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The Effect of Scalding Conditions on the Xanthophyll Content and Color of Broiler Skin1
1880
A. H. CANTOR AND M. L. SCOTT
Poley, W. E., W. O. Wilson, A. L. Moxon and J. B. Taylor, 1941. The effect of selenized grains on the rate of growth in chicks. Poultry Sci. 20:171-179. Rotruck, J. T., A. L. Pope, H. E. Ganther, A. B. Swanson, D. G. Hafeman and W. G. Hoekstra, 1973. Selenium: biochemical role as a component of glutathione peroxidase. Science, 179: 588-590. Schwarz, K, J. G. Bieri, G. M. Briggs and M. L. Scott, 1957. Prevention of exudative diathesis in chicks by Factor 3 and selenium. Proc. Soc. Exp. Biol. Med. 95: 621-625. Scott, M. L., S. J. Hull and P. A. Mullenhoff, 1971. The calcium requirements of laying hens and the effects of dietary oyster shell upon shell quality.
Poultry Sci. 50: 1055-1063. Scott, M. L., M. C. Nesheim and R. J. Young, 1969. Nutrition of the Chicken. M. L. Scott and Associates, Ithaca, N.Y., 511 pp. Steel, R. G. D., and J. H. Torrie, 1960. Principles of Statistics. McGraw-Hill, New York, 481 pp. Thapar, N. T., E. Guenthner, C. W. Carlson and O. E. Olson, 1969. Dietary selenium and arsenic additions to diets for chickens over a life cycle. Poultry Sci. 48: 1988-1993. Thompson, J. N , and M. L. Scott, 1970. Impaired lipid and vitamin E absorption related to atrophy of the pancreas in selenium-deficient chicks. J. Nutr. 100: 797-809.
J. L . H E A T H AND O. P . THOMAS
Department of Poultry Science, University of Maryland, College Park, Maryland 20742 (Received for publication February 25, 1974)
ABSTRACT Extended exposure of the breast skin and feather tract to scald water at various temperatures was studied. The xanthophyll content was determined using acetone extraction followed by spectrophotometry. The color was determined with a color difference meter. Carcasses exposed to the scald water for 60, 120 or 180 seconds at 54, 57 or 60° C. had no change in either xanthophyll content or color of the breast skin and feather tract attributable to length of exposure at each temperature."The effect of temperature was determined and when increased above 54° C , a reduction of yellow color and xanthophyll content of the skin occurred. Reduction in yellow color and increased redness of feather tract was detected when the temperature was increased. Exposure to scald water for 180 to 240 seconds produced no difference in yellow color of the skin at either 50, 52 or 54° C. Xanthophyll content of skin decreased as the exposure time increased from 180 to 240 seconds at 50° C. The length of exposure produced no changes in the feather tract. An increase in temperature from 50 to 52° C. produced a decrease in xanthophyll but no detectable change of the yellow color in the skin and feather tract. A decrease in xanthophyll and yellow skin color attributable to length of exposure occurred at 55° C. when exposure time was increased from 60 to 120 seconds. No effect of exposure time was found when scalded for 60, 120 or 240 seconds at 52° C. A decrease in xanthophyll content and yellow color of the skin attributable to an increase in temperature from 52 to 55° C. was found. POULTRY SCIENCE 53: 1880-1885, 1974
INTRODUCTION
REVIOUS work at this laboratory (Heath Pand Thomas, 1973, 1974) demonstrated that the xanthophyll content and yellow color of broiler skin were affected during the feather removal operation. In the earlier 1. Scientific Article No. A1932, contribution No. 4856 of the Maryland Agricultural Experiment Station (Department of Poultry Science).
paper, the xanthophyll content and yellow color of broiler breast skin and feather tract were decreased as the scald water temperature was increased from 50 to 53 to 56° C. A decrease in xanthophyll content but not yellowness occurred in this same experiment as length of exposure to 53° C. scald water was increased by 15 seconds from 30 to 75 seconds. No significant changes were found to occur in the feather tract attributable to
Downloaded from http://ps.oxfordjournals.org/ at New York University on June 6, 2015
The Effect of Scalding Conditions on the Xanthophyll Content and Color of Broiler Skin1
XANTHOPHYLL CONTENT AND COLOR OF BROILER SKIN
The previous work (Heath and Thomas, 1973, 1974) indicated that scald water temperature was the major factor to be considered in xanthophyll and yellow color retention of broiler skin during scalding. Length of exposure to the scald water was examined at 2 temperatures (53 and 55° C.) each for different exposure times. At the lower temperature (53° C.) for the shorter exposure time (30-75 sec.) a decrease in xanthophyll content but not yellow color was found. In the second paper, (Heath and Thomas, 1973) longer exposure times were used (60, 120 and 180 sec.) at a higher temperature (55° C.) and no significant differences in xanthophyll content were found, color of the skin was not determined. This indicated that prolonged periods of scald could be used without decreasing the xanthophyll content of the skin. Other color changes in the skin were not previously evaluated. Increased length of exposure to the scald water could be of practical importance to broiler processors especially when picking problems are a factor. The purpose of this experimentation was to further investigate the effect of extended exposure to the scald water at different temperatures on the xanthophyll content and color of broiler skin. EXPERIMENTAL PROCEDURE The broilers used in these experiments were reared and processed according to the proce-
dure outlined by Heath and Thomas (1974) with the following exceptions. The carcasses were picked for 60 seconds. The water used to wash the carcasses during picking was adjusted to 30° C. to prevent the effect of scald water temperature continuing during picking. A skin sample was removed from the left side of the carcass. The area removed started at the anterior end of the sternal feather tract and continued to the posterior end (Lucas and Stettenheim, 1972). The sample included the sternal feather tract and the skin between the sternal and pectoral feather tracts. This produced a rectangular sample of skin and feather tract large enough to provide sufficient sample for each analysis. The samples were removed from the carcass immediately following feather removal and stored in plastic bags at -10° C. until analysis could be accomplished. The samples were removed from the freezer and allowed to thaw for one hour at room temperature. The xanthophyll was extracted and the amount present determined by the procedure outlined in Heath and Thomas (1973). An additional sample of skin and feather tract was removed from each carcass of experiment 3 and percent moisture determined in a forced draft oven at 100° C. for 24 hours. The xanthophyll content was expressed as meg./100 cm. 2 and meg./g. (wet weight) in all three experiments and as meg./g. (dry weight) in experiment 3. The surface color of the sample was determined with a Hunter Lab Model D-25 Color and Color-Difference Meter as described by Heath and Thomas (1973). This instrument measured the color as seen in average daylight similar to the way the human eye responds to the stimulus of color. Color was expressed in the three dimensions of L, a and b. The L dimension measured lightness of the sample and varied from black (0) to perfect white (100). The a dimension measured redness when positive (+), gray when zero (0) and
Downloaded from http://ps.oxfordjournals.org/ at New York University on June 6, 2015
length of scald water exposure. In the latter paper, it was found that picking as well as scalding reduced the xanthophyll content of both the breast skin and feather tract. In contrast to the earlier paper, no difference in the xanthophyll content was found attributable to length of exposure to scald water. The skin color was not determined. The cuticle could have been removed from the samples in the second paper (Heath and Thomas, 1974) because longer exposures of 60, 120 and 180 seconds and a higher scald water temperature of 55° C. were used.
1881
1882
J. L. HEATH AND O. P. THOMAS
of xanthophyll was recorded but the color was not affected in experiment 2 and 55° C. was the temperature between the two temperatures in experiment 1 where the decrease in xanthophyll and yellow color occurred. The scald exposure times included the range of both experiments and were widely separated to more easily detect differences.
Experiment 1. One-hundred-eighty broilers were used to determine the effect of length of exposure to scald water at various temperatures on the xanthophyll content and color of breast skin and feather tract. The present experiment was designed to study the effect of prolonged scald water exposure at temperatures below (54° C.) and above (57 and 60° C.) those previously found to reduce xanthophyll content and yellow color of the skin.
RESULTS AND DISCUSSION
Experiment 2. One-hundred-eighty broilers were used to evaluate the influence of scalding at temperatures less than the previous experiments but for longer periods of time. In experiment 1 of this paper, a reduction attributable to temperature was discovered when the temperature was increased to 57 from 54° C. The temperatures of this experiment (50, 52 and 54° C.) were selected to have a minimum of influence. The scald water exposure times of 120, 180 and 240 seconds were longer than normally used. They were chosen because of the lack of effect found using shorter exposure times in experiment 1, particularly at 54° C. It could be advantageous to scald at these prolonged times and reduced temperature if the color and appearance of the product could be maintained. Experiment 3. One-hundred-twenty broilers were scalded at 52 and 55° C. for 60, 120 and 240 seconds. The temperatures were chosen based on the results of the first two experiments. The lower temperature (52° C.) was the temperature at which a reduction
Experiment 1. The length of time the carcasses were exposed to the scald water had no effect on the xanthophyll content or yellow color of either the skin or feather tract (Tables 1 and 2). As expected from previous work, temperature was the major factor affecting xanthophyll content and yellow color of the carcass. A reduction (P s 0.01) in xanthophyll content and yellow color occurred in the skin as the temperature was increased from 54 to 57° C. (Table 1). Increasing the temperature from 57 to 60° C. resulted in no further change in either xanthophyll content or yellow color. The feather tract (Table 2) had no change in xanthophyll content but did have a decrease (P s 0.01) in yellowness as the temperature was increased from 54 to 57° C. As was the case with the skin, no differences were found when the temperature was increased from 57 to 60° C. The skin and feather tract apparently underwent a removal of all or part of the cuticle when scalded above 54° C. which caused a reduction in xanthophyll and yellow color. Although a color change was found, the feather tract content of xanthophyll did not decrease significantly. The amount of xanthophyll contributed by the remaining and lipid portion of the tissue was apparently large enough to make the loss nonsignificant. The lipid underlying the feather tract contains large amounts of xanthophyll and was not removed prior to analysis. The increased amounts of xanthophyll found in this tissue as compared to the skin was evidenced by the larger values found when expressed as
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greenness when negative (—). The b dimension measured yellowness when positive (+); grey when zero (0) and bluness when negative (-)• The data were analyzed using the analysis of variance technique and the Student-Newman-Keuls test presented in Steel and Torrie (1960).
1883
XANTHOPHYLL CONTENT AND COLOR OF BROILER SKIN
TABLE 1.—The xanthophyll content and color of broiler breast skin after scalding at either 54, 57 or 60° C. for 60, 120 and 180 seconds' Scald temp.
•c.
Scald time sees.
Xanthophyll meg./g. meg. /100 c m . 2
b
Color L
a
54 54 54
60 120 180
I3.8c» 12.1bc 14.8c
4. Id 3.3cd 4. Id
+21.lb +20.6b +20.7b
72.1a 70.6a 75.5b
-3.6bc -3.3bcd -1.8cde
57 57 57
60 120 180
6.7a 5.5a 8.5ab
3.1bcd 2.4abc 1.9ab
+ 15.7a + 14.6a + 15.2a
76.7b 78.1b 78.6b
-3.0bcd -5.8a -5.0ab
60 60 60
60 120 180
6.8a 6.8a 8.6ab
2.4abc 1.8a 2.1abc
+ 17.8a + 16.5a + 16.2a
78.0b 76.4b 76.0b
-2.3cd -1.3de -O.le
TABLE 2.—The xanthophyll content and color of broiler breast feather tract after scalding at either 54, 57 or 60° C. for 60, 120 and 180 seconds' Scald temp. °C.
Scald time sees.
54 54 54
60 120 180
74.1» 76.2 75.8
3.2 3.7 3.5
+21.2b +22.4b +21.6b
68.3 69.9 69.1
+0.3a -0.1a 0.0a
57 57 57
60 120 180
76.6 76.6 77.1
3.6 3.5 3.4
+ 17.9a + 17.4a + 17.4a
70.0 69.7 68.8
+ 1.4b + 1.3b + 1.6bc
60 60 60
60 120 180
69.1 68.8 79.4
3.7 3.5 3.7
+ 18.8a + 18.2a + 16.4a
68.8 69.1 67.9
+2.0bc + 1.7bc +2.5c
Xanthophyll meg. /100 cm. meg. / g .
b
Color L
a
1. The broilers were picked for 60 seconds. *Values in columns followed by different letters are significantly (P £ 0.01) different.
per cm. 2 . The reduction in yellowness resulted in an increase (P < 0.01) in lightness of the skin. This was a result of the removal of the cuticle. The feather tract did not have an increase in lightness even though a decrease in yellowness was found. This could have been due to the yellow lipid attached to the sample and the thickness caused by this tissue not allowing light to be reflected back from the white background tile. The feather tract became more red (P < 0.01) as the temperature of the scald water was increased, especially from 54 to 57° C. The red color of the carcass, especially the feather tract, wing and tail tips presents a problem in many processing plants.
This experiment indicated that the length of time the carcasses were exposed to the scald water for up to 180 seconds would not affect the yellow color. The overall color of the carcass would be enhanced by not increasing the temperature of the scald water, especially above that which resulted in cuticle removal. If processing can be benefited by increasing the length of time the carcasses are exposed to the scald water at these temperatures, it can apparently be done and adverse color changes will not result. Experiment 2. The length of time the carcasses were exposed to the scald water caused a decrease (P s 0.01) in xanthophyll content
Downloaded from http://ps.oxfordjournals.org/ at New York University on June 6, 2015
1. The broilers were picked for 60 seconds •Values in columns followed by different letters are significantly (P = 0.01) different.
1884
J. L. HEATH AND O. P. THOMAS
No changes were found when temperature was increased from 52 to 54° C. or when the xanthophyll/gm. and yellow color were examined. The lightness of the skin and feather tract was affected (P < 0.01) by the scalding conditions. The lightness was apparently not affected to the same degree as in experiment 1 because of the lack of change in yellowness. The a values were significantly (P =s 0.01) different only in the feather tracts. The increased redness found in the first experiment were not encountered here. Although the differences were small and could be attributable to both temperature and length of
TABLE 3.—The xanthophyll content and color of broiler breast skin after scalding at either 50, 52 or 54" C. for 120, 180 and 240 seconds' Scald temp.
•c.
Scald time sees.
Xanthophyll meg./g. mcg./ioolcm. 2
b
Color L
a
50 50 50
120 180 240
17.9b* 17.1b 11.5a
5.1c 4.1bc 3.0ab
+22.3ab +26.7b +23.4ab
77. lab 75.3ab 73.9a
-2.9 -2.1 -1.4
52 52 52
120 180 240
9.6a 9.4a 9.5a
2.6a 2.4a 2.6a
+22.3ab +20.7a +24.3ab
76. lab 74.5ab 78.9b
-1.4 -2.2 -3.1
54 54 54
120 180 240
12.1a 9.5a 10.6a
2.6a 3.0ab 3.3ab
+22.5ab +23.4ab +22.9ab
73.8a 73.1a 73.7a
-1.4 -2.6 -3.7
1. The broilers were picked for 60 seconds. •Values in columns followed by different letters are significantly (P £ 0.01) different.
TABLE 4.— The xanthophyll content and color of broiler breast feather tract after scalding at either 50, 52 or 54° C. for 120, 180 and 240 seconds' Scald temp.
•c.
Scald time Sees.
Xanthophyll meg./100 cm. 2 meg/g.
b
Color L
a
50 50 50
120 180 240
68.7ab* 80.1b 73.7b
2.6ab 3.0ab 3.1b
+21.9ab +24.3b +23.3ab
66.8ab 66.4a 67.6abc
+ 1.0bc + 1.0bc + 1.3d
52 52 52
120 180 240
53.2a 53.4a 54.5a
2.5ab 2.6ab 2.5ab
+21.8ab +22.6ab +22.6ab
67.0abc 67.5abc 69.2bc
+ 1.8e + 1.2cd +0.9b
54 54 54
120 180 240
53.1a 52.7a 53.0a
2.4a 2.5ab 2.6ab
+20.8a +21.8ab +21.6a
69.3c 68.4abc 68.7abc
+0.4a +0.9b +0.2a
1. The broilers were picked for 60 seconds. *Values in columns followed by different letters are significantly (P £ 0.01) different.
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but not yellow color of the skin (Table 3). The decrease occurred when the scald time was increased from 180 to 240 seconds at 50° C. At 52 and 54° C., the length of exposure caused no differences. There were no differences attributable to length of exposure when the feather tract was examined. A decrease (P < 0.01) in xanthophyll content but not yellow color of the skin occurred when the temperature was increased from 50 to 52° C. Increasing the temperature from 52 to 54° C. produced no differences. A decrease (P s 0.01) in xanthophyll/cm. 2 of feather tract was found as the temperature was increased from 50 to 52° C. (Table 4).
1885
XANTHOPHYLL CONTENT AND COLOR OF BROILER SKIN
TABLE 5.—The xanthophyll content and color of broiler breast skin after scalding at 52 and 55° C. for either 60, 120 or 240 seconds' Color
Xanthophyll meg./g. (wet)
meg./g. (dry)
°C.
Scald time sees.
b
L
a
52 52 52
60 120 240
29.5a* 29.6a 30.0a
6.4a 6.9a 7.0a
14.9a 15.0a 16.8b
+Tl.\a +27.5a +26.6a
74.6a 75.9a 75.8a
-0.4b -2.0a -1.7a
55 55 55
60 120 240
30.1a 16.4b 13.9b
6.9a 3.8b 3.3b
15.6a 8.5c 7.2c
+26.5a + 18.2b + 19.3b
75.8a 77.8b 78.9b
-2.6a -3.1c -2.9c
Scald temp.
meg./100 cm. 2
1. The broilers were picked for 60 seconds. *Values in columns followed by different letters are significantly (P : 0.01) different.
Experiment 3. The length of time the carcasses were exposed to the scald water at 55° C. produced a decrease (P < 0.01) in xanthophyll content and yellow color (Table 5). The decrease occurred as the scald time was increased from 60 to 120 seconds. There was no difference found when the carcasses scalded at 52° C. for the different times were examined. A significant (P s 0.01) difference in xanthophyll content and yellow color was found to occur when carcasses scalded at
52° C. were compared to those scalded at 55° C. with the exception of those scalded at 55° C. for 60 seconds. This was expected from the results of the previous experiments. The lightness values increased (P £ 0.01) as the yellow color decreased. This followed the trend established in experiment 1. The a values indicated the samples became more green as the temperature was increased and the time lengthened beyond 60 seconds. This experiment established that the length of exposure to the scald water was a factor only at the temperatures where the cuticle was removed. This experiment agreed with the previous experiments in that the length of exposure to the scald water can be used as a possible alternative to increasing temperature without adversely affecting skin color. This was especially important at the lower temperatures where the cuticle remained intact. REFERENCES Heath, J. L., and O. P. Thomas, 1973. The xanthophyll content and color of broiler skin after scalding. Poultry Sci. 52: 967-971. Heath, J. L., and O. P. Thomas, 1974. The effect of feather removal during processing on the xanthophyll content of broiler skin. Poultry Sci. 53: 291295. Lucas, A. M., and P. R. Stettenheim, 1972. Avian Anatomy Integument, Part II, Agriculture Handbook 363, U.S. Government Printing Office, Washington, D.C.
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scald, the trend of decreasing redness as temperature increased from 52 to 54° C. was evident. The results indicated that the cuticle was not removed under the conditions of this experiment although a decrease in xanthophyll content was found. This could be attributed to a "splotchy" removal but because the yellowness and lightness values were determined at the exact same location on the tissue and these measurements did not follow the same trends, the answer could be a partial removal over the surface. Although some xanthophyll was removed, at these lower temperatures the carcasses could be scalded for prolonged periods with no detrimental color changes. It would be advantageous from a skin color standpoint to scald at lower temperatures for longer periods than at the higher temperatures.
A. H. CANTOR AND M. L. SCOTT
Poley, W. E., W. O. Wilson, A. L. Moxon and J. B. Taylor, 1941. The effect of selenized grains on the rate of growth in chicks. Poultry Sci. 20:171-179. Rotruck, J. T., A. L. Pope, H. E. Ganther, A. B. Swanson, D. G. Hafeman and W. G. Hoekstra, 1973. Selenium: biochemical role as a component of glutathione peroxidase. Science, 179: 588-590. Schwarz, K, J. G. Bieri, G. M. Briggs and M. L. Scott, 1957. Prevention of exudative diathesis in chicks by Factor 3 and selenium. Proc. Soc. Exp. Biol. Med. 95: 621-625. Scott, M. L., S. J. Hull and P. A. Mullenhoff, 1971. The calcium requirements of laying hens and the effects of dietary oyster shell upon shell quality.
Poultry Sci. 50: 1055-1063. Scott, M. L., M. C. Nesheim and R. J. Young, 1969. Nutrition of the Chicken. M. L. Scott and Associates, Ithaca, N.Y., 511 pp. Steel, R. G. D., and J. H. Torrie, 1960. Principles of Statistics. McGraw-Hill, New York, 481 pp. Thapar, N. T., E. Guenthner, C. W. Carlson and O. E. Olson, 1969. Dietary selenium and arsenic additions to diets for chickens over a life cycle. Poultry Sci. 48: 1988-1993. Thompson, J. N , and M. L. Scott, 1970. Impaired lipid and vitamin E absorption related to atrophy of the pancreas in selenium-deficient chicks. J. Nutr. 100: 797-809.
J. L . H E A T H AND O. P . THOMAS
Department of Poultry Science, University of Maryland, College Park, Maryland 20742 (Received for publication February 25, 1974)
ABSTRACT Extended exposure of the breast skin and feather tract to scald water at various temperatures was studied. The xanthophyll content was determined using acetone extraction followed by spectrophotometry. The color was determined with a color difference meter. Carcasses exposed to the scald water for 60, 120 or 180 seconds at 54, 57 or 60° C. had no change in either xanthophyll content or color of the breast skin and feather tract attributable to length of exposure at each temperature."The effect of temperature was determined and when increased above 54° C , a reduction of yellow color and xanthophyll content of the skin occurred. Reduction in yellow color and increased redness of feather tract was detected when the temperature was increased. Exposure to scald water for 180 to 240 seconds produced no difference in yellow color of the skin at either 50, 52 or 54° C. Xanthophyll content of skin decreased as the exposure time increased from 180 to 240 seconds at 50° C. The length of exposure produced no changes in the feather tract. An increase in temperature from 50 to 52° C. produced a decrease in xanthophyll but no detectable change of the yellow color in the skin and feather tract. A decrease in xanthophyll and yellow skin color attributable to length of exposure occurred at 55° C. when exposure time was increased from 60 to 120 seconds. No effect of exposure time was found when scalded for 60, 120 or 240 seconds at 52° C. A decrease in xanthophyll content and yellow color of the skin attributable to an increase in temperature from 52 to 55° C. was found. POULTRY SCIENCE 53: 1880-1885, 1974
INTRODUCTION
REVIOUS work at this laboratory (Heath Pand Thomas, 1973, 1974) demonstrated that the xanthophyll content and yellow color of broiler skin were affected during the feather removal operation. In the earlier 1. Scientific Article No. A1932, contribution No. 4856 of the Maryland Agricultural Experiment Station (Department of Poultry Science).
paper, the xanthophyll content and yellow color of broiler breast skin and feather tract were decreased as the scald water temperature was increased from 50 to 53 to 56° C. A decrease in xanthophyll content but not yellowness occurred in this same experiment as length of exposure to 53° C. scald water was increased by 15 seconds from 30 to 75 seconds. No significant changes were found to occur in the feather tract attributable to
Downloaded from http://ps.oxfordjournals.org/ at New York University on June 6, 2015
The Effect of Scalding Conditions on the Xanthophyll Content and Color of Broiler Skin1
XANTHOPHYLL CONTENT AND COLOR OF BROILER SKIN
The previous work (Heath and Thomas, 1973, 1974) indicated that scald water temperature was the major factor to be considered in xanthophyll and yellow color retention of broiler skin during scalding. Length of exposure to the scald water was examined at 2 temperatures (53 and 55° C.) each for different exposure times. At the lower temperature (53° C.) for the shorter exposure time (30-75 sec.) a decrease in xanthophyll content but not yellow color was found. In the second paper, (Heath and Thomas, 1973) longer exposure times were used (60, 120 and 180 sec.) at a higher temperature (55° C.) and no significant differences in xanthophyll content were found, color of the skin was not determined. This indicated that prolonged periods of scald could be used without decreasing the xanthophyll content of the skin. Other color changes in the skin were not previously evaluated. Increased length of exposure to the scald water could be of practical importance to broiler processors especially when picking problems are a factor. The purpose of this experimentation was to further investigate the effect of extended exposure to the scald water at different temperatures on the xanthophyll content and color of broiler skin. EXPERIMENTAL PROCEDURE The broilers used in these experiments were reared and processed according to the proce-
dure outlined by Heath and Thomas (1974) with the following exceptions. The carcasses were picked for 60 seconds. The water used to wash the carcasses during picking was adjusted to 30° C. to prevent the effect of scald water temperature continuing during picking. A skin sample was removed from the left side of the carcass. The area removed started at the anterior end of the sternal feather tract and continued to the posterior end (Lucas and Stettenheim, 1972). The sample included the sternal feather tract and the skin between the sternal and pectoral feather tracts. This produced a rectangular sample of skin and feather tract large enough to provide sufficient sample for each analysis. The samples were removed from the carcass immediately following feather removal and stored in plastic bags at -10° C. until analysis could be accomplished. The samples were removed from the freezer and allowed to thaw for one hour at room temperature. The xanthophyll was extracted and the amount present determined by the procedure outlined in Heath and Thomas (1973). An additional sample of skin and feather tract was removed from each carcass of experiment 3 and percent moisture determined in a forced draft oven at 100° C. for 24 hours. The xanthophyll content was expressed as meg./100 cm. 2 and meg./g. (wet weight) in all three experiments and as meg./g. (dry weight) in experiment 3. The surface color of the sample was determined with a Hunter Lab Model D-25 Color and Color-Difference Meter as described by Heath and Thomas (1973). This instrument measured the color as seen in average daylight similar to the way the human eye responds to the stimulus of color. Color was expressed in the three dimensions of L, a and b. The L dimension measured lightness of the sample and varied from black (0) to perfect white (100). The a dimension measured redness when positive (+), gray when zero (0) and
Downloaded from http://ps.oxfordjournals.org/ at New York University on June 6, 2015
length of scald water exposure. In the latter paper, it was found that picking as well as scalding reduced the xanthophyll content of both the breast skin and feather tract. In contrast to the earlier paper, no difference in the xanthophyll content was found attributable to length of exposure to scald water. The skin color was not determined. The cuticle could have been removed from the samples in the second paper (Heath and Thomas, 1974) because longer exposures of 60, 120 and 180 seconds and a higher scald water temperature of 55° C. were used.
1881
1882
J. L. HEATH AND O. P. THOMAS
of xanthophyll was recorded but the color was not affected in experiment 2 and 55° C. was the temperature between the two temperatures in experiment 1 where the decrease in xanthophyll and yellow color occurred. The scald exposure times included the range of both experiments and were widely separated to more easily detect differences.
Experiment 1. One-hundred-eighty broilers were used to determine the effect of length of exposure to scald water at various temperatures on the xanthophyll content and color of breast skin and feather tract. The present experiment was designed to study the effect of prolonged scald water exposure at temperatures below (54° C.) and above (57 and 60° C.) those previously found to reduce xanthophyll content and yellow color of the skin.
RESULTS AND DISCUSSION
Experiment 2. One-hundred-eighty broilers were used to evaluate the influence of scalding at temperatures less than the previous experiments but for longer periods of time. In experiment 1 of this paper, a reduction attributable to temperature was discovered when the temperature was increased to 57 from 54° C. The temperatures of this experiment (50, 52 and 54° C.) were selected to have a minimum of influence. The scald water exposure times of 120, 180 and 240 seconds were longer than normally used. They were chosen because of the lack of effect found using shorter exposure times in experiment 1, particularly at 54° C. It could be advantageous to scald at these prolonged times and reduced temperature if the color and appearance of the product could be maintained. Experiment 3. One-hundred-twenty broilers were scalded at 52 and 55° C. for 60, 120 and 240 seconds. The temperatures were chosen based on the results of the first two experiments. The lower temperature (52° C.) was the temperature at which a reduction
Experiment 1. The length of time the carcasses were exposed to the scald water had no effect on the xanthophyll content or yellow color of either the skin or feather tract (Tables 1 and 2). As expected from previous work, temperature was the major factor affecting xanthophyll content and yellow color of the carcass. A reduction (P s 0.01) in xanthophyll content and yellow color occurred in the skin as the temperature was increased from 54 to 57° C. (Table 1). Increasing the temperature from 57 to 60° C. resulted in no further change in either xanthophyll content or yellow color. The feather tract (Table 2) had no change in xanthophyll content but did have a decrease (P s 0.01) in yellowness as the temperature was increased from 54 to 57° C. As was the case with the skin, no differences were found when the temperature was increased from 57 to 60° C. The skin and feather tract apparently underwent a removal of all or part of the cuticle when scalded above 54° C. which caused a reduction in xanthophyll and yellow color. Although a color change was found, the feather tract content of xanthophyll did not decrease significantly. The amount of xanthophyll contributed by the remaining and lipid portion of the tissue was apparently large enough to make the loss nonsignificant. The lipid underlying the feather tract contains large amounts of xanthophyll and was not removed prior to analysis. The increased amounts of xanthophyll found in this tissue as compared to the skin was evidenced by the larger values found when expressed as
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greenness when negative (—). The b dimension measured yellowness when positive (+); grey when zero (0) and bluness when negative (-)• The data were analyzed using the analysis of variance technique and the Student-Newman-Keuls test presented in Steel and Torrie (1960).
1883
XANTHOPHYLL CONTENT AND COLOR OF BROILER SKIN
TABLE 1.—The xanthophyll content and color of broiler breast skin after scalding at either 54, 57 or 60° C. for 60, 120 and 180 seconds' Scald temp.
•c.
Scald time sees.
Xanthophyll meg./g. meg. /100 c m . 2
b
Color L
a
54 54 54
60 120 180
I3.8c» 12.1bc 14.8c
4. Id 3.3cd 4. Id
+21.lb +20.6b +20.7b
72.1a 70.6a 75.5b
-3.6bc -3.3bcd -1.8cde
57 57 57
60 120 180
6.7a 5.5a 8.5ab
3.1bcd 2.4abc 1.9ab
+ 15.7a + 14.6a + 15.2a
76.7b 78.1b 78.6b
-3.0bcd -5.8a -5.0ab
60 60 60
60 120 180
6.8a 6.8a 8.6ab
2.4abc 1.8a 2.1abc
+ 17.8a + 16.5a + 16.2a
78.0b 76.4b 76.0b
-2.3cd -1.3de -O.le
TABLE 2.—The xanthophyll content and color of broiler breast feather tract after scalding at either 54, 57 or 60° C. for 60, 120 and 180 seconds' Scald temp. °C.
Scald time sees.
54 54 54
60 120 180
74.1» 76.2 75.8
3.2 3.7 3.5
+21.2b +22.4b +21.6b
68.3 69.9 69.1
+0.3a -0.1a 0.0a
57 57 57
60 120 180
76.6 76.6 77.1
3.6 3.5 3.4
+ 17.9a + 17.4a + 17.4a
70.0 69.7 68.8
+ 1.4b + 1.3b + 1.6bc
60 60 60
60 120 180
69.1 68.8 79.4
3.7 3.5 3.7
+ 18.8a + 18.2a + 16.4a
68.8 69.1 67.9
+2.0bc + 1.7bc +2.5c
Xanthophyll meg. /100 cm. meg. / g .
b
Color L
a
1. The broilers were picked for 60 seconds. *Values in columns followed by different letters are significantly (P £ 0.01) different.
per cm. 2 . The reduction in yellowness resulted in an increase (P < 0.01) in lightness of the skin. This was a result of the removal of the cuticle. The feather tract did not have an increase in lightness even though a decrease in yellowness was found. This could have been due to the yellow lipid attached to the sample and the thickness caused by this tissue not allowing light to be reflected back from the white background tile. The feather tract became more red (P < 0.01) as the temperature of the scald water was increased, especially from 54 to 57° C. The red color of the carcass, especially the feather tract, wing and tail tips presents a problem in many processing plants.
This experiment indicated that the length of time the carcasses were exposed to the scald water for up to 180 seconds would not affect the yellow color. The overall color of the carcass would be enhanced by not increasing the temperature of the scald water, especially above that which resulted in cuticle removal. If processing can be benefited by increasing the length of time the carcasses are exposed to the scald water at these temperatures, it can apparently be done and adverse color changes will not result. Experiment 2. The length of time the carcasses were exposed to the scald water caused a decrease (P s 0.01) in xanthophyll content
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1. The broilers were picked for 60 seconds •Values in columns followed by different letters are significantly (P = 0.01) different.
1884
J. L. HEATH AND O. P. THOMAS
No changes were found when temperature was increased from 52 to 54° C. or when the xanthophyll/gm. and yellow color were examined. The lightness of the skin and feather tract was affected (P < 0.01) by the scalding conditions. The lightness was apparently not affected to the same degree as in experiment 1 because of the lack of change in yellowness. The a values were significantly (P =s 0.01) different only in the feather tracts. The increased redness found in the first experiment were not encountered here. Although the differences were small and could be attributable to both temperature and length of
TABLE 3.—The xanthophyll content and color of broiler breast skin after scalding at either 50, 52 or 54" C. for 120, 180 and 240 seconds' Scald temp.
•c.
Scald time sees.
Xanthophyll meg./g. mcg./ioolcm. 2
b
Color L
a
50 50 50
120 180 240
17.9b* 17.1b 11.5a
5.1c 4.1bc 3.0ab
+22.3ab +26.7b +23.4ab
77. lab 75.3ab 73.9a
-2.9 -2.1 -1.4
52 52 52
120 180 240
9.6a 9.4a 9.5a
2.6a 2.4a 2.6a
+22.3ab +20.7a +24.3ab
76. lab 74.5ab 78.9b
-1.4 -2.2 -3.1
54 54 54
120 180 240
12.1a 9.5a 10.6a
2.6a 3.0ab 3.3ab
+22.5ab +23.4ab +22.9ab
73.8a 73.1a 73.7a
-1.4 -2.6 -3.7
1. The broilers were picked for 60 seconds. •Values in columns followed by different letters are significantly (P £ 0.01) different.
TABLE 4.— The xanthophyll content and color of broiler breast feather tract after scalding at either 50, 52 or 54° C. for 120, 180 and 240 seconds' Scald temp.
•c.
Scald time Sees.
Xanthophyll meg./100 cm. 2 meg/g.
b
Color L
a
50 50 50
120 180 240
68.7ab* 80.1b 73.7b
2.6ab 3.0ab 3.1b
+21.9ab +24.3b +23.3ab
66.8ab 66.4a 67.6abc
+ 1.0bc + 1.0bc + 1.3d
52 52 52
120 180 240
53.2a 53.4a 54.5a
2.5ab 2.6ab 2.5ab
+21.8ab +22.6ab +22.6ab
67.0abc 67.5abc 69.2bc
+ 1.8e + 1.2cd +0.9b
54 54 54
120 180 240
53.1a 52.7a 53.0a
2.4a 2.5ab 2.6ab
+20.8a +21.8ab +21.6a
69.3c 68.4abc 68.7abc
+0.4a +0.9b +0.2a
1. The broilers were picked for 60 seconds. *Values in columns followed by different letters are significantly (P £ 0.01) different.
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but not yellow color of the skin (Table 3). The decrease occurred when the scald time was increased from 180 to 240 seconds at 50° C. At 52 and 54° C., the length of exposure caused no differences. There were no differences attributable to length of exposure when the feather tract was examined. A decrease (P < 0.01) in xanthophyll content but not yellow color of the skin occurred when the temperature was increased from 50 to 52° C. Increasing the temperature from 52 to 54° C. produced no differences. A decrease (P s 0.01) in xanthophyll/cm. 2 of feather tract was found as the temperature was increased from 50 to 52° C. (Table 4).
1885
XANTHOPHYLL CONTENT AND COLOR OF BROILER SKIN
TABLE 5.—The xanthophyll content and color of broiler breast skin after scalding at 52 and 55° C. for either 60, 120 or 240 seconds' Color
Xanthophyll meg./g. (wet)
meg./g. (dry)
°C.
Scald time sees.
b
L
a
52 52 52
60 120 240
29.5a* 29.6a 30.0a
6.4a 6.9a 7.0a
14.9a 15.0a 16.8b
+Tl.\a +27.5a +26.6a
74.6a 75.9a 75.8a
-0.4b -2.0a -1.7a
55 55 55
60 120 240
30.1a 16.4b 13.9b
6.9a 3.8b 3.3b
15.6a 8.5c 7.2c
+26.5a + 18.2b + 19.3b
75.8a 77.8b 78.9b
-2.6a -3.1c -2.9c
Scald temp.
meg./100 cm. 2
1. The broilers were picked for 60 seconds. *Values in columns followed by different letters are significantly (P : 0.01) different.
Experiment 3. The length of time the carcasses were exposed to the scald water at 55° C. produced a decrease (P < 0.01) in xanthophyll content and yellow color (Table 5). The decrease occurred as the scald time was increased from 60 to 120 seconds. There was no difference found when the carcasses scalded at 52° C. for the different times were examined. A significant (P s 0.01) difference in xanthophyll content and yellow color was found to occur when carcasses scalded at
52° C. were compared to those scalded at 55° C. with the exception of those scalded at 55° C. for 60 seconds. This was expected from the results of the previous experiments. The lightness values increased (P £ 0.01) as the yellow color decreased. This followed the trend established in experiment 1. The a values indicated the samples became more green as the temperature was increased and the time lengthened beyond 60 seconds. This experiment established that the length of exposure to the scald water was a factor only at the temperatures where the cuticle was removed. This experiment agreed with the previous experiments in that the length of exposure to the scald water can be used as a possible alternative to increasing temperature without adversely affecting skin color. This was especially important at the lower temperatures where the cuticle remained intact. REFERENCES Heath, J. L., and O. P. Thomas, 1973. The xanthophyll content and color of broiler skin after scalding. Poultry Sci. 52: 967-971. Heath, J. L., and O. P. Thomas, 1974. The effect of feather removal during processing on the xanthophyll content of broiler skin. Poultry Sci. 53: 291295. Lucas, A. M., and P. R. Stettenheim, 1972. Avian Anatomy Integument, Part II, Agriculture Handbook 363, U.S. Government Printing Office, Washington, D.C.
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scald, the trend of decreasing redness as temperature increased from 52 to 54° C. was evident. The results indicated that the cuticle was not removed under the conditions of this experiment although a decrease in xanthophyll content was found. This could be attributed to a "splotchy" removal but because the yellowness and lightness values were determined at the exact same location on the tissue and these measurements did not follow the same trends, the answer could be a partial removal over the surface. Although some xanthophyll was removed, at these lower temperatures the carcasses could be scalded for prolonged periods with no detrimental color changes. It would be advantageous from a skin color standpoint to scald at lower temperatures for longer periods than at the higher temperatures.