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Measurement of Egg Yolk Color by Means of the Colorimeter1
Measurement of Egg Yolk Color by Means of the Colorimeter 1 H. L. MAYFIELD AND E. R. HALBROOK Departments of Home Economics and Poultry Industry, Montana State College, Agricultural Experiment Station, Bozeman, Montana _ (Received for publication November 5, 1948)
HE color of the yolk of egg has received considerable attention for it is known to affect the desirability of the egg. A yolk that is either too highly colored or too pale is objectionable. Palmer (1915) (1919) reported that specific feeds affected the color of the egg yolk and that the color was due almost entirely to the pigment, xanthophyll. A brief review of the methods devised for the measurement of this color indicates that Ridgway's (1912) color standards were used as a basis for grading in the earlier work. Later, color standards were designed especially for yolk color [Parker, Gossman and Lippincott (1925); Sharp and Powell (1930)]. A more usable standard of comparison was offered by Heiman and Carver (1936) with the introduction of their Yolk Color Roter, but workers still found it difficult to get good color matches. For that reason more objective measurements were sought. Titus, Fritz and Kauffman (1938) used a Bausch and Lomb rotating-prism color analyzer and recorded results in the Munsell system of color notation. Gish, Payne and Peterson (1940) made quantitative chemical determinations of the xanthophyll content of egg yolk while Bohren, Thompson and Carrick (1945) analyzed for total carotinoids by extraction with ethyl ether and 1
Contribution from Montana State College, Agricultural Experiment Station. Paper No. 213. Journal Series.
reading at 4400 A° in a KWSZ photometer. Schertz (1925) used 80 percent acetone as the fluid for extracting xanthophyll from dried cowpea leaves and measured the pigment at 435.8 millimicrons using a spectrophotometer. He reported that carotene and xanthophyll had similar light absorbing powers. At this station, while making routine yolk color analyses with an Egg Color Chart (Vernon and Whitfield), an attempt was made to check the visual gradings by means of a more objective measurement with an Evelyn Photoelectric Colorimeter. Making use of the method reported by Schertz (1925) (1938) for the quantitative extraction and measurement of xanthophyll, a procedure was developed which the authors wish to suggest as a simple method for a comparative analysis of the color of egg yolk. METHOD
Each yolk, free from albumen, was first graded for color using an Egg Color Chart (Vernon and Whitfield). In order to make comparison and to allow for variation in grading, each of the six letters A to F, were assigned three grade points, making possible a score ranging from 1 to 18. The yolk was then thoroughly mixed and a 5 gram sample was weighed into each of two 125 ml. Erlenmeyer flasks. Twenty ml. of acetone was added to 462
Downloaded from http://ps.oxfordjournals.org/ at Kainan University on April 7, 2015
T
MEASUREMENT OF YOLK COLOR
RESULTS AND DISCUSSION
In order to compare results, the egg yolk color measurements are given in Table 1. The values representing optical TABLE 1.—Egg yolk color measured by means of the photoelectric colorimeter together with the corresponding visual grades Number of Eggs
Optical Density ( 2 - l o g G)*
Average Color Grade (Visual)
4 6 4 7 8 3 8 11 1 2 1 0 1
3- 4 4- 5 5- 6 6- 7 7- 8 8- 9 9-10 10-11 11-12 12-13 13-14 14-15 15-16
5.0 6.8 7.5 8.0 9.8 12.7 12.8 12.6 14.0 14.5 15.0 16.0
* Optical Density values are multiplied by 100.
density have been grouped and the averages of the corresponding visual color grades are shown. When the optical density values are compared with the corresponding color grade, it will be noted that as the density value increases the visual color grade is also increased. There was good agreement between the values obtained on the duplicate samples analyzed for color by means of the photoelectric colorimeter. Moreover, it appeared that the instrument detected smaller differences than could be measured visualSince the method was designed for comparative purposes only, no attempt was made to quantitatively remove the pigment from the coagulated precipitate. SUMMARY
An objective method is presented for the comparative analysis of the color of egg yolk, using acetone as the extracting fluid and a photoelectric colorimeter for the measurement. REFERENCES
Association of Official Agricultural Chemists, 1945. Official and Tentative Methods of Analysis. Sixth Ed., 600. Published by Association of Official Agricultural Chemists, Washington, D. C. Bohren, B. B., C. R. Thompson, and C. W. Carrick, 1945. The transfer of carotinoid pigments to the egg yolk. Poultry Sci., 24: 356-362. Gish, C. L., L. F. Payne, and W. J. Peterson, 1940: The effect of grass silage on color of egg yolk. Poultry Sci., 19: 154-156. Heiman, V., and J. S. Carver, 1935. The yolk color index. U. S. Egg and Poul. Mag., 41: 40-41. Palmer, L. S., 1915, Xanthophyll. The principal natural yellow pigment of the egg yolk, body fat and blood serum of the hen. The physiological relation of the pigment to the xanthophyll of plants. J. Biol. Chem. 23: 261-279. , 1919. The influence of specific feeds and certain pigments on the color of the egg and body fat of fowls. J. Biol. Chem. 39: 331-337. Parker, S. L., S. S. Gossman, and W. H. Lippincott, 1925. Studies on egg quality. I. Introductory note
Downloaded from http://ps.oxfordjournals.org/ at Kainan University on April 7, 2015
each flask from a burette and the mixture stirred with a glass stirring rod to loosen the coagulated material. The final concentration of acetone in this mixture was 89 percent. It was then mixed for 5 minutes with an electric stirrer, using a cork in the flask and over the rod of the stirrer to minimize evaporation. The mix was then centrifuged for 10 minutes and the clear liquid transferred to colorimeter tubes, which were then stoppered and kept in subdued light until the readings were made. The tubes must be slightly warm, 35°C. at the time of reading, otherwise the acetone extract becomes cloudy due to the fat present. Measurements were made on an Evelyn Photoelectric Colorimeter with the galvanometer set at 100° for clear acetone. A 440 millimicron filter was used as is recommended for carotene (Association of Official Agricultural Chemists, 1945). The transmission readings were later converted to values representing optical density (2 —log G).
463
464
RESEARCH NOTES
on variations in yolk color. Poultry Sci. 5: 121— 145. Ridgway, R., 1912. Color standards and color nomenclature. Pub. by the author. 43 pages, 53 plates. Sharp, P. F., and C. K. Powell, 1930. Decrease in interior quality of hens' eggs during storage as indicated by the yolk. J. Ind. Eng. Chem. 22: 908910. Schertz, F. M., 1925. The quantitative determination of xanthophyll by means of the spectrophotom-
eter and the colorimeter. J. Agr. Res. 30: 253261. , 1938. Isolation of chlorophyll, carotene, and xanthophyll by improved methods. J. Ind. Eng. Chem. 30: 1073-1075. Titus, H. W., J. C. Fritz and W. R. Kauffman, 1938. Some observations on egg yolk color. Poultry Sci. 17: 38-15. Vernon, W. M., and W. R. Whitfield, Egg Color Chart, Poultry Department, Iowa State College, Ames, Iowa. (Personal communication.)
A C T I V I T Y O F A V I T A M I N B12 C O N C E N T R A T E F O R C H I C K GROWTH AND HATCHABILITY* R. G. LINDSTROM, P . R. M O O R E , C. F . P E T E R S E N , AND A. C. W I E S E Departments of Poultry Husbandry and Agricultural Chemistry, University of Idaho, Moscow, Idaho (Received for publication February 14, 1949)
Crystalline vitamin B12, isolated from liver by Rickes et al. (1948) was shown by Ott et al. (1948) to give response similar to the animal protein factor (APF) required for chick growth. Preparations of a microbiologically produced material by Stokstad et al. (1948) have also been shown to be highly active as a source of A P F , when measured by chick assay. A vitamin P>i2** concentrate (4.4 ug. of B12 per gram) was fed a t a 1% level to A P F depleted chicks to determine its effect upon chick growth and to A P F depleted laying hens to determine the effect upon hatchability. T h e concentrate was used to supplement both a synthetic and a natural type chick diet. The synthetic diet contained alpha soybean protein, cerelose, soybean oil, salts, amino * Published with the approval of the Director of the Idaho Agricultural Experiment Station as Research Paper No. 292. ** Supplied through the courtesy of Dr. Green, of Merck and Co., Rahway, N. J.
acids, and vitamins A, D , and B-complex supplements. The natural type diet contained wheat bran, ground corn, oats and wheat, soybean oil meal, dehydrated alfalfa meal, salts, a n d vitamins A, D , and riboflavin. The results in Table I indicate TABLE 1.—Comparison of a vitamin Bu concencentrate and condensed fish solubles as sources of a chick growth factor
Diet and supplement Synthetic basal Synthetic b a s a l + 3 % C.F.S. Synthetic b a s a l + 1 % B12 Soybean oil meal basal S.B.O.M.+3% C.F.S. S.B.O.M. + l % Bi2 cone.
No. chicks
Av. 4-week wt. in grams
6 6 6
192.6 248.1 224.7
20 20 20
185.7 281.1 271.2
t h a t a concentrate which contained 4.4 ug. of B12 per gram, fed a t a 1 % level, was as effective in promoting chick growth as 3 % condensed fish solubles.
Downloaded from http://ps.oxfordjournals.org/ at Kainan University on April 7, 2015
Research Notes
HE color of the yolk of egg has received considerable attention for it is known to affect the desirability of the egg. A yolk that is either too highly colored or too pale is objectionable. Palmer (1915) (1919) reported that specific feeds affected the color of the egg yolk and that the color was due almost entirely to the pigment, xanthophyll. A brief review of the methods devised for the measurement of this color indicates that Ridgway's (1912) color standards were used as a basis for grading in the earlier work. Later, color standards were designed especially for yolk color [Parker, Gossman and Lippincott (1925); Sharp and Powell (1930)]. A more usable standard of comparison was offered by Heiman and Carver (1936) with the introduction of their Yolk Color Roter, but workers still found it difficult to get good color matches. For that reason more objective measurements were sought. Titus, Fritz and Kauffman (1938) used a Bausch and Lomb rotating-prism color analyzer and recorded results in the Munsell system of color notation. Gish, Payne and Peterson (1940) made quantitative chemical determinations of the xanthophyll content of egg yolk while Bohren, Thompson and Carrick (1945) analyzed for total carotinoids by extraction with ethyl ether and 1
Contribution from Montana State College, Agricultural Experiment Station. Paper No. 213. Journal Series.
reading at 4400 A° in a KWSZ photometer. Schertz (1925) used 80 percent acetone as the fluid for extracting xanthophyll from dried cowpea leaves and measured the pigment at 435.8 millimicrons using a spectrophotometer. He reported that carotene and xanthophyll had similar light absorbing powers. At this station, while making routine yolk color analyses with an Egg Color Chart (Vernon and Whitfield), an attempt was made to check the visual gradings by means of a more objective measurement with an Evelyn Photoelectric Colorimeter. Making use of the method reported by Schertz (1925) (1938) for the quantitative extraction and measurement of xanthophyll, a procedure was developed which the authors wish to suggest as a simple method for a comparative analysis of the color of egg yolk. METHOD
Each yolk, free from albumen, was first graded for color using an Egg Color Chart (Vernon and Whitfield). In order to make comparison and to allow for variation in grading, each of the six letters A to F, were assigned three grade points, making possible a score ranging from 1 to 18. The yolk was then thoroughly mixed and a 5 gram sample was weighed into each of two 125 ml. Erlenmeyer flasks. Twenty ml. of acetone was added to 462
Downloaded from http://ps.oxfordjournals.org/ at Kainan University on April 7, 2015
T
MEASUREMENT OF YOLK COLOR
RESULTS AND DISCUSSION
In order to compare results, the egg yolk color measurements are given in Table 1. The values representing optical TABLE 1.—Egg yolk color measured by means of the photoelectric colorimeter together with the corresponding visual grades Number of Eggs
Optical Density ( 2 - l o g G)*
Average Color Grade (Visual)
4 6 4 7 8 3 8 11 1 2 1 0 1
3- 4 4- 5 5- 6 6- 7 7- 8 8- 9 9-10 10-11 11-12 12-13 13-14 14-15 15-16
5.0 6.8 7.5 8.0 9.8 12.7 12.8 12.6 14.0 14.5 15.0 16.0
* Optical Density values are multiplied by 100.
density have been grouped and the averages of the corresponding visual color grades are shown. When the optical density values are compared with the corresponding color grade, it will be noted that as the density value increases the visual color grade is also increased. There was good agreement between the values obtained on the duplicate samples analyzed for color by means of the photoelectric colorimeter. Moreover, it appeared that the instrument detected smaller differences than could be measured visualSince the method was designed for comparative purposes only, no attempt was made to quantitatively remove the pigment from the coagulated precipitate. SUMMARY
An objective method is presented for the comparative analysis of the color of egg yolk, using acetone as the extracting fluid and a photoelectric colorimeter for the measurement. REFERENCES
Association of Official Agricultural Chemists, 1945. Official and Tentative Methods of Analysis. Sixth Ed., 600. Published by Association of Official Agricultural Chemists, Washington, D. C. Bohren, B. B., C. R. Thompson, and C. W. Carrick, 1945. The transfer of carotinoid pigments to the egg yolk. Poultry Sci., 24: 356-362. Gish, C. L., L. F. Payne, and W. J. Peterson, 1940: The effect of grass silage on color of egg yolk. Poultry Sci., 19: 154-156. Heiman, V., and J. S. Carver, 1935. The yolk color index. U. S. Egg and Poul. Mag., 41: 40-41. Palmer, L. S., 1915, Xanthophyll. The principal natural yellow pigment of the egg yolk, body fat and blood serum of the hen. The physiological relation of the pigment to the xanthophyll of plants. J. Biol. Chem. 23: 261-279. , 1919. The influence of specific feeds and certain pigments on the color of the egg and body fat of fowls. J. Biol. Chem. 39: 331-337. Parker, S. L., S. S. Gossman, and W. H. Lippincott, 1925. Studies on egg quality. I. Introductory note
Downloaded from http://ps.oxfordjournals.org/ at Kainan University on April 7, 2015
each flask from a burette and the mixture stirred with a glass stirring rod to loosen the coagulated material. The final concentration of acetone in this mixture was 89 percent. It was then mixed for 5 minutes with an electric stirrer, using a cork in the flask and over the rod of the stirrer to minimize evaporation. The mix was then centrifuged for 10 minutes and the clear liquid transferred to colorimeter tubes, which were then stoppered and kept in subdued light until the readings were made. The tubes must be slightly warm, 35°C. at the time of reading, otherwise the acetone extract becomes cloudy due to the fat present. Measurements were made on an Evelyn Photoelectric Colorimeter with the galvanometer set at 100° for clear acetone. A 440 millimicron filter was used as is recommended for carotene (Association of Official Agricultural Chemists, 1945). The transmission readings were later converted to values representing optical density (2 —log G).
463
464
RESEARCH NOTES
on variations in yolk color. Poultry Sci. 5: 121— 145. Ridgway, R., 1912. Color standards and color nomenclature. Pub. by the author. 43 pages, 53 plates. Sharp, P. F., and C. K. Powell, 1930. Decrease in interior quality of hens' eggs during storage as indicated by the yolk. J. Ind. Eng. Chem. 22: 908910. Schertz, F. M., 1925. The quantitative determination of xanthophyll by means of the spectrophotom-
eter and the colorimeter. J. Agr. Res. 30: 253261. , 1938. Isolation of chlorophyll, carotene, and xanthophyll by improved methods. J. Ind. Eng. Chem. 30: 1073-1075. Titus, H. W., J. C. Fritz and W. R. Kauffman, 1938. Some observations on egg yolk color. Poultry Sci. 17: 38-15. Vernon, W. M., and W. R. Whitfield, Egg Color Chart, Poultry Department, Iowa State College, Ames, Iowa. (Personal communication.)
A C T I V I T Y O F A V I T A M I N B12 C O N C E N T R A T E F O R C H I C K GROWTH AND HATCHABILITY* R. G. LINDSTROM, P . R. M O O R E , C. F . P E T E R S E N , AND A. C. W I E S E Departments of Poultry Husbandry and Agricultural Chemistry, University of Idaho, Moscow, Idaho (Received for publication February 14, 1949)
Crystalline vitamin B12, isolated from liver by Rickes et al. (1948) was shown by Ott et al. (1948) to give response similar to the animal protein factor (APF) required for chick growth. Preparations of a microbiologically produced material by Stokstad et al. (1948) have also been shown to be highly active as a source of A P F , when measured by chick assay. A vitamin P>i2** concentrate (4.4 ug. of B12 per gram) was fed a t a 1% level to A P F depleted chicks to determine its effect upon chick growth and to A P F depleted laying hens to determine the effect upon hatchability. T h e concentrate was used to supplement both a synthetic and a natural type chick diet. The synthetic diet contained alpha soybean protein, cerelose, soybean oil, salts, amino * Published with the approval of the Director of the Idaho Agricultural Experiment Station as Research Paper No. 292. ** Supplied through the courtesy of Dr. Green, of Merck and Co., Rahway, N. J.
acids, and vitamins A, D , and B-complex supplements. The natural type diet contained wheat bran, ground corn, oats and wheat, soybean oil meal, dehydrated alfalfa meal, salts, a n d vitamins A, D , and riboflavin. The results in Table I indicate TABLE 1.—Comparison of a vitamin Bu concencentrate and condensed fish solubles as sources of a chick growth factor
Diet and supplement Synthetic basal Synthetic b a s a l + 3 % C.F.S. Synthetic b a s a l + 1 % B12 Soybean oil meal basal S.B.O.M.+3% C.F.S. S.B.O.M. + l % Bi2 cone.
No. chicks
Av. 4-week wt. in grams
6 6 6
192.6 248.1 224.7
20 20 20
185.7 281.1 271.2
t h a t a concentrate which contained 4.4 ug. of B12 per gram, fed a t a 1 % level, was as effective in promoting chick growth as 3 % condensed fish solubles.
Downloaded from http://ps.oxfordjournals.org/ at Kainan University on April 7, 2015
Research Notes