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Experiments Relating to the Spoilage of Washed Eggs
Experiments Relating to the Spoilage of Washed Eggs M. WAYNE MILLER, V. JOUKOVSKY AND ALBERT KRAGHT
Washington Co-operative Farmers Association, 201 Elliott Avenue West, Seattle, Washington (Received for publication June 6, 1949)
D
Funk (1938) presented work showing that under the conditions of his experiments eggs cleaned in a solution of sodium hydroxide kept equally as well as clean eggs which had not been washed. This work indicated the possibility of using sodium hydroxide in the wash water of commercial machines, thus getting away from the spoilage problem. A commercial egg washing machine in operation at the Washington Co-operative Farmers Association was found to give good results from the standpoint of egg spoilage when operating during the cold winter months. However, when the
Results in this trial were entirely negative in that no more rots were observed in the dirty eggs washed in clean water, or 27
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weather became warm in the late spring and summer a severe rot problem developed in the washed eggs. Additions of sodium hydroxide to the wash water in this machine, as suggested by Funk (1938), did not seem to eliminate or decrease the number of rots. Because of our experience with the failure of the commercial washing machines to give satisfactory results during warm weather, we felt it important to institute experiments in our laboratory designed to find methods of washing eggs which would eliminate the. problem of spoilage. Trial 1 was set up using lots of 180 dirty eggs. Four treatments were used in which dirty eggs were left unwashed, were washed in clean water, were washed in a sodium hydroxide solution and were soaked in 1% sodium hydroxide solution for several hours before washing. One lot from each treatment was held at room temperature for four weeks and duplicate lots were prepared at the same time and stored for six months in cold storage. Repeat washings were made in the months of February, April, June and August. In this and all subsequent experiments, except where temperatures are shown, the water temperature for washing the eggs varied between 65 and 72 degrees F. The results of these tests are shown in Table 1.
URING the last year there has been considerable discussion of the problem of washing eggs because of the introduction of a great many commercial egg washing machines. Some of these machines have been advertised as the solution to the problem of spoilage in washed eggs. For years it has been recognized that washed eggs have a greater loss in cold storage than eggs which have not been washed. For this reason either dry cleaning by abrasive methods or the storing of clean eggs have been recommended for cold storage. Although some commercial egg washing machines have been in use for many years, it has been generally recognized that a marketing problem exists where eggs from these machines must be sold. Sometimes many of the eggs washed on the machines rot while at other times they seem to keep as well as unwashed eggs.
28
M. WAYNE MILLER, V. JOUKOVSKY AND ALBERT KRAGHT
TABLE 1.—Number of inedible eggs per lot of 180 eggs at time of observation
February Egg treatment
Dirty Eggs Washed—Clean Water Washed—1% Sodium Hydroxide Water Soaked—1% Sodium Hydroxide Water
April
Room Cold temperature I „fe 4wks. 6 m o s 1 3
Room
temper-, ature 4wks.
June Room
Cold s 0 l ^°e 6mos
-
August Room
Cold
Cold s lorage 6Km o s
ature "aZrJ•£»? "S 4wks. 6 m o s ' 4wks.
^-
0 0
2
0
0
0
fectants, were used in the wash water. Apparently the accumulation of filth and bacteria from the eggs introduced a condition whereby the eggs became inoculated with rot forming bacteria during the washing process. Pritsker (1941) demonstrated the importance of maintaining an internal pressure in eggs while washing them. He used the percent hatchability as a criterion to determine the effect of the different washing procedures. Funk (1943) reported a pasteurization
TABLE 2.—Summary of trial 2
Kind of eggs and treatment
Lot no.
Clean Special A
7 8 9
Dirties
a u
u «
u a
« «
Before After processing processing
Pasteurized Oil Dipped Not Oiled
ooo
1 2 3
Process
Holding time at room room temperature
5 weeks
Pasteurized Oil Dipped Not Oiled
0 0 0
5 weeks
a
«
a
B Albumen hei
Sht
;
perml.atthe end
^g{iing p
43.0 19.5 ' 12.5
<100 <100 <100
47.6 25.3 14.8
300 2,500,000 7,000,000
47.0 26.3 18.1
<100 <100 10,500,000
13 14 15
Clean eggs dipped in water containing broken black rots
Pasteurized Oil dipped Not oiled
0 0 0
4 weeks
16 17 18
Clean eggs dipped in water containing broken black rots
Pasteurized Oil dipped Not oiled
1 week
4 weeks
38.7 18.6 15.0
<100 3,000,000 110,000,000
19 20 21
Clean eggs dipped in water containing broken black rots
Pasteurized Oil dipped Not oiled
2 weeks
4 weeks
30.0 16.6 13.8
<100 10,000,000 65,000,000*
* Five black rots not included.
u
« a
«
1
«
a
u
«
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in the eggs washed in the sodium hydroxide, than in the unwashed eggs. This illustrates one phase of the egg washing problem which probably accounts for the many statements that have been made that egg washing is a safe practice. Under some conditions washed eggs do not rot. In spite of our failure to produce rots in the washing experiment we continued to have rots develop in eggs washed on the commercial machine until it was necessary to completely abandon it even though sodium hydroxide, and later other disin-
29
SPOILAGE OF WASHED EGGS
mine some of the factors causing eggs to rot and methods of washing which might eliminate this problem. Because of our failure in the first experiment to introduce conditions that would cause the eggs to rot we felt it necessary to start with heavily contaminated water. This was accomplished by breaking black rot eggs into the wash water prior to the specific treatment that was introduced. Our first attempts were based on the assumption that the eggs could be washed and then
TABLE 3.—Summary of trial 3
Lot
Size of lot
Kind of eggs
1
36
Dirty
2
36
Dirty
3
36
Dirty
4
36
Dirty
5
36
Dirty
6 7
36 36
Dirty Dirty
Treatment
Disinfectant in rinse water
Temperatureof rinse
water Washed in water containing black rots Washed in water containing black rots Washed in water containing black rots Washed in water containing black rots Washed in water containing black rots Not washed Washed in clean water and broken out for initial count
£°l!£s * om temperature*
Bacteria count of non rots per- ml.
None . 0 1 % Roccal .0025% Roccal . 25% Sodium pentachlorophenol . 10% Sodium pentachlorophenol
80° F.
7
120° F.
15
** **
80° F.
10
**
120° F. . 16
**
0
**
no
* Determined by candling. ** Count not determined because of large number of rots in most lots.
eggs of high quality, when placed in water containing broken out black rot eggs, could be treated by the Funk process of pasteurization and prevent any rots from developing and maintain a low bacteria content subsequent to treatment. In fact, even when eggs, inoculated in this manner, were allowed to set for either one or two weeks prior to pasteurization, rots were prevented and the bacteria content kept low; whereas, eggs not pasteurized in that manner either developed rots or increased bacteria numbers to tremendous proportions. A study was then undertaken to deter-
treated with the disinfectant in the rinse water to destroy the surface bacteria on the shell. Experiment 3 is outlined in Table 3. One lot was left as an unwashed control and another lot was broken out immediately after washing to determine the bacteria content in the eggs at the time the experiment was started. The eggs which were disinfected after inoculation were exposed to disinfectant solution for fifteen seconds immediately after washing. At the end of two and one-half weeks, or sufficient time for rots to develop in the positive control, the eggs were candled,
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procedure in which it was indicated that spoilage in shell eggs may be eliminated or greatly reduced by holding eggs in oil for ten minutes at 140 degrees F. Trial 2 was set up to determine whether eggs which had been heavily inoculated with rot forming bacteria could be treated by a pasteurization procedure such as Funk (1943) recommended. In this experiment lots of three dozen eggs each were treated according to the outline shown in Table 2. This table shows that
30
M. WAYNE MILLER, V. JOUKOVSKY AND ALBERT KRAGHT TABLE 4.—Summary of trial 4
Lot Size of lot 1
36
Kind of eggs Dirty
36
Dirty
3
36
Dirty
4
36
Dirty
5 6
36 36
Dirty Dirty
Treatment
Washed in water containing black rots Washed in water containing black rots Washed in water containing black rots Washed in water containing black rots Not washed Washed in clean water and broken out for initial count
None .02% Roccal . 5 % Sodium pentachlorphenol in water . 25% Sodium pentachlorophenol in oil*
Rots at 2 | weeks room temperature
Bacteria count of non-rots per ml.
90° F.
20
**
90° F.
14
**
131° F.
17
**
0
64,000,000
0
8,100,000 3,150,000
* Would not completely dissolve. Dipped in oil 1 hour after washing. ** Not determined because of large number.
the rots removed and the remaining eggs of normal appearance were to be used for determination of the bacteria count. For determination of the bacteria count in the non-rots the eggs were dipped in a sterilizing solution, broken out individually and all normal appearing eggs mixed together in a Waring blender for sampling. Actually the final bacteria count was not made on this group because
of the high percentage of rots which developed in the various washed lots. It is apparent from this trial that the addition of Roccal or sodium pentachlorophenol to a rinse water following washing did not prevent the development of rots in the washed eggs. We were not certain whether this failure was due to the low concentration of the disinfectant used or whether disinfecting the eggs after washing is not
TABLE 5.—Summary of trial 5
Lot
Size of lot
Kind of eggs
1
36
Dirty
Not washed or processed
2
36
Dirty
3
36
Dirty
4
36
Dirty
5
36
Dirty
6
36
Dirty
7
36
Dirty
Washed in water containing broken black rots, not oiled Washed in water containing broken black rots and oiled Washed in water containing broken black rots and oiled Washed in water containing broken black rots and oiled Washed in water containing broken black rots and oiled with oil with .25% pentachlorophenol Washed with clean water and broken out for initial count
Treatment
Black rots Oil removed by temperature candling at two weeks 0 19 Room temp. 140° F.
0
Other rots when broken out
Bacteria per ml. in non-rots
2 green 3 mixed 0
35,000,000 not determined 134,000,000
1
2 green 5 mixed 2 mixed
200,000,000
140° F.
1
4 mixed
220,000,000
Room temp.
0
1 green 9 mixed
132,000,000
—
56,000*
* A few black rots were removed from eggs used in this experiment before intermingling into the various lots.
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2
Temperature of rinse water
Disinfectant in rinse water or oil
31
SPOILAGE OF WASHED EGGS
an effective treatment. Experiment 4 was similar to experiment 3 except that higher concentration of the disinfecting materials in the rinse water was used. The result of this trial showed that rots developed in the first three lots during the two weeks that the eggs were held indicating that disinfecting the eggs after washing is not the solution of the problem. It is of interest to note that in candling at the end of the holding
be terminated. The results show that even though very few rots could be detected in the oiled lots when candled, all of these lots contained green or mixed rots when broken out. This was also true of lot one, which was not washed, indicating that the bacteria contamination came from the dirt on the eggs and not from any treatment which we had given them. Green rots are bacterial rots which, in the early stage of deterioration, have a
Lot no.
Size of lot
Kind of eggs
1 2
36 36
Dirty Dirty
3
36
Dirty
4
36
Dirty
Treatment
Not washed Washed in water containing broken black rots Washed in water used for lot §2, 5 minutes after adding 1% Roccal Washed in water prepared as in lot #2, heated S minutes 144° F.-1SS° F .
Bacteria per ml. wash water
Number Mold black spots rots
Mixed Green rots rots
Bacteria per ml. in non-rot
32,000,000
0 7
0 0
0 2
0 18
53,000,000 124,000,000
Sterile
0
0
0
1
1,320,000
1
4
4
0
840,000
period no rots were observed in the eggs of lot four which had been dipped in oil containing sodium pentachlorophencl. However, when eggs of this lot were then broken out they were of poor quality as indicated by the high bacterial count of 64,000,000 per milliliter. Apparently oil processed eggs do not develop black rots to the same extent that untreated eggs do. Experiment 5 was outlined to determine the effect of treating the inoculated, washed eggs with processing oil, with and without pentachlorophenol to see whether the protection which was obtained by oiling in the previous experiment was due to the oil or the disinfectant in the oil. The eggs were held for two weeks during which time the presence of rots in lot two indicated that the experiment could
1,180
greenish colored albumen, a normal physical appearance and an offensive, sweetish odor difficult to describe. These eggs cannot usually be detected by candling. They are inedible. This trial rather definitely established the fact that oil prevented the development of a large number of black rots. Apparently from results obtained with lot three, processing with oil, without disinfectant in the oil was just as effective in preventing the development of black rots as oil containing disinfectant. At this point in the series of experiments it was decided that treating the eggs after washing would not prevent rots, therefore, if we were to be successful we should attempt to treat the wash water rather than the eggs after washing. In trial 6, the wash water was treated as shown in Table 6. The bacteria count
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TABLE 6.—Summary of trial 6
32
M. WAYNE MILLER, V. JOUKOVSKY AND ALBERT KRAGHT
in the wash water in lot two was 32,000,000 bacteria per milliliter. In lot three it was treated with 1 percent Roccal for five minutes before washing at which time the water was sterile. In lot four the wash water prepared the same way as in lot two was heated for five minutes at temperatures that varied from 144° to 155° F. The bacteria of the wash water was reduced to 1,180 per milliliter after five minutes.
Experiment 7 is a repetition of experiment 6 except that one lot was included in which water was treated both with heat and chemical. The outline of this experiment and the results are given in Table 7. The bacteria content of the wash water was 18,800,000 per milliliter before treatment. Less than 10 bacteria per mil. remained in the wash water in the three treated groups at the time the eggs were
TABLE 7.—Summary of trial 7 Size of lot
Kind of eggs
1 2 3 4
36 36 36 36
DirtyDirty Dirty Dirty
5
36
Dirty
6
36
Dirty
Bacteria per ml. wash water
Treatment
Broken out for initial count Not washed Washed in water containing black rots Washed in water like above after heating 5 minutes at 145° F. Washed in water containing broken black rots plus 1% Roccal for 5 minutes Washed in water containing broken black rots treated for 5 minutes with 1% Roccal and heat at 145° F.
After holding the washed eggs for approximately four weeks black rots had developed in the positive control and the observations on the eggs were made at that time. Lot one which was untreated had no rots or mold spots, although the eggs did have a high bacteria content at the end of the trial. Lot two which was washed in untreated water containing black rot inoculum, contained seven black rots, two mixed rots and when broken out many of the remaining eggs had green albumen, typical of green rot. The lot treated with Roccal contained one egg with green albumen and the remaining eggs had a bacteria content of 1,320,000 per milliliter which is considerably less than the unwashed eggs of lot one. This was the first successful experiment we had indicating the possibility of washing eggs without developing rots.
Number black rots
NumBacteria ber ml. green in per non-rots rots
—
20 32,400,000 18,700,000 7,000,000
18,800,000 10
3 7 0
10
2
4,430,000
10
1
5,100
8-
—
washed. The result of this experiment showed that the eggs treated with heat and chemical kept just as well as lot two which was the untreated group. It should be pointed out, in connection with this experiment, that even though dirty eggs were used which had a low initial bacteria count, the presence of the organisms causing rots apparently had gained access to the eggs during the experiment so that an occasional rot did develop in these eggs. It is obvious therefore that any treatment of dirty eggs will not prevent all rots from developing unless some type of pasteurization process is used which will destroy all rot forming organisms, or the eggs must be washed before the rot forming bacteria contaminates the egg. It was observed in the course of this experiment that eggs receiving the heat treatment had more stuck yolks than eggs receiving the chemical treatment.
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Lot no.
33
SPOILAGE OF W A S H E D E G G S
Experiment 8 was used to check whether heat t r e a t m e n t would cause this condition. The outline and results of this experiment are given in Table 8. T h e evidence in regard to stuck yolks is not very conclusive, however, the results do not indicate t h a t heat t r e a t m e n t is responsible for the sticking of the yolk to the shell. Some green rots were found in all of the treated lots a t the end of the experiment.
mental conditions are established. Failures of commercial egg washing machines are probably due to the fact t h a t the accumulation of filth and bacteria in the wash water inoculates the egg with rot forming organisms. Eggs can be successfully washed provided the wash water remains sterile, if the egg is not already infected. I t will be advantageous to have the wash water
Lot no.
Size of lot
Kind of eggs
Treatment
Bacteria per ml. wash water after washing
Stuck yolks when candled*
Black rots
Suspicious when candled
Green rots
Mixed rots
SusBacteria P.OOUS P ^ J j "
0
1
3
1
36
Dirty Immediate breakout
2
36
Dirty Not washed
0
0
3
36
Dirty Washed in water containing black rots water at 74" 3,800,000
0
11
9
6
1
0
4
36
Dirty Washed in water containing black rots, 1% RoccaT, 82° F.
10
3
0
2
2
0
2
620,000
5
36
Dirty Washed in water containing black rots, 1% RoccaT 135° F.
10
0
0
4
2
1
0
9,400,000
6
36
Dirty Washed in water containing black rots, 1% RoccaT, 150° F.
3
180
200
500
* The only stuck yolks in any lot were those which were readily broken loose in the candling process.
While no green rots were found in the untreated control one mixed rot and three suspicious eggs were observed in t h a t lot thus indicating t h a t the appearance of these eggs in lots four, five and six was not due to the failure of the t r e a t m e n t b u t due t o organisms in the eggs a t the time they were washed. As a result of this series of experiments the following conclusions can be made in regard to washing eggs. CONCLUSIONS Washing sult in the tions must inoculated velop into
eggs does not necessarily redevelopment of rots. Condibe such t h a t the egg becomes with organisms t h a t will derots when favorable environ-
warmer t h a n the egg during the washing process. Processing of washed eggs in oil tends to reduce the percentage of black rots t h a t develop b u t does not prevent the formation of green and mixed rots. Washing of dirty eggs even under the best washing procedures will not entirely eliminate the development of rots, if the eggs have been inoculated prior to washing. REFERENCES Funk, E. M., 1938. Improving the keeping quality of eggs by cleaning with sodium hydroxide. Mo. Agr. Exp. Sta. Bal. 277. Funk, E. M., 1943. Pasteurization of shell eggs. Mo. Agricultural Exp. Sta. Bui. 364. Pritsker, I. Y., 1941. Researches on the hatching qualities of eggs. II. Disinfection of egg shells under increased pressure within the egg. Poultry Sci. 20: 102-103.
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T A B L E 8.—Summary of trial 8
Washington Co-operative Farmers Association, 201 Elliott Avenue West, Seattle, Washington (Received for publication June 6, 1949)
D
Funk (1938) presented work showing that under the conditions of his experiments eggs cleaned in a solution of sodium hydroxide kept equally as well as clean eggs which had not been washed. This work indicated the possibility of using sodium hydroxide in the wash water of commercial machines, thus getting away from the spoilage problem. A commercial egg washing machine in operation at the Washington Co-operative Farmers Association was found to give good results from the standpoint of egg spoilage when operating during the cold winter months. However, when the
Results in this trial were entirely negative in that no more rots were observed in the dirty eggs washed in clean water, or 27
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weather became warm in the late spring and summer a severe rot problem developed in the washed eggs. Additions of sodium hydroxide to the wash water in this machine, as suggested by Funk (1938), did not seem to eliminate or decrease the number of rots. Because of our experience with the failure of the commercial washing machines to give satisfactory results during warm weather, we felt it important to institute experiments in our laboratory designed to find methods of washing eggs which would eliminate the. problem of spoilage. Trial 1 was set up using lots of 180 dirty eggs. Four treatments were used in which dirty eggs were left unwashed, were washed in clean water, were washed in a sodium hydroxide solution and were soaked in 1% sodium hydroxide solution for several hours before washing. One lot from each treatment was held at room temperature for four weeks and duplicate lots were prepared at the same time and stored for six months in cold storage. Repeat washings were made in the months of February, April, June and August. In this and all subsequent experiments, except where temperatures are shown, the water temperature for washing the eggs varied between 65 and 72 degrees F. The results of these tests are shown in Table 1.
URING the last year there has been considerable discussion of the problem of washing eggs because of the introduction of a great many commercial egg washing machines. Some of these machines have been advertised as the solution to the problem of spoilage in washed eggs. For years it has been recognized that washed eggs have a greater loss in cold storage than eggs which have not been washed. For this reason either dry cleaning by abrasive methods or the storing of clean eggs have been recommended for cold storage. Although some commercial egg washing machines have been in use for many years, it has been generally recognized that a marketing problem exists where eggs from these machines must be sold. Sometimes many of the eggs washed on the machines rot while at other times they seem to keep as well as unwashed eggs.
28
M. WAYNE MILLER, V. JOUKOVSKY AND ALBERT KRAGHT
TABLE 1.—Number of inedible eggs per lot of 180 eggs at time of observation
February Egg treatment
Dirty Eggs Washed—Clean Water Washed—1% Sodium Hydroxide Water Soaked—1% Sodium Hydroxide Water
April
Room Cold temperature I „fe 4wks. 6 m o s 1 3
Room
temper-, ature 4wks.
June Room
Cold s 0 l ^°e 6mos
-
August Room
Cold
Cold s lorage 6Km o s
ature "aZrJ•£»? "S 4wks. 6 m o s ' 4wks.
^-
0 0
2
0
0
0
fectants, were used in the wash water. Apparently the accumulation of filth and bacteria from the eggs introduced a condition whereby the eggs became inoculated with rot forming bacteria during the washing process. Pritsker (1941) demonstrated the importance of maintaining an internal pressure in eggs while washing them. He used the percent hatchability as a criterion to determine the effect of the different washing procedures. Funk (1943) reported a pasteurization
TABLE 2.—Summary of trial 2
Kind of eggs and treatment
Lot no.
Clean Special A
7 8 9
Dirties
a u
u «
u a
« «
Before After processing processing
Pasteurized Oil Dipped Not Oiled
ooo
1 2 3
Process
Holding time at room room temperature
5 weeks
Pasteurized Oil Dipped Not Oiled
0 0 0
5 weeks
a
«
a
B Albumen hei
Sht
;
perml.atthe end
^g{iing p
43.0 19.5 ' 12.5
<100 <100 <100
47.6 25.3 14.8
300 2,500,000 7,000,000
47.0 26.3 18.1
<100 <100 10,500,000
13 14 15
Clean eggs dipped in water containing broken black rots
Pasteurized Oil dipped Not oiled
0 0 0
4 weeks
16 17 18
Clean eggs dipped in water containing broken black rots
Pasteurized Oil dipped Not oiled
1 week
4 weeks
38.7 18.6 15.0
<100 3,000,000 110,000,000
19 20 21
Clean eggs dipped in water containing broken black rots
Pasteurized Oil dipped Not oiled
2 weeks
4 weeks
30.0 16.6 13.8
<100 10,000,000 65,000,000*
* Five black rots not included.
u
« a
«
1
«
a
u
«
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in the eggs washed in the sodium hydroxide, than in the unwashed eggs. This illustrates one phase of the egg washing problem which probably accounts for the many statements that have been made that egg washing is a safe practice. Under some conditions washed eggs do not rot. In spite of our failure to produce rots in the washing experiment we continued to have rots develop in eggs washed on the commercial machine until it was necessary to completely abandon it even though sodium hydroxide, and later other disin-
29
SPOILAGE OF WASHED EGGS
mine some of the factors causing eggs to rot and methods of washing which might eliminate this problem. Because of our failure in the first experiment to introduce conditions that would cause the eggs to rot we felt it necessary to start with heavily contaminated water. This was accomplished by breaking black rot eggs into the wash water prior to the specific treatment that was introduced. Our first attempts were based on the assumption that the eggs could be washed and then
TABLE 3.—Summary of trial 3
Lot
Size of lot
Kind of eggs
1
36
Dirty
2
36
Dirty
3
36
Dirty
4
36
Dirty
5
36
Dirty
6 7
36 36
Dirty Dirty
Treatment
Disinfectant in rinse water
Temperatureof rinse
water Washed in water containing black rots Washed in water containing black rots Washed in water containing black rots Washed in water containing black rots Washed in water containing black rots Not washed Washed in clean water and broken out for initial count
£°l!£s * om temperature*
Bacteria count of non rots per- ml.
None . 0 1 % Roccal .0025% Roccal . 25% Sodium pentachlorophenol . 10% Sodium pentachlorophenol
80° F.
7
120° F.
15
** **
80° F.
10
**
120° F. . 16
**
0
**
no
* Determined by candling. ** Count not determined because of large number of rots in most lots.
eggs of high quality, when placed in water containing broken out black rot eggs, could be treated by the Funk process of pasteurization and prevent any rots from developing and maintain a low bacteria content subsequent to treatment. In fact, even when eggs, inoculated in this manner, were allowed to set for either one or two weeks prior to pasteurization, rots were prevented and the bacteria content kept low; whereas, eggs not pasteurized in that manner either developed rots or increased bacteria numbers to tremendous proportions. A study was then undertaken to deter-
treated with the disinfectant in the rinse water to destroy the surface bacteria on the shell. Experiment 3 is outlined in Table 3. One lot was left as an unwashed control and another lot was broken out immediately after washing to determine the bacteria content in the eggs at the time the experiment was started. The eggs which were disinfected after inoculation were exposed to disinfectant solution for fifteen seconds immediately after washing. At the end of two and one-half weeks, or sufficient time for rots to develop in the positive control, the eggs were candled,
Downloaded from http://ps.oxfordjournals.org/ at University of Michigan on April 19, 2015
procedure in which it was indicated that spoilage in shell eggs may be eliminated or greatly reduced by holding eggs in oil for ten minutes at 140 degrees F. Trial 2 was set up to determine whether eggs which had been heavily inoculated with rot forming bacteria could be treated by a pasteurization procedure such as Funk (1943) recommended. In this experiment lots of three dozen eggs each were treated according to the outline shown in Table 2. This table shows that
30
M. WAYNE MILLER, V. JOUKOVSKY AND ALBERT KRAGHT TABLE 4.—Summary of trial 4
Lot Size of lot 1
36
Kind of eggs Dirty
36
Dirty
3
36
Dirty
4
36
Dirty
5 6
36 36
Dirty Dirty
Treatment
Washed in water containing black rots Washed in water containing black rots Washed in water containing black rots Washed in water containing black rots Not washed Washed in clean water and broken out for initial count
None .02% Roccal . 5 % Sodium pentachlorphenol in water . 25% Sodium pentachlorophenol in oil*
Rots at 2 | weeks room temperature
Bacteria count of non-rots per ml.
90° F.
20
**
90° F.
14
**
131° F.
17
**
0
64,000,000
0
8,100,000 3,150,000
* Would not completely dissolve. Dipped in oil 1 hour after washing. ** Not determined because of large number.
the rots removed and the remaining eggs of normal appearance were to be used for determination of the bacteria count. For determination of the bacteria count in the non-rots the eggs were dipped in a sterilizing solution, broken out individually and all normal appearing eggs mixed together in a Waring blender for sampling. Actually the final bacteria count was not made on this group because
of the high percentage of rots which developed in the various washed lots. It is apparent from this trial that the addition of Roccal or sodium pentachlorophenol to a rinse water following washing did not prevent the development of rots in the washed eggs. We were not certain whether this failure was due to the low concentration of the disinfectant used or whether disinfecting the eggs after washing is not
TABLE 5.—Summary of trial 5
Lot
Size of lot
Kind of eggs
1
36
Dirty
Not washed or processed
2
36
Dirty
3
36
Dirty
4
36
Dirty
5
36
Dirty
6
36
Dirty
7
36
Dirty
Washed in water containing broken black rots, not oiled Washed in water containing broken black rots and oiled Washed in water containing broken black rots and oiled Washed in water containing broken black rots and oiled Washed in water containing broken black rots and oiled with oil with .25% pentachlorophenol Washed with clean water and broken out for initial count
Treatment
Black rots Oil removed by temperature candling at two weeks 0 19 Room temp. 140° F.
0
Other rots when broken out
Bacteria per ml. in non-rots
2 green 3 mixed 0
35,000,000 not determined 134,000,000
1
2 green 5 mixed 2 mixed
200,000,000
140° F.
1
4 mixed
220,000,000
Room temp.
0
1 green 9 mixed
132,000,000
—
56,000*
* A few black rots were removed from eggs used in this experiment before intermingling into the various lots.
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2
Temperature of rinse water
Disinfectant in rinse water or oil
31
SPOILAGE OF WASHED EGGS
an effective treatment. Experiment 4 was similar to experiment 3 except that higher concentration of the disinfecting materials in the rinse water was used. The result of this trial showed that rots developed in the first three lots during the two weeks that the eggs were held indicating that disinfecting the eggs after washing is not the solution of the problem. It is of interest to note that in candling at the end of the holding
be terminated. The results show that even though very few rots could be detected in the oiled lots when candled, all of these lots contained green or mixed rots when broken out. This was also true of lot one, which was not washed, indicating that the bacteria contamination came from the dirt on the eggs and not from any treatment which we had given them. Green rots are bacterial rots which, in the early stage of deterioration, have a
Lot no.
Size of lot
Kind of eggs
1 2
36 36
Dirty Dirty
3
36
Dirty
4
36
Dirty
Treatment
Not washed Washed in water containing broken black rots Washed in water used for lot §2, 5 minutes after adding 1% Roccal Washed in water prepared as in lot #2, heated S minutes 144° F.-1SS° F .
Bacteria per ml. wash water
Number Mold black spots rots
Mixed Green rots rots
Bacteria per ml. in non-rot
32,000,000
0 7
0 0
0 2
0 18
53,000,000 124,000,000
Sterile
0
0
0
1
1,320,000
1
4
4
0
840,000
period no rots were observed in the eggs of lot four which had been dipped in oil containing sodium pentachlorophencl. However, when eggs of this lot were then broken out they were of poor quality as indicated by the high bacterial count of 64,000,000 per milliliter. Apparently oil processed eggs do not develop black rots to the same extent that untreated eggs do. Experiment 5 was outlined to determine the effect of treating the inoculated, washed eggs with processing oil, with and without pentachlorophenol to see whether the protection which was obtained by oiling in the previous experiment was due to the oil or the disinfectant in the oil. The eggs were held for two weeks during which time the presence of rots in lot two indicated that the experiment could
1,180
greenish colored albumen, a normal physical appearance and an offensive, sweetish odor difficult to describe. These eggs cannot usually be detected by candling. They are inedible. This trial rather definitely established the fact that oil prevented the development of a large number of black rots. Apparently from results obtained with lot three, processing with oil, without disinfectant in the oil was just as effective in preventing the development of black rots as oil containing disinfectant. At this point in the series of experiments it was decided that treating the eggs after washing would not prevent rots, therefore, if we were to be successful we should attempt to treat the wash water rather than the eggs after washing. In trial 6, the wash water was treated as shown in Table 6. The bacteria count
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TABLE 6.—Summary of trial 6
32
M. WAYNE MILLER, V. JOUKOVSKY AND ALBERT KRAGHT
in the wash water in lot two was 32,000,000 bacteria per milliliter. In lot three it was treated with 1 percent Roccal for five minutes before washing at which time the water was sterile. In lot four the wash water prepared the same way as in lot two was heated for five minutes at temperatures that varied from 144° to 155° F. The bacteria of the wash water was reduced to 1,180 per milliliter after five minutes.
Experiment 7 is a repetition of experiment 6 except that one lot was included in which water was treated both with heat and chemical. The outline of this experiment and the results are given in Table 7. The bacteria content of the wash water was 18,800,000 per milliliter before treatment. Less than 10 bacteria per mil. remained in the wash water in the three treated groups at the time the eggs were
TABLE 7.—Summary of trial 7 Size of lot
Kind of eggs
1 2 3 4
36 36 36 36
DirtyDirty Dirty Dirty
5
36
Dirty
6
36
Dirty
Bacteria per ml. wash water
Treatment
Broken out for initial count Not washed Washed in water containing black rots Washed in water like above after heating 5 minutes at 145° F. Washed in water containing broken black rots plus 1% Roccal for 5 minutes Washed in water containing broken black rots treated for 5 minutes with 1% Roccal and heat at 145° F.
After holding the washed eggs for approximately four weeks black rots had developed in the positive control and the observations on the eggs were made at that time. Lot one which was untreated had no rots or mold spots, although the eggs did have a high bacteria content at the end of the trial. Lot two which was washed in untreated water containing black rot inoculum, contained seven black rots, two mixed rots and when broken out many of the remaining eggs had green albumen, typical of green rot. The lot treated with Roccal contained one egg with green albumen and the remaining eggs had a bacteria content of 1,320,000 per milliliter which is considerably less than the unwashed eggs of lot one. This was the first successful experiment we had indicating the possibility of washing eggs without developing rots.
Number black rots
NumBacteria ber ml. green in per non-rots rots
—
20 32,400,000 18,700,000 7,000,000
18,800,000 10
3 7 0
10
2
4,430,000
10
1
5,100
8-
—
washed. The result of this experiment showed that the eggs treated with heat and chemical kept just as well as lot two which was the untreated group. It should be pointed out, in connection with this experiment, that even though dirty eggs were used which had a low initial bacteria count, the presence of the organisms causing rots apparently had gained access to the eggs during the experiment so that an occasional rot did develop in these eggs. It is obvious therefore that any treatment of dirty eggs will not prevent all rots from developing unless some type of pasteurization process is used which will destroy all rot forming organisms, or the eggs must be washed before the rot forming bacteria contaminates the egg. It was observed in the course of this experiment that eggs receiving the heat treatment had more stuck yolks than eggs receiving the chemical treatment.
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Lot no.
33
SPOILAGE OF W A S H E D E G G S
Experiment 8 was used to check whether heat t r e a t m e n t would cause this condition. The outline and results of this experiment are given in Table 8. T h e evidence in regard to stuck yolks is not very conclusive, however, the results do not indicate t h a t heat t r e a t m e n t is responsible for the sticking of the yolk to the shell. Some green rots were found in all of the treated lots a t the end of the experiment.
mental conditions are established. Failures of commercial egg washing machines are probably due to the fact t h a t the accumulation of filth and bacteria in the wash water inoculates the egg with rot forming organisms. Eggs can be successfully washed provided the wash water remains sterile, if the egg is not already infected. I t will be advantageous to have the wash water
Lot no.
Size of lot
Kind of eggs
Treatment
Bacteria per ml. wash water after washing
Stuck yolks when candled*
Black rots
Suspicious when candled
Green rots
Mixed rots
SusBacteria P.OOUS P ^ J j "
0
1
3
1
36
Dirty Immediate breakout
2
36
Dirty Not washed
0
0
3
36
Dirty Washed in water containing black rots water at 74" 3,800,000
0
11
9
6
1
0
4
36
Dirty Washed in water containing black rots, 1% RoccaT, 82° F.
10
3
0
2
2
0
2
620,000
5
36
Dirty Washed in water containing black rots, 1% RoccaT 135° F.
10
0
0
4
2
1
0
9,400,000
6
36
Dirty Washed in water containing black rots, 1% RoccaT, 150° F.
3
180
200
500
* The only stuck yolks in any lot were those which were readily broken loose in the candling process.
While no green rots were found in the untreated control one mixed rot and three suspicious eggs were observed in t h a t lot thus indicating t h a t the appearance of these eggs in lots four, five and six was not due to the failure of the t r e a t m e n t b u t due t o organisms in the eggs a t the time they were washed. As a result of this series of experiments the following conclusions can be made in regard to washing eggs. CONCLUSIONS Washing sult in the tions must inoculated velop into
eggs does not necessarily redevelopment of rots. Condibe such t h a t the egg becomes with organisms t h a t will derots when favorable environ-
warmer t h a n the egg during the washing process. Processing of washed eggs in oil tends to reduce the percentage of black rots t h a t develop b u t does not prevent the formation of green and mixed rots. Washing of dirty eggs even under the best washing procedures will not entirely eliminate the development of rots, if the eggs have been inoculated prior to washing. REFERENCES Funk, E. M., 1938. Improving the keeping quality of eggs by cleaning with sodium hydroxide. Mo. Agr. Exp. Sta. Bal. 277. Funk, E. M., 1943. Pasteurization of shell eggs. Mo. Agricultural Exp. Sta. Bui. 364. Pritsker, I. Y., 1941. Researches on the hatching qualities of eggs. II. Disinfection of egg shells under increased pressure within the egg. Poultry Sci. 20: 102-103.
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T A B L E 8.—Summary of trial 8