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The Effect of End-Point Cooking Temperature and Storage on the Color of Turkey Meat1
The Effect of End-Point Cooking Temperature and Storage on the Color of Turkey Meat1 ALBERTA H E L M K E AND G. W.
FRONING
Poultry Science Department, University of Nebraska, Lincoln, Nebraska 68503 (Received for publication April 21, 1971) INTRODUCTION
A R I A B L E S affecting color of further processed poultry have been a concern of processors for some time. Some factors involved have been elucidated with recent research. Such aspects as age, sex and strain (Froning, 1968); dietary or chill water nitrates and nitrites (Froning et al., 1969a; Mugler et al., 1970); exhaust fume inhalation prior to slaughter (Froning et al., 1969b); and oven gases (Pool, 1956) have been found to affect poultry meat color in varying degrees. End-point cooking temperatures and poultry meat color have received little emphasis in previous studies. End-point cooking temperatures and color has been studied in red meat products. W a t t s (1954) identified the insoluble brown pigments in cooked m e a t as denatured globin ferric hemichromogen. Tappel (1957) concluded t h a t pink pigments found in underdone cooked beef were undenatured oxymyoglobin. Bernofsky et al. (1959) also found t h a t pigments extractable from cooked fresh beef were mainly oxymyoglobin. T h e y further observed t h a t the pigment remaining undenatured in a piece of cooked meat depends upon its temperature and how long it has been held a t t h a t temperature. Denaturation of myoglobin in meat was noted to be considerable at temperatures 1
Published with the approval of the Director as Paper No. 3109, Journal Series, Nebraska Agricultural Experiment Station. The work reported was conducted under Nebraska Agricultural Experiment Station project No. 22-18.
EXPERIMENTAL M e a t used in these experiments was obtained from 24-week old Broad Breasted White male turkeys raised a t the University of Nebraska poultry complex. Turkeys were slaughtered using a sub-scald temperature of 59°C. and chilled overnight in ice slush. Carcasses were vacuumpackaged, blast frozen and stored at -29°C. Experiment 1. Thighs and drumsticks were thawed and deboned. This meat was ground in a cold H o b a r t food chopper, using a 3.0 mm. grider plate. Fibrous cellulose casings were stuffed with 454 g. of uniformly composited meat. Two copperconstantan thermocouples were inserted into the center of each roll. The rolls were wrapped in aluminum foil and cooked in an electric rotating rack oven a t 177°C. Three replications were cooked to endpoint temperatures of 60° (140°F.), 66° (150°F.), 71° (160°F.), 77° (170°F.), or 82°C. (180°F.). A 2°C. storage period of 2 hours (0 days), 5 days or 10 days was used for each end-point temperature. A Gardner C-4 Color Difference Meter was used to determine L, ai, and bi, values on freshly-sliced surfaces. An 8 mm.-thick slice was pressed against a clean petri dish and the color reading was taken on an
1832
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V
a t which thermal denaturation of the pigment is negligible in pure solution. This study was designed to investigate temperature variables as they affect poultry meat color and regenerated pigments in the stored cooked product.
1833
C O L O R OF T U R K E Y M E A T
area possessing no large air holes or connective tissue masses. Ten readings were made on each roll. A visual score was also recorded on each sliced surface, using a 5-point rating scale, 1-being normal cooked color, 2-slightly pink, 3-pink, 4very pink and 5-extremely pink.
Another phase of this study investigated storage color effects b y comparing stored samples to a hot control. Ground meat links (10X2.5 cm.) involving three replications were cooked to final internal temperatures of 71° or 82°C. using the water bath procedure. Links from each of these temperatures were stored 5 or 10
TABLE 1.—Experiment 1—Mean1 color values for ground dark meat turkey rolls cooked to 5 end-point temperatures and stored at 2°C. End-point temperature (°C.) Data
L Values
Storage (days) 0 5 10
Grand Mean 3 aL Values
0 5 10
Grand Mean 3 t>L Values
0 5 10
Grand Mean3" Visual Scores
Grand Mean 3 1
0 5 10
60 (140°F.)
66 (150°F.)
71 (160°F.)
77 (170°F.)
49.0 50.1 49.4
50.4 50.9 50.6
50.8 50.7 51.2
50.4 50.4 50.6
50.2 50.7 50.7
49.5"
50.7"°
50.9°
50.5"°
50.6"°
24.8 23.1 25.8
22.8 22.8 23.2
21.7 23.8 21.6
21.4 21.7 20.8
19.9 21.3 20.7
24.5"
23.0 a "
22.3"°
21.3 r f
20.6 d
12.7 12.4 12.7
12.5 12.5 12.3
12.5 12.5 11.9
12.5 12.7 12.1
12.6 12.6 12.0
12.6"
12.4»
12.3"
12.4»
12.'M
2.4 2.5 2.3
2.0 2.1 2.0
1.7 2.1 2.0
1.7 2.1 2.0
1.5 2.1 2.0
2.4"
2.1"
2.0"
1.9"
1.9"
82 (180°F.)
Storage grand mean2 50.2» 50.6" 50.5"
22.1" 22.5* 22.4"
12.6" 12.5" 12.2"
1.9* 2.2" 2.1"
Mean of 30 values from 3 turkey rolls. Grand mean of 5 temperatures for each storage time. Grand mean of 3 storage periods for each temperature. abcbe G r a nd means not having the same subscripts within a column or line of a data group are significantly different at 5% level using Duncan's multiple range test. 2 3
Downloaded from http://ps.oxfordjournals.org/ at Karolinska Institutet University Library on May 29, 2015
Experiment 2. Thighs and legs were thawed, deboned, ground, and mixed as described in Experiment 1. Ground meat was stuffed into Precision Nojax size 36 sausage casing with a chilled Vogt manual sausage stuff er. Links (20X2.5 cm.) were wrapped in foil or heat resistant plastic film and cooked in a constant temperature water b a t h at 82.2°C. T h e internal temperature was recorded on a recording potentiometer. End-point temperatures and storage periods were the same as used in
Experiment 1. After the desired temperature was reached, the link was transferred to an ice bath for quick cooling. These links had less temperature differential from center to outside surface than t h a t encountered with larger rolls. I t was felt t h a t this reduced temperature differential would give more uniform color readings. Color difference meter readings were recorded as described in Experiment 1.
1834
A. HELMKE AND G. W. FRONING
(Snedecor, 1957). Duncan's multiple range test was used to determine significant differences in mean values (LeClerg el al., 1966). RESULTS AND DISCUSSION
Experiment 1. Results of Experiment 1 are shown in Table 1. L values were significantly increased at higher end-point temperatures. Storage times of 5 and 10 days resulted in a slight but significant increase of L values of cooked dark meat. Froning (1968) reported that Lvalues were somewhat higher in cooked turkey meat as compared to uncooked meat. It would appear that advancing end-point temperatures also lighten the color. Gardner ar, values (redness) of cooked meat were observed to decrease significantly at higher end-point temperatures. Storage variables did not significantly influence Gardner aL values. Visual scores for redness significantly decreased from 60° to 66°C. and remained similar there-
Date L Values
60
66
71
77
82
0 5 10
44.6 46.3 44.9
44.8 43.4 50.0
48.8 50.9 50.3
51.1 51.4 51.9
51.5 52.2 52.2
45.3"
46.1"
50.0 b
51.5"
52.0 b
39.6 38.0 39.5
38.7 40.8 34.2
34.7 32.7 32.6
29.4 31.3 27.3
25.6 26.6 26.6
39.0*
37.9"
33.3 b
29.3"
26.2 d
13.3 13.5 13.4
13.3 13.4 12.8
13.0 12.9 12.9
12.6 12.9 13.0
12.8 12.9 13.1
13.4"
13.2<*
12.9 b "
12.8 bc
12.9'
Grand Mean 3 aL Values
0 5 10
Grand Mean 3 t>L Values
Grand Mean 3 1
End-point temperature (°C.)
Storage (days)
0 5 10
ft 2 2
TABLE 2.—Experiment 2—Mean1 color values for ground dark meat turkey links cooked to 5 end-point temperatures and stored at 2°C.
48.2" 48.9" 49.9>
33.6» 33.9" 32.0»
13.0" 13.1" 13.0"
Mean of 30 values from 3 turkey links. Grand mean of 5 temperatures for each storage time. Grand mean of 3 storage periods for each temperature. abwie Grand means not having the same subscripts within a column or line of a data group are significantly different at 5% level using Duncan's multiple range test. 2
3
Downloaded from http://ps.oxfordjournals.org/ at Karolinska Institutet University Library on May 29, 2015
days at 2°C. prior to color measurements. The control link was evaluated while still hot (0 days). Measurements included Gardner values and visual color readings. Gardner readings were taken through a plastic film rather than a petri dish. Myoglobin extraction and absorbance. Several thin cross-sectional slices of cooked ground meat links, totaling 10 g., were added to 25 ml. of chilled, deionized water in a micro-Waring blendor. This mixture was blended at low speed for 20 sec. and the suspension filtered through Whatman No. 42 filter paper which had been washed with deionized water. After discarding the first 3-4 ml. of filtrate, an aliquot of the following filtrate was used for an absorbance spectrum. The scan was made from 400-600 nm. using a Beckman Model DB-G spectrophotmeter and Beck man recorder. Statistics. Analysis of variance with the " F " test was used to determine significant differences in treatment and storage data
1835
COLOR OF TURKEY MEAT
Previous work by Froning (1969a) indicated regeneration of a pink pigment during storage. Storage results in the present studies have failed to show this phenomenon. Since control samples have been evaluated after 2 hours storage, it was decided to make control evaluations while hot. Results are presented in Table
TABLE 3.—Mean1 color values for ground dark meat turkey links cooked to 2 end-point temperatures and stored at 2°C (Controls evaluated while warm)
Data
Storage l,uay:v
L Values
0 5 10
Grand Mean 3 &L Values
0 5 10
Grand Mean 3 bL Values
0 5 10
Grand Mean 3 Visual Scores
Grand Mean 3
0 5 10
End-point temperatures (°C.)
„ ^
f
71
82
mean 2
49.2 46.9 47.6
48.5 48.5 47.9
48.8" 47.7" 47.8"
47.9"
48.3"
16.8 23.0 22.2
12.5 17.3 17.7
20.7"
15.9 b
8.8 13.7 10.0
10.0 12.8 10.0
10.8"
11.0"
1.2 3.2 2.8
1.0 2.7 2.7
2.4"
2.1"
14.7" 20.1b 20.0 b
9.4" 13.2 b 10.0"
1.1" 2.9 b 2.8 b
1
Mean of 30 values from 3 turkey links. Grand means of 2 temperatures for each storage time. 3 Grand means of 3 storage periods for each temperature. ab Grand means not having the same subscripts within each column of a data group are significantly different at 5% level using Duncan's multiple range test. 2
3. When evaluating control samples warm, a regenerated pink pigment was noted to appear as indicated by significantly higher aL values and visual scores with storage. Results showed that the regenerated pigment apparently develops within two hours. The nature of this pigment needs further study. Perhaps a portion of the myoglobin present is only partially denatured upon cooking. Absorbance Spectra of Extracted Pigments. Figure 1 shows absorbance spectra of extracted pigments from each of the end-point temperature groupings. The absorbance maxima were at or close to 540 nm. and 580 nm. for meat extracts from
Downloaded from http://ps.oxfordjournals.org/ at Karolinska Institutet University Library on May 29, 2015
after. Storage for 5 or 10 days significantly increased visual redness over that observed at 0 days storage. Gardner bL values were not changed substantially by end-point temperature or storage variables. There was a significant drop in bL values of cooked meat stored for 10 days but the magnitude of this change was quite small. Experiment 2. The effects of end-point temperature on color of links cooked to five end-point temperatures are reported in Table 2. Gardner L values were increased significantly with advancing endpoint temperatures when comparing lightness values of the 60° and 66°C. grouping to those obtained in the 71°, 77°, and 82°C. grouping. Gardner aL values of cooked dark meat declined significantly with increasing temperatures beyond 66°C. These results somewhat paralleled those of Bernofsky et al. (1959) who observed higher red meat myoglobin denaturation rates from 65° to 80°C. This study, as in Experiment 1, indicate that increased reddening may become particularly important when end-point temperatures are below 71°C. (160°F.). Endpoint temperatures below 71°C. would not normally occur in processing plants but nevertheless, processing temperatures could possibly become out of control from time to time. Storage grand means indicated aL values were not significantly affected at any of the storage periods. Gardner bL values showed a slight but significant decline with advancing endpoint temperatures
1836
A. H E L M K E AND G. W.
100-
l'-l
807060. 50.
60°C
i
90.
66°c 82°C
7\\1 ?A:»H
>' tfil
30. 20.
v\'\
•A\\
\\w
•y* *"**--..
#V"^^
A^l
'^"lir^-c^' " ' ^ ' ^
10.
advancing end-point temperatures. A regenerated pink pigment appeared to develop within a 2 hour storage period. T h e absorption spectra of extracted pigments from turkey meat cooked to endpoint temperatures from 60°C-77°C. indicated peak maxima which were analogous to t h a t normally reported for oxymyoglobin. Extracted pigment from turkey meat, which was cooked to 82°C., had a spectra quite different than t h a t observed at lower temperatures. Results of the spectral analyses were quite similar to those previously reported by red meat researchers.
V! k oo
^50
500
550
6(
WAVELENGTH Cnm)
FIG. 1. Experiment 3—Absorbance spectra of water extracts from ground dark meat turkey links cooked to 60°, 66°, 71°, 77° or 82°C. end-point temperature and stored 0 days (2 hr.) at 2°C.
links cooked to end-point temperatures from 60°C. to 77°C. T h e American M e a t Institute Foundation (1960) characterized oxymyoglobin spectrally b y relatively sharp peaks at 540 nm. and 580 nm. This indicates the presence of undenatured pigment in the water extract. As end-point temperature increased from 60° to 7 7 ° C , these peaks diminished in magnitude. Extracts from links cooked to 82°C. showed a quite different absorbance spectra than t h a t observed at other endpoint temperatures. Absorbance of the extract from 82°C. links produced slight peaks at 550 nm. and 520 nm. T h e Soret peak a t approximately 410 nm. decreased in magnitude with advancing end-point temperatures. SUMMARY
Gardner a L values (redness) decreased and L (lightness) values increased with
REFERENCES American Meat Foundation, 1960. The Science of Meat and Meat Products, W. H. Freeman and Company, San Francisco, California. Bernofsky, C , J. B. Fox, Jr. and B. S. Schweigert, 1959. Biochemistry of myoglobin. VII. The effect of cooking on myoglobin in beef muscle. Food Research, 24: 339-343. Froning, G. W., J. Daddario and T. E. Hartung, 1968. Color and myoglobin concentration in turkey meat as affected by age, sex and strain. Poultry Sci. 47:1827-1835. Froning, G. W., J. Daddario, T. E. Hartung, T. W. Sullivan and R. M. Hill, 1969a. Color of poultry meat as influenced by dietary nitrates and nitrites. Poultry Sci. 48: 668-674. Froning, G. W., F. B. Mather, J. Daddario and T. E. Hartung, 1969b. Effect of automobile exhaust fume inhalation by poultry immediately prior to slaughter on color of meat. Poultry Sci. 48: 485-487. LeClerg, E. L., W. H Leonard and A. G. Clark, 1966. Field Plot Techniques, 2nd Ed., Burgess Fubl. Co., Minneapolis, Minn. Mugler, D. J., J. D. Mitchell and A. A. Adams, 1970. Factors affecting turkey meat color. Poultry Sci. 49: 1510-1513. Pool, M. F., 1956. Why does some cooked turkey turn pink? Turkey World, January, page 68. Snedecor, G. W., 1957. Statistical Methods Applied to Experiments in Agriculture and Biology. Iowa State College Press, Ames, Iowa. Tappel, A. L., 1957. Reflectance spectral studies of the hematin pigments of cooked beef. Food Research,' 22: 404-407.
Downloaded from http://ps.oxfordjournals.org/ at Karolinska Institutet University Library on May 29, 2015
ko.
FRONING
FRONING
Poultry Science Department, University of Nebraska, Lincoln, Nebraska 68503 (Received for publication April 21, 1971) INTRODUCTION
A R I A B L E S affecting color of further processed poultry have been a concern of processors for some time. Some factors involved have been elucidated with recent research. Such aspects as age, sex and strain (Froning, 1968); dietary or chill water nitrates and nitrites (Froning et al., 1969a; Mugler et al., 1970); exhaust fume inhalation prior to slaughter (Froning et al., 1969b); and oven gases (Pool, 1956) have been found to affect poultry meat color in varying degrees. End-point cooking temperatures and poultry meat color have received little emphasis in previous studies. End-point cooking temperatures and color has been studied in red meat products. W a t t s (1954) identified the insoluble brown pigments in cooked m e a t as denatured globin ferric hemichromogen. Tappel (1957) concluded t h a t pink pigments found in underdone cooked beef were undenatured oxymyoglobin. Bernofsky et al. (1959) also found t h a t pigments extractable from cooked fresh beef were mainly oxymyoglobin. T h e y further observed t h a t the pigment remaining undenatured in a piece of cooked meat depends upon its temperature and how long it has been held a t t h a t temperature. Denaturation of myoglobin in meat was noted to be considerable at temperatures 1
Published with the approval of the Director as Paper No. 3109, Journal Series, Nebraska Agricultural Experiment Station. The work reported was conducted under Nebraska Agricultural Experiment Station project No. 22-18.
EXPERIMENTAL M e a t used in these experiments was obtained from 24-week old Broad Breasted White male turkeys raised a t the University of Nebraska poultry complex. Turkeys were slaughtered using a sub-scald temperature of 59°C. and chilled overnight in ice slush. Carcasses were vacuumpackaged, blast frozen and stored at -29°C. Experiment 1. Thighs and drumsticks were thawed and deboned. This meat was ground in a cold H o b a r t food chopper, using a 3.0 mm. grider plate. Fibrous cellulose casings were stuffed with 454 g. of uniformly composited meat. Two copperconstantan thermocouples were inserted into the center of each roll. The rolls were wrapped in aluminum foil and cooked in an electric rotating rack oven a t 177°C. Three replications were cooked to endpoint temperatures of 60° (140°F.), 66° (150°F.), 71° (160°F.), 77° (170°F.), or 82°C. (180°F.). A 2°C. storage period of 2 hours (0 days), 5 days or 10 days was used for each end-point temperature. A Gardner C-4 Color Difference Meter was used to determine L, ai, and bi, values on freshly-sliced surfaces. An 8 mm.-thick slice was pressed against a clean petri dish and the color reading was taken on an
1832
Downloaded from http://ps.oxfordjournals.org/ at Karolinska Institutet University Library on May 29, 2015
V
a t which thermal denaturation of the pigment is negligible in pure solution. This study was designed to investigate temperature variables as they affect poultry meat color and regenerated pigments in the stored cooked product.
1833
C O L O R OF T U R K E Y M E A T
area possessing no large air holes or connective tissue masses. Ten readings were made on each roll. A visual score was also recorded on each sliced surface, using a 5-point rating scale, 1-being normal cooked color, 2-slightly pink, 3-pink, 4very pink and 5-extremely pink.
Another phase of this study investigated storage color effects b y comparing stored samples to a hot control. Ground meat links (10X2.5 cm.) involving three replications were cooked to final internal temperatures of 71° or 82°C. using the water bath procedure. Links from each of these temperatures were stored 5 or 10
TABLE 1.—Experiment 1—Mean1 color values for ground dark meat turkey rolls cooked to 5 end-point temperatures and stored at 2°C. End-point temperature (°C.) Data
L Values
Storage (days) 0 5 10
Grand Mean 3 aL Values
0 5 10
Grand Mean 3 t>L Values
0 5 10
Grand Mean3" Visual Scores
Grand Mean 3 1
0 5 10
60 (140°F.)
66 (150°F.)
71 (160°F.)
77 (170°F.)
49.0 50.1 49.4
50.4 50.9 50.6
50.8 50.7 51.2
50.4 50.4 50.6
50.2 50.7 50.7
49.5"
50.7"°
50.9°
50.5"°
50.6"°
24.8 23.1 25.8
22.8 22.8 23.2
21.7 23.8 21.6
21.4 21.7 20.8
19.9 21.3 20.7
24.5"
23.0 a "
22.3"°
21.3 r f
20.6 d
12.7 12.4 12.7
12.5 12.5 12.3
12.5 12.5 11.9
12.5 12.7 12.1
12.6 12.6 12.0
12.6"
12.4»
12.3"
12.4»
12.'M
2.4 2.5 2.3
2.0 2.1 2.0
1.7 2.1 2.0
1.7 2.1 2.0
1.5 2.1 2.0
2.4"
2.1"
2.0"
1.9"
1.9"
82 (180°F.)
Storage grand mean2 50.2» 50.6" 50.5"
22.1" 22.5* 22.4"
12.6" 12.5" 12.2"
1.9* 2.2" 2.1"
Mean of 30 values from 3 turkey rolls. Grand mean of 5 temperatures for each storage time. Grand mean of 3 storage periods for each temperature. abcbe G r a nd means not having the same subscripts within a column or line of a data group are significantly different at 5% level using Duncan's multiple range test. 2 3
Downloaded from http://ps.oxfordjournals.org/ at Karolinska Institutet University Library on May 29, 2015
Experiment 2. Thighs and legs were thawed, deboned, ground, and mixed as described in Experiment 1. Ground meat was stuffed into Precision Nojax size 36 sausage casing with a chilled Vogt manual sausage stuff er. Links (20X2.5 cm.) were wrapped in foil or heat resistant plastic film and cooked in a constant temperature water b a t h at 82.2°C. T h e internal temperature was recorded on a recording potentiometer. End-point temperatures and storage periods were the same as used in
Experiment 1. After the desired temperature was reached, the link was transferred to an ice bath for quick cooling. These links had less temperature differential from center to outside surface than t h a t encountered with larger rolls. I t was felt t h a t this reduced temperature differential would give more uniform color readings. Color difference meter readings were recorded as described in Experiment 1.
1834
A. HELMKE AND G. W. FRONING
(Snedecor, 1957). Duncan's multiple range test was used to determine significant differences in mean values (LeClerg el al., 1966). RESULTS AND DISCUSSION
Experiment 1. Results of Experiment 1 are shown in Table 1. L values were significantly increased at higher end-point temperatures. Storage times of 5 and 10 days resulted in a slight but significant increase of L values of cooked dark meat. Froning (1968) reported that Lvalues were somewhat higher in cooked turkey meat as compared to uncooked meat. It would appear that advancing end-point temperatures also lighten the color. Gardner ar, values (redness) of cooked meat were observed to decrease significantly at higher end-point temperatures. Storage variables did not significantly influence Gardner aL values. Visual scores for redness significantly decreased from 60° to 66°C. and remained similar there-
Date L Values
60
66
71
77
82
0 5 10
44.6 46.3 44.9
44.8 43.4 50.0
48.8 50.9 50.3
51.1 51.4 51.9
51.5 52.2 52.2
45.3"
46.1"
50.0 b
51.5"
52.0 b
39.6 38.0 39.5
38.7 40.8 34.2
34.7 32.7 32.6
29.4 31.3 27.3
25.6 26.6 26.6
39.0*
37.9"
33.3 b
29.3"
26.2 d
13.3 13.5 13.4
13.3 13.4 12.8
13.0 12.9 12.9
12.6 12.9 13.0
12.8 12.9 13.1
13.4"
13.2<*
12.9 b "
12.8 bc
12.9'
Grand Mean 3 aL Values
0 5 10
Grand Mean 3 t>L Values
Grand Mean 3 1
End-point temperature (°C.)
Storage (days)
0 5 10
ft 2 2
TABLE 2.—Experiment 2—Mean1 color values for ground dark meat turkey links cooked to 5 end-point temperatures and stored at 2°C.
48.2" 48.9" 49.9>
33.6» 33.9" 32.0»
13.0" 13.1" 13.0"
Mean of 30 values from 3 turkey links. Grand mean of 5 temperatures for each storage time. Grand mean of 3 storage periods for each temperature. abwie Grand means not having the same subscripts within a column or line of a data group are significantly different at 5% level using Duncan's multiple range test. 2
3
Downloaded from http://ps.oxfordjournals.org/ at Karolinska Institutet University Library on May 29, 2015
days at 2°C. prior to color measurements. The control link was evaluated while still hot (0 days). Measurements included Gardner values and visual color readings. Gardner readings were taken through a plastic film rather than a petri dish. Myoglobin extraction and absorbance. Several thin cross-sectional slices of cooked ground meat links, totaling 10 g., were added to 25 ml. of chilled, deionized water in a micro-Waring blendor. This mixture was blended at low speed for 20 sec. and the suspension filtered through Whatman No. 42 filter paper which had been washed with deionized water. After discarding the first 3-4 ml. of filtrate, an aliquot of the following filtrate was used for an absorbance spectrum. The scan was made from 400-600 nm. using a Beckman Model DB-G spectrophotmeter and Beck man recorder. Statistics. Analysis of variance with the " F " test was used to determine significant differences in treatment and storage data
1835
COLOR OF TURKEY MEAT
Previous work by Froning (1969a) indicated regeneration of a pink pigment during storage. Storage results in the present studies have failed to show this phenomenon. Since control samples have been evaluated after 2 hours storage, it was decided to make control evaluations while hot. Results are presented in Table
TABLE 3.—Mean1 color values for ground dark meat turkey links cooked to 2 end-point temperatures and stored at 2°C (Controls evaluated while warm)
Data
Storage l,uay:v
L Values
0 5 10
Grand Mean 3 &L Values
0 5 10
Grand Mean 3 bL Values
0 5 10
Grand Mean 3 Visual Scores
Grand Mean 3
0 5 10
End-point temperatures (°C.)
„ ^
f
71
82
mean 2
49.2 46.9 47.6
48.5 48.5 47.9
48.8" 47.7" 47.8"
47.9"
48.3"
16.8 23.0 22.2
12.5 17.3 17.7
20.7"
15.9 b
8.8 13.7 10.0
10.0 12.8 10.0
10.8"
11.0"
1.2 3.2 2.8
1.0 2.7 2.7
2.4"
2.1"
14.7" 20.1b 20.0 b
9.4" 13.2 b 10.0"
1.1" 2.9 b 2.8 b
1
Mean of 30 values from 3 turkey links. Grand means of 2 temperatures for each storage time. 3 Grand means of 3 storage periods for each temperature. ab Grand means not having the same subscripts within each column of a data group are significantly different at 5% level using Duncan's multiple range test. 2
3. When evaluating control samples warm, a regenerated pink pigment was noted to appear as indicated by significantly higher aL values and visual scores with storage. Results showed that the regenerated pigment apparently develops within two hours. The nature of this pigment needs further study. Perhaps a portion of the myoglobin present is only partially denatured upon cooking. Absorbance Spectra of Extracted Pigments. Figure 1 shows absorbance spectra of extracted pigments from each of the end-point temperature groupings. The absorbance maxima were at or close to 540 nm. and 580 nm. for meat extracts from
Downloaded from http://ps.oxfordjournals.org/ at Karolinska Institutet University Library on May 29, 2015
after. Storage for 5 or 10 days significantly increased visual redness over that observed at 0 days storage. Gardner bL values were not changed substantially by end-point temperature or storage variables. There was a significant drop in bL values of cooked meat stored for 10 days but the magnitude of this change was quite small. Experiment 2. The effects of end-point temperature on color of links cooked to five end-point temperatures are reported in Table 2. Gardner L values were increased significantly with advancing endpoint temperatures when comparing lightness values of the 60° and 66°C. grouping to those obtained in the 71°, 77°, and 82°C. grouping. Gardner aL values of cooked dark meat declined significantly with increasing temperatures beyond 66°C. These results somewhat paralleled those of Bernofsky et al. (1959) who observed higher red meat myoglobin denaturation rates from 65° to 80°C. This study, as in Experiment 1, indicate that increased reddening may become particularly important when end-point temperatures are below 71°C. (160°F.). Endpoint temperatures below 71°C. would not normally occur in processing plants but nevertheless, processing temperatures could possibly become out of control from time to time. Storage grand means indicated aL values were not significantly affected at any of the storage periods. Gardner bL values showed a slight but significant decline with advancing endpoint temperatures
1836
A. H E L M K E AND G. W.
100-
l'-l
807060. 50.
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advancing end-point temperatures. A regenerated pink pigment appeared to develop within a 2 hour storage period. T h e absorption spectra of extracted pigments from turkey meat cooked to endpoint temperatures from 60°C-77°C. indicated peak maxima which were analogous to t h a t normally reported for oxymyoglobin. Extracted pigment from turkey meat, which was cooked to 82°C., had a spectra quite different than t h a t observed at lower temperatures. Results of the spectral analyses were quite similar to those previously reported by red meat researchers.
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FIG. 1. Experiment 3—Absorbance spectra of water extracts from ground dark meat turkey links cooked to 60°, 66°, 71°, 77° or 82°C. end-point temperature and stored 0 days (2 hr.) at 2°C.
links cooked to end-point temperatures from 60°C. to 77°C. T h e American M e a t Institute Foundation (1960) characterized oxymyoglobin spectrally b y relatively sharp peaks at 540 nm. and 580 nm. This indicates the presence of undenatured pigment in the water extract. As end-point temperature increased from 60° to 7 7 ° C , these peaks diminished in magnitude. Extracts from links cooked to 82°C. showed a quite different absorbance spectra than t h a t observed at other endpoint temperatures. Absorbance of the extract from 82°C. links produced slight peaks at 550 nm. and 520 nm. T h e Soret peak a t approximately 410 nm. decreased in magnitude with advancing end-point temperatures. SUMMARY
Gardner a L values (redness) decreased and L (lightness) values increased with
REFERENCES American Meat Foundation, 1960. The Science of Meat and Meat Products, W. H. Freeman and Company, San Francisco, California. Bernofsky, C , J. B. Fox, Jr. and B. S. Schweigert, 1959. Biochemistry of myoglobin. VII. The effect of cooking on myoglobin in beef muscle. Food Research, 24: 339-343. Froning, G. W., J. Daddario and T. E. Hartung, 1968. Color and myoglobin concentration in turkey meat as affected by age, sex and strain. Poultry Sci. 47:1827-1835. Froning, G. W., J. Daddario, T. E. Hartung, T. W. Sullivan and R. M. Hill, 1969a. Color of poultry meat as influenced by dietary nitrates and nitrites. Poultry Sci. 48: 668-674. Froning, G. W., F. B. Mather, J. Daddario and T. E. Hartung, 1969b. Effect of automobile exhaust fume inhalation by poultry immediately prior to slaughter on color of meat. Poultry Sci. 48: 485-487. LeClerg, E. L., W. H Leonard and A. G. Clark, 1966. Field Plot Techniques, 2nd Ed., Burgess Fubl. Co., Minneapolis, Minn. Mugler, D. J., J. D. Mitchell and A. A. Adams, 1970. Factors affecting turkey meat color. Poultry Sci. 49: 1510-1513. Pool, M. F., 1956. Why does some cooked turkey turn pink? Turkey World, January, page 68. Snedecor, G. W., 1957. Statistical Methods Applied to Experiments in Agriculture and Biology. Iowa State College Press, Ames, Iowa. Tappel, A. L., 1957. Reflectance spectral studies of the hematin pigments of cooked beef. Food Research,' 22: 404-407.
Downloaded from http://ps.oxfordjournals.org/ at Karolinska Institutet University Library on May 29, 2015
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