PHYSICAL AND "lCRPOiIOLOG ICAL PROPLf'RTIS OF HARD-COOKEl
A!ND PIC'J TE EGGS
Stevan Alex Anyalel
A DISSERIATIOQ Pl'r:NTED TO THE CRA' TT CO1'CIL CF
liH: 1:';VE\ SIT' U) FL.OR';9 1
IN PARTIAL F0Lil.l.l iT OfH TI: iQUL i t .lrnS FOr!
DECR.L OF [OLIUG OF PHI! OSOPHY
UNV';v rSITY Or F LOI!A
The author is grateful to Drs. Jack L. Fry and J. L. Oblinger,
Co-chairmen ef his supervisory committee, for their generous and
unending assistance in the accomplishment of this research and/or
reviewing this dissertation. The author would also like to thank
Drs. S. E. Grigsby, A. Z. Palmer, R. H. Harms and R. Littell for
their advice and assistance.
To his mother and father and to Mr. and Mrs. Clifton E. Bain,
the author extends his gratitude for their faith and encouragement
throughout the times this research was being conducted.
His deepest appreciation goes to his wife, Gw.'.n, who was constant
in her support and encouragement.
A special word of thanks is giver to the ,mer,betrs of the Poultry
Science faculty and staff for their part in taste panels and other
research activities A special th;nl s is extended to Dr. D. M. Janky
for his critique of this dissertation.
TABLE OF CONTENTS
ACKNOWLEDGEMENTS . . . . . . . . . . . . ii
LIST OF TABLES . . . . . ..... ... . . ... v
LIST OF FIGURES . . . . . . .. . ... . ....... v
ABSTRACT . . . ..... . . . . . . . . . . vii
INTRODUCTION . . . . . . .... .. . . . . 1
LITERATURE REVIEW . . . . . . . . . . .. ... 3
STORAGE STABILITY OF HARD-COOKED EGGS . . . . . . ..23
Experimc nta. Procedure . . . . . . . ... 24
Results and Discussion . . . . . . . .25
THERMAL DESTRUCTION OF MICROORGANISMS IN EGG PICKLING SOLUTIONS .29
Experimental Procedire .... . . . . ..... ...30
Results and Discussion . . . . . . ... .32
MICROBIAL GROWTH IN PICKLED EGGS . . . . . . . . 38
Experimental Procedure . . . . .. .. . . .39
Results and Discussion . . . . . . . . .41
THE EFFECT OF STORAGE TIME Ci SHELL EGGS ON DISCOLORATION OF EGG
ALBUMEN IN HARD-COOKED EGGS .. . . . ..... .. .. .51
Experimental Procedure . . . . . . . . . .51
Results and Discussion . . .... . .. . .... 53
QUALITY AND ACCEPTABILITY OF PICKLED CHICKEN EGGS . . ... 61
Experimental Procedure . . . . . . . . .. .61
Results and Discussion . . . . . . . . 63
STRUCTURE AND MICRO-STRUCTURE OF HARD--COOKED EGGS . . ... .74
Experimental Procedure . . . . . . . .. .. .75
Results and Discussion . . . . . . . .. .. .75
ACCEPTABILITY OF PICKLED QUAIL EGGS. . . . . . . ... 80
Experimental Procedure . . . . . . . . . ..80
Results and Discussion . . . . . . . . .. 81
CONCLUSION . . . . . . .. . . . . . . . .84
LIST OF REFERENCES . . . . . . . . . . . . 86
BIOGRAPHICAL SKETCH . . . . . . . . ... ... .. 93
LIST OF TABLES
1. The composition of the hen's egg . . . . . . . . 6
2. Egg pickling recipes (for one quart of pickled eggs) ...... 31
3. Acidity (pH) of the pickling solutions . . . . . . .. 34
4. Microbiological content of each spice and ingredient ...... 36
5. Viability of microorganisms present in "Dill Egg" from all
experiments in which the pickling solution was heated ...... 42
6. Viability of microorganisms present in "Dill Egg" from all
experiments in which the pickling solution was not heated . .. 43
7. Interior quality change of shell eggs at selected lengths of
storage . . . . . . . . ... .. . . . . . 58
8. Taste panelists' evaluation of "Red Beet" pickled eggs stored
for 14 weeks at 4C. and 220C. . . . . . ...... 65
9. Taste panelists' evaluation of "Dill Egg" pickled eggs stored
for 14 weeks at 4C. and 22C. . . . . . . . . ... 69
10. Taste panelists' evaluation of "Dark and Spicy" pickled eggs
stored for 14 weeks at 4C. and 22'C. . . . . . . ... 70
11. Proportion of albuimen layers . . . . . . . . . 77
LIST OF FIGURES
1. Plate counts of peeled and shell hard-cooked eggs stored at 250C. .26
2. Plaie counts of peeled and shell hard-cooked eggs stored at 5C. . 27
3. Thermal destruction curve for egg pickling solutions ..... . 35
4. Titration curve of "Dill Egg" solution (3:1) stored at 250C. .. .45
5. Titration curve of "Dill Egg" solution (1.6:1) stored at 250C. ... 46
6. Titration curve of 5% w/w acetic acid and dilutions of acetic acid 47
7. Acetic acid equilibrium curve for "Dill Egg" solutions . . .. 48
8. Acetic acid equilibrium curve for pickled egg solution plotted from
Acton and Johnson's (1973) data . . . . . . . . . 50
9. Dominrant wavelength of albumen from eggs hard-cooked after storage
at 18.50C. . . ... ....... . . . . . . . .. 54
10. Luminosity intensity of albumen from eggs hard-cooked after
storage at 18.5C. . . . . . . . .... . ... ..55
11. Excitation purity of albumen from eggs hard-cooked after storage
at 18.5C . . . . . . . . . . . . . 56
12. Haugh unit score of eggs stored at 1 C. . . . . . . 59
13. Discoloration of "Red Beet" pickled eggs stored for 10 weeks at
4C. and 22C. . . . . . . . ... . . . 67
14. Discoloration of "Dark and Spicy" pickled eggs stored for 10 weeks
at 4C. and 22C. . . . . . . ..... . . .71
15. The three major albumen layers differentially stained with red beet
juice with la Iinations visible il the thick albumen . . .. ..76
16. Frequency distribution of consumer acceptance of five pickled quail
egg recipes. .... . . . .... ..... . . ... .82
Abstract of Dissertation PresenLed to the Graduate Council
of the University of Florida in Partial Fulfillnwnt of the
Requirements for the Degree of Doctor of Philosophy
PHYSICAL AND HMICROIOLOGICAL PROPERTIES OF HARD-COOKFD
AND PICKLED LGGS
Stevan Alex Angalet
Chairman: Jack L. Fry
Co-chairman: J. L. Oblinger
Major Department: Animal Science
This research was conducted to evaluate physical and microbiological
properties of hard-cooked and pickled eggs. Fickled eggs are peeled hard-
cooked eggs immersed in a solution of vinegar and spice, which imparts a
different flavor to the eggs.
The quality of the eggs, for preparation as pickled eggs, ias found
to be dependent upon the interior shell egg quality. A brown discoloration
of hard-cooked egg albujmen was found to be associated with the loss of
interior shell egg quality. The ease of peeling the eggshell and the
smoothness of the albumenr surface improved with the age and/or in ri'se
in the pH of the egg. lhe dela!' bh-t-,,'en peeling the hard-cooked egg and
using it in a food product or as a food allows for growth of microorganisms.
Bacteria! counts of peeled eggs held at 25C. for four days increased from
zero to 1.0 x 10 organisms per gri.: of egg. Storage at 5C. did not
result in \ nmeasuraehl amount .If r:,rcth.
Five egg pickling recipe; were studied in this investigation ("Red
Beet", "Dill Egg","Dark and Spicy", "Kansas Spicy" and "Sweet and Sour"),
prepared from natural spices and ingredients. The egg pickling solutions
required a minimal amount of heat processing for pasteurization. Microbial
assay showed that the greatest contamination was from the peeled hard-
cooked eggs. However, within a short time the highly acidic pickling
solution destroyed a majority of the viable microorganisms. The pH of
the pickling solutions was increased by the addition of alkaline hard-
cooked eggs until an equilibrium pH was reached. The lower the ratio of
solution to eggs the higher the pH at equilibrium. A minimum ratio of
solution to egg was 1.6:1 (v/w) for an equilibrium pH of 4.0. The shift
in pH of the pickling solution was similar to the dilution of acetic acid.
"Red Beet", "Dark and Spicy" and "Dill Egg" pickled eggs were subjected
tc a 1.1-ueek storaj. period at 22%C. and 4'C. and quality was assayed by a
taste panel. Only "Dill Egg" maintained its quality at 22C. storage.
However, only "Red Beet" pickled eggs did not store well at 4C. The
greatest defects were discoloration of the albumen and development of off-
flavor in the region of the yolk for all three pickled egg recipes.
The "Red Beet" egg pickling solution was found to be differentially
absorbed by the hard-cooked egg album. The chalaza and the thick white
did not absorb as much pigment as the thin white, and appeared lighter
pink in color. This staining technique is suggested as a method to observe
the relationship of the albuiien layers with a minimum of distortion and
Three pickled egg recipes ("Dill Egg", "Kansas Spicy" and "Sweet and
Soui") of the five recipes. of pickled quail eggs were equally well accepted
by taste panelists. The taste panelists indicated that these thrte
pickled quail egg recipes are an acceptable product. The type of seasoning
spice and the color of the individual eggs '.'ere the most important
criteria in the taste panelists' evaluation of the recipes.
Pickled eggs are an effective means of utilizing small and pee wee
size eggs, which are under-utilized today. It is also a commercially
feasible method of marketing a hard-cooked egg product.
Over the last 25 years Florida has evidenced an increasing number of
laying hens. In 1972 it reached a peak of 12,283,000 and these birds
produced 2.8 billion eggs. From 1972 to 1974 the number of layers
decreased slightly to 11,778,000. However, the production of eggs remained
the same. Florida now is ranked seventh nationwide in egg production
(Kalch and Douglas, 1974). This same level of egg production was also
projected for 1974. A gross income of $101,500,000 is expected in 1975,
at the 1974 price of 43.5 per dozen eggs (Kalch, 1975).
About 1.2% of all eggs produced by caged layers are small and pee wee
(Ch!:isLi.ms t a!., 1973). Tlhe nu:;mber of small and pe we: eggs p,-.duceC'
in Florida in 1973 was 33,672,000. The projected value of Florida small
eggs would be approximately S815,143. Small and pee wee eggs are about 3/4
the size of large eggs. The nutritional levels of the egg contents per unit
weight of large and small eggs are equal. Dendy (1975) reported that the
average 1974 prices for a dozen small and large size eggs were 29.05 and
44.10<, respectively. The price of small eggs represented 66% of that of
large size eggs. It appears that the full potential profit from small
eggs is not being realized by the egg producer. If small and pee wee eggs
could be used effectively for ht.ir-coo!nrig and subsequent pickling, the
demand could be greatly increased. This could result in increasing the
price received for these eggs.
This loss of profit and limited ;dar'et may be reversed by the further
processing of smali alJ ptc' we g-:,, CNii suci, iethod m y be pickling
eggs, a ceurilc;:t prrc;ct, which 'c.l d i- detail iccr approximately $1.50 for
ten uggs. The pickling solution of vincrgdr and spices imparts a distinct
flavor and is a preservative. If a market can be developed for pickled
eggs, the gross return could be $5,050,800. This would be 6.5 times the
value of the eggs as commercially marketed table eggs.
The advent of an automated egg cooker and peeler has provided a
potentially enlarged market for the sale of hard-cooked eggs. Hard-
cooked eggs have been used sparingly as a ready-to-eat food because of
the preparation time required. Recently some distributors of hard-cooked
eggs in plastic wrap for vending machines and small commercial pickled egg
operations have come into existence.
The objectives of this research were to study:
1) The storage potential of hard-cooked eggs.
2) The extent and degree of color change of egg albumen associated
with egg sLoi' e.
3) The bacterial problem of hard-cooked eggs, pickling spices and
pickled eggs as they relate to product spoilage.
4) The consumer acceptance of pickled eggs over a three-month period
to determine the color and flavor stability of the product.
LITE, ATURE REVIEW
Miller et al. (1960) surveyed the consumer acceptance of several
methods of preparing eggs. They found that 28% of the people preferred
fried eggs, 25% scrambled, 19%' soft-boiled, 14% poached, 9% hard-cooked,
1 raw and 3% had no preference. The development of an automatic egg
cooking and peeling machine has given the food industry the capacity to
rapidly produce a large number of hard-cooked eggs (Anon., 1973).
However, the survey of Miller et al. (1960) showed that hard-cooked eggs
make up a small percentage of the total egg consumption. A product of
hard-cooked eggs is pickled eggs, through which this method of preparation
can find greater acceptance, lhe pickling of eggs has been practiced in
the home for many years, but only limited information has been developed
concerning processing and ingredient factors that could affect pickled egg
The egg has maximum interior quality and monetary value as al article
of food at the time it is laid. Deterioration of the egg as a dietary
commodity is continuous (Romanoff and Romanoff, 1949). The opened egg is
so perishable that methods for its preservation are adapted from those
ordinarily used to prevent the decomposition of other foodstuffs (Romanoff
and Romanoff. 1949). Historically, such compounds and techniques as low p1H,
spices, salt, sugar, smoking and low' water activity have been used to
preserve foods (Frazier, 1967). Pickling of eggs embodies all of these to
preserve eggs. Preservation is not the main purpose of egg pickling today.
Eggs are now available in quianit y and the year-round. The novel and unique
flavor that pickling imports is the desirable attribute.
Ihe egg is a product ol the h.n which is a self-contained nurturing
environment for embroynic development (Romanoff and Romanoff, 1949). Birds'
eggs have been used as food by human beings since antiquity. "Compared
with the hen's egg, no other single food of animal origin is eaten and
relished by so many peoples the world over; none is served in such a
variety of ways (Romanoff and Romanoff, 1949, p. 575). Of the three
most important dietary essentials (protein, fat and carbohydrate) the egg
is composed largely of the first two. Its proteins are relatively complete
and are very well digested and assimilated. Eggs also are a good source
of essential vitamins and minerals except that the egg contents are low
in calcium and void of vitamin C (Romanoff and Romanoff, 1949).
The structure of the egg is inseparably linked to its biological
potential to maintain the continuity of life (Romanoff and Romanoff, 1949).
Fundamentally, the egg is comprised of a minute center of life, about
which are arranged relatively enormous amounts of inanimate food substances,
enclosed in a protective structure. Its structural elements are arranged
with great precision, and their total organization is essential to the
specific function of each part.
The yolk is the most important part of the egg. It contains the mass
of nutritive material that supports embryonic development and the germ cell.
It consists of 12 concentric layers of alternating yellow and white yolk
material. The yolk is enclosed in a thin, pliable envelope, the vitelline
or yolk membrane (Romanofl and Romanoff, 1949).
The albumen surrounds the yolk and is enclosed by the shell and
membranes. It is a clear material of yellowish tint. In the albu:mien is
the cialazo, part of the chalazif .e:ou layer, a ropy structure of spirals
at the t.'o poles of the yolk. The chalazac become twisted and taut, and
their tension pulls the yolk nearer to the geometric center of the egg.
The whole body of the albumen is composed of four concentric layers.
The chalaziferous layers makes up 2.7% of tne albumen, the inner thin 16.8%,
the thick 57.3% and the outer thin 23.3'/ (Romanoff and Romanoff, 1949).
There are two shell inembranes that surround the albumen. The inner
membrane is in contact with the outer thin albumen ir all but the polar
regions of the egg where some of the mucin fibers of the thick albumen
penetrate to the me;mbrane. The outer surface of the inner membrane is
firmly cemented to the inside of the outer membrane, except in a small area
usually at the blunt end of the egg. This space between the two membrane
is the air cell (Romanoff and Romanoff, 1949).
The shell is a relatively smooth, hai-d, calcareous deposit around the
outer shell membrane. The shell is composed of four structural components
which include the pores and cuticle. The pores allow gas transfer between
the inside and the outside. The cuticle is a proteinaceous coating that
acts as a protective covering over the pores.
The percentages of the yolk, albumen and shell of the egg are dependent
upon egg weight and other factors such as genetic differences, seasonal
change, age of the bird, individual variation within species, intensity of
laying, time of day when the egg is laid, environment, physical condition of
the laying hen, and the kind and amount of feed and drugs (Romanoff and
Romanoff, 1949). Since the late forties the laying hen has been improved
through genetic selection. As a result the modern laying hen lays 227 eggs
per year in the United States as compared to 174 in 1950 (McGregor and Stiles,
1973). As can be seen in Table 1, the yolk and shell percentages have
decreased, while the albumen percentage has increased. The increased rate
of production may be, in part, responsible for the difference in the
Table 1. The composition of the hen'sg_
% Yolk % Albumen % Shell Type Reference
Romanoff and Romanoff, 1949
Marion et a!., 1964
Gardner and Young, 1972
Separation resulted in a loss of 1.13% of the original whole egg weight;
the loss is assumed to have been albumen.
percent composition of the egg contents.
The egg's structure and the unequal distribution of its chemical
constituents make the egg an unstable system. The interior of the egg is
imperfectly protected from the environment and is therefore exposed to
external forces. For these reasons, the egg is in a continual state of
readjustment, which takes place at a rate controlled largely by external
factors (Romanoff and komanoff, 1919).
Hlard-Cooking olf Shell Egg
Chick and Martin (1910) found that heat coagulation of albumen is
influenced by a variety of conditions. It does not occur instantaneously
at normal cooking temperatures, but is a time process in which heat is the
accelerator. Lowe (1955) pointed out, however, that coagulation occurs
almost instantaneously at high temperatures.
Coagulation begins at about 620C., and the albumen ceases to flow
when it reaches a temperature of about 65C. (Chick and Martin, 1910). At
70C. the coagulum is fairly firm, but tender, and it becomes very firm
at highe,- temperatures (Romanoff and Romanoff, 1949). Egg yolk begins to
coagulate at 650C. and ceases to flow when it reaches a temperature of
about 700C. (Romanoff and Romanoff, 1949). The coagulation reaction is
endothermic; heat is absorbed. Too much heat results in over-cooking,
regardless of whether the excess heat is the result of too high a temperature
or exposure to heat for too long a time.
When hard-cooking eggs in the shell, the proportion of water to eggs
and the size of the cooking container are essential considerations, in
addition to the temperature of the water. Griswold (1962) recommended
starting the cooking process with cold water and bringing it to a boil, or
starting with boiling water ai.d turning off the heat while the eggs cook.
Andross (1940) reported that when shell eggs are cooked at temperatures
as low at 850C., the yolk does not completely coagulate in 30 minutes.
Further, the white does not coagulate firmly in 1.5 hours when the cooking
water is held at 72C.
The dark green color around the yolk of hard-cooked eggs is caused
by the formation of ferrous sulfide (Tinkler and Soar, 1920). The ring can
be prevented or reduced by minimizing cooking time and immediately cooling
the cooked eggs by immersion in cold, running water (Irmiter et al., 1970).
High quality eggs have yolks which remain well centered after hard-
cooking and are thus more pleasing, especially when made into deviled eggs,
or sliced for salads and garnishings. Albumen thinning of stored eggs
results in a loss of thick white and gives the yolk more freedom of movement;
the yolk may also adhere to the shell membrane or displace out of the center
of the egg (Romannff and Romanoff, 1949) As the egg ages ',atcr shifts
from the albumen to the yolk, thus weakening the vitelline membrane and
causing yolk rupture (Feeney et al., 1956).
Because of the many variables in the raw eggs and the different quality
criteria hard-cooked eggs must meet, Jriiter et al. (1970) found it difficult
to suggest a superior method of cooking. The temperature of the heating
medium appeared to have more effect on the incidence of shell cracking than
any other factor. The boiling water method for hard-cooking eggs resulted
in fewer cracked eggs than the cold water method (Irmiter et al., 1970).
These authors also reported that the boiling water method rated highest in
all criteria and is the preferred method for hard-cooking eggs.
Ideally a hard-cooked egg should have the following attributes: 1) the
shell does not break during cooking, 2) the shell peels off easily and
does not adhere to the coagulated egg albuien, and 3) the yolk should be
,well cciin.ered and force from any dark ring (Irmiter et al., 1970). Several
factors can influence how well hard-cooked e'jgs can meet these criteria, e.g.,
temperature of the egg, pH of the albumen, temperature of the heating medium,
length of cooking time, strength of the shell and quality of the egg.
MicrobioloIyof the Egg
The interior of the newly-laid egg is usually free of microorganisms,
chiefly because of the natural protection provided by the cgg's physical
structure and by the chemical composition of the albumen (Romanoff and
Romanoff, 1949; Frazier, 1967; Jay, 1970). Contamination of the egg
contents can occur either before the egy is laid or shortly thereafter.
The shell can become contaminated by fecal matter from tie hen, from
contact with materials and equipment in the poultry house, by wash water
if the eggs are washed, by handling and by packing material (Frazicr, 1967).
Molds and bacteria from these sources can grow through a moistened shell
and into the egg. Since eggs usually are cooled proiiptly and stored at low
temperatures, contamination with low temperature bacteria such as those of
the genera Pseudomonas, Proteus and Achromobacter is undesirable. Gram-
positive cocci and rods and coliform bacteria occur in smaller numbers on
eggshells, as would anaerobes and miscellaneous bacteria as chance contaminants.
Occasionally, Salmonella bacteria may be in eggs from infected hens (Frazier,
1967). However, control for S. pullorum is based on a regular testing
program of breeding stock to assure freedom from this infection. Chickens
are tested by a tube agglutination of whole-blood method (Siegmund, 1973).
Cox et al. (1973) reported that there was no salmonella contamination of
egg neat among intact eggs from birds fed salmonella inoculum, though
salmonellae contamination of the shell surface did occur. Thus contamination
of the egg \with salmonella from the hfen is not likely to occur.
Species of bacteria or fungi on lte exterior of the egg vary according
to circ!umnii.daces. The approximate romiposition of the flora found in one
investigation (Romanoff and RoImanoff, 1949) was reported as:
Non-sporeforming rods 38%
Sporeforming rods 30
As a result of this contamination, the egg may eventually decompose, or it
may be responsible for the dissemination of disease among poultry or human
beings (Romanoff and Romanoff, 1949). In light of the natural protection
provided within the egg, it is one of the safest foodstuffs in man's diet.
The pores in the shell are normally impervious to microbial penetration,
They are filled with an organic substance (the cuticle) that, when dry,
does not permit bacteria or fungi to enter. However, if the cuticle is
dissolved or partially remnvpd hy abrasion, the pores are opened a!d
microfloral invasion is possible (Romanoff and Romanoff, 1949; Fromn and
Monroe, 1960). The shell membrane acts as a filter for removal cf many
of the microorganisms that succeed in penetrating through the pores of the
Several constituents of the albumen kill bacteria before they reach
the yolk with its abundance of utilizable food. The antibacterial action
of the egg albumen is partially due to the inability of many bacteria to
utilize native protein. The enzyme, lysozyme, hydrolyzes the mucopoly-
saccharides of the cell wall of both the live and dead cells. Not all
bacteria are equally susceptible to the action of lysozyme. Airborne species
are, in general, less resistant than those that may be isolated from the
human body. Bacteria becomes less susceptible to lysozyme when they are
grown in proximity to body tissuI containing the substance. Although its
rapidity of action increases with temperatures up to 60C., all lytic
power disappears upon heating to temperatures higher than 70C. (Romanoff
and Romanoff, 1949). Avidin aids in inhibiting bacterial growth in egg
albumen by depriving microorganisms of biotin. Those bacteria which can
synthesize biotin are not affected. Ovoconalbumen in the egg albumen can
completely inhibit various species of bacteria by binding or completing
iron, thus making the iron unavailable as a nutrient (Romanoff and Romanoff,
The bacteria upon surviving the defenses of the eggshell, shell
membranes and albumen will reach th yolk. The yolk material, because of
its nutrient content, and pH (6.8), is an excellent growth medium for most
organisms. More bacteria are found in the yolk than the albumen (Jay, 1970).
Once inside the yolk, bacteria grow in this nutritious medium where they
produce products of protein and amino acid metabolism such as hydrogen sulfide
and other foul smelling compounds.
Bacteria in eggs have been responsible in the past for many individual
cases and mass outbreaks of "food poisoning" (Romanoff and Romanoff, 1949).
Many species of the genus Salmonella cause "food poisoning" (Romanoff and
Romanoff, 1949; Frazier, 1967; Jay, 1970). This "food poisoning" is a food
infection where the actual presence and viability of the organism is
essential to produce the food poisoning symptoms. Raw eggs, partially
cooked eggs and especially products containing raw eggs are potentially
excellent media for growth of Salmonella organisms. However, the cooking
of hard-cooked eggs to a rmini!rum of 680C. is sufficient to destroy the
Salmonella organism (Frazier, 1967). As a safeguard against salmonella
it has been recommended in the code of Federal Regulations that all liquid
egg products except albumen, he pasteurized at 60"C. (140F.) for not less
than 3.5 minutes or to have been found free of salmonella (Frazier, 1967).
Some microorganisms may be present in the egg which are resistant to
thenral treatment. HUlphers (1939) found that hens contract tuberculosis
when inoculated with material from eggs infected with Mycohacterium avium
when the eggs had been boiled for three minutes, whereas four minutes of
boiling apparently rendered the eggs sterile. According to L'wenstein
(1925), the avian tubercle bacillus remains viable in the albumen after
three minutes of cooking, and in the yolk five to ten minutes.
The hard-cooking process exceedsthe time and temperature required
for pasteurization of egg products. As a result, the hard-cooked egg
could be considered commercially sterile. However, the process of removing
the shell reintroduces the microbial problem through contamination by
hands, equipment and rinse water.
Microbiology of Pickled Eggs
The pickling of eggs in a vinegar solution involves the use of low
pH!, spices, salt, sugar and smske derivatives to lower water activity and
to provide flavoring and coloring of hard-cooked eggs.
If the microbial population of the spices is excessive, they may
contaminate the product to a point where spoilage may occur (Sharf, 1966).
Sporeforming bacteria in spices have been implicated in spoilage of canned
foods and processed meat products (Julseth and Deibel, 1974), The potential
spoilage organisms include protcolytic and thermophilic sporeformers.
Krishnaswamny ct al. (1971) found many spoilage and potential pathogenic
microor(ianisms in spices from India; these included C. perfringens and E.
Pickled cog products are spice-containing and therefore are suspect,
Acton and Johnson (1973) reported that sporefomiing bacteria present in
egg pickling solutions were viable after 50 (days of storage. Trongpanich
and Dadsocn (1974) imported on th: microbiological quality of hard-cooked
brine-pickle d duck teggs stored at 3"C. for four weeks. At the end of four
weeks there was a high number of organisms present (1.7 x 105 organisms
per gram of egg).
Chung and Goepfert (1970) employed three strains of Salmonella (S.
anatum, S. senftenberg and S. tennessee) to determine the minimum pH value
as determined by 13 acidulants that would permit the initiation of growth
of Salmonella in laboratory media. The most permissive group includes
tartaric, hydrochloric and citric acids in which growth was initiated at
values as low as pll 4.05. The most restrictive class was composed of adipic
and pimelic acids and the short-chain volatile fatty acids, acetic and
propionic. The minimum pH at which salmonella grew in acetic acid was pH
5.40. Levine and Fellers (1940) reported that acetic and propionic acids
at pH 4.9 limited growth of food spoilage microorganisms.
Salmonella typhimurium was able to survive in apple cider having a pH
value less than 4 (Anon., 1975). Multiplication of the salmonella in the
cider need not occur to create a problem if the cider was heavily contaminated
when it was produced. Evidence suggests that S. typhimurium can produce
disease with an inoculum of only 104 organisms (Anon., 1975).
The potential for product spoilage or "food poisoning" is, therefore,
still a possibility for pickled egg products even though the acid content is
high. Microorganisms can be introduced by the egg, spices and other
Peel abiliV of Hard-Coonked ggs
Hard-cooked, freshly laid eggs are difficult to peel without tearing
the albumen. As an egg ages during storage, certain physical and chemical
changes occur in t.he composition of the egg and the ease of peeling
increases (Ronm.noff and Romnioff, 1940). It has been observed that the pH
of the albuLpn rises firom, 7.C to ;s high as 9.7; this change is accompanied
by a bre.l.doiwn in the thick albumen structure (Romanoff and Romanoff, 1949).
Swanson (1959) and Reinke and Spencer (1964) indicated that ease of peeling
was related to the change in pH of the albumen. Above pH 8.6 to 8.7, they
found that little or no difficulty in peeling was experienced. Similarly,
Fuller and Angus (1969), in their study of the pH of both uncooked albumen
and homogenized albumen from hard-cooked eggs, indicated that the "cross-
over" from poor to good peeling characteristics corresponded to pl! values
8.6 to 8.9 of raw egg whites. Swanson (1959) and Reinke et al. (1973)
reported that freshly laid eggs could be made to peel easily if they were
exposed to ammonia fumes until the pH of the albumen reached 8.7, and that
stored eggs could be made to peel with difficulty if they were exposed to
carbon dioxide until the pH of the albumen was lowered below 8.7.
In a study by Fry et al. (1966), albumen structure was broken down by
gamma irradiation without significant pH increase. The Haugh units of the
irradiated eggs were reduced to about 50% of that of non-irradiatc controls.
The average albumen pH value of irradiated fresh eggs was 8.39 while the
control was 8.22 at 0 days storage. Both irradiated and fresh eggs peeled
with difficulty, indicating that peeling ease was influenced by pH rather
than albumen quality per se.
Reinke et al. (1973) suggested that peeling ease was related to pll of
albumen rather than to dehydration, although a weight loss of two grams or
greater might have some influence on peeling ease. Cotterill and Gardner
(1956) demonstrated that low concentrations of carbon dioxide would maintain
albumen quality of eggs stored at room temperature as effectively as
refrigeration under nornal conditions. The presence of CO2 prevents the
deterioration of ovomucin in the thick white. Almquist and Lorenz (1932)
observed that, in the presence of excess CO2, ovomucin fibers of the firm
white contract and squeeze out a liquid solution of other proteins. Thus,
in the presence of sufficient CO2, the ovomuicin fibers are not degraded
and a pH of 8.6 or lower is maintained. Because of these factors the
albumen adheres to the shell, making peeling more difficult.
Hydrogen sulfide was found by MacDonnell et al. (1951) to have a
thinning effect on the albumen of eggs. Albumen of old eggs was markedly
thinned by H2S treatment and the pll values of the albumen components were
decreased to those characteristic of fresh eggs. Both fresh and old eggs
treated with I12S were difficult to peel, providing further evidence that
peeling quality is related to album pH rather than albumen thinning (Reinke
et al., 1973).
Reinke et al. (1973) found that all fresh eggs containing old egg
contents and all old eggs containing old egg contents peeled easily. Old
eggs containing fresh egg contents and fresh eggs containing fresh egg
contents peeled with varying degrees of difficulty. It appeared that pH
oF Lhe transferred aelbuimen was the ilnfluncing ficto, on peclirin quality
as the transfer of old egg contents of high p1i resulted in an easy-to-pe:.1
egg, while the reverse was true of the transfer of fresh egg contents of
low pH. Cotterill et al. (1959) indicated that fresh egg white is strongly
buffered in the regions of pll 6.4 and p1I 10.3, and that the buffering
capacity is minimal at pH 8.3. The p!l of the transferred albumen could
modify the pH of the adhering albumer and membrane and affect peeling
Low viscosity values for adhering albumen nay he responsible in part
for determining the peeling quality, since a less viscous albumen may not
adhere as strongly to the membrane as a more viscous albumen. Reinke et al,
(1973) noted an inverse relationship to exist between pl and viscosity of
adhering albumen. A high p11 was usually accompanied by a low viscosity
reading. Conrad and Scott (1939) .lihowed that a breakdown of thick gel
structure occiiurd after esrcape of CO2, concurrently with increased p!, and
possibly the extension or change in elasticity of the ovomucin fibers.
The integrity of the ovomucin-lysozyme complex has been reported to be
dependent on pH (Cotterill and Winter, 1955). Consequently, when CO2 was
added to eggs, thus lowering the albumen pH, the ovomucin fibers of the
adhering albumen are possibly contracted or at least reverted to their
original elasticity, and resulted in lower peelability.
Froning et al. (1960) reported that, as CO2 in the storage atmosphere
was increased, there was a marked decrease in the percentage of ovomucin
in the outer thin white and a marked increase in the percentage of ovomucin
in the thick white during storage. Brooks and Hale (1961), however,
concluded that ovomucin chains are linked together, such as by assuming
an ovomucin-lysozyme complex cross-linked into a network.
One of the main differences between fresh and old eggs was the
deterioration of the adhering albumen layer adjacent to the membrane.
Albumen from the small end of a hard-cooked egg contained fiber-like struc-
tures which stained dark purple, indicating the presence of mucin. The
adhering albumen had soni structural material present which accounted for
its viscosity being slightly higher than that of thin albumen. This fiber-
like material was not visible after aging or NH3 treatment (Reinke et al.,
An additional difference between fresh and old eggs was the appearance
of a dark staining border between the inner shell membrane and the adhering
albumen. The border was wider and/or darker in old eggs and contained
mucin. Fuller and Angus (1969), in their gross examination of shell
membranes, also observed that the membranes from eggs which peeled cleanly
were compact and tore easily fioir both the shell and egg white. They found
that the membranes from eggs which peeled po.crly were not compact, but could
only be torn in: layers and alhered firtly to the shell.
It is possible that when pH of eggs is low, ovomucin fibers (in
albumen) may protrude into the membrane, while ovomucin fibers (in the
membrane) may extend into the albumen, to form the narrow border observed
in fresh eggs. However, when pH of eggs is high, these fibers may be
affected in such a way that they pull apart, forming the wide border
observed in old eggs (Reinke et al., 1973).
Hard et al. (1963b), in their study of methods of preserving interior
egg quality, noted that even after eight weeks of storage at 00C. some
difficulty in peeling was experienced if eggs were coated with oil or silicone
grease or if maintained in an atmosphere containing 95% carbon dioxide.
Britton and Hale (1972) found that fresh and old eggs which were oiled when
fresh had increased peeling times and that oiled eggs had greater peeling
Fuller and Angus (1969) indicated that peeling properties of hard-cooked
eggs could be altered by the addition of 1%, 5% and 10% NaCl or CaCI2 to
the cooking medium. These treatments did not, however, affect the peeling
quality of eggs collected within eight hours of oviposition. Addition of
NaC1 to the cooking medium of eggs stored at 10 to 130C. for 24 hours
enhanced peeling properties, while the addition of CaC12 made peeling more
difficult. The effect of addition of NaCl disappeared by the second day of
storage of uncooked shell eggs.
Spencer and Tryhnew (1973) reported that, if hard-cooked eggs are not
aged sufficiently before cooking, storage after cooking will not remedy the
problem of difficulty in peeling.
The research of these authors indicates that the ideally suited egg
for successful hard-cooking is one which has an albumen pH above 8.7 and a
firm albumen ti. keep the yolk centered. In order for such an egg to have
a pH above 8.7, it should have been stored a sufficient length of time to
allow enough CO2 to escape. Fresh eggs should not be oiled or stored in
a CO2 atmosphere because this inhibits the rise of albumen pH to 8.7, thus
impairing good peelability.
Color and Flavor of Hard-Cooked and Pickled Eggs
Dodge et al. (1965), Baker and Darfler (1969) and Schnell et al. (1969)
reported that hard-cooked eggs developed a brown discoloration of the
albumen due to the Maillard reaction. The longer the eggs were cooked the
browner the albumen beccime. Dodge et al. (1965) found that ultraviolet
irradiation was a factor in discoloration. Baker and Darfler (1969)
reported that, as the pH of the albumen was increased, the amount of color
increased. Color increased gradually up to a pH of 8.5 and then increased
The Maillard reaction (Meyer, 1968) involves the reducing groups of
glucose or similar sugars and the arino groups of protein. This reaction
results in the development of the brown color. McWeeny et al. (1969)
found that the Maillard reaction does not begin until "free" SO2 has almost
disappeared from the system. A pH of 5.6 and above inhibits the Maillard
reaction:. No inhibition of the Maillard reaction occurs at pH 4.3 or below.
Sherwood (1958) reviewed shell egg quality and concluded that pink
albumen and yolk color are dependent upon the hen's diet and that watery
albumen may be the result of chemicals or illness.
Flavor is one of the most important factors influencing acceptability
of eggs (Hard et al., 1963a; Romanoff and Romanoff, 1949). Taste panel
evaluations indicate that richness, mustiness and astrigency of the yolk
are masked or diluted by the presence of egg white. Adjectives used to
describe eggs which were rated as acceptable in the study by Hard et al,
(1963a) were "fresh", "mild" and "sweet". Koehler and Jacobson (1966)
reported musty and earthy qualities in stored eggs, and less sulfurr"
and hydrolyzedd protein" flavor in the yolks from stored than from
fresh eggs. Miller et al. (1960) found that customers did not distin-
guish between the flavor of eggs of different ages. Although taste
panels differentiated between flavor of newly laid and stored eggs
(Dawson et al., 1956), consumers may be accustomed to variation and may
not respond to small differences in flavor.
Koehler and Jacobson (1966) and McCammon et al. (1934) showed that
no significant differences in flavor were associated with the color of
the egg yolk, although dark-colored yolks tended to be rated as slightly
objectionable. Palmer (1972) reported that eggs stored near odorous
substances can absorb odors and exhibit flavor changes. Banwart et al.
(1957) reported that an off-flavor in stored oiled eggs after soft-
cookinn was more drtectable in the white than in the yolk.
A bitter off-flavor of hard-cooked eggs develops with the increase of
the Maillard reaction (Baker and Darfler, 1969). Arroyo and Lillard (1970)
screened several sulfur-containing amino acids in reaction with glucose.
They found that when the amino acid, cysteine, completed with glucose, an
overcooked egg odor developed; this was attributed to the presence of H2S.
However, when methionine completed with glucose, a boiled potato odor
McCready (1973) reported that flavor scores were highest when egg Mnd
pickling solution temperatures were at least 650C. at the time eggs and
pickling solutions were combined, and when aging was conducted at a storage'
temperature of 24'C. Panel scores indicated that a pickling solution of
24C. or less and a storage (aging) temperature of 3C. inhibited pickled
egg flavor developmei,t during a 24-hour test period,
Physical Properties of Pic!:led Egqgs
Acetic acid (CH3COOH) is used as a fixative in histology and as a
food preservative (Ilunason, 1962). The rate of acid penetration in hard-
cooked eggs was judged by Acton and Johnson (1973) to be determined by the
rate of diffusion of acetic acid into the egg white and by the initial
acid strength of the pickling solution. They indicated that the pH of eggs
pickled in 3 or 5% acetic acid vinegar solutions required six days to
equilibrate with the pH of the pickling solution. Ball and Saffores (1973)
reported the equilibrated pH to raoge from 4.0 to 5.1 after six to seven
days of storage.
Ball and Saffores (1973) reported that eggs lost 4 to 12% of their
weight during pickling. Eggs pickled in weaker acid solutions lost more
weight. They posutlated that the egg whiCe was losing moisture to the
pickling solution and the yolk. A noticrable tocugheorin of egs '-hite
occurred during pickling (Ball and Soffores, 1973). Initial forces required
to shear cooked egg white averaged 0.6 kg./g. and the force to shear
pickled egg white ranged up to 1.6 kg./g. The addition of salt to pickling
solutions increased the magnitude of weight loss, changes in egg white solids
and tended to increase toughness, but did not affect the equilibrated pH
(Ball and Saffores, 1973).
Cunninghar and Cotterill (1964) reported that native egg albumen protein
components had an isoelectric point of pH 4.0 which is also the point of
maximum viscosity. In the study of Fall and Saffores (1973), equilibrated
pH's were close to or lower than the isoelertric point of egg white proteins.
Eggs exhibited minimal values for volume and water holding capacity when the
albumen pruoeins were at their isoelectric points. lhe loss of moisture and
toughqoning of the pickled egg white could result from proteins assuming
these ;!:inimal physical characteristics. lhe process could be synerasis, the
loss of moisture from a gel by contraction of the gel.
Panel evaluations conducted by McCready (1973) indicated significant
differences between the tenderness of eggs pickled in solutions containing
zero to 40% sugar. Eggs pickled in solutions containing 45 to 60% sugar
were rated significantly lower in tenderness. The shear values of pickled
eggs, reported as p.s.i./g. of egg, were significantly greater than the
shear values of non-pickled, hard-cooked eggs. Sugar concentrations of 25%
or greater significantly decreased the tenderness of pickled eggs as
indicated by shear values. Eggs pickled in solutions containing no sugar
had weight losses ranging from 6.2 to 9.0%, and additional losses in weight
occurred as the percentage of sugar increased and the pH values became
greater than 5.0. Adding salt to pickling solutions created osmotic forces
that result in further dehydration of pickled egg white (Ball and Saffores,
Ball and Saffores (1973) reported that turbidity of the pickling
solution may resi;lt from suspension of pickling spices or yolk material
from exposed yolks. Splitting of egg white that exposes yolks may be the
result of combined forces of syneresis in egg white and expansion of yolk
as it takes up moisture. These same authors also reported that off-centered
yolks in eggs with weak albumen also contribute to splitting of the egg
Frazier (1967) has reported that oxidation of acetic acid in vinegar to
CO2 and H20 can be brought about by the acetic acid bacteria themselves
during the vinegar-making process if there is a shortage of alcohol or an
excessive amount of aeration. This may also occur in a finished product to
reduce the acidity. Further, ferrous iron may be oxidized to the ferric
form and combine with tannins, phosphate or protein to produce haze in the
acetic acid. Cloudiness also may be caused by salts or tin or copper.
Iron acting upon tannin or oxidase may be responsible for darkening of
vinegar (Frazier, 1967). It is speculated that potential contamination
and/or pickling ingredients may also influence the quality of the pickling
solution causing discoloration, change in acid strength, and development
STORAGE STABILITY OF HARD-COOKED EGGS
Numerous investigators have reported on the factors involved in
the preparation and pickling of hard-cooked eggs. The majority of this
work has dealt with either the investigation of peeling attributed
(Fuller and Angus, 1969) or the use of various pickling solutions on
hard-cooked eggs (Ball and Saffores, 1973; Cunningham et al., 1970;
Maurer, 1972; and McCready, 1973). A few of these investigations have
also been on the organoleptic acceptability of the product after varying
storage periods. Spencer and Tryhnew (1973) found that storage of hard-
cooked shell eggs at 1.1C. for up to 21 days resulted in lower taste
panel scores after only one week of storage and that, after 21 days
storage, serious off-flavors were detected by panel members. Britton and
Hale (1972) found that bacterial counts of hard-cooked eggs were initially
quite low; however, they considered the eggs spoiled after 10 days at 40C.
In their report dealing with the pH and rate of acid penetration in
eggs undergoing the pickling process, Acton and Johnson (1973) found that
eggs pickled in a 3% acetic acid pickling solution were bacteriologically
The investigation reported herein was undertaken to examine the effect
of storage at two different temperatures (5 and 25C.) on the bacteriological
quality of both peeled and unpeeled hard-cooked eggs.
Medium size eggs were collected from Babcock B-300 Leghorn hens
at the University of Florida Poultry Science Department. All eggs were
washed and graded on an Aquamagic egg processing machine (National Poultry
Equipment Co., Renton, Wash.) containing a detergent-sanitizer Egclor
(Sanfax Chemicals, Atlanta, Ga.) in accordance with the manufacturer's
specifications. The washed eggs were placed into clean molded pulpboard
filler flats and held in a cooler at 130C. for four days. All eggs used
in these investigations were obtained from laying flocks maintained on a
Hard-Cooking and Peeling Procedure
A total of 320 eggs were placed in a stear,;-jacketed kettle and completely
covered with cold water whiic was brought to a boil. The heat was then
reduced, and the eggs were simmered for 15 minutes. The steam was turned
off and the eggs were cooled under running tap water. Prior to peeling
each batch of eggs or after any interruption of the peeling procedure, all
personnel washed their hands using a hand sanitizer rinse, Klenzade
Mikroklene DF (25 p.p.m., Economics Laboratory, Inc., St. Paul, Minn.).
Half of the hard-cooked eggs were peeled and the remainder were left
in the shell. Peeled and shell hard-cooked eggs were then placed into
sterile one-pint tMason jars (three eggs/iar). An equal number of jars
containing peeled and shell hard-cooked eggs were placed in storage at 5
and 25"C. The higher temperature was selected since it roughly corresponds
to the room temeL-rature at which hard-cooked eggs are often stored in
conm'ercial esta il ishmcnts.
Bacteriolo gical Samping Erocedure
Three eggs from each of the four storage conditions were blended
individually at each sampling. Each egg was aseptically placed in a
sterile blender jar and a 1:10 dilution prepared using 0.1% peptone
diluent and blending for two minutes. Subsequent serial dilutions were
prepared by transferring 11 ml. aliquots to 99 ml. 0.1% peptone blanks.
Samples were plated r-, quadruplicate into Plate Count Agar (Difco) and
duplicate plates of appropriate dilutions were incubated at 22 and 350C.,
Results and Discussion
Microbiological dlta obtained from peeled and shell hard-cooked eggs
stored at 250C. over a period of 24 days are shown in Figure 1. Each point
on the figure represents ai: average of plate counts from the three eggs
from one jar sampled individually at a particular time. Visible sliminess
was noted on the peeled eggs after four days storage, and discrete bacterial
colonies were observed on the sixth day of storage.
This sliminess and subsequent colony formation corresponded to
populations of appri.; latelyy 1.0 x 107 organisms/g. Discoloration on
shell hard-cooked eggs were noted only after 13 days storage. Bacterial
numbers leveled off ofter the tenth day of storage and remained at about
1.3 x 108 organisms/g. for the balance of the storage period at 250C.
Microbiological data From storage of peeled and shell hard-cooked eggs
at 5C. are shco'n L: Figur; 2. Bacterial development was not evident on
peeled hard-cooked e-.s stored at 5C. until after 21 days of storage.
Shell hard-cooked ejgs displayed sporadic counts over the storage period.
At no time during the 24-day storage period was there any visible slime or
colony formation on either group of eggs.
0 tbio) -6/C@LJa3piq jo saaqmin
(OLU0,7) *6/PLjD33 Eq 0 SJaquIlN
Total counts on eggs prior to hard-cooking ranged from 0 to 30
organisms/g. (approximately 1500 organisms/egg). The low counts observed
on eggs immediately after cooking indicate that most bacterial problems
encountered with hard-cooked eggs would be directly related to post-
cooking contamination. Sources of such contamination would be improperly
cleaned equipment, poor hand washing and poo quality wash water supply.
Efforts were made in this study to use conditions that were not too far
removed from what might be expected in commercial practices. However,
some of the variables encountered in this study would be eliminated if
automatic cooking, peeling and packaging becomes widely available (Anon.,
A source of bacteria that contributed to the microflora of the hard-
cooked eggs in this study was the water used in the actual processing of
the eggs. Plate counts of cooking water sampled ir-.diately after cooking
showed no viable bacteria present in a 10 ml. undiluted sample; however,
rinse water used during the cooling, peeling and rinsing procedures showed
a count of 20 organisms each, in two 10 ml. samples.
Peeled hard-cooked eggs stored at 50C. did not support as much bacterial
growth as did shell hard-cooked eggs. This might be explained by the
presence of a higher bacterial load on the surface of shell-hard-cooked
eggs. This may have been the result of a more thorough rinsing of the
peeled hard-cooked eggs during preparation. It is also possible that the
growth of microorganisms was somewhat restricted at 50C. Position of the
eggs in the jar (top, middle or bottom) did not have an effect on bacterial
growth. Counts obtained at incubation temperatures of 22 and 350C. were not
significantly different, indicating that bacteria on these eggs were capable
of growth at either incubation temperature.
THERMAL DESTRUCTION OF MICROORGANISMS IN EGG PICKLING SOLUTIONS
The advent of an automatic egg cooking and peeling machine has given
the food industry the capacity to rapidly produce a large number of hard-
cooked eggs (Anon., 1973). One of the potential products is pickled eggs.
Cunningham et al. (1970) and Maurer (1972) reported procedures and recipes
for pickling eggs in the home. However, only limited information is
available concerning commercial processing and ingredient factors which
may affect the final quality of pickled eggs.
When used in egg pickling solutions, spices enhance both flavor and
appearance. However, various researchers have shown that if the micro-
biological population of the spice is excessive, the organisms may contami-
nate the product, and result in a spoilage problem or a health hazard.
Cunningham et al. (1970) and Maurer (1972) have suggested that heating a
pickling solution to boiling and then simmering it for five minutes would
result in sterilization of the pickling solution. This concept should be
refined for application of the pickling process to commercial processing.
Acton and Johnson (1973) reported that the acid strength of pickling
solutions was decreased by 20 to 23% by the addition of spices to the vinegar
solution. They hypothesized that this was probably due to the absorption
and neutralization of acetic acid (vinegar) by the pickling spice ingredients,
They also demonstrated that acid penetration into the alkaline hard-cooked
egg can shift tne pH1 up,,wad in the egg pickling solution.
The toxic effects on microorganisms -hat can be observed at unfavorable
pll values are not a direct result of high hydrogen ion and hydroxide ion
concentration (Stanier et al., 1963). Undissociated molecules of acidic
and basic substances can penetrate into cells much more readily than the
corresponding ions. At low pH values, weak acids, which exist to a
considerable extent in undissociated form, can enter cells and damage them
by changing the internal pl, whereas strong acids cannot. In slightly
acid environments, a weak acid (acetic acid) is toxic to microorganisms,
whereas a strong acid, HC1, has relatively little effect on these organisms.
The toxicity of acetic acid disappears under neutral or alkaline conditions,
where the molecule is almost completely ionized (Stanier et al., 1963).
The objectives of this investigation were: 1) to determine if
microorganisms could survive in the high acid environment of pickling
solutions and 2) to determine the appropriate heating time for sterilization
of egg picklirg sol1itions.
Spices and pickling ingredients were purchased at local retail markets.
Each of these materials was assayed for microbial content as described in
the Recommended Methods for the Mi crobioloqical Examination of Foods (Sharf,
Five recipes for egg pickling solutions (Maurer, 1972) (Table 2) were
evaluated as to the time required to effect thermal destruction of the
microorganisms present. Each solution was heated in a one-liter beaker on
a Corning electric hot plate with a magnetic stirrer. Each pickling
solution was brought to boiling and then simmered for ten minutes. Aliquots
of an appropriate volume of pickling solution were drawn at zero time, eight
minutes, 16 minutes, boiling (25 minutes) and every two minutes thereafter
for ten minutes.
TabjIe 2. qi ckl i recie (for one ua~~~~_1
Table 2. Egg picking reci es qor on _qatrtkof _p icEkIed Ls]
1) Red Beet Eggs
1 cup red beet juice
1 cup cider vinegar2
1 teaspoon brown sugar
a few small canned red beets
2) Dilled Eggs
1 1/2 cups white vinegar
1 cup water
3/4 teaspoon dill seed
1/4 teaspoon white pepper
3 teaspoons salt
1/4 teaspoon mustard seed
1/2 teaspoon onion juice
1/2 teaspoon minced garlic
3) Sweet and Sour Eggs
4) Kansas Spicy Eggs
1 1/2 cups apple cider
1 cup white vinegar
2 teaspoons salt
1 teaspoon mixed pickling spice
1 clove peeled garlic
1/2 sliced onion
1/2 teaspoon mustard seed
5) Dark and Spicy Eggs
1 1/2 cups cider vinegar
1/2 cup water
1 tablespoon dark brown sugar
2 teaspoons granulated sugar
1 teaspoon mixed pickling spice
1/4 teaspoon liquid smoke or
hickory smoke salt
1 1/2 cups apple cider
1/2 cup cider vinegar
1 package (12 oz.) red cinnamon candy
1 tablespoon mixed pickling spice
2 teaspoons salt
1 teaspoon garlic salt
2Changed from 1/2 cup to 1 cup.
Two methods for assaying the presence of viable microorganisms were
used. In trial 1, the procedure of Sharf (1966) was used. Ten ml. of
pickling solution was divided equally among three petri dishes and poured
with approximately 25 ml. of Plate Count Agar (Difco). The plates were
incubated at 320C. for 48 hours and then examined to determine the total
number of microorganisms present. Each heating trial was replicated twice.
An ideal transfer aliquot of pickling solution was sought for use in
trial 2. It was necessary to increase the environmental pH by reducing
the acidity of the agar to a level which would support microbial growth.
White vinegar was used because of its high acidity (pH 2.5). Aliquots
of vinegar (3.0 ml., 1.0 ml., 0.5 ml. and 0.1 ml.) were pipetted into
25 ml. of Plate Count Agar and the pH then determined. The 0.1 ml.
aliquot was selected for subsequent use in microbial evaluations of the
pick ing solutions.
In trial 2, a 0.1 ml. aliquot of pickling solution was placed in a
petri dish and poured with 25 ml. of Plate Count Agar. Three petri dishes
were prepared at each sampling tine. The same incubation and replication
procedure as in trial 1 was used.
The criteria for thermal destruction time was established as the
heating time necessary for development of no viable growth after 48 hours
at 320C., on all three pour plates of the same sampling period.
The pH of all the solutions was measured by a Corning pl' meter at
each step of the process to detect changes in pH as a result of the
addition of an ingredient. The pH of the agar was also measured when
the pickling solution was added to determine that the agar's pH (final
pH 7.0 at 25C.) ws not sufficiently altered to inhibit bacterial growth.
Results and Discussion
The division of ten ml. of picklin; solution equ lly amoory three
petri dishes, in trial 1, resulted in no observable microbial growth.
The pickling solutions ranged in p1l from 2.8 to 3.5 (Table 3). The pH
of these pour plates was measured and found to be less than 4.5, too low
for effectively monitoring the extent of microbial destruction. Thus,
this method, discussed by Sharf (1966), was not appropriate for assaying
microbial destruction in egg pickling solutions.
The volume of egg pickling solution, which would be suitable to enable
detection of viable bacterial growth was determined to be 0.1 ml. This
aliquot is the smallest practical transferable amount. Only the 0.1 ml.
aliquot, yielding an agar pH of abuut 6.8, was considered acceptable for
use in trial 2. The environment of the agar, with its pH approaching
neutrality through dilution, and its limited buffering capacity, was
sufficiently adjusted to support growth, if any viable microorganisms were
The egg pickling solutions varied in amount of heat needed to reach
total destruction of the microorganisms present (Figure 3). No egg pickling
solution required a longer heating time for total destruction of the
bacteria than that necessary to reach boiling. The "Dark and Spicy" egg
pickling solution took as little as 16 minutes for total microbial
destruction while the other solutions took as long as 25 minutes. The
"Red Beet" egg pickling solution was found to have too few organisms to
plot a thermal destruction curve. The difference in heating time required
to kill microorganisms apparently is dependent upon the thermal protection
that ingredients may give the microorganisms and the number of microorganisms
introduced by the various spices. The standard aerobic plate counts for
each spice and ingredient used in the egg pickling solutions are presented
in table 4.
Table 3. Acidit y_(pl of tlpi ckli solu tion
Reci pe___ pH
Red Beet Egg 3.55
Dill Egg 2.80
Swcet and Sour 3.27
Kansas Spicy 3.10
Dark and Spicy 3.15
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Table 4. Microbiological content of each ic and ingredient
Ingredient Mi croorgani sms_ _
Liquid Number per ml.
Cider vinegar 0
White vinegar 0
Tap wvter 10
Red beet juice 450
Apple cider 0
Solids Number per g.
Brown sugar 10
Dill seed 180
White pepper 120,000
Mustard seed 160
Red cinnamon candy 10
Mixed pickling spice 10
Garlic salt 700
Smoke salt 250
Yellow', onion 120
_Minced garlic 21,000
The reported heating sequence of Cuninigham et al. (1970) and Maurer
(1972) is more than adequate to sterilize the egg pickling solutions used
in these investigations. Sporeforming bacteria were expected to be able
to grow when the environmental conditions were suitable for growth. Even
with the agar at a pH of 6.8, an optimal pH for microbial growth, very few
organisms grew. It is apparent that the combination of heat and acid was
enough to destroy spores as well as vegetable cells.
Several other observations can he reported as a result of this
investigation. The decrease in the ocid strength of the pickling medium
due to the addition of spices observed by Acton and Johnson (1973) was
observed in the "Dill Egg" pickling solution as the spices were added. In
the other four egg pickling recipes the addition of spices tended to
decrease the pH and increase the acid strength. The thermal treatment did
not affect the pH of the egg pickling solutions. The pH values of the egg
pickling solutions were the same before and after heating. As with other
foods, thermal processing is useful in minimizing the effect of microbiologi-
MICROBIAL GROWTH IN PICKLED EGGS
The preparation of pickled eggs involves the use of vinegar,
seasoning and heat treatment, not unlike the procedure for preparing
dill pickles. The principles used in commercial dill pickle processing
may relate to egg pickling. A unique similarity of the two is a rapid
increase in the pH of the pickling solution. If the increase in pH
exceeds 4.0 microbial problems may result.
Monroe et al. (1969) recommended that the internal product temperature
of dill pickles should be 1650F. (73.5C.) with a 15-minute holding period
and an equilibrated acidity sufficient to maintain a brine pH of 4.0 and
below to assure protection from spoilage. Bell et al. (1972) found that a
95% equilibrium would occur in 50 hours for fresh packaged pickles (40%
brine to 60% pickles). These authors found that in a commercial operation
little acid penetration occurs before the heating starts.
Acton and Johnson (1973) reported the presence of 540 sporeforming
bacteria per ml. of egg pickling solutions after 50 days of storage as
opposed to half this number of organisms present at 20 days of storage.
Low microbial counts are achieved in commercial dill pickling by loi' pH
and thermal processing.
The "Dill Egg" recipe has been found earlier to contribute the
greatest number of microorg'anisnms and was studied in this investigation.
The objectives were three-fold: 1) to determine whether microorganisms
in the pickling solution can miiltiply during storage, 2) to determine
whether sterilizing the egg pickling solution was necessary for safe
pickled eggs and 3) to determine the percenL equilibrium for pickled eggs
during short-term storage.
Large and medium size eggs were collected from Babcock B-300 Leghorn
hens. All eggs were cleaned as in Chapter 1, placed into clean molded
pulpboard filler flats and held in a cooler at 18.50C. and 75% relative
humidity for one week prior to hard-cooking. The eggs were all hard-
cooked by the cold water method (Irmiter et al., 1970).
Microbiological assay was conducted on the eggs and the pickling
solutions in all experimental groups following the fore-mentioned
sampling pattern. The egg or eggs were assayed as in Chapter 1, and the
solution was assayed as described in Chapter 2.
Experiment 1. A total of ten large size eggs (average weight 56
grams) :wre collected. Each peeled egg (average weight 50 grams) was
placed into a one-pint Mason jar. The "Dill Egg" pickling solution was
heated to boiling and simmered five minutes. Approximately 150 ml. of
hot (80"C.) pickling solution was poured over the egg in each jar. The
ratio of pickling solution to egg was 3:1 (v:w). The ten jars, each
containing one eggs, were stored at 250C. Two jars were selected at
random and the egg a-n solution sampled for microbiological analysis at
0, 1, 2, 48, and 168 hours of storage.
Experiment 2. A total of 24 medium size eggs (average weight 49 grams)
were collected. Two peeled eggs (average weight 44 grams each) were placed
into a one-pint M ason jar. Approximately 176 ml. of hot (800C.) pickling
solution wasas poured over the eggs in six of the jars and an equal ai.ount of
unheated pickling solution was poured oer the eggs in each of the
remaining six jars. The 12 jars of pickled eggs were stored at 250C.
The ratio of pickling solution to egg in each jar was 2:1 (v:w). One
jar from each treatment of "Dill Egg" pickling solution was selected at
random and sampled for microbiological analysis of both eggs and solution
at 0, 4, 8, 12, 30, and 52 hours of storage.
Experiment 3. The procedure of experiiment 1 was duplicated for a
total of 14 medium size eggs. Two jars were selected at random and
sampled for microbiological analysis following 0, 1, 2, 3, 4, 24, and 48
hours of storage.
Experiment 4. A total of 12 medium size eggs were collected. Each
peeled egg was placed into a one-pint Mason jar. The "Dill Egg" pickling
solution was prepared but unheated. Approximately 132 ml. of the pickling
solution was poured over the egg in each jar. The ratio of pickling
solution to egg in each jar was 3:1 (v:w). The 12 jars of pickled eggs
were stored at 25C. Two jars were selected at random and sampled for
microbiological analysis following 0, 4, 8, 24, 48, and 168 hours of
Titration for Acidity
The liquid portion of the pickled "Dill Egg" was evaluated for acetic
acid content. The acid content was measured (weight/volume) by titrating
a 10 ml. sample with a O.l00 N NaOH solution to p[l 7.5 as measured with a
Sargent Model LS, glass electrode, pH meter. Acid titration curves were
recorded for two trials of "Dill Egg" and of 5% w/w acetic acid (vinegar)
at several dilutions.
Trial 1. Eight large size eggs were collected and prepared as in
experiment 1 for the microbiological study. Ihe eight jars of pickled eggs
were stored at 250C. One jar was selected at random and a ten l1. aliquot
sampled following 0, 1, 2.5, 5, 10, 24, 50, and 168 hours of storage. A
single sample was removed from each jar and a jar was sampled only once.
Trial 2. Twenty-four medium size eggs were hard-cooked and peeled.
Three peeled eggs were placed into a one-pint Mason jar. The "Dill Egg"
pickling solution was heated to boiling and simnlered five minutes.
Approximately 211 ml. of hot (80C). pickling solution was poured over
the eggs in each jar. The ratio of pickling solution to egg in each jar
was 1.6:1 (v:w). The eight jars were stored and sampled as in trial 1.
The percent equilibrium was calculated as the percent difference
between the titrated volume of 0.1000 N NaOH of the time-sample from 0
time as compared to the volume difference that existed between the 168 hour
sample and 0 time.
Percent equilibrium = Volume (at 0 time sample-time) X 100
Volume (at 0 time 168 hours)
The percent equilibrium was plotted linearly on the Y-axis and the log of
the tine, in hours, on the X-axis. A least squares line was plotted and
the point at which it intersected 100 percent equilibrium indicated the
time required to reach equilibrium.
Results and Discussion
Regardless of ti.e procedure for the preparation of pickled eggs with
"Dill Egg" Solution, there was a marked reduction in the number of viable
microorganisms. The data of the four experiments were combined into two
tables. Table 5 is a composite of imicobial counts of eggs and solutions
for the heated "Dill Egg" solutions and Table 6 is the composite for the
unheated "Di11 Egg" solutions.
The number of eggs per jar or the different solution to egg ratio did
0- 0- C 00D 0
C C\C C C C
C\Jd Li) 0 0) C 0
-- -- --- -- ^ ^ ^ ^ ^ -
*r- C C C- C-
C- C\ CM N
i +- o o <~
- itC3 cO o r- - - -
co. Cr 3
co : Co)
1) C- CM CC) CC C C)
not appear to have any effect upon the number of viable microorganisms
present in the pickling solution. The unheated "Dill Egg" solution
appeared to maintain a stable number of viable microorganisms. However,
the solution either destroyed or diluted the microorganisms present on
the peeled eggs. As would be expected, heating the pickling solution
greatly reduced the number of viable microorganisms.
The change in pH and acetic acid concentration during the first 50
hours appeared to be one of dilution. Acton and Johnson (1973) and Ball
and Saffores (1973) stated that the acetic acid migrated into the albumen
of the hard-cooked egg and water migrated away from the albumen to the yolk
and the pickling solution. The titration curves for "Dill Egg" pickling
solutions (3:1) and (1.6:1) are plotted in Figures 4 and 5, respectively,
and are very similar Lo the cuives for thi several dilutions of 5% w/r
acetic acid (Figure 6).
The egg albumen did not act as a buffer to dampen the inflection point
during titration. However, the alkaline groups of the albumen did reduce
the number of hydronium ions in the solution. These two physical (dilution)
and chemical (neutralization) effects are evidenced by an increase in plH and
reduction in volume of sodium hydroxide required to reach a pH of 7.5.
The lonwr the ratio of solution to egg the higher the pH was raised
in the pickled egg solution. lhe ratio (1.6:1) exceeded an equilibrium pH
of 4.0. This is undesirable if the recommendation of Monroe et al. (1969)
is to be foilowied. However, when the percent equilibrium was plotted in
Figure 7, the 1.6:1 ratio required 80 hours to reach 955 equilibrium and the
3:1 ratio took 70 hours. The six to seven days time to reach equilibrium
presented by Acton and Johnson (1973) and Ball and Safforcs (1973) is of
cj c I
() 0un q pO
(<<;1 ui*.rqiLin bo ppe oiV sav
C ) )
L--I I I I
questionable application. The plotting of Acton and Johnson's data
(Figure 8), according to the procedure of Bell et al. (1972), yielded
a 100% equilibrium after 20 hours. Therefore, the data of Acton and
Johnson (1973) and that of this investigation are in agreement on the
time required for 95% acid equilibrium. This time ranged between 20 and
80 hours depending upon the solution to egg ratio.
The equilibrium pH attained in dill pickles as a result of the degree
of acid penetration reported by Bell et al. (1972) was the same in pickled
eggs in this investigation. The adjustment of pH of the pickling solution
was dependent upon time and the ratio of solution to eggs (v/w). A ratio
of 1.6:1 was found to yield an equilibrated pH of 4.1, which could develop
into a microbial problem if the product is improperly handled or pH rises
to a level better suited for microbial growth.
(I C: b I C
u1 \1 DL
3 4 U
THE EFFECT OF STORAGE TIME OF SHELL EGGS Oi DISCOLORATION
OF EGG ALDUMEN IN HARD-COOKED EGGS
Baker and Darfler (1969) and Schinll et al. (1969) reported a
brown discoloration of the albumen of hard-cooked eggs which was due to
the Maillard reaction. The longer the eggs were cooked the browner the
albumen would become in addition to the green ring formation around the
This investigation was undertaken to determine if the length of
storage of refrigerated day-old shell eggs would develop the brown
discoloration of the hard-cooked egg albumen, following conventional
Medium size eggs were collected from Babcock B-300 Leghorn hens.
All eggs were washed as in Chapter 1 and placed into clean molded pulpboard
filler flats and held in a cooler at 18.5 C. and 75% relative humidity
from one day to 12 weeks. Three replications were conducted with different
laying diets and lcrgths of shell egg storage.
Replication 1. Eggs were collected at random from a laying flock
maintained on a uniform laying diet. A total of 100 medium size eggs were
collected. Ten eggs were sampled at random for evaluation of albumen
discoloration following 1. 3, 4, 5, 6, 7, 8, 10, and 12 weeks of storage.
Replication 2. This replication was conducted the same way as
replication 1, except only 90 medium size eggs were collected. Ten eggs
were sampled at random for evaluation of albumen discoloration following
l, 2, 3, 4, 5, 6, 8, 10,and 12 weeks of storage.
Replication 3. Eggs were collected at random from several laying
flocks. A total of 100 medium size eggs were collected. Ten eggs were
sampled at random for evaluation of albumen discoloration following 1, 2,
3, 4, 5, 6, 7, 8, 9, and 10 weeks of storage.
Interior Eg Quality
A total of 180 medium size eggs were collected at random from several
flocks of laying hens and stored at 18.50C. and 75% relative humidity.
One hundred of these eggs were broken out for Haugh unit scores and 80 of
these eggs were candled for air cell depth (Anon., 1972). Ten eggs were
sampled at random each week for Haugh unit score and eight eggs were sampled
each week for air cell depth measurements. The storage time was identical
to that in replication 3.
Ten eggs from each sampling period were placed large end up in cold
water, hard-cooked by the cold water method (Irmiter et al., 1970), peeled
and sliced with a commercially available egg slicer perpendicular to the
long axis. The slices uere wrapped in llandi-wrapR to prevent moisture loss
prior to being examined for albumen discoloration.
An albumen slice containing no yolk and a diameter greater than 25 mm.
was placed in the viewing port of an IDL COLOR-LYER (Kcllmorgen Corporation,
Color Systems Division, Attleboro, Mass.). The COLOR-EYE values were
converted to dominant wavelength, e citation purity and luminosity which
represent a mathematical description of the ag-q albumen color, thus eliminating
possible biases of human judgement. The procedure of Fry and Damron (1971)
was used to obtain values for dominant wavelength, excitation purity and
luminosity from the COLOR-EYE readings.
The analysis of variance was calculated for the pooled data for each
variable (dominant wavelength, luminosity, excitation purity and laugh
units) across storage treatments by using the Statistical Analysis System
(Service, 1972). The data were plotted and the least squares line was
obtained (Freund, 1967). A correlation coefficient was computed (Freund,
1967) to deteniine the degree to which variables vary together or a measure
of the intensity of their association.
Results and Discussion
A dcr':cning of hard-cooIed egg alhumen was observed as storano tire
of the uncooked eggs increased. The alhumen did not look brown as
suggested by Baker and Darfler (19G9) but appeared as a gray-brown.
The dominant wavelength increased significantly from an average of
570 nm. to 572 nm. during 12 weeks of storage (Figure 9). The luminosity
values changed significantly be decreasing from 76.5 to 75.5 during 12
weeks (Figure 10). The excitation purity (Figure 11) changed significantly
at the 0.01 level. The dominant wavelength, luminosity and excitation
purity were all highly and equally correlated (+.88) with storage time..
The increase in dominant wavelength and decrease in uminosi:ty indicated
that the egg became darker with storage. Further, the slight increase in
excitation purity indicated greater color intensity.
The non-uniform fed laying flock yielded an albumen discoloration
similar to that oF the uniformly fed flock. The longer the eggs were
stored under this condition (18.5"C. and 75% relative humidity), the more
1 2 3 4 5 6 7 8 9 10 11 12
Figure 9. Coninant wavelength of albumen from eggs hard-cooked
after storage at 18.5C.
I I I I I I I
1 2 3 4 5 6 7
8 9 10 11 12
Figure 10. Luminosity intensity of albumen froil eggs hard-cooked
after storage it 18.50C.
1 2 3 4 5 6 7 8 9 10 11 12
1 2 3 4 5 6 7 8 9 10 11 12
Figure 11. Excitation purity of albumen
after storage at 18.5C.
from eggs hard-cooked
off-white (gray-brown) the albumen became.
The interior quality (Table 7) reflects the degree of deterioration
undergone by the shell eggs in this storage condition. The interior
quality of eggs as measured by laugh units decreased in value linearly as
the storage time increased (Figure 12) with a correlation coefficient of
0.82. The air cell depth increased as the storage time increased (Table 7).
The discoloration of egg albumen appears to be reciprocal to the deterioration
of the interior quality of the shell egg.
The eggs for Haugh unit scores and air cell depth were collected from
a flock of birds with an unknown rate of production and age of lay. The
Haugh unit measurements of the first group of eggs were made after one week
of storage. Fry et al. (1965) reported that the decline in Haugh unit
scores during the first seven days is by far the larger than the second
and third seven-d:.y periods for eggs stored at 560F.(13.50C) and 65%'
relative humidity. The loss of CO2, increase in pH and water loss during
the first seven days of storage cause weakening of the albumen which results
in a reduction of Haugh unit scores. A range of 10.9 to 13.5% loss in
Haugh 'nit score was observed in the first seven days (Fry et al., 1965).
If the average percent Haugh unit score loss of 12.2% was used, the intital
Haugh unit score for these eggs would have been 64.4 (USDA Grade A). This
is still lower than desirable for an initial Haugh unit score. The initial
Haugh unit score may have been lowered by the warm summer temperatures.
Wilcox and Wilson (1962) reported that birds after eight months of production
had an initial Ilaugh unit score of 69. This does not differ much from the
64.4 Haugh unit score extrapolated from the seven-day Haugh unit score in
It is apparent from this research that as the interior quality of the
shell egg decreases it is accompanied by a discoloration of the hard-cooked
Table 7. Interior quality change of shell eggs at selected lengths
Storage bbunon Air Cell
time Haugh, USDA Depth2 USDA
,eekys)1 units ____ qility ____ i __ uality __
1 56.7 B 1/8 AA
2 60.3 A 1/8 AA
3 46.4 B 3/16 A
4 48.1: B 3/16 A
5 53.9' B 1/4 B
6 43.9: B 1/4 B
7 50.7. B 1/4 B
8 37.0f' B 1/4 B
9 41.0' B 1/4 B
10 39.4- B 5/16 B
Average of ten eggs
Average of eight eggs
I JI-__ ___I_ I I I I
1 2 3 4 5 6 7 8 9 10
Storage weekss )
Figure 12. Haugh unit score of eggs stored at 18.50C.
egg albumen. Since a p1l of .87 was achieved after one week of storage and
discoloration increased gradually throughout the storage period, the
conclusion by Baker and Darfler (1969), that the increase in pH was the
cause of hard-cooked egg white discoloration, may not be valid. However,
significant discoloration did not occur until after six or more weeks of
storage. This development may affect the consumer's acceptance of hard-
cooked egg products prepared from eggs held in storage or of low USDA
QUALITY AND ACCEPTABILITY OF PICi.LED CHICKEN EGGS
Various researchers have evaluated pickled hard-cooked chicken eggs
(Cunningham et al., 1970; Vaurer, 1972; and McCready, 1973) and brine-
pickled duck eggs (Trongpanich and Dawson, 1974). Two of the pickled
egg recipes suggested by Mlaurer (1972), "Red Beet" and "Dark and Spicy",
contribute a characteristic color as well as flavor to the pickled hard-
cooked eggs. Red beet juice is used in the "Red Beet" recipe. The red
beet (Beta vulgaris) is a rich source of red pigments. The class of
colored substances containing both the betacyanins (red pigments) and
betaxanthin yellow ; pigments) are termed as betalcins (Von Elbe and Maing,
1973). The betacyanins found in beets include betanin (the major pigment),
isobetanin, prebetanin, isoprebetanin and the betaxanthinrs, vulgaxanthin I
and vulgaxanthin II. These pigments are water soluble and naturally occur
as zwitterions (Von Elbe and Maing, 1973). In the "Dark and Spicy" recipe
the brown surface color is contributed by all the ingredients.
This study was conducted to evaluate the acceptability of chicken eggs
pickled in three pickling solutions and stored for a period of three months
at two storage temperatures (4C. and 22C.).
Experi irenta l; P rocked u,-e
Eggs were collected froimi Babcock B-300 Leghorn hens maintained in
laying cages with wire floors. All eggs were washed as in Chapter I and
placed into clean molded puilph~ard filler flats and held in a cooler at
18.5C. and 75% relative himidily for one weeP prior to hard-cooking.
A total of 324 large size eggs were collected. The eggs were hard-
cooked by the cold-water method (irmlter et al., 1970) and peeled. Three
eggs were placed into clean one-pint Mason jars, for a total of 108 jars.
Three egg pickling solutions ("Dill Egg", "Red Beet" and "Dark and
Spicy"; Table 2), as described by Maurer (1972), were prepared by heating
to boiling. Enough hot solution (80C.) was then poured over the eggs
for a ratio of pickling solution to egg of 1.6:1 (v/w). Eighteen jars of
pickled eggs from each recipe were stored at room temperature (22?C.) and
18 jars were stored at refrigerated temperature (40C.).
One jar of each of the three pickled egg recipes was randomly removed
from each storage temperature after 1, 2, 6, 10, and 14 weeks of storage
and presented to a taste panel. Each storage period was replicated three
times or three consecutive days. Fightcen control eggs were prepared for
each recipe five days prior to each taste panel evaluation. Preparation of
the control eggs was identical to that of the treatment eggs and they were
stored at 22C. In the evaluation at one week of storage the control and
treatment eggs were from the same preparation.
The paired-comparison test suggested by Dawson et al. (1964) was used
to select the different sample. The three eggs of each recipe and storage
treatment were sliced into sixths longitudinally as were an equal number of
control pickled eggs. Individuals from the Poultry Science Department were
previously exposed to tasting pickled eggs and as a result were considered
to be experienced panelists. The panelists sampled six pairs of eggs each
day with one pair comnpared at a tiim. The eggs were served at room temperature
(22C) on a nine-inch plate with a treatment slice placed on the extreme right
ani the control on the extreme left. The panelists were asked to evaluate
separately whether the treaLitunt egg was the same as or different than
the control egg in color, taste and overall quality. If a difference was
detected, then the panelist was asked to say whether the treatment egg
was better or worse than the control. A minimum of three to 10 paired-
comparisons was necessary for the binomial-distribution statistics (Dawson
et al., 1964).
The number of panelists available each day varied from six to 12. Each
panelist was separated from others by dividers. Water was provided between
samples. No attempt was made to alter the normal room lighting (Fluorescent).
The binomial-distribution compared the fraction of panelists who
reported no difference at week one with the fraction of panelists who
reported no difference at each of the other four storage times. A two
sided z statistic was used to determine if there was any significant
difference relating change in quality to storage time. A significant
difference was present between the treatment and control when the rejection
probability of 0.05 was reached. The null hypothesis of Ho:pl = p2 was
used in this investigation. The test statistic
z = l 2__
S11 + E
for binomial comparisons (Mlendenhall, 1971) was used to calculate the
Results and DiscuIssion
Hard-cooked eggs immersed in "Red Beet" pickling solution for seven
days at 220C. developed a bright red-violet color in the albumen and the yolk,
This was an appealing color to mi;ny and may be associated with holiday
use. The "Red Beet" eggs stored at 40C. had only slightly less color
development than those stored at 220C. The "Dill Egg" pickled eggs had
essentially no color change. The "Dark and Spicy" eggs had a brownish
color at the exterior surface of the albumen but little or no penetration
of the color into the egg.
The taste panelists noticed a marked difference after two weeks of
storage in color, taste and overall quality of the "Red Beet" pickled eggs
stored at both 22C. and 40C. (Table 8). Visually the color changed from
a bright purple-red in the fresh solution to a murky brown. The pigment
absorbed by the hard-cooked egg discolored but not as rapidly as in the
solution. This difference was a result of color fading from red to pink in
the albumen. The red color of the solution progressively turned brown in
the presence of harJ-coo!ked cgy subsequent to two ,weeks of stoag:, at 220C.
It was observed that if the egg was removed after one week of storage the
light red color of the solution remained stable for more than one month at
220C. The presence of hard-cooked eggs affected the stability of the
betalain pigment, possibly in much the same way as previously reported for
red beets per se and in other food products.
Von Elbe and Maing (1973) observed that when gels were formed with
betalains the resulting color was lightest at pH 5.0 as compared to pH 2.5
and 8.5. Storage for 16 days resulted in fading of the color in all gels
with tho'.e at pH 5.0 being least affected (Von Elbe and Maing, 1973). In
the range of pH 3.5 to 7.0 the spectrum of betalain had a maximum absorption
at 537 and 538 nm. (Von Elbe and tMaing, 1973). Studies have shown that the
stability of betalain is greatest at pi 5.0 and the pigment degrades
following first-order kinetics. The half-life at 25C. for betalain in a
model system at pH 5.0 has hee: calculated as 1,1530 1 100 minutes (Von Elbe
Table 8. Taste panelists' evaluation of "Red Beet" pickled eggs stored
for 14 weeks at 4'C. and 22'C.1
_____ SStorage (weeks___
Attribute 1 2 6 10 14
4C. Color .66 .10** .13** .03** .22**
Taste .63 .30** .22** .17** .37"
Overall .63 .40 .19*k .07** .44
220C. Color .57 .00** .00**
Taste .43 .20 .25
Overall .54 .23** .16** -
Number of panelists 35 30 32 29 27
Expressed as the fraction of panelists who reported no difference
between the control and the trcatient emjs.
*Significant difference at the 0.05 level.
**Significant difference at the 0.01 level.
et al., 1974b). Betalain, like other nlitural pigments, is subject to
degradation by air and light. Therefore, products containing betanin must
be protected against long exposures to air and light. Darkening or browning
of beet products by oxidation both before and after processing has been
reported by Von Elbe et al. (1974b). Livingston et al. (1954) studied
the role of trace metal contamination in discoloration of beet puree and
reported that both iron and copper accelerate darkening.
The panelists reported that after six weeks of storage at 4C. "Red
Beet" eggs were significantly different in color and overall quality (Table
8 ). The "Red Beet" eggs stored at 22C. for 10 weeks were removed from
testing when the solution and eggs were brown throughout (Figure 13) and
had an objectionable straw-like or stale odor. The eggs stored at 4C.
were presented to the taste panelists and'received significantly different
scores for color, taste and ro'vrall quality. The panelists comin:nted that
at 14 weeks of storage at 4C. the discoloration and off-flavor was developed
to a lesser degree than at 10 wees of storage. A possible explanation for
this result is that the eggs stored for 1, 2, 3, 6, and 10 weeks were
prepared on the same day. The eggs stored for 14 weeks were prepared on
another day. The eggs were fro'L the same Flock but were collected one month
apart. Also, the availability of the same supply of canned red beets was
not constant. It is conceivable that the egg source, brand of canned red
beets and other unidentified procedural changes could cause this reduction
in deterioration of the "Red Beet" pickled eggs stored at 4C.
Color deterioration of the "Red Beet" eggs first occurred in the solution,
followed by the darkening and loss of red color at the surface of the eggs,
a fading of the red color in the albuiecn to pink and a slow darkening inward
of the ynlk. Von Elbe et al. (1974a) indicated that color changes of
sausage colored with beta:i'ii ;ire very small during storage. They pointed
Figure 13. Discoloration of "Red Beet" pickled eggs stored
for 10 weeks at 4C. and 220C. (Left: 5 days at
220C.; Middle: 10 weeks at 4C.; Right: 10 weeks
out that a protective effect of beLaaiin in protein foods exists and is
adequate to permit use of betilains as food colorants.
The evidence of this investigation showed that the albumen was the
last portion of the jar of "Red Dect" pickled eggs that darkened, which
may be due to the protective action of proteins. The absence of eggs in
the pickling solution prevented the continued discoloration of the red beet
pigment. The low pl of the pic!l1ing solution did not prevent the occurrence
of fading or darkening when egos were present in the solution.
"Dill Egg" was free of significant change in quality during this investi-
gation, at both storage temperatures, with exception of taste between the
treatment eggs and control after two weeks storage at 22C. (Table 9). There
was no significant color change observed for "Dill Egg" during this investi-
gation in either the piciling solution or'the eggs.
"Dark and Spicy" pickled cggs stored at 22C. for six: weeks were found
to be significantly different in taste and overall quality (Table 10). After
ten weeks of storage the "Dark and Spicy' eggs stored at 4"C. were signifi-
cantly different only in color. Hoieever, after six weeks of stora~- at 220C.
differences were found in color, taste and overall quality (Table 10); taste
panel evaluations indicated that a further decline in quality occurred as
storage time increased to 14 weeks.
The discoloration in the "Dark and Spicy" eggs did not appear to be one
of penetration of the color of the solution (Figure 14) but may be related to
the discoloration observed in other egg producLs. The bitter and stale off-
flavor observed in the yolk of these eggs may also be related to flavor
deterioration in dehydrated erjg products.
Dodge et al. (1965) and Daker and Darfler (1969) reported that hard-
cooked eggs developed a bro;n discoloration of the albumen due to the
Maillard reaction. In addition to the glucose-protein reaction resulting
Table 9. Taste panelists' evaluation of "Dill 9gq" pickled eggs
stcred for 14 wooks at 4C. and 22C.
______ Storaqe weeKs)____
Attribute 1 2 6 10 14
40C. Color .71 .77 .91 .66 .78
Taste .49 .67 .59 .55 .63
Overall .49 .67 .66 .45 .70
220C. Color .80 .83 .84 .62 .70
Taste .66 .33** .28** .28** .37*
Overall .66 .50 .50 .38* .52
Number of panelists 35 30 32 29 27
Expressed as the fraction of pneilisi-s uho reported no difference
between the conLrol and the treatment eggs.
*Significant difference at the 0.05 level.
**Significant difference at the 0.01 level.
Table 10. Taste panelists' evaluation of "Dark and Spicy" pickled eggs
stored for 14 weeks at 4C. and 22"C.1
Attribute 1 2 6 10 14
.63 .70 .41 .38* .48
.71 .47* .50* .41* .33**
Number of panelists
ExpF-reed as the fraction of pcnclists ieho
between the control and the t ei:cLient eggs.
32 29 27
reported no difference
*SigniFicant difference at the 0.05 level.
**Significant difference at the 0.01 level.
Figure 14. Discoloration of "Dark and
10 weeks at 4C. and 220C.
Middle: 10 weeks at 40C.;
Spicy" pickled eggs stored
(Left: 5 days at 220C.;
Right: 10 weeks at 220C.).
in a brown color, researchers have presented evidence that some deteriora-
tive changes occurring in dried whole eggs and yolks are independent of the
glucose-protein reaction (Hill and Sebring, 1973). The results of testing
led these authors to suggest that the reaction was between a cephalin amino
group and aldehydes. Fevold et al. (1946) and Boggs and Fevold (1946)
presented evidence that the major changes resulting in loss of palatability
takes place in the fatty constituents of the egg. Whole egg tends to
develop stale or stored flavors during storage, which in part might be due
to the lipid oxidation (Kw in and Norgaard, 1966). Kline et al. (1951a, b)
pointed out that glucose is the reactive aldehyde involved in the cephalin
amine-aldehyde reaction. The changes which occurred in the phospholipid
fraction of stored whole egg powder were essentially eliminated by the
removal of glucose from the liquid before drying. The glucose-cephalin
reaction is in"clvcd in off-Flavor dev'eipment.
Changes in flavor and odor during storage of dehydrated eggs is quite
noticeable. Flavor stability of whole egg powder can be improved to a
certain extent by acidifying the liquid to a pH of 5.5 before drying. This
inhibits the browning reaction involving the glucose and protein but does
not stop it completely (Berquist, 1973). Boggs and Fevold (1946) reported
that excessive acidity is detrimental to the flavor of dried eggs.
The pickling process is somewhat similar to dehydration in that the egg
loses about 5% of its weight. The Maillard reaction is preferentially
selected for by a low pll (4.3) and an absence of SO2 (Mcleeny et al., 1969).
As a result the potential for albumen discoloration and off-flavor is present.
As a result of this investigation, it has been observed that the egg
pickling recipe significantly affects the shelf-life potential of pickled
hard-cooked eggs. The "Red Reot" pickled eggs did not have a reasonable
shelf-life at these two storage condiLions and may not be practical for
The shelf-life of "Dill Egg" and "Uark and Spicy" eggs could be
successfully extended by refrigeration at 40C. for 14 weeks. The "Dill
Egg" pickled egg recipe could have the greatest commercial potential due
to its resistance to color and flavor deterioration at 40C.
STRUCTURE AND MICRO-STRUCTURE OF HARD-COOKED EGGS
Many researchers have studied the internal structure of the egg.
Romanoff (1943) described the gross structure of the albumen of a newly
laid chicken egg. Almquist and Lorenz (1932), Cole (1938) and Conrad and
Scott (1939) observed ovomucin fibers in thick egg white. Schaible et al,
(1935) demonstrated a means of revealing stratified layers within the thick
egg white by breaking a fresh egg into distilled water and slitting the
envelope of thick white. After a time, ovomucin and some globulins are
precipitated on the edges of the cut surface showing approximately six
laminations regularly spaced about one sm. apart. The thick white is not
a homogeneous gel but is composed of bands and layers (Almquist and Lorenz,
1932; Moran and Hale, 1936). Scott and Huang (1941) reported that the
fibers are laid down, not as disconnected small fibers, but rather as sheets
or layers with a mesh or sieve-like appearance.
It has been observed in earlier investigations of "Red Beet" pickled
eggs that the albumen was differentially stained pink. The red beet (Beta
vulgaris) is a rich source of red colored, water soluble pigments.
The objectives of this investigation were two-fold: 1) to determine if
this differential penetration of red beet pigment was based upon the chemical
composition of the albumen layers and 2) to demonstrate the presence of
stratification in the thick albumen of hard-cooked chicken eggs.
Experi metal Proceduar
Medium and large size eggs from Babcock B-300 Leghorn hens were
collected. The eggs were washed and stored as in Chapter I for one week
prior to cooking. All the eggs were hard-cooked by the cold water method
(Irmiter et al., 1970). Three peeled eggs were placed into a one-pint
Mason jar. Approximately 211 ml. of hot (80C.) "Red Beet" pickling
solution were poured over the eggs in each jar. The ratio of pickling
solution to egg in each jcr was 1.6:1 (v/w). The jars of "Red Beet"
pickled eggs were stored at 4C. and 22C. for various lengths of time.
The eggs were sliced into nine sections, three rfn. thick, yielding
eight profiles of each egg. The banding observed on each slice was traced
on clear acetate. The tracings were xeroxed, each section cut out and
then grouped as to the three major albumer layers, outer thin, thick and
inner thin, and the paper weighed to obtain an approximate percentage
of each albumen layer.
Results and Discussion
The color differentiation observed was well defined and seemed to
outline the three major albumen layers (Figure 15). The percentages
obtained from the weighed paper portions were similar to the ratios given
by Brooks and Hale (1959) for inner thin, thick and outer thin albumen layers
(Table 11) obtained using the "screen" technique described by Holst and
Almquist (1931). Romanoff (1943) found that the albumen of the ncwly-laid
chicken egg is differentiated into four layers with distinct chemical and
physical properties. The ratio of the albumen layers (Table 11) confirmed
the assumption that the difference in chemical composition of the albumen
layers was related to the uptake of hetalain pigment. The boundary (or
interface) between the outer thin a;nd thick albumen, as seen by color
Figure 15. The three major albumen layers differentially
stained with red beet juice with laminations
visible in the thick albumen.
Table 11. Proportion of albumen laers
1 1 2
ayer _Mean_ Rangel R_~ 2
Outer thin 29.6 24.0 32.5 13.9 38.0
Thi cl 43.2 36.0 48.0 35.4 54.0
Tnner thin 27.3 22.0 33.0 18.1 39.0
Experimental (n = 6).
Brooks and Hale, 1959.
differentiation, could Le torn wiith a little force (Figure 15). Separation
was also possible between the colored boundary between thick and inner thin.
The physical separation along the boundary between the various albumen
layers was most easily accomplished in the pointed region of the hard-
cooked egg and became more increasingly difficult as the blunt end of the
egg was approached. The thick albuimn was the only layer observed to have
a series of light and dark pink colored layers or la:.inations (Figure 15).
A separation of the individual layers was possible and even separations
within a single lamination. This was also easily accomplished in the
pointed end of the egg. This agreed with data obtained by Scott and Huang
(1941) that indicated that the mucin is laid down, not as disconnected small
fibers, but rather as sheets or layers. The inner thin and outer thin were
not composed of layers but peeled away in chunks. This was due to the lower
amount. uf Gvoilucii in the thiin chtes (C:rools and 'ial 1961).
Baker and Stadeiman (1957) related that housewives complained about
a large chalaza as a hinderance in cooking The chalaza showed up well in
the cross sections of "Red Deet" pickled eggs because it did not take up the
betalain pigment as intensely as the surrounding albur~ien and appeared lighter
in color. The thick albumen exhibited laminations as reported by several
researchers. The layers were composed of two chemically different materials;
one was light in color (due to ovomucin fibers) and one was dark in color
(due to a small concentration of ovomucin fibers). It is interpreted that
the uvomucin fibers in the thick albumen and chalaza are compact bundles
which prohibit the absorption of betalin pigments.
As can be seen in Figure 15, the inner thin albumen did not encircle
the yolk but was concentrated in the pointed end of the egg. The thick
albumen was likewise concentrated in the pointed end of the egg. The
majority of the lamin nations were present in the pointed end, with the widest
band of lamination occurring there, and thinned as it wrapped around the
yolk to the blunt end. The individual layer of lamination also thinned
from a width of 1.0 mm. to an unmeasurable width. Regardless of the
position of the egg during hard-cooking, the inner thin albumen was not
found in the blunt end of the egg. The research conducted by Romanoff
(1943) indicated that the inner thin albumen is the second layer, surrounding
the yolk and it enwraps the inner most chalaziferous layer. The thick
albumen surrounds the inner thin albumen and consLitutes the third and
concentric layer of albumen (Romanoff, 1943). These findings are contradic-
tory to what was observed in this investigation.
The chalaza was rarely found in the polar ends of the egg but off to
one of the sides, regardless of the cooking position.
The "Red Beet" pickled eggs stored at 40C. required a month for the
color to penetrlae and equilibrate sufficiently, in order to observe differ-
entiation clearly. The low storage temperature m-ay have slowed the rate of
penetration of the betalain pigment, permitting a more discernible difference.
The "Red Beet" eggs stored at 22C. were red-purple after five days of
storage and the entire albumen was colored to the same degree, which made
for poor differentiation. After one week of storage at 220C., the red
color began to degrade and for a time improved contrast was observed.
The differential staining possible with the use of red beet juice is
a potential technique to demonstrate the position of the several albumen
layers and their relationship to the egg as a whole. This technique has the
added advantage of measuring the percentage of the three albumen layers,
which is usually done by the "pipette" method (Rom~noff, 1943). and the
"screen" method of Holst and Alnquist (1931).
ACCEPTABILITY OF PICKLED QUAIL EGGS
Various researchers have evaluated hard-cooked chickens eggs in
pickling solutions (Cunningham et al., 1970; Haurer, 1972; McCrcady, 1973)
and brine-pickled duck eggs (Trongpanich and Dawson, 1974).
This study was conducted to evaluate the acceptability of quail eggs
pickled in five egg pickliing solutions.
Eggs were collected from ohbwhite quail housed in wire floor cages.
The eggs were placed on clean molded puloboard filler flats and held in a
cooled at 18.5'C. and 75-80% relative humidity for one week.
The eggs were hard-cooked by the cold water method (Irmiter et al.,
1970), peelei and placed in clear one-quart Mason jars, 40 eggs per jar.
Five egg pickling solution recipes (Table 2) developed by Faurer (1972) were
used in this investigation. The hot solutions (800C.) were poured over the
eggs and the jars were sealed. The cooled j,.s were then held in a
refrigerator (5"C.) for one week.
The design and analysis procedures for taste panels outlined by Street
and Carroll (1972) were used in this investigation. The participants in
this consuta: acceptance taste panel of pickled quail eggs were members of
groups whose mieetins were held in Gainesville, Florida, They were either
from poultry interest groups or homemakers clubs. The participants were
asked to take part in this taste panel during their coffee breaks and the
procedure wao very informal. The participants wi-re asked to express their
feelings (consu acr acceptuaoc) about pickled quail eggs from each recipe.
This was done by scoring the egg product on a seven-point hedonic scale:
excellent (+3), very good (12), good (+1), average (0), poor (-1), very poor
(-2), and terrible (-3). A frequency distribution was constructed from
Consumer acceptance scoring was performed on eggs from' all five recipes
in four trials, representing cach of the four groups of participants: trial
1 (16 individuals), trial 2 (14 individuals), trial 3 (35 individuals) and
trial 4 (64 indi. iduJls). The consumer acceptance data were pooled yielding
a total of 129 panelists. As can be seen the groups of participants were
not of the same size. Some people refused to participate and others sampled
less than five recipes. The results of a panelist were used only if all
five recipes were scored. The panelists b' and large were men; however,
records as to the ratio of men to wcmrn wc're not. rai;,tained,
A criterion of acceptability was established as the sum of the panelists
scoring the pickled quail egg product in the excellent (+3), very good (+2)
and good (+1) categories. Products accepted by more than 70% of the
panelists were judged to be of such acceptability that a potential market
for pickled quail eggs may exist. Those below 70%' would not be of sufficient
acceptability to warrant processing or marketing of that product.
Results and Discussion
Three recipes for pickling solutions were found to meet the criterion
of acceptability of 70/; "Kansas Spicy" was scored in the top three
categories by 74% of the panelists and "Sweet and Sour" and "Dill Egg" by
71% each (Figure 16). "Red Beet" was moderately acceptable with 67% and
"Dark and Spicy" was least acceptable at 572.
The majority of those who tasted the pickled eggs demonstrated
discriminatory judgmiient when tasting. A total of 103 panelists (or 80%)
| --o |
E'__ I 0
CuJ > U'
r U) G)
c C [
------ I-------------- + 4-1 a
selected and scored the recipes lhait they individually found acceptable
and others which were unacceptable. Only 26 panelists (or 207) found all
the recipes to their liking. This was based on the individual scoring of
all recipes with either an excellent (+3), very good (1,2) or good (+1).
Not one of the panelists gave eggs from ill of the recipes an average score
(0); likewise, no panelists scored the eggs of all five recipes in the
combiind unacceptable categories of poor (-1), very poor (-2) and terrible
The difference in acceptance between individual recipes was possible
due to the type of seasoning spice and the color of the pickled eggs. It
could be a possibility that if someone did not like or was unaccustomed to
either a certain spice or color, the recipe would be rated low. If the
panelist favored a certain spice or color the recipe would be rated high.
Additional factors affecting iihe acceptanrce scores miiht have been the age,
six, social background, health or the panelist, a panelist's like or dislike
for eggs, a)d the time of day at which the taste panels were conducted. It
is felt, however, that the data reported herein indicate that pickled quail
eggs are an acceptable market product.
The effect of microorgf.nismns on hcrd-cooked and pickled eggs was
observed to be minimal in this investigation when appropriate storage
temperatures were utilized. Deterioration of color and flavor of pickled
eggs .was the greatest factor in reduction of shelf-life and loss of taste
The quality of the eggs, for preparation as pickled eggs, is dependent
upon the interior shell egg quality. A brown discoloration of hard-cooked
egg albumen was found to be associated with the loss of interior shell
egg quali ty. The ease of peeling the eggshell and the smoothness of the
albumen sur' raOL i1provc-d ',ith tl.h age arnd/or increase in the p! of the egg.
The delay between peeling the hard-cookled egg and using it in a food
product or as a food allows for growth of microorganisms. Peeled eggs
held at 25C. for four days increased from zero to 1.0 x 108 organisms per
gram of egg. Storage at 50C. did not result in a measurable amount of
Five egg pickling recipes were studied in this investigation ("Red
Beet", "Dill Egg", 'Dark and Spicy", "Kansas Spicy" and "Sweet and Sour"),
prepared from natural spices and ingredients. The egg pickling solutions
required a minincal amiount of heat processing for pasteurization. Microbial
assay showed that the greatest contamination was from the peeled hard-cooked
eggs. However, within a short time the highly acidic pickling solution
destroyed a majorityy of ill viable microorganisms. The pl of the pickling
solutions was increased by the addition of alkaline hard-cooked eggs until
an equilibrium pH was reached. The lower the ratio of solution to eggs
the higher the pH at equilibrium. A miniiiiium ratio of solution to egg
would be 1.6:1 (v/w) for an equilibriumi piH of 4.0. The shift in pH of the
pickling solution was similar to the dilution of acetic acid.
"Red Beet", "Dark and Spicy" and "Dill Egg" pickled eggs were subject
to a 14-vweek storage at 220C. and 4C. and quality was assayed by a taste
panel. Only "Dill Egg" maintained its quality at 22C. storage. However,
only "Red Beet" pickled eggs did not store well at 4C. The greatest
defects were discoloration of the albumen and development of off-flavor in
the region of the yolk.
The "Red Beet" egg pickling solution .:as found to be differentially
absorbed by the hard-cooked egg albumen. The chalaza and the thick white
did not absorb as much pigment as the thin white, and appeared lighter pink
in color. This stainirn technique may be used as a method to observe the
relation of the albumen layers with a minimum of distortion and destruction.
Three pickled egg recipes ("Dill Egg", "Kansas Spicy" and "Sweet and
Sour") of the five recipes of pickled quail eggs were equally well accepted
by taste panelists. This indicated that pickled quail eggs are an acceptable
market product. liie acceptance of an individual pickled egg recipe was due
to the type of seasoning spice and the color of the pickled eggs.
Pickled eggs are an effective means of utilizing small and pee wee size
eggs, which are under-utilized today. It is also a feasible method of
marketing cunlmercially a hard-coo!,ed egg product.
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