Ionizing Irradiation of Fresh Shell Eggs1,2

UNIDENTIFIED FACTORS AND REPRODUCTION

Washington for vitamins and antioxidants used in these experiments. REFERENCES Arscott, G. H. and G. F. Combs, 1953. Further evidence for an unidentified hatchability factor in condensed fish solubles. Poultry Sci. 32: 730-733. Couch, J. R., 0 . Olcese, B. C. Sanders and J. V. Halick, 1950. Vitamin B^ APF concentrates, dried whey, fish solubles and liver fraction " L " in the nutrition of the mature fowl. J. Nutrition, 42: 473-186. Dieckert, J. W., and J. R. Couch, 1951. The liver " L " hatchability factor in the nutrition of the mature fowl. Poultry Sci. 30: 935. Grau, C. R., and P. A. Zweigart, 1952. Studies of purified diets for egg production and hatchability. Poultry Sci. 31: 919. Jacobs, R. L., J. F. Elam, J. H. Quisenberry and J. R. Couch, 1953. Dehydrated alfalfa meal as a

319

source of vitamins and unidentified factors for the mature fowl. Poultry Sci. 32:812-816. Jensen, L. S., 1954. Investigations on an unidentified growth factor in grass juice required by chicks and poults. Unpublished Ph.D. thesis, Cornell University, Ithaca, New York. Patterson, E. B., 1955. Unidentified growth factor studies with rats, chickens, turkeys and Lactobacillus Leichmannii. Unpublished Ph.D. thesis. State College of Washington, Pullman, Washington. Stephenson, E. L., and B. B. Clower, 1952. The influence of an unidentified factor found in fish solubles on hatchability. Poultry Sci. 31:936-937. Stephenson, E. L., C. Dickson and B. D. Barnette, 1954. An unidentified forage juice factor necessary for optimum reproduction in White Wyandotte hens. Poultry Sci. 33: 1083. Waibel, P. E., A. D. Morrison and L. C. Norris, 1955. Production of depleted chicks by feeding maternal diets deficient in unidentified growth factors. Poultry Sci. 34:1322-1329.

Ionizing Irradiation of Fresh Shell Eggs1-2 RICHARD W. PARSONS AND W. J. STADELMAN Poultry Science Department, Purdue University, Lafayette, Indiana (Received for publication September 10, 1956)

T

HE application of ionizing radiation to various foodstuffs, for the purpose of sterilization has received considerable attention in the last decade from such workers as: Gaden et al. (1951); Nickerson et al. (1950); and Proctor et al. (1955, 1956). This interest stems from a recognition of the value such a system of cold sterilization would have for both civilian and military food handling procedures. It has become increasingly evident, 1

Journal paper No. 1023. Contribution from Purdue Agricultural Experiment Station as a collaborator under North Central Region cooperative research project entitled, "Maintaining quality of poultry products in market channels." 2 A resume of this paper was presented at the 45 th annual meeting of the Poultry Science Association, North Carolina State College, Raleigh, North Carolina, 1956, Poultry Science 35:1164.

with the bulk of the current research, that irradiation in addition to providing many of the theoretical advantages, results in undesirable changes largely in the form of off-odor and flavor (Gaden et al., 1951; Proctor and Goldblith, 1951; and Proctor etal., 1955). The only known research involving irradiation of fresh shell eggs was reported during the 1954 Poultry Science meeting by McArdle et al. (1954). These authors indicated that 500,000 rep dosage was necessary experimentally to sterilize eggs inoculated with 10,000 cell suspensions of Escherichia coli, Pseudomonas fiuorescens and Micrococcus aureus. This level of irradiation was reputed to have weakened the yolk membranes and reduced Grade A eggs to Grade B or C. They further indi-

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R. W. PARSONS AND W. J. STADELMAN

cated that no change was noted in pH or lysozyme activity. Working with purified albumen McArdle and Desrosier (1955) report a liberation of the free sulfhydryl groups and an associated straight line increase in relative viscosity. The purpose of this present investigation has been an evaluation of the effect of less severe irradiation treatment than originally reported by this station (McArdle et al., 1954) on the quality of fresh shell eggs. EXPERIMENTAL METHOD

A flock of 100 hens including pure breeds and crosses was used to supply the eggs for this study. The individual albumen index calculated in Haugh units was established for each hen's eggs from eighteen breakout examinations over a period of thirty days and immediately preceding the period in which the irradiation work was undertaken. These hens were trapnested throughout the period of this study. Albumen height measurements were taken immediately following egg breakout. One operator broke all eggs taking albumen height measurements with a specially adapted tripod micrometer and stainless steel breakout table. Treated eggs were coded to prevent identification and subsequent bias on the part of the breakout operator. During the irradiation each egg was handled and treated separately. A mechanical device was designed to hold one egg at a time in a horizontal position rotating the egg on its own axis. This holding device was situated so that the surface of the egg shell was approximately six inches away from the mouth of the ionization chamber. Random selection was used in placing the eggs within the specific treatment groups in setting up the initial test. Eggs

from specific hens which had demonstrated wide variations in their albumen index were not used. An attempt was made to use the same hen's eggs, originally selected at random, throughout the entire five tests. It was this latter observed difference that has been statistically analyzed using an analysis of variance. Thus the variable used in the statistical analysis was the difference between the Haugh units observed following treatment and the albumen index, average Haugh unit, established for each hen's eggs. A comparison of eggs broken out immediately following treatment with those held under refrigeration for 24 hours showed differences between these groups as significant at a 1 percent level. Those eggs having been held overnight had an average value of —24.6 plus or minus 1.1 as against those eggs broken out immediately following irradiation with an average value of —18.7 plus or minus .84 (Table 1). Each test consisted of six specific irradiation levels for differing periods of time. Six eggs were used for each irradiation level giving a total of three dozen eggs per test. The several treatments are listed below: 1. 2. 3. 4. 5. 6.

14 Seconds—1X103 reps. 42 Seconds—3X103 54 Seconds—IX10" 54 Seconds—3X10* 108 Seconds—IX105 166 Seconds—3 X 10s

The six levels of irradiation (test series) were repeated five times. The first two replicates having been irradiated in the afternoon and held in a still air egg refrigerator* for 24 hours at approximately 54°F. before being broken out for evaluation. The second group of three replicates * Refrigeration equipment provided by the courtesy of the Universal Metal Fabricators, Inc., Saginaw, Michigan.

IONIZING IRRADIATION OF SHELL E G G S

321

TABLE 1.—Averages of the treatments by groups, groups over all treatments and treatments over all groups Treatment (irradiation) Group A*

Bt

1

2

3

4

5

6

-2.3 -9.5

-2.4 -8.2

-2.1 -4.6

-8.1 -16.9

-43.7 -53.2

-53.6 -55.0

Average -18.7 -24.6

' Broken out immediately following irradiation. ' Broken out following 24 hours of refrigeration.

were treated similarly as group one except that they were broken out directly following irradiation on the same afternoon. RESULTS AND DISCUSSION

In establishing the albumen quality of the eggs laid by the hens used in these studies thirteen breakout examinations were conducted over a month's time. An analysis of the Haugh unit variations observed in these examinations has since shown that between 3.7 and 6.8 observations, within any given month were sufficient for a 95 percent confidence level. All treated eggs had an unnatural odor best described as an ozone odor. The severity of this odor increased with increased dosage. Accompanying this odor development was an apparent physical change in the character of the thick albumen. Here again this change was in the direction of increased dosage. The interaction of groups (those eggs broken out immediately as against those eggs held for 24 hours) by treatments were not significant at the 5 percent level. Here again Table 1 shows the means investi-

gated for this interaction. For those eggs broken out directly following treatment differences due to treatment, the six irradiation levels, were significant at a 1 percent level. An examination of the treatment means has shown that the means for treatment 1, 2, 3, and 4 were significantly different from treatments 5 and 6. However, no significant differences were found between treatments 1, 2, 3 or 4 nor between treatments 5 and 6. The differences between replicates as measured in average values for each irradiation over all hens and in treatments were significant (Table 2). The interaction of treatments with replicates was found to be significant at the 5 percent level. The information contained in Table 2 indicates the regularity of the treatment by replication means. SUMMARY

An albumen quality index was established for each bird of a flock of 100 pure and cross bred hens. The observed difference between these indices and the Haugh

TABLE 2.—Averages of treatments by replications, replication over all treatments and treatment over all replications, of eggs in group A (Broken out directly following irradiation) Treatment (irradiation)

1 2 3

Treatment averages

1

2

3

4

5

6

Replicate average

-3.5 -3.7 -7.7

-1.2 -4.2 -5.8

2.9 -2.9 1.3

-12.1 -11.5 -5.8

-41.1 -58.4 -41.5

-47.3 -52.6 -49.0

-21.2 -28.5 -23.4

-4.9

-3.7

-47.0

-49.6

.43

-9.8

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R. W. PARSONS AND W. J. STADELMAN

unit measurements of treated (irradiated) eggs was the variable used to test the effect of irradiation. Differences resulting from the six irradiation treatments were significant at a 1 percent level. Likewise, treatments 1, 2, 3 and 4 were significantly different from treatments 5 and 6. However, no significant differences were found between treatments 1, 2, 3 and 4 nor between 5 and 6. The differences observed in replicates were significant as measured in average values for each radiation over hens and treatment. The interaction of treatments with replicates was found not to be significant at the 5 percent level. Under the conditions of this study, fresh shell eggs were sufficiently damaged to rule out ionizing irradiation as a prospective method of cold sterilization for fresh shell market eggs. The report by McArdle el al. would lend support to this conclusion. These authors have stated that a 500,000 rep dosage, considerably higher than the 1.000-300.000 rep dosage range reported detrimental herein, was sufficient to sterilize fresh shell eggs artificially inoculated in the laboratory.

ACKNOWLEDGEMENT

The kind cooperation of the Physics Department, particularly of their Dr. J. W. MacKay, co-developer of the Purdue linear accelerator used in this research, has made this work possible. REFERENCES Gaden, E. L., Jr., E. J. Henley and V. P. Collins, 1951. Preservation of milk by radiation. Food Technol. 5: 506-509. McArdle, F. J., and N. Desrosier, 1955. Influence of ionizing radiation on the protein components of selected foods. Food Technol. 9: 527-532. McArdle, F. J., W. Marion and N. W. Desrosier, 1954. Sterilization of shell eggs by ionization. Poultry Sci. 33:1070. Nickerson, J. T. R., S. A. Goldblith and B. E. Proctor, 1950. A comparison of chemical changes in mackerel tissues treated by ionizing radiation. Food Technol. 4: 84-88. Proctor, B. E., and S. A. Goldblith, 1952. Biochemical prevention of flavor and chemical changes in foods and tissues sterilized by ionizing radiations. Food Technol. 6: 237-242. Proctor, B. E., J. T. R. Nickerson and J. J. Licciardello, 1956. Cathode ray irradiation of chicken meat for the extension of shelf life. Food Res. 21: 11-20. Proctor, B. E., J. T. R. Nickerson, J. J. Licciardello and E. E. Lockhart, 1955. Extension of food storage life by irradiation. Food Technol. 9: 523

NEWS AND NOTES (Continued from page 301) CONNECTICUT NOTES

WORLD POULTRY CONGRESS

Daniel K. Andrews was appointed Instructor in Poultry Science at the University of Connecticut, effective September 1, 1956. He graduated from the University of Maine in 1949 and received a M.S. degree at Kansas State College in 1951. He has been pullorum inspector at the University of Maine, and broiler production supervisor at Chambersburg, Maryland. He was on the staff of the U.S.D.A. Inspection and Grading Division, Sioux City, Iowa, and was Poultry Instructor at the State University of New York at Delhi. His duties will include 4-H Club poultry extension and teaching, filling the position vacated by Owen S. Trask, who has assumed new duties dealing with older youth education in Connecticut.

The Council of the World Poultry Science Association has decided to postpone the 11th World Poultry Congress until the summer of 1958. Mexico City will probably be the site for the congress. PENB NOTES

Dr. James W. Gwin, General Manager, the Poultry and Egg National Board, has resigned effective February 5, to become Manager, Marketing Section of the Sales Service Division, Ralston Purina Company, St. Louis, Mo. Prior to joining PENB in 1955, Gwin was Director of the Maryland Extension Service. At the annual meeting of the Poultry and Egg National Board held in Chicago, January 31-Febru(Continued on page 328)