomly selected for processing from each of the duplicate groups (four birds from each nitrate level) at ages 16, 20 and 24 weeks. In the second experiment nitrate-nitrogen levels of 0, 75, 150 and 300 p.p.m. were given to poults. Again two birds were randomly se-
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OLOR in poulty products strongly influences consumer acceptance. Two closely related heme pigments, myoglobin and hemoglobin, make uncooked poultry flesh pink to red. Consumers often object to variation from that normal appearance of uncooked meat or from the normal white to golden-brown of cooked turkey. Pool (1956) reported that turkey meat acquired a pink color when oven roasted in an uncovered container. He concluded this discoloration resulted from small amounts of nitric oxide and carbon monoxide (frequently found in oven atmosphere) combining with heme pigments of the bird. Froning and Hartung (1967) studied effects of age, sex and strain on color and texture of turkey meat, reporting that Gardner L values of uncooked and cooked meat decreased (meat darkened) with age of the bird. (Gardner L refers to light reflectance, aL to redness and b L to yellowness.) They found that uncooked dark meat had significantly more redness (higher aL values) with increasing age of birds and that aL values of cooked dark meat from toms trended upward with advancing age of birds. Froning and Hartung (1967) also found significant strain difference in aL values of cooked meat from toms. In 1968 Froning et al. fed Broad Breasted White Turkeys dietary nitrate at 0, 300 and 600 p.p.m. and nitrate at 0, 25 and 50
TURKEY MEAT COLOR
immediately cooled and held at room temperature at least 24 hours before color measurements of cooked samples were taken. The Gardner Automatic Color Difference Meter (Model AC-1) was used to ascertain color difference values (Rd. a & b values) for both uncooked and cooked samples. The instrument was standardized with a white ceramic tile having these values: Rd, 88.0; a, —1.6; b, 3.3. Two samples were prepared from each half turkey and placed in a Gardner Color Difference Meter Glass Cell 2\ inches in diameter. Care was taken to expose only freshly cut meat surfaces for color measurements. Duplicate readings were made, but the cell was rotated between the first and second readings. Each of the four Rd, a and b readings was recorded for each half turkey. Color values were averaged, then transformed to corresponding L, aL and bj, values for analysis. In the third experiment half of each cooked sample from experiment 1 was ground with a portable, manual meat grinder. The ground samples and cooked whole samples of experiment 1 were then subjected to color measurements concurrently, using procedures of the two previous experiments. L, aL and bi, color values of the ground samples were compared with similar cooked-sample values. All results were evaluated statistically using analysis of variance, Snedecor (1967). RESULTS AND DISCUSSION Effects of nitrate-nitrogen in drinking water, age of bird, nitrate-nitrogen in chill water, cooking and various interactions on Gardner L, aL and b L values are presented in Table 1. Levels of nitrate-nitrogen in the drinking water had no significant (P < 0.01) effect on turkey-meat color. Age, nitrate-nitrogen in chill water and cooking significantly (P < 0.01) affected all three Gardner color values.
Downloaded from http://ps.oxfordjournals.org/ at University of North Dakota on May 19, 2015
lected for processing from each of the duplicate groups; but only 20-week-old hens and 24-week-old toms were selected. All turkeys were bled at slaughter by a "Kosher" cut after electrical stunning. Feathers were removed in a Spin-Pik picker after the birds were sub-scaled at approximately 60° C. All were eviscerated immediately, split down the back into equal halves and weighed. In experiment 1, half of each carcass was placed in 18°C. tap water with no nitrates added; the other half, in tap water with 600 p.p.m. nitratenitrogen added. In the second experiment similar chill water was used but with four levels of nitrate-nitrogen: 0, 200, 400, and 600 p.p.m. Halves from the same bird were never placed in the same chill water. Carcasses were chilled in tap water for the 24 hour period to permit ample time for exposure to nitrate-nitrogen in water at the 18° C. temperature. Halves were removed from water and drained before being weighed and packaged in air-evacuated plastic Cryovac bags. They then were placed immediately in a — 10°C. freezer, where they remained until thawed for testing. All were thawed 12 hours at approximately 25°C. before being evaluated for color and cooked. In experiments 1 and 2 the pectoralis major and minor muscles were removed from each carcass half. A sample of uncooked white meat was removed from those muscles and used for color evaluation. To determine results on cooking turkey meat under hermetic conditions requested by industry, the remainder of each pectoralis major and minor muscle was placed in a size 404 by 700 can. Eight grams of salt were added and the can filled with boiling water. The cans were sealed with a Dixie hand-operated can sealer and placed in an autoclave for cooking under hermetic conditions at 115°C. for 65 minutes at 13 psi. The cans were removed from the autoclave,
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D. J. MUGLER, J. D. MITCHELL AND A. W. ADAMS
TABLE 1.—Effects of indicated factors on Gardner L, a t and PL values of turkey carcasses evaluated by analysis of variance Source
M.S.(L)
d.f. 4 2 8 45 1 4 2 8 45 1 4 2 1 2 4 8 8 90
M.S.(a L )
4.64 141.45** 5.06 6.72
M.S.(b L )
1.06 58.90** 4.27 2.06
4.96 113.26** 1.99 3.02
69.36** 296.50** 0.41 1.01 1.42 5.80** 6.99* 1.25 2.88 1.16 20616.85** 459.18** 3.99 1.21 96.38** 1.91 10.49 77.10** 0.20 0.02 1.25 1.35 6.90 0.26 2.09 0.84 4.45 1.59
14.74** 0.39 0.10 0.95 0.86 1869.53** 0.95 13.52** 101.56** 7.75* 0.77 0.95 3.09 1.67
** —F
Meat from older turkeys was significantly ( P < 0 . 0 1 ) redder (had higher aL values) than meat from younger turkeys. That, reflected in Table 2, confirmed the findings of Froning and Hartung (1967). Gardner L values of turkey meat in each age group were significantly (P < 0.01) less than those in the next younger age group tested, indicating that meat darkened with advancing age of bird. B L values were also reduced in older age groups, indicating decreasing yellow pigment with age of bird. Nitrate-nitrogen in the chill water made the meat significantly (P < 0.01) redder. All nitrate-nitrogen chill-water treatments used in the second experiment except those at the 200 and 400 p.p.m. levels (Table 3) were significantly (P < 0.01) different. That suggested that a minimum nitrateTABLE 2.—Mean carcass color values (ax,) of turkeys of 3 different ages* Age, weeks
16
20
24
Mean (Xi):
13.299
14.276
15.009
* LSD = 0.70. Each Xi differs significantly from each of the others at 0.01 level.
TABLE 3.—Mean carcass color values (a£) of turkeys of 4 different chill water treatments*
Mean(Xi):
15.617
14.869
14.495 12.692
* LSD =0.44. Means not underscored by the same line are significantly different at 0.01 level.
Downloaded from http://ps.oxfordjournals.org/ at University of North Dakota on May 19, 2015
E (nitrate-nitrogen in drinking H2O) D (Age) EXD Error C (nitrate-nitrogen in chill H 2 0 ) CXE CXD EXDXC Error B (Cooking) BXE BXD BXC BXCXD BXCXE BXDXE BXCXDXE Error
nitrogen level of 200 p.p.m. in chill water was required to increase red color significantly. Nitrate in the chill water significantly (P < 0.01) decreased Gardner L and b L values. Redness decreased when the meat was cooked in sealed cans; aL values were significantly (P < 0.01) lower for cooked than for uncooked turkey meat. Gardner L and bi, values of cooked meat were significantly (P < 0.01) higher than those of uncooked meat. Interactions (Table 1) that significantly (P < 0.01) affected aL values were: between age and chill water and between chill water and cooking. Significant (P < 0.01) interactions affecting L values also existed among age, nitrate level in drinking water and nitrates in the chill water. The interaction between age and cooking also was significant (P < 0.01) in its affect on L values. Interactions significantly (P < 0.01) affecting bh values were: between cooking and age and between cooking and chill water. The interactions among cooking, chill water and age were also significant (P<0.05). Grinding cooked turkey meat significantly (P < 0.01) decreased Gardner aL values, indicating that grinding through a portable meat grinder reduced redness. Ground, cooked turkey meat had significantly (P < 0.01) higher Gardner L and b L values than had unground meat from the same sample. Both cooking and grinding lightens the color of turkey meat and makes it more yellow.
TURKEY MEAT COLOR
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TABLE 4.—Correlation coefficients among indicated variables that affect color of turkey meat* 1 5 6 7
0.012 -0.006 0.036
2 -0.113 0.297* -0.256*
3
4
5
6
-0.056 0.473* -0.074
0.965* -0.589* 0.837*
-0.702* 0.851*
-0.621*
7
Correlation coefficients between the variables involved in experiment 1 are presented in Table 4. Cooking and L values correlated significantly (P < 0.0S) and positively as did cooking and bL values; L and b L values; chill water and aL values; and age and aL values. Conversely, cooking and aL values correlated significantly (P < 0.05) and negatively, as did L and aL values; b L and aL values; and age and b L values. SUMMARY Effects of nitrate-nitrogen in drinking water, age of bird, nitrate-nitrogen in chill water, cooking and grinding on the color of turkey meat were studied. Broad Breasted Bronze turkeys of both sexes were exposed to 0, 75, 150, 300 and 450 p.p.m. nitratenitrogen in the drinking water. They were processed at 16, 20 and 24 weeks of age and chilled in water containing 0, 200, 400 and 600 p.p.m. nitrate-nitrogen. The pectoralis major and minor muscles were cooked under hermetic conditions in sealed cans at 115°C. for 65 minutes at 13 psi. Color of turkey meat was measured with a Gardner Color Difference Meter before and after cooking and before and after grinding.
The levels of nitrate-nitrogen in the drinking water used in this study did not significantly affect color of turkey meat. Turkey meat from older birds was significantly (P < 0.01) redder than meat from younger birds. Nitrate-nitrogen in the chill water produced significantly (P < 0.01) more redness in turkey meat. The minimum nitratenitrogen level in chill water to increase red color significantly is 200 p.p.m. Red color was decreased significantly (P < 0.01) when the meat was cooked in sealed cans. Grinding cooked turkey meat also significantly (P < 0.01) decreased redness. REFERENCES Froning, G. W., J. Daddario, T. E. Hartung and T. W. Sullivan, 1968. Color of turkey meat as influenced by dietary nitrates and nitrites. Poultry Sci. 47: 1672-1673. Froning, G. W., and T. E. Hartung, 1967. Effect of age, sex and strain on color and texture of turkey meat. Poultry Sci. 46: 1261. Pool, M. F., 1956. Why does some cooked turkey turn pink? Turkey World, January, p. 69, 7274. Snedecor, G. W., 1967. Statistical Methods. The Iowa State College Press, Ames, Iowa.
APRIL 15-17. 6TH INTERNATIONAL ZOOTECHNOLOGY SYMPOSIUM, MILAN, ITALY.
Downloaded from http://ps.oxfordjournals.org/ at University of North Dakota on May 19, 2015
* r > . 1 7 (P<0.05) 1—Nitrate-nitrogen level in drinking water 2—Age 3—Nitrate-nitrogen in chill water 4—Cooking 5—L value 6—aL value 7—bL value
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Contribution No. 783, Dept. of Dairy and Poultry Science, Kansas Agricultural Experiment Station, Manhattan 66502. 2 Present address: Director, Product Planning, John Labatt Ltd., London 10, Ontario, Canada.
p.p.m. from 14 weeks; they then processed the birds, packaged them and froze them until ready for color evaluation. Dietary nitrate and nitrite significantly increased visual scores of both cooked and uncooked meat samples and Gardner aL values of uncooked white meat. In this study we investigated several other parameters involving Gardner color difference values. The data reported here describes the effects of nitrate nitrogen in drinking water, age of bird, nitrate-nitrogen in chill water, cooking under hermetic conditions and grinding on turkey meat color. MATERIALS AND METHODS
Duplicate groups of Kimber Broad Breasted Bronze poults were brooded and reared in a naturally ventilated brooding and rearing house. In experiment 1, each group consisted of 40 sexed poults (20 males and 20 females). In experiment 2, 38 straight-run poults were used. Samples of cooked meat from experiment 1 were ground in experiment 3 to determine how grinding cooked meat affected Gardner color values. In experiment 1 poults from day old to date of processing drank well water containing levels of sodium nitrate equivalent to 0, 75, 150, 300, and 450 p.p.m. nitratenitrogen. Two turkeys were randomly selected for processing from each of the duplicate groups (four birds from each nitrate level) at ages 16, 20 and 24 weeks. In the second experiment nitrate-nitrogen levels of 0, 75, 150 and 300 p.p.m. were given to poults. Again two birds were randomly se-
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Downloaded from http://ps.oxfordjournals.org/ at University of North Dakota on May 19, 2015
OLOR in poulty products strongly influences consumer acceptance. Two closely related heme pigments, myoglobin and hemoglobin, make uncooked poultry flesh pink to red. Consumers often object to variation from that normal appearance of uncooked meat or from the normal white to golden-brown of cooked turkey. Pool (1956) reported that turkey meat acquired a pink color when oven roasted in an uncovered container. He concluded this discoloration resulted from small amounts of nitric oxide and carbon monoxide (frequently found in oven atmosphere) combining with heme pigments of the bird. Froning and Hartung (1967) studied effects of age, sex and strain on color and texture of turkey meat, reporting that Gardner L values of uncooked and cooked meat decreased (meat darkened) with age of the bird. (Gardner L refers to light reflectance, aL to redness and b L to yellowness.) They found that uncooked dark meat had significantly more redness (higher aL values) with increasing age of birds and that aL values of cooked dark meat from toms trended upward with advancing age of birds. Froning and Hartung (1967) also found significant strain difference in aL values of cooked meat from toms. In 1968 Froning et al. fed Broad Breasted White Turkeys dietary nitrate at 0, 300 and 600 p.p.m. and nitrate at 0, 25 and 50
TURKEY MEAT COLOR
immediately cooled and held at room temperature at least 24 hours before color measurements of cooked samples were taken. The Gardner Automatic Color Difference Meter (Model AC-1) was used to ascertain color difference values (Rd. a & b values) for both uncooked and cooked samples. The instrument was standardized with a white ceramic tile having these values: Rd, 88.0; a, —1.6; b, 3.3. Two samples were prepared from each half turkey and placed in a Gardner Color Difference Meter Glass Cell 2\ inches in diameter. Care was taken to expose only freshly cut meat surfaces for color measurements. Duplicate readings were made, but the cell was rotated between the first and second readings. Each of the four Rd, a and b readings was recorded for each half turkey. Color values were averaged, then transformed to corresponding L, aL and bj, values for analysis. In the third experiment half of each cooked sample from experiment 1 was ground with a portable, manual meat grinder. The ground samples and cooked whole samples of experiment 1 were then subjected to color measurements concurrently, using procedures of the two previous experiments. L, aL and bi, color values of the ground samples were compared with similar cooked-sample values. All results were evaluated statistically using analysis of variance, Snedecor (1967). RESULTS AND DISCUSSION Effects of nitrate-nitrogen in drinking water, age of bird, nitrate-nitrogen in chill water, cooking and various interactions on Gardner L, aL and b L values are presented in Table 1. Levels of nitrate-nitrogen in the drinking water had no significant (P < 0.01) effect on turkey-meat color. Age, nitrate-nitrogen in chill water and cooking significantly (P < 0.01) affected all three Gardner color values.
Downloaded from http://ps.oxfordjournals.org/ at University of North Dakota on May 19, 2015
lected for processing from each of the duplicate groups; but only 20-week-old hens and 24-week-old toms were selected. All turkeys were bled at slaughter by a "Kosher" cut after electrical stunning. Feathers were removed in a Spin-Pik picker after the birds were sub-scaled at approximately 60° C. All were eviscerated immediately, split down the back into equal halves and weighed. In experiment 1, half of each carcass was placed in 18°C. tap water with no nitrates added; the other half, in tap water with 600 p.p.m. nitratenitrogen added. In the second experiment similar chill water was used but with four levels of nitrate-nitrogen: 0, 200, 400, and 600 p.p.m. Halves from the same bird were never placed in the same chill water. Carcasses were chilled in tap water for the 24 hour period to permit ample time for exposure to nitrate-nitrogen in water at the 18° C. temperature. Halves were removed from water and drained before being weighed and packaged in air-evacuated plastic Cryovac bags. They then were placed immediately in a — 10°C. freezer, where they remained until thawed for testing. All were thawed 12 hours at approximately 25°C. before being evaluated for color and cooked. In experiments 1 and 2 the pectoralis major and minor muscles were removed from each carcass half. A sample of uncooked white meat was removed from those muscles and used for color evaluation. To determine results on cooking turkey meat under hermetic conditions requested by industry, the remainder of each pectoralis major and minor muscle was placed in a size 404 by 700 can. Eight grams of salt were added and the can filled with boiling water. The cans were sealed with a Dixie hand-operated can sealer and placed in an autoclave for cooking under hermetic conditions at 115°C. for 65 minutes at 13 psi. The cans were removed from the autoclave,
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D. J. MUGLER, J. D. MITCHELL AND A. W. ADAMS
TABLE 1.—Effects of indicated factors on Gardner L, a t and PL values of turkey carcasses evaluated by analysis of variance Source
M.S.(L)
d.f. 4 2 8 45 1 4 2 8 45 1 4 2 1 2 4 8 8 90
M.S.(a L )
4.64 141.45** 5.06 6.72
M.S.(b L )
1.06 58.90** 4.27 2.06
4.96 113.26** 1.99 3.02
69.36** 296.50** 0.41 1.01 1.42 5.80** 6.99* 1.25 2.88 1.16 20616.85** 459.18** 3.99 1.21 96.38** 1.91 10.49 77.10** 0.20 0.02 1.25 1.35 6.90 0.26 2.09 0.84 4.45 1.59
14.74** 0.39 0.10 0.95 0.86 1869.53** 0.95 13.52** 101.56** 7.75* 0.77 0.95 3.09 1.67
** —F
Meat from older turkeys was significantly ( P < 0 . 0 1 ) redder (had higher aL values) than meat from younger turkeys. That, reflected in Table 2, confirmed the findings of Froning and Hartung (1967). Gardner L values of turkey meat in each age group were significantly (P < 0.01) less than those in the next younger age group tested, indicating that meat darkened with advancing age of bird. B L values were also reduced in older age groups, indicating decreasing yellow pigment with age of bird. Nitrate-nitrogen in the chill water made the meat significantly (P < 0.01) redder. All nitrate-nitrogen chill-water treatments used in the second experiment except those at the 200 and 400 p.p.m. levels (Table 3) were significantly (P < 0.01) different. That suggested that a minimum nitrateTABLE 2.—Mean carcass color values (ax,) of turkeys of 3 different ages* Age, weeks
16
20
24
Mean (Xi):
13.299
14.276
15.009
* LSD = 0.70. Each Xi differs significantly from each of the others at 0.01 level.
TABLE 3.—Mean carcass color values (a£) of turkeys of 4 different chill water treatments*
Mean(Xi):
15.617
14.869
14.495 12.692
* LSD =0.44. Means not underscored by the same line are significantly different at 0.01 level.
Downloaded from http://ps.oxfordjournals.org/ at University of North Dakota on May 19, 2015
E (nitrate-nitrogen in drinking H2O) D (Age) EXD Error C (nitrate-nitrogen in chill H 2 0 ) CXE CXD EXDXC Error B (Cooking) BXE BXD BXC BXCXD BXCXE BXDXE BXCXDXE Error
nitrogen level of 200 p.p.m. in chill water was required to increase red color significantly. Nitrate in the chill water significantly (P < 0.01) decreased Gardner L and b L values. Redness decreased when the meat was cooked in sealed cans; aL values were significantly (P < 0.01) lower for cooked than for uncooked turkey meat. Gardner L and bi, values of cooked meat were significantly (P < 0.01) higher than those of uncooked meat. Interactions (Table 1) that significantly (P < 0.01) affected aL values were: between age and chill water and between chill water and cooking. Significant (P < 0.01) interactions affecting L values also existed among age, nitrate level in drinking water and nitrates in the chill water. The interaction between age and cooking also was significant (P < 0.01) in its affect on L values. Interactions significantly (P < 0.01) affecting bh values were: between cooking and age and between cooking and chill water. The interactions among cooking, chill water and age were also significant (P<0.05). Grinding cooked turkey meat significantly (P < 0.01) decreased Gardner aL values, indicating that grinding through a portable meat grinder reduced redness. Ground, cooked turkey meat had significantly (P < 0.01) higher Gardner L and b L values than had unground meat from the same sample. Both cooking and grinding lightens the color of turkey meat and makes it more yellow.
TURKEY MEAT COLOR
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TABLE 4.—Correlation coefficients among indicated variables that affect color of turkey meat* 1 5 6 7
0.012 -0.006 0.036
2 -0.113 0.297* -0.256*
3
4
5
6
-0.056 0.473* -0.074
0.965* -0.589* 0.837*
-0.702* 0.851*
-0.621*
7
Correlation coefficients between the variables involved in experiment 1 are presented in Table 4. Cooking and L values correlated significantly (P < 0.0S) and positively as did cooking and bL values; L and b L values; chill water and aL values; and age and aL values. Conversely, cooking and aL values correlated significantly (P < 0.05) and negatively, as did L and aL values; b L and aL values; and age and b L values. SUMMARY Effects of nitrate-nitrogen in drinking water, age of bird, nitrate-nitrogen in chill water, cooking and grinding on the color of turkey meat were studied. Broad Breasted Bronze turkeys of both sexes were exposed to 0, 75, 150, 300 and 450 p.p.m. nitratenitrogen in the drinking water. They were processed at 16, 20 and 24 weeks of age and chilled in water containing 0, 200, 400 and 600 p.p.m. nitrate-nitrogen. The pectoralis major and minor muscles were cooked under hermetic conditions in sealed cans at 115°C. for 65 minutes at 13 psi. Color of turkey meat was measured with a Gardner Color Difference Meter before and after cooking and before and after grinding.
The levels of nitrate-nitrogen in the drinking water used in this study did not significantly affect color of turkey meat. Turkey meat from older birds was significantly (P < 0.01) redder than meat from younger birds. Nitrate-nitrogen in the chill water produced significantly (P < 0.01) more redness in turkey meat. The minimum nitratenitrogen level in chill water to increase red color significantly is 200 p.p.m. Red color was decreased significantly (P < 0.01) when the meat was cooked in sealed cans. Grinding cooked turkey meat also significantly (P < 0.01) decreased redness. REFERENCES Froning, G. W., J. Daddario, T. E. Hartung and T. W. Sullivan, 1968. Color of turkey meat as influenced by dietary nitrates and nitrites. Poultry Sci. 47: 1672-1673. Froning, G. W., and T. E. Hartung, 1967. Effect of age, sex and strain on color and texture of turkey meat. Poultry Sci. 46: 1261. Pool, M. F., 1956. Why does some cooked turkey turn pink? Turkey World, January, p. 69, 7274. Snedecor, G. W., 1967. Statistical Methods. The Iowa State College Press, Ames, Iowa.
APRIL 15-17. 6TH INTERNATIONAL ZOOTECHNOLOGY SYMPOSIUM, MILAN, ITALY.
Downloaded from http://ps.oxfordjournals.org/ at University of North Dakota on May 19, 2015
* r > . 1 7 (P<0.05) 1—Nitrate-nitrogen level in drinking water 2—Age 3—Nitrate-nitrogen in chill water 4—Cooking 5—L value 6—aL value 7—bL value