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Impact of egg handling and conditions during extended storage on egg quality

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The international trade of shell eggs has become more important in recent years in order to feed a growing worldwide population, meet food manufacturing demands, and address supply issues during disease outbreaks or product recalls. The primary barriers for the export and import of shell eggs are: whether to wash eggs and egg storage temperature. The current study was undertaken to compare egg quality factors as influenced by egg washing and storage temperature. Three lots of nest run white shell eggs were collected on consecutive d from a commercial in-line egg production facility. The treatment and storage conditions were selected to encompass the primary egg handling and storage conditions utilized throughout the world: washed; washed, oiled; and unwashed stored at 4°C; and unwashed stored at 22°C. Eggs were assessed weekly from 0 to 15 wk. Percent egg weight loss was greatest for the unwashed 22°C eggs (15.72%) and least for washed, oiled 4°C (0.33%, P < 0.0001). Less than 24 h at 22°C had a greater impact on yolk shape measurements decline than 15 wk at 4°C (P < 0.05). After 15 wk, average Haugh unit scores for all refrigerated treatments were still Grade A, and unwashed 22°C dropped from Grade AA to almost Grade B in one week. Room temperature storage of eggs rapidly declines egg quality. Egg treatment did not impact egg quality factors when stored at 4°C. Washing and oiling eggs before refrigerated storage did suppress the rate of egg weight loss.
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Impact of egg handling and conditions during extended storage on egg quality
D. R. Jones,,1G. E. Ward,,P. Regmi,and D. M. Karcher
USDA Agricultural Research Service, US National Poultry Research Center, Athens, GA; Department of
Poultry Science, University of Georgia, Athens, GA; and Department of Animal Sciences, Purdue University,
West Lafayette, IN
ABSTRACT The international trade of shell eggs has
become more important in recent years in order to feed
a growing worldwide population, meet food manufac-
turing demands, and address supply issues during dis-
ease outbreaks or product recalls. The primary barriers
for the export and import of shell eggs are: whether to
wash eggs and egg storage temperature. The current
study was undertaken to compare egg quality factors
as influenced by egg washing and storage temperature.
Three lots of nest run white shell eggs were collected on
consecutive d from a commercial in-line egg production
facility. The treatment and storage conditions were se-
lected to encompass the primary egg handling and stor-
age conditions utilized throughout the world: washed;
washed, oiled; and unwashed stored at 4C; and un-
washedstoredat22
C. Eggs were assessed weekly from
0 to 15 wk. Percent egg weight loss was greatest for
the unwashed 22C eggs (15.72%) and least for washed,
oiled 4C (0.33%, P<0.0001). Less than 24 h at 22C
had a greater impact on yolk shape measurements de-
cline than 15 wk at 4C(P<0.05). After 15 wk, average
Haugh unit scores for all refrigerated treatments were
still Grade A, and unwashed 22C dropped from Grade
AA to almost Grade B in one week. Room temperature
storage of eggs rapidly declines egg quality. Egg treat-
ment did not impact egg quality factors when stored at
4C. Washing and oiling eggs before refrigerated storage
did suppress the rate of egg weight loss.
Key words: egg, washing, oiling, storage, quality
2018 Poultry Science 0:1–8
http://dx.doi.org/10.3382/ps/pex351
INTRODUCTION
The washing of eggs for human consumption has
been a topic of debate for over 50 years. The United
States was the first country to require the washing of
table eggs destined to consumers. US washing stan-
dards require the use of spray washers, warm water,
warm sanitizing rinse, and high-velocity air drying.
Japan and Australia also have adopted egg-washing
practices, while many countries—including the United
Kingdom and EU—have resisted the practice. The
United States began washing eggs in an effort to
reduce egg spoilage (Moats, 1978). Specific require-
ments such as wash water temperature (32Cor11
C
warmer than warmest egg) and 100 to 200 ppm chlo-
rine sanitizing rinse (USDA, 2008) were put in place
to deter the potential movement of organisms on the
shell surface from entering through the pores during
washing.
Historic concerns associated with the washing of ta-
ble eggs have focused on the removal of the cuticle.
Published by Oxford University Press on behalf of Poultry Science
Association 2017. This work is written by (a) US Government em-
ployee(s) and is in the public domain in the US.
Received September 22, 2017.
Accepted October 25, 2017.
1Corresponding author: deana.jones@ars.usda.gov
The cuticle serves as the first line of defense on an in-
tact egg to water, gas, and microbial movement through
the pores. Washing was regarded as an impediment to
cuticle integrity, which would then result in greater ex-
ternal microbial penetration and rapid loss in egg qual-
ity. More modern shell and cuticle analysis has resulted
in researchers reporting both cuticle damage and no
change in cuticle structure due to washing (Kim and
Slavik, 1996; Wang and Slavik, 1998; Leleu et al., 2011;
Gole et al., 2014a,b; Liu et al., 2016).
Over the past 20 yr, there have been drastic changes
in laying hen housing, production, and management
throughout the world. Furthermore, food safety con-
cerns have resulted in additional changes in con-
sumer egg-handling practices. The interest in inter-
national trade of table eggs and breaking stock for
further processed products has increased in recent
year, due in part to the impact of highly pathogenic
avian influenza and other production-related concerns
on egg availability in impacted areas of the world.
Differences in egg handling, processing, and storage
practices around the world have presented barriers
in the international trade of table eggs and break-
ing stock. The current study was conducted to as-
sess the impact of commonly practiced egg han-
dling and storage conditions on physical egg quality
characteristics.
1
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2JONES ET AL.
Table 1 . Explanation of egg treatment and storage condition.
Treatment name Washed Oiled
Storage
temperature
Was h ed 4CYesNo4
C
Washed, oiled 4CYes Yes 4
C
Unwashed 4CNoNo 4
C
Unwashed 22CNoNo 22
C
MATERIALS AND METHODS
Egg Collection and Treatment
White shell eggs were collected on 3 consecutive days
from a single flock at a commercial in-line shell egg
production facility. Each day (replicate), 1,800 nest run
eggs were collected and placed in refrigerated storage
(<7C) in accordance with US law (FDA, 2009). On
the third day of collection, all eggs were transported to
the research location and placed in 4C overnight before
initiating assignment to treatments.
Eggs were assigned to one of 4 treatments: washed,
4C storage; washed, oiled, 4C storage; unwashed,
4C storage; and unwashed, 22C storage (Table 1).
Eggs assigned to washed treatments were washed as
described by Jones et al. (2014)accordingtoUSDA
voluntary requirements (USDA, 2008)withawash
water temperature of approximately 48C and pH
11. Eggs assigned to the washed and oiled treat-
ment were placed on rollers and lightly misted with
a food-grade mineral oil (Lineleer 5; Linder Oil Com-
pany, Ossian, IN) after drying. Eggs were assessed by
a USDA Agricultural Marketing Service egg grader,
and downgrades (cracks, loss, or B grade as defined
in USDA, 2000) were removed before storage was
initiated.
After treatment, all eggs were placed in appropri-
ately labeled, clean, foam, 12-egg cartons. Cartons were
then placed in cardboard cases, each containing 30
dozen eggs from each treatment/replicate combination.
An additional 36 eggs (3 cartons) from each treat-
ment/replicate combination were grouped according to
storage temperature and placed in cardboard cases for
egg weight loss determination.
Egg Quality Determinations
Egg Weight Loss Thirty-six eggs from each
treatment/replicate combination were numbered and
weighed, and total volume of shell was determined
(VSP300, Texture Technologies, Hamilton, MS) accord-
ing to the methods of Jones et al. (2017). Week 0
measurements were made immediately after treatment.
Eggs were then placed in the appropriate storage envi-
ronment according to treatment assignment. The same
eggs were weighed weekly throughout the 15 wk of stor-
age. If an egg became cracked during the course of the
study, the data associated with the egg was removed
from the data set before analysis. Volume of shell and
egg weight was utilized to calculate specific density
(g/ml) and percent weight loss.
Physical Egg Quality Each week of storage, up to
24 intact eggs from each treatment/replicate combina-
tion were assessed for a variety of physical quality fac-
tors. Week 0 assessments were conducted the day after
treatments were assigned to ensure eggs equilibrated
to storage temperatures, since many egg quality factors
are highly influenced by egg temperature (Keener et al.,
2006). Egg physical quality assessments were conducted
according to the methods of Jones et al. (2017): static
compression shell strength and deformation, albumen
height, Haugh unit, yolk index, and vitelline membrane
strength and deformation.
Briefly, static compression shell strength was mea-
sured with a texture analyzer (TA-XTplus, Texture
Technologies) equipped with a 10 kg load cell and
7.6 cm diameter aluminum compression disc (TA-30,
Texture Technologies). The egg was presented on its
side in an egg holder with posts (TA-650, Texture Tech-
nologies). A test speed of 2 mm/s and trigger force of
0.001 kg were utilized. Albumen height and Haugh unit
(Haugh, 1937) were assessed with a TSS QCD system
(Technical Services and Supplies, Dunnington, York,
UK).
Yolk index was determined by measuring yolk height
with a tripod micrometer (S-6428, B.C. Ames, Inc.,
Melrose, MA) and yolk width with a digital microm-
eter (Thermo Fisher Scientific, www.fishersci.com).
The yolk was separated from albumen before vitelline
membrane strength and deformation were measured
with a texture analyzer (TA-XTplus, Texture Tech-
nologies) equipped with a 1 kg load cell and 7.6
diameter aluminum compression disc (TA-30, Tex-
ture Technologies) according to the procedures of
Jones et al. (2010).
Statistical Analysis
Data collected during the study were subjected to
an analysis of variance (ANOVA) utilizing proc GLM
analysis in SAS (SAS Institute, 2002). Treatment, repli-
cate, and wk of storage were the main effects. Up
to n = 384 intact eggs were analyzed for each treat-
ment/replicate combination during physical quality as-
sessment. Weight loss was calculated on an individual
egg basis and was converted to a percentage change
in weight before analysis. Means were separated by
the least square method. Egg physical quality mea-
surements were monitored for the unwashed 22C eggs
through 6 wk of storage, ceasing the measurements be-
cause egg quality had declined past the point of mini-
mum detection limits. Therefore, egg quality statistical
analysis was conducted in two phases: 0 to 6 wk of stor-
age for all treatments and 0 to 15 wk of storage for the
refrigerated treatments.
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EGG WASHING AND STORAGE IMPACTS ON QUALITY 3
(a)
(b)
Figure 1. Interaction of treatment and extended storage (P
<0.0001) on egg weight (a) and specific density (b).
RESULTS AND DISCUSSION
Egg Weight and Specific Density
The interaction of treatment and week of storage (P
<0.0001) on egg weight and specific density is shown in
Figure 1. The greatest decline in egg weight and specific
density is seen in the unwashed 22C treatment, with
the slightest change seen in the washed, oiled 4C eggs.
The washed and unwashed 4C eggs were similar in
response, with the washed eggs having a slightly heavier
egg weight and unwashed eggs having a slightly greater
specific density.
The percentages of weight loss during storage for each
treatment are presented in Tables 2to 4. The monthly
cumulative percentage of egg weight loss is shown in
Table 2. Washed, oiled, refrigerated eggs had the least
weight loss each month, while the unwashed room tem-
perature eggs had the greatest (P<0.0001). Washed
and unwashed refrigerated eggs experienced similar cu-
mulative weight loss throughout the storage period,
with the washed eggs having slightly less cumulative
weight loss each month. At the end of the 15-week
storage period, cumulative percentage weight losses (P
<0.0001) for the treatments were 0.33%, washed, oiled
4C; 1.51 and 1.59% washed and unwashed 4C, re-
spectively; and 15.72% unwashed 22C. Oliveria et al.
(2009) and Aygun and Sert (2013) placed unwashed
eggs in refrigerated and room temperature storage and
found a much higher percent weight loss than the cur-
rent study. Conversely, the percent weight loss for the
washed and unwashed refrigerated eggs in the current
study is similar to that reported by Keener et al. (2006)
for commercially washed eggs during refrigerated
storage.
The rate of egg weight loss among the treatments
during each month of storage is shown in Table 3.
As with previous discussions of egg weight loss, the
washed, oiled, refrigerated eggs experienced very little
weight loss each month (greatest change in weight was
0.17%) compared to the other treatments (P<0.0001).
The rate of weight loss each month was almost identical
for the washed and unwashed refrigerated eggs. The
unwashed room temperature eggs experienced 4.5 to
5.5% weight loss each month through 12 wk of storage.
This monthly percent weight loss is similar to the
findings of Pujols et al. (2014) for unwashed room
temperature eggs. Weight loss slowed for all treatments
between 12 to 15 wk of storage. While this was only
a 3-week storage period, the rates of weight loss seen
for all treatments were at least half of the previous
4-week period, indicating a slowing of egg weight loss
after 12 wk of storage, regardless of treatment and
storage temperature. Differences in weight loss between
the replicate sets of eggs occurred in the second and
fourth month of storage (Table 4;P<0.05). Each
time differences between replicates occurred, replicate
2 had a lower rate of change in egg weight, but the
differences were <0.1%. For a 56 g egg, this would be
56 mg, which is not practical for detection by standard
open-top laboratory balances and not perceivable.
Table 2 . Percent loss of egg weight during defined lengths of egg storage at refrigerated and
non-refrigerated temperatures.
Treatment
0 to 4 wks
(% loss)
0to8wks
(% loss)
0to12wks
(% loss)
0to15wks
(% loss)
Was h ed 4C0.48
b±0.04 0.86b±0.07 1.32b±0.10 1.51b±0.11
Washed, oiled 4C0.17
c±0.05 0.19c±0.07 0.30c±0.10 0.33c±0.12
Unwashed 4C0.58
b±0.04 0.94b±0.07 1.40b±0.10 1.59b±0.11
Unwashed 22C4.67
a±0.04 8.91a±0.07 13.78a±0.10 15.72a±0.11
P-value 0.0001 0.0001 0.0001 0.0001
a-c: Means within a column with different letters significantly different; P<0.05.
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4JONES ET AL.
Table 3 . Rate of egg weight loss throughout extended egg storage at refrigerated and non-
refrigerated temperatures.
Treatment
0 to 4 wks
(% loss)
4to8wks
(% loss)
8to12wks
(% loss)
12 to 15 wks
(% loss)
Was h ed 4C0.48
b±0.04 0.37b±0.03 0.47b±0.04 0.19b±0.02
Washed, oiled 4C0.17
c±0.05 0.02c±0.03 0.11c±0.04 0.03c±0.02
Unwashed 4C0.58
b±0.04 0.35b±0.03 0.47b±0.04 0.19b±0.02
Unwashed 22C4.67
a±0.04 4.45a±0.03 5.35a±0.04 2.25a±0.02
P-value 0.0001 0.0001 0.0001 0.0001
a-c: Means within a column with different letters significantly different; P<0.05.
Table 4 . Rate of egg weight loss throughout extended storage as influenced by egg replicate
groups.
Treatment
0 to 4 wks
(% loss)
4 to 8 wks
(% loss)
8to12wks
(% loss)
12 to 15 wks
(% loss)
Rep 1 1.51 ±0.03 1.36a±0.03 1.65 ±0.03 0.69a±0.02
Rep 2 1.47 ±0.04 1.26b±0.03 1.54 ±0.04 0.63b±0.02
Rep 3 1.45 ±0.04 1.28b±0.03 1.61 ±0.03 0.68a±0.02
P-value NS 0.05 NS 0.05
a,b: Means within a column with different letters significantly different; P<0.05.
Table 5 . Treatment and storage condition impacts on egg physical quality factors average values during 6 wk of storage.
Treatment Haugh unit
Yolk height
(mm)
Yolk width
(mm) Yolk index
Shell
strength
(g force)
Vitelline
membrane
strength
(g force)
Vitelline
membrane
deformation
(mm)
Was h ed 4C 82.1 21.4 40.2 0.53 4214.2 155.7 7.8
Washed, oiled 4C 82.1 21.6 40.2 0.53 4275.0 151.7 7.7
Unwashed 4C 83.1 21.7 40.1 0.54 4280.4 155.0 7.8
Unwashed 22C 45.5 14.8 44.6 0.34 4299.8 129.9 4.8
SEM ±0.31 ±0.04 ±0.07 ±0.001 ±28.7 ±2.25 ±0.05
∗∗∗∗ ∗ ∗
: Treatment x week interaction; P<0.0001.
∗∗∗∗: Treatment x week x replicate interaction; P<0.0001.
Physical Egg Quality
All Treatments 0 to 6 wk of Storage After 6 wk
of storage, egg physical quality characteristics were be-
low detectable limits for the unwashed 22C treatment.
As such, analysis of physical egg quality characteris-
tics comparing all 4 treatments was limited to 0 to
6 wk of storage. The average egg quality values across
this storage period by treatment are presented in
Table 5. Shell strength was not influenced by treatment
or week of storage (P>0.05). There was a difference (P
<0.05) in static compression shell strength values be-
tween replicate sets of eggs: replicate 1: 4208.4bg force;
replicate 2: 4291.8ab g force; and replicate 3: 4301.8ag
force; ±25 g SEM. While the numeric values for shell
strength were different, practically the 100 g force range
between average replicate values would not be perceiv-
able by consumers or further processed egg products
manufacturers.
Both albumen height and Haugh unit were mon-
itored throughout the study. Analysis of this data
found the same trends, and thus only Haugh unit
values are presented for brevity. The interaction of
treatment x week of storage x replicate influenced (P
<0.0001) Haugh unit values (Figure 2). The lines
Figure 2. Interaction of treatment x extended storage x replicate
(P<0.0001) on Haugh unit scores; 0 to 6 wk of storage (replicates for
each treatment in corresponding color line indicated by 1 = solid, 2 =
dotted, and 3 = dashed).
delineating egg grades shown in Figure 2are based
on USDA grade standards (USDA, 2000). The re-
frigerated treatments/replicate combinations (washed,
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EGG WASHING AND STORAGE IMPACTS ON QUALITY 5
washed and oiled, and unwashed) followed a simi-
lar trend in Haugh unit scores through the 6-week
storage period. In general, at the end of the 6-week pe-
riod, refrigerated treatments remained AA grade (with
washed, oiled replicate 1 eggs having an average Haugh
unit score 70.3 = A grade). Unwashed 22C eggs had a 0
wk Haugh unit score of approximately 83, compared to
a value of approximately 87 for the refrigerated treat-
ments. This difference was due to <24 h storage at
22Cvs.4
C. After one week of storage, all refriger-
ated treatments had Haugh scores >83, whereas room
temperature eggs had scores at or below the minimum
for A grade classification (72 >Agrade60; USDA,
2000). Waimaleongora-Ek et al. (2009) stored unwashed
eggs at room temperature and found a 30-point drop in
Haugh unit scores after one wk, and Pujols et al. (2014)
reported a 12-point drop under the same conditions. In
the current study, unwashed 22C eggs had an average
23-point drop in Haugh unit scores at one week. The 3
wk and 5 wk sample times of Pujols et al. (2014)had
similar Haugh unit scores for unwashed room tempera-
ture eggs as the current study.
Yolk shape measurements were influenced by treat-
ment x week of storage interaction (P<0.0001; Fig-
ure 3). As was seen with Haugh unit scores, the <24 h
storage at 22Cvs.4
C resulted in a 2 mm difference in
initial yolk height and yolk width measurements (Fig-
ures 3aand3b). This corresponded to a 0 wk yolk index
scoreof0.54for4
C treatments compared to 0.46 for
22C treatment. Through the 6 wk of storage, all re-
frigerated treatments had consistent yolk height, yolk
width, and yolk index values. The room temperature
eggs experienced a 7 mm reduction in yolk height, 5 mm
increase in yolk width, and 0.20 reduction in yolk in-
dex (45% reduction). Waimaleongora-Ek et al. (2009)
found similar changes in yolk index for unwashed eggs
stored at room temperature. During the 6 wk of stor-
age that all treatments were compared, eggs from the 3
refrigerated treatments never experienced yolk height,
yolk width, or yolk index values comparable to the 0 wk
values of the room temperature treatment. Therefore,
yolk shape measurements detected after 24 h at room
temperature were of poorer quality than those seen in
all 3 refrigerated treatments after 6 wk of storage.
Vitelline membrane force and deformation (elastic-
ity) were impacted by the interaction of treatment x
week of storage (Figure 4;P<0.0001). Unlike Haugh
unit and yolk shape measurements, vitelline membrane
strength for 0 wk was not different among the treat-
ments (Figure 4a). Vitelline membrane strength did de-
crease for all treatments over the 6 wk of storage, with
the 22C eggs experiencing a larger change (approxi-
mately 85 g force) compared to the 3 refrigerated treat-
ments (approximately 18 g force). The average deforma-
tion or elasticity of the vitelline membrane decreased
less than 1 mm for all the refrigerated treatments over
the 6 wk of storage, whereas the room temperature
treatment experienced a greater than 3 mm decline in
elasticity, indicating a more brittle membrane.
(a)
(b)
(c)
Figure 3. Interaction of treatment and extended storage (P
<0.0001) on yolk height (a), yolk width (b), and yolk index (c); 0
to6wkofstorage.
Refrigerated Treatments 0 to 15 wk Storage The
average egg quality values for each of the refriger-
ated treatments over 15 wk of storage are presented in
Table 6. Most egg quality parameters had significant
interactions among the main effects. Static compres-
sion shell strength was different (P<0.05) between
the treatments with the washed, oiled and unwashed
eggs having the greatest strength (4331.7 and 4299.4 g
force, respectively) compared to the washed (4216.4 g
force) eggs. As with the previous comparison among
all the treatments over 0 to 6 wk of storage, replicate
1 (4211.1 g force) eggs had lower (P<0.05) static
compression shell strengths compared to replicates 2
(4301.1 g force) and 3 (4335.2 g force), which were
similar.
Throughout the 15 wk of storage, Haugh unit values
had a general downward trend (Figure 5; refrigerated
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6JONES ET AL.
(a)
(b)
Figure 4. Interaction of treatment and extended storage (P
<0.0001) on vitelline membrane strength (a) and deformation (b);
0to6wkofstorage.
treatment x week of storage x replicate interaction; P
<0.05). All treatments were still A grade (USDA, 2000)
after 15 wk storage at 4C. Replicate 1 eggs from each
treatment (indicated by solid line of appropriate color
for treatment) reached A grade before replicates 2 (dot-
ted line) and 3 (dashed line). On average, refrigerated
treatments were grade AA through 8 wk of storage.
None of the refrigerated treatments was overall supe-
rior compared to the others for maintaining egg quality
in regards to Haugh unit scores. Liu et al. (2016) stored
washed and unwashed eggs in refrigeration and reported
greater Haugh unit scores in unwashed eggs. This was
not seen in the current study.
The impact of refrigerated treatments x week of stor-
age interactions on yolk shape measurements is pre-
Figure 5. Interaction of refrigerated treatment x extended storage
x replicate (P<0.05) on Haugh unit scores; 0 to 15 wk of storage
(replicates for each treatment in corresponding color line indicated by
1 = solid, 2 = dotted, and 3 = dashed).
sented in Figure 6(P<0.05). Over the 15 wk of 4C
storage, a slight decline in yolk height was observed
(Figure 6a). The greatest yolk heights were 22 mm at
the beginning of the study, and the lowest were 20.8 mm
towards the end of the study. Yolk width remained fairly
constant with the lowest and highest values (39.5 and
41 mm, respectively) occurring during the middle of
the storage period (Figure 6b). Yolk index (Figure 6c)
gradually declined from the greatest value of 0.54 to the
lowest value of 0.52 over the course of the 15 wk at 4C.
All of the yolk shape characteristics monitored exhib-
ited only minor changes over the course of the 15 wk of
storage with no particular treatment having preferable
yolk shape characteristics.
Vitelline membrane strength and deformation, as in-
fluenced by refrigerated treatment x week of storage in-
teractions (P<0.05), are presented in Figure 7.As4
C
progressed, vitelline membrane force values decreased
approximately 50 g (Figure 7a) from a high of 170 g
force to a low of 120 g force. Only a slight decrease
in vitelline membrane deformation (elasticity) was seen
during the 15 wk of storage (8.15 to 7 mm; Figure 7b).
As with other egg physical quality measurements
Table 6 . Refrigerated treatment and length of storage impacts on egg physical quality factors average values
during 15 wk of storage.
Treatment Haugh unit
Yolk height
(mm)
Yolk width
(mm) Yolk index
Shell
strength
(g force)
Vitelline
membrane
strength
(g force)
Vitelline
membrane
deformation
(mm)
Was h ed 4C 76.2 21.3 40.4 0.53 4216.4b142.7 7.5
Washed, oiled 4C 76.5 21.4 40.3 0.53 4331.7a145.2 7.6
Unwashed 4C 76.4 21.4 40.3 0.53 4299.4a143.6 7.6
SEM ±0.17 ±0.03 ±0.04 ±0.001 ±19.2 ±1.28 ±0.03
∗∗∗∗ ∗ ∗
a,b: Means within a column with different letters are significantly different; P<0.05.
: Treatment x week interaction; P<0.05.
∗∗∗∗: Treatment x week x replicate interaction; P<0.05.
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EGG WASHING AND STORAGE IMPACTS ON QUALITY 7
(a)
(b)
(c)
Figure 6. Interaction of refrigerated treatment and extended stor-
age (P<0.05) on yolk height (a), yolk width (b), and yolk index (c);
0to15wkofstorage.
compared across the washed; washed, oiled; and un-
washed eggs stored for 15 wk at 4C, no treatment had
a more or less favorable outcome on vitelline membrane
strength or deformation.
In all quality factors monitored over the course of
this storage study, the unwashed 22C had remarkably
lower egg quality after 6 wk of storage compared to
4C eggs after 15 wk of storage, regardless of treat-
ment. Average Haugh unit scores after 15 wk of 4C
storage were 64.5 (washed), 67.3 (washed, oiled), and
63.3 (unwashed). The unwashed 22C eggs had an av-
erage Haugh unit score of 60.6 after one wk of storage.
Average yolk height for all of the 4C treatments af-
ter 15 wk of storage was approximately 21 mm. The
unwashed 22C eggs had an average yolk height of
19.2mmat0wk(
<24 h at 22C before testing).
Yolk diameter and yolk index values followed a simi-
lar trend in that the lowest quality measurements for
the 4C treatments occurred at 15 wk of storage, and
these values were superior to the 0 wk measurements
for the 22C eggs after less than 24 h at room temper-
ature. Average vitelline membrane force after 15 wk of
(a)
(b)
Figure 7. Interaction of refrigerated treatment and extended stor-
age (P<0.05) on vitelline membrane strength (a) and deformation
(b); 0 to 15 wk of storage.
4C storage were 124.5 g force (washed), 132.7 g force
(washed, oiled), and 117.5 g force (unwashed). Similar
average vitelline membrane force values were found in
the unwashed 22C eggs at 3 and 4 wk of storage (127.8
and 121.9 g force, respectively). Average vitelline mem-
brane deformation for all refrigerated treatments were
between 7.2 and 7.5 mm at 15 wk of storage, which
was greater than the 0 wk value of 7.0 mm for the un-
washed 22C eggs. Among the refrigerated treatments,
the only significantly different quality factor was per-
cent weight loss. The washed and oiled eggs stored at
4C experienced a cumulative 0.33% weight loss com-
pared to 1.51 and 1.59% for the washed and unwashed
4C treatments, respectively. The unwashed 22Chada
15.72% weight loss over the 15 weeks. The washed and
oiled 4C eggs had a significantly lower rate of weight
loss at all analyzed intervals of storage compared to all
treatments.
Research findings conflict on egg washing and sub-
sequent cuticle integrity (Kim and Slavik, 1996;Wang
and Slavik, 1998; Leleu et al., 2011; Gole et al., 2014a,b;
Liu et al., 2016). Cuticle damage is thought to lead
to greater percent weight loss and quality decline dur-
ing refrigerated or room temperature storage. Cuticle
integrity was not assessed in the current study, but
washed and unwashed refrigerated eggs experienced
similar rates of egg weight loss throughout 15 wk of
storage. Washed, oiled, refrigerated eggs did have a
significantly lower rate of egg weight loss. Washing,
washing and oiling, or not washing did not impact
egg physical quality measurements in the current study
when eggs were stored in refrigeration.
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8JONES ET AL.
Refrigerated storage had the greatest impact on
maintaining egg quality factors. Less than 24 h at 22C
had a more profound impact on most yolk quality fac-
tors than 15 wk at 4C. Eggs that were washed and
oiled before 4C storage consistently had the lowest
weight loss of the treatments throughout the study,
with washed and unwashed eggs stored at 4Chav-
ing similar percent weight loss. Storing unwashed eggs
at 22C resulted in rapid percent weight loss and egg
quality decline.
ACKNOWLEDGMENTS
Inspection and grading services during treatment as-
signment were provided by Eric Saxton (USDA Agri-
cultural Marketing Service; Livestock, Poultry and Seed
Program). The authors appreciate the technical contri-
butions of Stephen Norris and Robin Woodroof (USDA,
Agricultural Research Service) and Kailynn VanDeWa-
ter (Purdue University). Student technical support was
provided by Emily Elder (Athens Academy) and Shaan
Guraya (Oconee County High School) through a stu-
dent intern volunteer program.
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