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A Staining Procedure for Detecting Cracked Eggs
A Staining Procedure for Detecting Cracked Eggs w. A. MOATS Meat Science Research Laboratory, SEA, USDA, Beltsville, Maryland 20705 (Received for publication August 31, 1981)
1982 Poultry Science 61:1007-1008 INTRODUCTION During collection, washing, and grading, a certain proportion of eggs is inevitably cracked to varying degrees. Large cracks are readily visible, but hairline cracks are virtually undetectable visually and are frequently missed in routine inspection and candling procedures in egg-grading plants. These cracks are objectionable if they later become visible at the consumer level. Cracked eggs can be detected by the sound emitted when two are lightly tapped together, a practice commonly known as belling. A commercial device for detecting cracked eggs sonically has been patented (Seaborn, 1970) but has not been adopted commercially. For the present study, the feasibility of developing a staining method to make cracks more readily visible was explored. The requirements of a staining method are 1) it should selectively stain cracks without leaving any permanent stain on intact shells and, 2) it should not leave objectional chemical residues on the shell surface which might contaminate the contents when the egg is broken out. The intense blue-black complex formed by starch with iodine is well known and appeared potentially suited to the purpose since the color fades as the iodine dissipates. The use of iodine as a sanitizing agent for shell eggs and elsewhere in the food industry is well established.
improved Lintner method) were purchased from the Sigma Chemical Co. A technical grade of starch of unspecified origin was also used. The staining solution was prepared as follows: .1 g of iodine and .4 g potassium iodide were dissolved in 100 ml of water to make the iodine solution. For the starch suspension 5 g of commercial starch was slurried in 10 ml of water and added to 1000 ml boiling water. The starch iodine was prepared by mixing 20 ml of the iodine solution with 100 ml of starch solution and was quite stable.
RESULTS AND DISCUSSION
MATERIALS AND METHODS
Detection of cracks with starch iodine solution was tested with eggs cracked by lightly tapping them on a laboratory bench. Cracks induced in this manner were frequently undetectable visually. However, when the eggs were dipped in a starch-iodine solution and rinsed with the water to remove the excess, the cracks were stained blue and were readily visible under a fluorescent light. The starchiodine solution was easily rinsed off the shells and did not leave a stain. When the eggs were viewed with a candling light, a broader blue line was readily visible where the stain had penetrated through the crack to the shell-membrane. This procedure was tested with 240 eggs collected at the packing station in a commercial plant and 8 cracked eggs were found which had been missed in normal inspection procedures.
Chemicals were reagent grade. Corn starch, potato starch, and potato starch (soluble,
Several types of starch were tested for their suitability for this procedure including corn
1007
Downloaded from http://ps.oxfordjournals.org/ at University of New Orleans on May 27, 2015
ABSTRACT Methods were explored of staining cracks in eggs which were not otherwise detectable visually. Use of a starch-iodine complex proved satisfactory for this purpose. The intense blue-black starch iodine complex stained cracks blue which made them readily visible under a fluorescent light. The stain also penetrated through the crack to the shell membrane forming a blue line readily visible with a candling light. The starch-iodine complex was easily rinsed off intact egg shells and did not permanently stain the eggs or leave objectionable residues on the shells. When the method was tested on eggs from commercial processing lines, 8 cracked eggs undetected by normal candling procedures were found from 240 eggs examined. (Key words.- cracked eggs, staining method, starch-iodine)
1008
MOATS
starch, potato starch, soluble potato starch (Linter method), and a technical grade of starch of unspecified origin. The best results were obtained with corn starch and technical grade starch. The potato starch gave a very viscous solution. Staining of cracks appeared somewhat less intense with the soluble starch preparation, perhaps because it was more readily rinsed out of the cracks. Application of this method in a commercial egg grading system will require development of
a suitable method of applying the staining solution to the eggs and rinsing off the excess before the eggs enter the candling station. This might be done by either spraying or dipping the eggs after washing. Methods for accomplishing this are being studied.
REFERENCES Seaborn, P. E., 1970. Method of and device for detecting cracks in eggs. US Patent 3,503,501.
Downloaded from http://ps.oxfordjournals.org/ at University of New Orleans on May 27, 2015
1982 Poultry Science 61:1007-1008 INTRODUCTION During collection, washing, and grading, a certain proportion of eggs is inevitably cracked to varying degrees. Large cracks are readily visible, but hairline cracks are virtually undetectable visually and are frequently missed in routine inspection and candling procedures in egg-grading plants. These cracks are objectionable if they later become visible at the consumer level. Cracked eggs can be detected by the sound emitted when two are lightly tapped together, a practice commonly known as belling. A commercial device for detecting cracked eggs sonically has been patented (Seaborn, 1970) but has not been adopted commercially. For the present study, the feasibility of developing a staining method to make cracks more readily visible was explored. The requirements of a staining method are 1) it should selectively stain cracks without leaving any permanent stain on intact shells and, 2) it should not leave objectional chemical residues on the shell surface which might contaminate the contents when the egg is broken out. The intense blue-black complex formed by starch with iodine is well known and appeared potentially suited to the purpose since the color fades as the iodine dissipates. The use of iodine as a sanitizing agent for shell eggs and elsewhere in the food industry is well established.
improved Lintner method) were purchased from the Sigma Chemical Co. A technical grade of starch of unspecified origin was also used. The staining solution was prepared as follows: .1 g of iodine and .4 g potassium iodide were dissolved in 100 ml of water to make the iodine solution. For the starch suspension 5 g of commercial starch was slurried in 10 ml of water and added to 1000 ml boiling water. The starch iodine was prepared by mixing 20 ml of the iodine solution with 100 ml of starch solution and was quite stable.
RESULTS AND DISCUSSION
MATERIALS AND METHODS
Detection of cracks with starch iodine solution was tested with eggs cracked by lightly tapping them on a laboratory bench. Cracks induced in this manner were frequently undetectable visually. However, when the eggs were dipped in a starch-iodine solution and rinsed with the water to remove the excess, the cracks were stained blue and were readily visible under a fluorescent light. The starchiodine solution was easily rinsed off the shells and did not leave a stain. When the eggs were viewed with a candling light, a broader blue line was readily visible where the stain had penetrated through the crack to the shell-membrane. This procedure was tested with 240 eggs collected at the packing station in a commercial plant and 8 cracked eggs were found which had been missed in normal inspection procedures.
Chemicals were reagent grade. Corn starch, potato starch, and potato starch (soluble,
Several types of starch were tested for their suitability for this procedure including corn
1007
Downloaded from http://ps.oxfordjournals.org/ at University of New Orleans on May 27, 2015
ABSTRACT Methods were explored of staining cracks in eggs which were not otherwise detectable visually. Use of a starch-iodine complex proved satisfactory for this purpose. The intense blue-black starch iodine complex stained cracks blue which made them readily visible under a fluorescent light. The stain also penetrated through the crack to the shell membrane forming a blue line readily visible with a candling light. The starch-iodine complex was easily rinsed off intact egg shells and did not permanently stain the eggs or leave objectionable residues on the shells. When the method was tested on eggs from commercial processing lines, 8 cracked eggs undetected by normal candling procedures were found from 240 eggs examined. (Key words.- cracked eggs, staining method, starch-iodine)
1008
MOATS
starch, potato starch, soluble potato starch (Linter method), and a technical grade of starch of unspecified origin. The best results were obtained with corn starch and technical grade starch. The potato starch gave a very viscous solution. Staining of cracks appeared somewhat less intense with the soluble starch preparation, perhaps because it was more readily rinsed out of the cracks. Application of this method in a commercial egg grading system will require development of
a suitable method of applying the staining solution to the eggs and rinsing off the excess before the eggs enter the candling station. This might be done by either spraying or dipping the eggs after washing. Methods for accomplishing this are being studied.
REFERENCES Seaborn, P. E., 1970. Method of and device for detecting cracks in eggs. US Patent 3,503,501.
Downloaded from http://ps.oxfordjournals.org/ at University of New Orleans on May 27, 2015