EDUCATION AND PRODUCTION
Egg Marketing in National Supermarkets: Egg Quality—Part 1
D. D. Bell,*,1 P. H. Patterson,† K. W. Koelkebeck,‡ K. E. Anderson,§ M. J. Darre,储 J. B. Carey,#
D. R. Kuney,** and G. Zeidler*
*Department of Animal Sciences, University of California, Riverside, California 92521; †Department of Poultry Science, The
Pennsylvania State University, University Park, Pennsylvania 16802; ‡Department of Animal Sciences, University of Illinois
at Urbana-Champaign, Urbana, Illinois 61801; §Department of Poultry Science, North Carolina State University, Raleigh,
North Carolina 27695; 储Department of Animal Science, University of Connecticut, Storrs, Connecticut 06269; #Department
of Poultry Science, Texas A&M University, College Station, Texas 77843; **University of California Cooperative Extension,
21150 Box Springs Road, Moreno Valley, California 92557
ABSTRACT Two surveys were conducted to determine
the quality of eggs offered to consumers in large supermarkets in various regions of the US. The first survey
was conducted in California (CA) in 1994 and included
38 samples of large (L) and extra large (XL) white eggs
in 15 markets. Individual eggs were weighed, candled,
and broken out for Haugh unit (HU) determination. Regional differences in age of eggs, the number of eggs
below 55 HU, and the percentage of cracked eggs were
observed. The second survey was conducted in California
(CA), Illinois (IL), Pennsylvania (PA), Texas (TX), North
Carolina (NC), and New England (NE). This study included brown and white eggs and samples from 115
stores in 38 cities. Significant age, egg weight, HU, and
cracked egg differences were observed between states.
Brown and white eggs were different relative to age and
HU, but egg weights and cracked eggs were statistically
the same. The two surveys, 1994 and 1996, within CA
demonstrated very similar measurements when L-white
eggs were compared.
(Key words: egg marketing, retail, egg quality, egg breakage)
2001 Poultry Science 80:383–389
Egg handling, processing, and marketing methods are
constantly changing as new technologies are developed
and adopted. In 1991, it was estimated that 81.4% of
all table eggs produced in the US were mechanically
gathered, and by 2000, this number would increase to
almost 92% (Bell, 1993). Today, practically all new layer
houses are equipped with mechanical egg gathering systems. In the same study, it was estimated that 47.1% of
all egg production came from in-line systems where eggs
are never touched by hand and that by 2000, 67.1% of
production would use this technology.
Along with these trends, the number of companies
producing eggs and the number of flocks have decreased, whereas the number of hens per company and
the average flock size have increased. In 1978, 34 companies owned one million or more layers, which represented 27% of the nation’s layers. Today, Egg Industry
magazine (Anonymous, 1999) estimates that 78% of the
laying hens in the U.S. are owned by only 61 companies
with greater than 1 million hens, and those companies
average more than three million hens each. These ownership and size-of-company trends have resulted in major
changes in the way eggs are handled from the packaging
plant to the retail outlet.
Very few studies of the way eggs are handled from
the packaging plant to the retail store or of the quality
of eggs available to the consumer have been conducted
during the past 50 yr in the U.S. An early study of egg
marketing in the Los Angeles area of California (CA)
indicated that by the time eggs reached the consumer,
they were 7 to 9 d old, and the interior quality had
deteriorated to the point that “the white is irregular in
shape and tends to flatten out” (Erdman et al., 1941). It
was stated that many egg producers were using evaporative coolers to cool their eggs and that leading distributors had installed merchandising refrigerators, even
though this was not a common practice at this time.
One of the more thorough studies of consumer egg
quality was conducted in 1958 by Virginia Polytechnic
Institute researchers (Buck, 1963). Eggs were purchased
from 39 different retail food stores in a single Virginia
city, and egg quality measurements were made. Large
Received for publication May 9, 2000.
Accepted for publication November 20, 2000.
1
To whom correspondence should be addressed: [email protected].
Abbreviation Key: CA = California; HU = Haugh unit; IL = Illinois;
L = large; NE = New England; N-CA = Northern California; PA =
Pennsylvania; S-CA = Southern California; TX = Texas; XL = extra large.
INTRODUCTION
383
384
BELL ET AL.
(L) eggs were determined to be 4.3 d old at the time of
consumer purchase. These eggs had 1.6% cracked or
leaking eggs as determined by noncandling observation.
Interior quality averaged 56 Haugh units (HU). Refrigerated eggs averaged five HU higher than those not refrigerated.
Surveys of egg quality in Australian stores demonstrated significant differences when summer and winter
months were compared (Hughes, 1982). Eggs were approximately 8 to 10 d old when sampled in retail stores.
Summer eggs were found to average 56 HU compared
to winter eggs at 65 HU. The retail trade practiced a 21d “use by” policy, and few stores used refrigerated
storage.
Other researchers have attempted to duplicate the
conditions observed in commercial practice in their laboratories and have measured complex relationships of
the effects of storage time, holding temperatures, oiling,
and packaging materials on egg quality deterioration.
Washington State researchers studied the combined effects of storage time and temperature on interior quality
(Baum, et al., 1960). Their results indicated that at a
storage temperature of 10 C (50 F), egg quality, as measured by HU, decreased by one unit for each day in
storage. Eggs with an initial interior quality of 80 HU
would be expected to decline to 70 HU in 10 d.
Sabrani and Payne (1978) studied the combined effects
of flock age, storage temperature, and oiling on interior
quality and egg weight loss as affected by the duration
of storage. Oiling and lower temperatures maintained
significantly higher HU and egg weight compared to
not oiling and higher temperatures. Eggs produced by
60 wk-old flocks and stored for 12 d at 12 C (54 F)
averaged 70 HU compared to 26 HU in nonoiled eggs
stored at 28 C (82.4 F). Under the same conditions, the
oiled eggs stored at the lower temperature lost 0.22% of
their original weight compared to 3.09% for the nonoiled
eggs stored at 28 C. Interior quality losses averaged 1.04
HU per day for nonoiled eggs compared to 0.41 HU per
day for oiled eggs.
Other researchers in Australia studied the question of
optimum egg collection intervals relative to storage time
and temperature (Macindoe, 1981). Eggs were collected
and held at 35 C (95 F) for 4, 8, 24, and 48 h to simulate
different egg collection intervals. Unoiled eggs were
stored at 15 C (55 F) or 30 C (86 F) for 3, 7, 14, or 21 d.
The interior quality of eggs stored at 15 C for 14 d decreased from an initial 87 to 60 HU when collected at
4-h intervals, a loss of 1.87 HU per day.
Today’s technology allows eggs to be processed the
same day the egg is laid. Electronic scales can be set to
assure accurate weights. Cracked egg detectors can reject 100% of cracked eggs, which is much more accurate
than a human operator. Rapid transportation systems
and modern retail outlets with refrigerated storage areas
and display cases should increase our ability to provide
the consumer with the freshest high quality products
possible.
The objective of this research was to document the
quality factors associated with modern merchandising
systems in use in the U.S. today. With such information,
it should be possible to single out problem areas for
now and to provide a baseline for assessments of quality
in the future.
MATERIALS AND METHODS
Survey 1
During June through November of 1994, a survey of
15 CA supermarkets was made to determine the age,
quality, and price of eggs. Three regions of the state
were chosen to represent the state. Fifteen different markets were visited in the morning hours and four onedozen cartons of eggs were purchased, representing
each brand of white L and extra large (XL) eggs in the
display case. A total of 38 four-dozen samples were used
in the study.
Most of the eggs were displayed in 15-dozen wire
baskets, and eggs selected for quality determination
were taken from the second or third layer and the center
of each layer in each basket. If one type of egg was
present in two or more baskets, the individual dozens
were taken from multiple baskets. The samples were
taken to a central location for quality measurements
during the afternoon of the day the sample was collected. The measurements included individual egg and
carton identification, single egg weights, candled egg
breakage, and HU determination. Age of the sample
was determined by coding on the cartons. USDA-graded
eggs were identified with the packing and sell-by dates.
Non-USDA samples were identified with sell-by dates,
and these were used to calculate pack dates. Current
date minus pack date yielded the approximate age of
the eggs within the carton. Forty-eight eggs were used
for egg weights and crack determination. The HU were
measured on 30 eggs per sample. Analysis was based
upon the entire sample.
Survey 2
Bell et al. (1997), Darre et al. (1997), and Patterson et
al. (1977) previously described this study, which included five states, California (CA), Illinois (IL), Pennsylvania (PA), North Carolina (NC), Texas (TX), and one
region, New England (NE). Samples were taken during
the period from June through August of 1996 in 38 cities
and 115 stores. A total of 771 dozen large white, brown,
and specialty eggs was sampled. Specialty egg results
were excluded from this report but are included in a
separate report.
The same sampling and measuring procedures described for Survey 1 were used in this survey with the
exception that three one-dozen cartons per sample were
used, and all 36 eggs were measured for HU. All data
presented in the tables and figures are based on individual carton measurements. The USDA (1990) egg weight
NATIONAL EGG QUALITY STUDY—PART 1
standards relative to individual egg and carton weights
were used in determining the number of under- and
overweight eggs.
Statistical Analysis
Separate one-way ANOVA were used to compare regions and egg size categories (L or XL), and eggs were
graded under USDA supervision (yes or no) for measurements made on a per sample basis (48 or 30 eggs)
for the first survey. One- and two-way ANOVA were
used to compare locations and egg type (white or brown)
on a per-carton basis for the second survey. In the first
survey, the samples were the replicates; in the second
survey, the individual cartons were used as replicates.
Egg ages in days were transformed to square roots and
percentages of eggs with defects (HU <55, underweight,
cracks, leaks) were transformed to the arcsin of the
square root of the proportion to homogenize the variances and normalize the data distributions for the analyses of variance. Mean separation was done with Fisher’s
Protected least significant difference test at P = 0.05,
using the harmonic mean number of cartons per treatment for the sample size.
Also, for the second survey, in addition to the ANOVA, chi-square tests of independence in two-way frequency tables were used to compare locations for percentage of cartons with serious defect levels. If the chisquare was significant, mean separation was done with
Fisher’s Protected least significant difference test at P =
0.05, using percentages transformed to the arcsin of the
square root of the proportion and an error term of 821
per harmonic mean number of cartons (Snedecor, 1967).
Linear regressions were calculated for the relationships
between egg age and weight per egg, albumen height,
and HU. Statistical analyses for both surveys were done
with SAS software (SAS, 1989).
RESULTS AND DISCUSSION
Survey 1
Sample data in Survey 1 were separated by region,
Northern (N)-CA or Southern (S)-CA; egg size (L and
XL); and whether or not the eggs were graded and packaged under USDA supervision (Table 1). Separation by
region revealed significant differences (P < 0.05) for the
age of the eggs with S-CA eggs averaging 12.7 d compared to 7.9 d for N-CA eggs. Egg quality means, as
measured by HU, were not significantly different (P
≥ 0.05) between the regions, but when measured as a
percentage of eggs below 55 HU within a sample, S-CA
eggs were significantly poorer (P < 0.05) with 22.3% of
the eggs below 55 HU compared to 9.2% for N-CA.
Previous research (Baum et al., 1960; Sabrani and Payne,
1978) has shown a loss of about one HU per day. The
current data appears to be in agreement. Significantly
(P < 0.05) more cracked eggs were produced in S-CA
(6.9%) compared to N-CA (3.6%). Egg weight, albumen
385
height, mean HU, and egg prices were not significantly
different (P ≥ 0.05).
Approximately 40% of the samples were XL eggs.
USDA weight regulations require individual L eggs to
weigh a minimum of 54.3 g and XL eggs to weigh 61.4
g. Weights per dozen, however, must average 56.7 g/
egg for L and 63.8 g/egg for XL. Average weights observed in this survey were 60.4 g for L eggs and 64.8 g
for XL eggs (P < 0.01) (Table 1). Underweight eggs are
defined as L eggs below 54.3 g/egg and XL below 61.4
g/egg. Underweight eggs averaged 4.7% for both sizes.
No significant differences (P ≥ 0.05) for any other trait
were observed relative to the size category.
The effect of USDA grading had no significant (P ≥
0.05) effect on age of eggs, egg weights, or interior quality. USDA eggs, however, had significantly higher prices
in the supermarket at $1.79/dozen compared to $1.43
(P < 0.01).
Survey 2
The 1996 survey of six U.S. regions was analyzed on
a per dozen basis for brown and white eggs. The overall
effects of shell color were also analyzed for the four
states with both types of eggs: CA, IL, PA, and TX (Table
2). Age of the eggs varied from the youngest in NE for
brown eggs (6.8 d) to the oldest in CA for brown eggs
(18.4 d). Brown eggs were significantly older (16.8 d vs.
11.9 d) than white eggs (P < 0.001). Figure 1 illustrates
the range in ages observed for combined white and
brown eggs in the survey. Twenty-five percent of the
eggs were 7 d or less in age; however, 13.8% were in
excess of 3 wk of age.
Individual egg weights for white eggs ranged from
58.4 g in PA to 60.5 g in CA. Significant differences
between locations with white eggs were observed (P <
0.05). No differences in brown egg weights were observed between locations (P ≥ 0.05) with brown and
white eggs weighing 59.6 g/egg. Cartons with underweight eggs (<54.3 g) averaged approximately 5%; however, no differences were observed between locations
or egg types (P ≥ 0.05). A significant (P < 0.001) linear
regression of egg age and egg weight was observed with
a slope of −0.060 g associated with each day of age
(Table 4).
The distribution of average egg weights is shown in
Figure 2. It is estimated that 6.2% of the cartons weighed
less than the USDA requirement for L eggs; however,
13.5% of the cartons met the USDA minimum weight
standards for XL eggs. Table 3 lists the state-by-state
averages for underweight and overweight cartons (8.1
vs. 10.5%, respectively). These means differed from the
data in Figure 2, because they were calculated as simple
means of the individual states. Texas had significantly
more (P < 0.05) underweight cartons than PA and NE
(15.9 vs. 4.2 and 5.0%, respectively).
Interior quality, as measured by HU, varied significantly (P < 0.05) between states. Illinois white eggs averaged 71.1 HU compared to 62.8 HU for white eggs in
386
BELL ET AL.
TABLE 1. California retail egg quality study results—1994 Survey 1 (based upon individual samples)1
Category
Region2
N-CA
S-CA
Egg size
L
XL
USDA6
Yes
No
Average
Age of
eggs
Weight
per egg
Underweight
eggs4
Albumen
height
(d)
(g)
(%)
(mm)
17
21
7.9
12.7*
62.5
61.9
3.9
4.0
4.8
4.6
23
15
11.1
10.1
60.4
64.8***
3.7
4.3
10
28
13.5
9.5
61.8
62.2
38
10.7
62.1
Samples3
Haugh
units
Haugh units
eggs < 55
Cracked
eggs5
Price
(%)
(%)
($/dozen)
65.1
61.4
9.2
22.3
3.6
6.9*
1.44
1.59
4.7
4.7
63.5
62.4
14.7
19.2
5.5
5.3
1.44
1.65
2.3
4.5
4.9
4.6
65.5
62.2
12.8
17.8
4.0
6.0
1.79**
1.43
3.9
4.7
63.0
16.4
5.4
1.52
Means within a column in a category are significantly different (*P < 0.05; **P < 0.01; ***P < 0.001).
Region: Northern California (N-CA), Southern California (S-CA).
3
Forty-eight eggs per sample, except 30 eggs were used for Haugh units.
4
Less than 54.3 g/egg for large eggs; < 61.4 g/egg for extra-large eggs.
5
Cracked: includes leakers.
6
USDA: under USDA supervision.
1
2
CA. Brown eggs had significantly lower HU than white
eggs (61.7 vs. 67.2, P < 0.001) and higher average age
(16.8 vs. 11.9 d, P < 0.001). The distribution of average
HU on a per-carton basis is illustrated in Figure 3. Only
30.5% of the cartons averaged >70 HU, whereas 19.5%
had <60 HU. Albumen height and HU were negatively
correlated with the age of the sample. Table 4 gives the
linear regression relationships observed (P < 0.001).
The HU means appear to be exceedingly low in relation to the age of eggs in this study and the age vs.
HU correlations listed in Table 4. Beginning HU levels
cannot be derived from the data in this survey, but typical levels may be assumed from breeder standards for
flocks of different ages. Private industry sources estimate that the average age of commercial egg laying
flocks in the U.S. in 1996 was 64 wk. Egg quality data
published by major breeders (Hy-Line International,
1996a,b, 1998; DeKalb Poultry Research, 1995, 1998) lists
HU estimates for 64-wk flocks at 82 HU.
The white egg flocks in the current study showed a
HU mean of 67.2 for 11.9-d-old eggs. This value represents an estimated loss of 1.24 HU/d compared to the
TABLE 2. Age of egg, egg quality, and egg weights by region and by shell color (B = brown, W = white), large eggs—1996 Survey 2
(based on individual cartons)
Region1
CA
IL
NC
NE
PA
TX
Shell color
(without NC and NE data)
B
W
Significance of F3
Shell color
Location × shell
Color
Shell
color
No.
of
cartons
Haugh
units
Haugh
units
eggs <55
Age
Weight
(%)
(mm)
39
117
15
81
54
15
42
108
27
33
(d)
18.4a
11.7cd
14.7cd
11.3cd
10.6d
6.8e
18.1ab
11.1d
13.7cd
16.1bc
(g)
B
W
B
W
W
B
B
W
B
W
60.2ab
60.5a
59.7ab
60.3a
59.8b
59.0bc
58.9bc
58.4c
59.5abc
59.1bc
6.7
4.0
3.3
2.6
2.5
3.4
4.2
4.2
8.7
7.3
(%)
(%)
(%)
4.4cd
4.6c
5.0b
5.5a
5.1b
4.6c
4.2d
5.1b
4.5cd
4.9b
61.1cd
62.8c
67.7b
71.5a
68.1b
64.0c
59.6d
68.9ab
62.7c
67.1b
23.1a
20.3a
8.9c
3.5d
8.3cd
18.9a
20.5a
7.0cd
23.9a
10.6bc
8.1ab
4.9bc
2.8c
4.0bc
7.4ab
9.5a
7.3ab
7.1ab
8.3ab
4.9bc
1.0
0.2
1.1
0.2
0.5
1.2
0.6
0.3
1.2
0.8
123
339
16.8a
11.9b
59.6
59.6
5.8
4.1
4.4b
5.0a
61.7b
67.2a
20.8a
11.1b
7.0
5.3
0.9a
0.3b
***
***
NS
NS
NS
NS
***
***
***
***
***
***
NS
NS
*
NS
Eggs
<54.3 g
Albumen
height
Cracked
eggs2
Means within a column across all regions with no common superscript differ significantly (P < 0.05).
Means within a column for shell color (without NC and NE data) with no common superscript differ significantly (P < 0.05).
1
CA = California; IL = Illinois; NC = North Carolina; NE = New England; PA = Pennsylvania; TX = Texas.
2
Includes cracks and leakers.
3
Means with NS are not statistically significant (P > 0.05); * and *** are significant (P ≤ 0.05 and 0.001, respectively).
a–e
a,b
Leaker
eggs
NATIONAL EGG QUALITY STUDY—PART 1
387
FIGURE 1. Distribution of egg ages; individual cartons—1996 (Survey 2).
FIGURE 3. Distribution of Haugh unit measurements; individual
cartons—1996 (Survey 2).
0.17 HU loss calculated from the HU and egg age data
in this study (P < 0.001, R2 = 0.031, Table 4). Obviously,
many other factors besides egg age affect the HU of
retail eggs. Sabrani and Payne (1978) showed similar
daily losses of HU for nonoiled eggs (1.04 HU/d). These
losses in HU would lead the authors to question the
current practice of oiling eggs in the packaging plant—
is it being done at all or is it being applied properly and
in the necessary quantity?
The incidence of cracked and leaking eggs for brown
and white eggs is listed by state and region (Table 2).
Leakers are included in the cracked egg total and are also
listed separately. USDA regulations for cracked eggs
allows up to 7% in samples at the final destination for
the eggs. Of the 10 combinations of location and shell
color listed in Table 2, six exceeded the 7% limit. Individual samples of three dozen eggs often exceeded 25%
cracks (Table 3). Mean sample results varied from 2.8%
for brown eggs in IL to 9.5% for brown eggs in NE (P
< 0.05). Locations did not differ (P ≥ 0.05) in the production of leakers, but brown eggs had more than white
eggs (0.9 vs. 0.3%, P < 0.05).
Figure 4 illustrates the frequency of various numbers
of cracked eggs (including leakers) per carton. Almost
one-half of the cartons sampled had one or more cracked
eggs, and 17% had two or more. The buyer of these eggs
would have identified the leakers without difficulty.
Leakers were present in about 5% of the cartons. The
remaining cracked eggs were cracks by legal definition
and might or might not have been detected by the
consumer.
Overall, the combined assessment of egg weight and
quality problems indicates major problems in producing
eggs that meet current regulations at destination (Table
3). Significant (P < 0.05) differences between locations
in the number of underweight cartons, cartons with
>50% of the eggs below 55 HU, and cartons with >25%
of the eggs below minimum egg weight standards were
observed, which demonstrates the ability of some processors and the inability of others to grade and transport
their eggs within current specifications. When major size
and quality defects are totaled (Table 3), IL had the
fewest overall defective cartons, whereas TX had the
most (7.9 vs. 38.1%, respectively, P < 0.05).
In general, the egg age was greater than expected,
considering what was accomplished 50 or more years
FIGURE 2. Distribution of egg weights; individual cartons − individual carton 1996 (Survey 2).
FIGURE 4. Number of cracked eggs (including leakers) per carton—
1996 (Survey 2).
388
BELL ET AL.
TABLE 3. Percentages of cartons with major weight and quality problems—1996 Survey 2
(based on individual cartons)
Region2
Trait measured
CA
NE
IL
NC
PA
TX
Region
mean
Eggs sampled (dozen)1
Underweight cartons (%) < 680 g (24 oz)
Overweight cartons (%) > 765 g (27 oz)
Major quality problems
Cartons with more than 25% cracked eggs (%)
Cartons with one or more leaking eggs (%)
Cartons with 50% or more eggs < 55 Haugh units
Cartons with 25% or more eggs < 54.3 g/egg
Total (major quality problems)
156
6.4ab
24.4a
20
5.0b
0.0d
96
5.3ab
14.0ab
54
11.7ab
8.3bc
150
4.2b
1.8cd
60
15.9a
14.3ab
8.1
10.5
4.5
3.2
11.5a
1.9b
21.1b
10.0
10.0
0.0b
5.0ab
25.0ab
1.8
4.4
0.0b
1.8b
8.0c
6.7
5.0
0.0b
1.7b
13.4bc
3.6
4.2
3.0ab
3.6ab
14.4bc
6.3
11.1
7.9a
12.7a
38.0a
5.5
6.3
3.7
4.5
20.0
Means within a row with no common superscripts are significantly different (P < 0.05).
White and brown eggs combined.
2
CA = California; NE = New England; IL = Illinois; NC = North Carolina; PA = Pennsylvania; TX = Texas.
a–c
1
TABLE 4. Significant regression analyses, Survey 2 19961
x
y
r
Intercept
Slope
P
Egg age (d)
Egg age (d)
Egg age (d)
Weight per egg (g)
Albumen height (mm)
Haugh units
−0.162
−0.219
−0.176
60.382
5.1317
68.106
−0.059766
−0.021094
−0.16837
0.001
0.001
0.001
n = 531 cartons.
1
ago (Erdman et al., 1941; Hughes, 1982) and the improvements in handling and transportation that have occurred
in recent years. Today’s large farms and larger and fewer
flocks may contribute to the wide swings in quality and
egg size observed in many of the samples surveyed in
the current study. Even though modern systems blend
eggs from different age flocks, the reduction in flock
numbers does result in more variation within a single
supplier to any given retailer.
The quality of eggs as measured by cracked eggs and
HU was poor. Much of this result was due to a failure
to remove cracked eggs from the consumer pack. This
failure can be attributed, in part, to improper settings
for the automatic cracked egg detectors or failure to
calibrate or monitor such components on the egg grading equipment. Interior egg quality (HU) was much
lower than the authors anticipated. Daily deterioration
of interior egg quality has been the focus of several
researchers (Baum et al., 1960; Sabrani and Payne, 1978;
Macindoe, 1981). Storage temperature and shell oiling
appear to be the two factors that contribute the most to
the rate of HU decrease. As mentioned earlier, there is
considerable doubt about the effectiveness of the oiling
procedure as it is being applied by the commercial industry today compared to the potential shown in earlier
studies. In some of the states surveyed, egg oiling is no
longer practiced.
Processors with in-line egg production and packaging, processing plant storage rooms with limited egg
storage capacities, and three to five store-door deliveries
per week should be able to provide the consumer with
eggs <7 d of age. However, in this study, only 25% of
the eggs met this standard.
ACKNOWLEDGMENTS
The authors gratefully acknowledge the technical assistance of Carol Adams for the statistical analyses included in this paper, the California Egg Commission for
financial support, and the many others within each
state for their help in collecting and measuring the
samples.
REFERENCES
Anonymous, 1999. More layers, lower prices predicted for
1999. Pages 1, 4, 6 in: Egg Industry. Watt Publishing Co.,
Mt. Morris, IL.
Baum, E. L., W. J. Stadelman, H. G. Walkup, and J. G. Darroch,
1960. An economic analysis of egg quality changes as influenced by time and temperature. Technical Bulletin 35.
Washington State University, Pullman, WA.
Bell, D. D., 1993. The egg industry of California and the USA
in the 1990s: A survey of systems. World’s Poult. Sci. J.
49:58–64.
Bell, D. D., P. H. Patterson, K. E. Anderson, K. W. Koelkebeck,
J. B. Carey, and M. J. Darre, 1997. National retail egg quality
studies, Part 1: White egg results. Poultry Sci. 76(Suppl
1):55. (Abstr.).
Buck, J. T., 1963. Egg quality in retail food stores. Bulletin 544.
Virginia Polytechnic Institute, Blacksburg, VA.
Darre, M. J., J. B. Carey, K. W. Koelkebeck, P. H. Patterson,
D. D. Bell, and K. E. Anderson, 1997. National retail egg
quality studies, Part 2: Brown egg results. Poultry Sci.
76(Suppl.1):56. (Abstr.).
DeKalb Poultry Research, 1995. Pullet and Layer Management
Guide—DeKalb XL. DeKalb Poultry Research, DeKalb, IL.
DeKalb Poultry Research, 1998. Pullet and Layer Management
Guide—DeKalb Delta White. DeKalb Poultry Research, DeKalb, IL.
NATIONAL EGG QUALITY STUDY—PART 1
Erdman, H. E., G. B. Alcorn, and A. T. Mace, 1941. Egg marketing in the Los Angeles area. Bulletin 656. University of
California, Berkeley, CA.
Hughes, R. J., 1982. Egg quality control in Australia. World’s
Poultry Sci. J. 38:186–193.
Hy-Line International, 1996a. Commercial Management
Guide—W-77. Hy-Line International, West Des Moines, IA.
Hy-Line International, 1996b. Commercial Management
Guide—W-36. Hy-Line International, West Des Moines, IA.
Hy-Line International, 1998. Commercial Management
Guide—W-98. Hy-Line International, West Des Moines, IA.
Macindoe, R. N., 1981. Egg quality, collection and storage.
Poult. Int. (May):162, 164, 166, 168.
389
Patterson, P. H., M. J. Darre, K. E. Anderson, K. W. Koelkebeck,
J. B. Carey, and D. D. Bell, 1977. National retail egg quality
studies, Part 3: Specialty egg results. Poultry Sci.
76(Suppl.1):56. (Abstr.).
Sabrani, M., and C. G. Payne, 1978. Effect of oiling on internal
quality of eggs stored at 28 and 12 degrees C. Br. Poult.
Sci. 19:567–571.
SAS Institute, 1989. SAS/STAT威 Guide for Personal Computers. Version 6. 4th ed. SAS Institute Inc., Cary, NC.
Snedecor, G. W., and W. G. Cochran, 1967. Statistical Methods.
6th ed. Iowa State University Press, Ames, Iowa.
United States Department of Agriculture, 1990. Egg grading
manual. Agricultural Marketing Service, Agricultural
Handbook Number 75. USDA, Washington, DC.