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Volatile Indicators of Deterioration in Liquid Egg Products
Volatile Indicators of Deterioration in Liquid Egg Products MONA L. BROWN, D. MICHAEL HOLBROOK,' EDWARD F HOERNING,2 MICHAEL G. LEGENDRE and ALLEN J. ST. ANGELO US Department of Agriculture, Agricultural Research Service, Southern Regional Research Center, New Orleans, Louisiana 70179 (Received for publication November 4, 1985)
1986 Poultry Science 65:1925-1933 INTRODUCTION
MATERIALS AND METHODS
In the US, the acceptability of liquid egg products for human consumption is based partly on the odor of the product as perceived by trained and licensed US Department of Agriculture (USDA) egg product inspectors. The volatile components formed during deterioration of uncooked egg products have not been extensively investigated. A number of studies on egg volatiles have been reported, but in most cases, the eggs were either boiled before analysis (Cronin andBeswick, 1974; Flanders et al., 1981; 1983) or were heated during the process of volatiles extraction or analysis (MacLeod and Cave, 1975, 1976; Rayner et al., 1980). Sato et al. (1973) identified amines, alcohols, aldehydes, and ketones in the volatiles from unheated, fresh egg whites but did not investigate volatile components of deteriorated products. Additional studies of egg volatiles are discussed in a review by Maga (1982). The present investigation was undertaken to determine whether one or more volatile components of liquid egg products, heated only during pasteurization (52 to 61 C), could be correlated with the detection of an unacceptable odor and serve as a marker of initial product deterioration.
Egg Products. Batches of fresh, pasteurized, liquid egg products (whole, yolk, and albumen) obtained from four egg processing plants (designated as B, C, N, and S) were placed in 30-lb lacquered tins. Headspace was provided to enhance odor detection. Each batch was stirred and smelled by a panel of five trained USDA inspectors. Egg odor was characterized as satisfactory, eggy, slightly sour, sour, slightly putrid, or putrid. (Only products judged satisfactory or eggy would be acceptable for human consumption .) After evaluation of odor, one or more 6-oz. samples were withdrawn into sterile plastic cups, capped, and stored in a freezer at -20 to -23 C for subsequent analysis. Batches of egg product were then allowed to deteriorate over a period of days, during which time they were moved to a warmer or cooler environment as deemed necessary to accelerate or retard spoilage. Cans 1 to 25 were maintained at product temperatures ranging from 14 to 22 C. Products in Cans 26 to 35 were maintained at 7 to 16 C. Products were periodically evaluated for odor and sampled after storage times ranging from 13 to 183 hr. The original sample numbering system is retained, although only selected samples were analyzed by the methodology described here. Purge and Trap. Initial purge and trap analyses were conducted with a simple system in which volatiles were purged at room temperature from a sample in a 25-ml impinger (Supelco, Inc.3) into a glass tube packed with about .3 gTenax GC. Desorption of the volatiles was accomplished by heating the trap in the inlet
Poultry Division, Agricultural Marketing Service. Washington, DC 20250. 2 Poultry Division, Agricultural Marketing Service, Gastonia, NC 28054. Reference to a brand or firm name does not constitute endorsement of the brand by the USDA over others of a similar nature not mentioned.
1925
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ABSTRACT Pasteurized, liquid egg products were allowed to deteriorate over a period of days. Products were periodically evaluated for odor and sampled for analysis of volatile components by combined purge and trapgas chromatography. Peaks were identified by mass spectrometry. In general, first detection of unacceptable odor in whole egg, albumen, or yolk samples was accompanied by the appearance of significant amounts of dimethyl sulfide. Concentrations of dimethyl disulfide, dimethyl trisulfide, and ethanol increased on further deterioration of the products. (Key words: liquid egg product, odor, volatile components, gas chromatography, dimethyl sulfide)
1926
BROWN ET AL.
the same retention time as the one observed from the purge and trap concentrator. Flow rates for nitrogen, hydrogen, and air were 35, 60, and 100 ml/min, respectively. The GC column was 2.44 m x 3.2 mm o.d. (8 ft X 1/8 in) stainless steel, packed with Tenax GC 80/100 mesh, coated with 6% poly-m-phenoxylene (polyMPE). The column temperature was increased from ambient to 60 C within less than a minute, then programmed to 200 C at 10/min. A Hewlett Packard Lab Automation System 3356 was used for data acquisition and analysis. Calibration of Flame Photometric Detector. Calibration curves were made for dimethyl sulfide (DMS), dimethyl disulfide (DMDS), and dimethyl trisulfide (DMTS),. Standard solutions of DMS and DMDS (ICN Pharmaceuticals, Inc.) in ethanohmethanol (1:1) were prepared. Five microliters of solution were injected into a plug of glass wool placed in a glass liner, which was then inserted in the heated inlet of the GC (Rayner et al., 1980). Carrier gas passing through the liner transferred the volatiles to the GC column, which was then programmed as previously described. The log-log curves of peak area vs micrograms of sample were straight lines with slopes of 1.74 and 1.81 for DMS and DMDS, respectively. The response and the efficiency of the purge and trap/GC procedure were checked by analyzing standard solutions of DMS and DMDS added to 3 ml water. Essentially the same calibration curves were generated as by the direct GC method. The DMTS curve was prepared by purge and trap/GC analysis of technical grade DMTS (Columbia Organic Chemical Co., Inc.). Corrections were made for the presence of about 20% DMDS in the sample. The slope of the log-log curve was 1.87. Gas Chromatography-Mass Spectrometry. Selected egg samples of 3 to 7 g, placed in a 25 ml sample holder, were purged for 1 hr on the purge and trap concentrator and the volatiles collected on a removable Tenax trap inserted in the purge line between the sampler and the standard trap in the instrument. To prevent breakthrough on the first trap when large samples of putrid products were purged, the trap was surrounded by a plastic sleeve packed with dry ice (Suzuki and Bailey, 1985). Subsequent desorption of the standard trap and GC analysis indicated that all volatiles were retained on the removable trap. The trap with adsorbed volatiles was placed in the external inlet of a GC interfaced with a mass spectrometer (MS), the Finnigan 4000 GC/MS/DS. Volatiles were desorbed
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of a gas chromatograph (GC) at 225 C for 20 min. The trap was then removed and analysis carried out. ATekmar semi-automatic purge and trap concentrator, Model LSC-3 (Westendorf, 1981), interfaced with the GC, was used for the majority of the analyses. A 152.4 x 6.4 mm (6 x 1/4-in) stainless steel trap packed with 5A molecular sieve was installed in the purge gas line just before the sampler assembly to remove traces of a sulfur-containing contaminant that comes from the concentrator and has a retention time very near that of dimethyl sulfide. The 5-ml needle sparge sampler supplied with the instrument was modified to eliminate leaks by replacing the cap and plastic connector to the conical test tube with a 27.2-mm long glass tube and appropriately sized Swagelok fitting with Teflon ferrules. A few grams of frozen sample were drilled out of the cup with an electric drill and 4.8 mm (3/16-in) steel bit and allowed to thaw in a small, capped vial. The thawed samples were treated as follows: 1 g of whole egg was weighed into a sample holder; .5 ml deionized water was added as diluent and 10 (xl decanol were added as antifoam agent. One gram of albumen was weighed into a sample holder and 10 (xl decanol were added. Two grams of yolk, which is a stiff paste after freezing and thawing, were mixed thoroughly with 5 g deionized water in a 50 ml Erlenmeyer flask; 1 g of the mixture was weighed into the sample holder and 10 (JL! decanol were added. Nitrogen was bubbled through the sample at 14 ml/min for 30 min at room temperature. The volatiles were trapped on a 203 X 6.4 mm (8 X 1/4 in) stainless steel trap packed with .6 g Tenax GC, 60/80 mesh. Initially, volatiles were desorbed from the trap for 20 min at 225 C onto the head of the GC column, maintained at ambient temperature. During the course of the work, it was determined that desorption from the trap and temperature programming of the GC column could be done simultaneously, which shortened analysis time and resulted in better definition of early peaks. Gas Chromatography. The gas chromatograph was aTracor Model 222. The detector was a Tracor Model 100AT, a combination flame photometric detector (FPD) used in the sulfur mode and flame ionization detector (FID). A molecular sieve 5A trap was installed in the carrier gas line just past the flow regulator/meter to remove a sulfur-containing contaminant with
INDICATORS OF DETERIORATION IN LIQUID EGG PRODUCTS
at 225 C onto aTenax-poly MPE column, which was then heated from ambient temperature to 200 C at 5/min. Peak identities were assigned by comparing mass spectra and retention times of the sample volatiles with those of known compounds, with the exception of the methanethiol peak, which was identified by computer match of its spectrum with the MS library spectrum for methanethiol. RESULTS AND DISCUSSION
bles 1 to 4. In batches of whole egg maintained at temperatures between 14 and 22 C, a slightly sour odor was first detected between 20 and 40 hr (Table 1). Commercial source of the batches did not appear to be a factor in the rate of deterioration. In the batches maintained at somewhat lower temperatures, a slightly sour odor was first detected after 67 hr (Table 2). With one exception, Sample 7C2, the DMS concentration was negligible in whole egg samples drawn before a slightly sour odor was observed by any panelist. (Traces of DMS and DMDS are probably due to contaminants not completely removed from the purge and trap concentrator.) In all samples judged unacceptable by two or more panelists, DMS was above 20 ppb. Sample 12C6, with a DMS concentration of 13.3 ppb, was judged unacceptable by one panelist. Albumen fractions, held at 14 to 22 C, deteriorated more slowly than whole egg or yolk products; organoleptic indications of poor quality appeared after 120 or 136 hr (Table 3). Slower decomposition would be expected because of the differences in protein composition of egg yolk and albumen (Parkinson, 1966). Sample 22S11 is the major exception to the correlation between detection of the slightly sour odor and large increase in DMS. The five panelists judged the odor as eggy, while the GC data would indicate a poorer quality. In Can 23S, sulfur components were beginning to increase in Samples 11 and 11(1), although none of the panelists detected a slightly sour odor. The batch of egg yolk held at 14 to 22 C showed the first organoleptic sign of spoilage and an increase in DMS from trace amounts to 15 ppb after 36 hr (Table 4). Concentrations of DMS were, in general, lower in unacceptable yolk samples than in unacceptable whole egg or albumen samples. The additional handling required in preparation of the yolk samples for analysis may have resulted in loss of DMS. To determine the reproducibility of the DMS analysis, duplicate analyses were run on each of 15 cups of frozen, whole egg having significant DMS concentrations. Deviation from the mean ranged from 1.7 to 15.8%. However, in each case, the DMS concentration was lower in the second aliquot drilled from a sample cup than in the first and continued to decrease when third and fourth aliquots were analyzed. For some samples, replicate cups were available. Analysis of DMS in first aliquots taken from two, three, or four replicate cups of seven differ-
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The first approach to analysis of egg product volatiles was essentially that of Rayner et al. (1980), where .1 g sample was heated in the GC inlet at 100 C and the volatiles were swept by carrier gas onto the GC column. Analysis by this "direct GC" technique of 50 samples, drawn from 17 cans of whole egg product, showed that the ethanol content tended to increase as the samples deteriorated-from .3 ppm in satisfactory to 300 ppm in putrid samples. Ethanol also increased with deterioration of albumen and yolk fractions. For whole, albumen, and yolk samples of the same odor category, ethanol was highest in albumen and lowest in whole egg samples. However, there was no significant difference in ethanol concentration between the eggy (nine samples judged eggy by at least four of the five panelists) and slightly sour (nine samples judged slightly sour by at least four of five panelists) categories, i.e., between an acceptable and an unacceptable product. Additionally, heating the sample at 100 C generated some volatile compounds not originally present, the most obvious being hydrogen sulfide and methanethiol. With the purge and trap technique, volatiles were removed from the egg products at room temperature. Larger samples could be used and, because little water is retained on Tenax, it did not interfere with chromatographic separation of the volatiles. In preliminary experiments with the simple purge and trap system, consecutive pairs of eggy/slightly sour samples drawn from five cans of whole egg were analyzed. Concentrations of DMS were below 1 ppb in the eggy samples and ranged from 28 to 60 ppb in the slightly sour ones. Samples from 16 other cans of egg product were analyzed on the commercial purge and trap concentrator, which permitted use of a larger trap and eliminated its handling between analyses. Sample history, odor evaluation and concentrations of DMS, DMDS, and DMTS for these samples are summarized in Ta-
1927
1928
BROWN ETAL. TABLE 1. Volatile sulfur components determined in pasteurized whole egg products allowed to deteriorate at 14 to 22 C
Can 1
Sample no
Storage time
Odor category 2
DMS 3
DMDS
5 Sat 1 E / 4 SS 5P 5 P
tr 4 84.9 80.5 81.4
tr
(hr) IB
7C
11B
12C
14S 17C 18N
1
sppu;
4 5 9 14
24 36 63 183
1 2 3 4 5 6 7
0 13 20 24 36 40 45
5 Sat 4 Sat/1 E 5 SS 2 SS/3 S 1 SS/2 SP/2 P 1 SP/4 P 5P
tr 14.1 55.0 34.1 40.1 40.4 49.3
tr
4 5 6 7 8 9
24 36 40 45 50 63
5 Sat 1 Sat/4 E 2 E/3 SS 1 SS/3 S / l SP 2 SP/3 P 5P
tr tr 32.5 26.4 38.4 38.0
tr
1 2 3 4 5 6 7 9
0 13 20 24 36 40 45 63
5 Sat 5 Sat 5 Sat 5 Sat 5SS 1 E / l SS/1 S/2 SP 2 SS/3 SP 5 P
tr tr tr tr 78.5 63.6 54.5 58.6
tr
1 4 5 6 7 8 9
0 24 36 40 45 50 63
4 Sat/1 E 4 Sat/1 E 1 Sat/4 E 4 E / l SS 2E/3S 2 S / l SP/2 P 5 P
tr tr 1.4 13.3 41.5 54.3 56.4
tr tr
3 4
20 24
5 Sat 2 E/l SS/2 S
tr 72.1
tr
4 5
24 36
4 Sat/1 E 1 E/3 SS/1 S
tr 45.6
tr
4 5
24 36
5 Sat 2 SS/3 S
0 55.8
tr
.4 18.5 >86s .4 .4 .4 .8 1.2 2.0 .5 .6 .7 1.3 2.5 .4 .4 .3 .4 .4 .8 5.7
.4 .4 .5 1.3 2.0 .4
0 0 2.6 >58s 0 0 0 0 .3 .3 1.1 0 0 0 .3 .5 .8 0 0 0 0 0 0 .2 .7 0 0 0 0 0 .4 .6 0 0 0
.8 .5
.2 0 0
B,C,N,S = Processing plants.
2
Sat = Satisfactory; E = eggy; SS = slightly sour; S = sour; SP = slightly putrid; P = putrid. Five panelists.
3
DMS = Dimethyl sulfide, DMDS = dimethyl disulfide, DMTS = dimethyl trisulfide.
*tr = Trace. 5
Electrometer saturated at selected attenuation.
ent samples, showed the average deviation from the mean ranged from 3.6 to 9.5%. For comparison with the samples frozen in a freezer after sensory evaluation, a few random samples were frozen in liquid nitrogen within 5 min and then stored in the freezer. For those
samples with significant amounts of DMS, DMS concentration in the "liquid nitrogen" samples averaged about 40% lower than in the ' 'freezer'' samples, indicating that some microbial/enzymatic action continued during slower freezing of the product. Ethanol, determined by both di-
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8N
DMTS
INDICATORS OF DETERIORATION IN LIQUID EGG PRODUCTS
1929
TABLE 2. Volatile sulfur components determined in pasteurized whole egg products allowed to deteriorate at 7 to 16 C
Can 1
Sample no.
Storage t i m e
Odor category 2
DMS3
DMDS
(hr) 28B
31B
35B
1
sPpo;
1 8 9 10 11 12 13 15
0 52 67 70 76 79 91 100
5 5 5 5 1 5 3 5
Sat E SS SS SS/4 S S SP/2 P P
tr4 tr 69.1 56.7 56.7 91.2 74.2 70.6
tr tr
1 7 8 9 10 11 12 13 15
0 47 52 67 70 76 79 91 100
4 Sat/1 E 5E 5 E 3 E / 2 SS 5 SS 1 SS/4 S 5 S 1 S/4 SP 5 P
tr tr tr 39.6 50.6 49.2 23.6 37.9 57.7
tr tr tr 1.0 .7 .8 1.0 1.1 2.0
0 0 0 0 0 0 0
1 6 7 8 9 10 11 12 13 15
0 42 47 52 67 70 76 79 91 100
4 Sat/1 E 1 Sat/4 E 5 E 5 E 5 SS 5 SS 1 SS/4 S 5 S 1 S/4 SP 5P
tr tr tr tr 23.0 45.6 49.3 43.0 49.1 54.8
tr tr
0 0 0 0 0 0 0 0
8 9
52 67
5 E 2 E / 3 SS
0 72.7
.4 .5 .4 .8 1.1 2.9
.4 .4 .5 .9 .8 1.0 1.5 2.2 .4 .3
0 0 0 0 0 .4 .5 .7
.3 .5
.3 .6 0 0
B,C,N,S = Processing plants.
2
Sat = Satisfactory; E = eggy; SS = slightly sour; S = sour; SP = slightly putrid; P = putrid. Five panelists.
3
DMS = Dimethyl sulfide, DMDS = dimethyl disulfide, DMTS = dimethyl trisulfide.
"tr = Trace.
rect GC and purge and trap/GC, was also significantly lower in liquid nitrogen samples. Concentrations of DMDS and DMTS tended to increase as the egg products deteriorated but exhibited no sharp increase with the first detection of unacceptable odor. Methyl thioacetate was detected in putrid whole egg samples 1B9, IB 14, and 12C9 and in putrid albumen 22S15. Methanethiol was detected only in IB 14 and 22S15. Chromatograms obtained on analysis of whole egg samples from Can IB by the commercial purge and trap/GC method, with simultaneous desorption of the trap and temperature programming of the GC column, are shown in Figures 1 to 4. The significant difference between
the volatile profiles of the satisfactory and slightly sour samples is the size of the DMS peak. Amount of ethanol purged from the samples increased as the products deteriorated but, as was observed on direct GC analysis, there was no sharp increase in ethanol with the first detection of an unacceptable odor. In the GC/MS analysis of samples containing DMTS, the mass spectrum of the peak with the retention time (ca 15 min) of DMTS was, in some instances, identical with that of the DMDS peak, having the molecular ion 94 of DMDS and not the molecular ion 126 of DMTS. In egg samples high in DMTS and in the commercial preparation of DMTS, spectra for both DMDS and DMTS were obtained at the position of
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30B
DMTS
1930
BROWN ETAL. TABLE 3. Volatile sulfur components determined in pasteurized egg albumen allowed to deteriorate at 14 to 22 C
Can1
Sample no.
Storage time
Odor category 2
DMS3
DMDS
0 0 0
0 0 0 0
(hr) 21S
23S
1
i.ppu,i •
1 10 11(1) 12 12(2) 13 13(2) 14
0 92 120 136 144 164 169 183
5 Sat 1 Sat/4 E 5E 2 E/3 SS 1 E/2 S S / 2 S 2 SS/3 S 4S/1 P 5 S
tr 4 tr .5 17.0 29.7 36.3 36.2 31.8
tr .5 .5 .9 1.1 1.5 1.5 1.5
1 8 9 10 11 11(1) 12 13 14 15
0 50 63 92 116 120 136 164 183 351
5 Sat 3 Sat/2 E 2 Sat/3 E 2 Sat/3 E 5E 1 E / 4 SS 4 SS/1 S 1 SS/4 S 5S 5P
tr tr tr tr 58.2 32.9 44.1 23.9 17.0 9.8
tr .5 .3 .3 1.2 .8 .8 1.3 1.8 62.7
1 10 11 11(1) 12 12(1) 12(3) 13 14
0 92 116 120 136 139 148 164 183
5 Sat 1 Sat/4 E 5E 5E 3 E / l SS/1 S 1 E/3 SS/1 S 2 SS/3 S 1 SS/4 S 5S
tr tr 3.1 9.9 75.0 43.6 33.2 30.1 19.4
tr .5 .6 .8 1.6 1.5 1.1 1.2 1.0
.2 .3 .4 .4 .4
.4 .3 .3 .4 .6 10.6 0 0 0 .3 .4 .5 .3 .4 .3
B,C,N,S = Processing plants.
2
Sat = Satisfactory; E = eggy; SS = slightly sour; S = sour; SP = slightly putrid; P = putrid. Five panelists.
3
DMS = Dimethyl sulfide, DMDS = dimethyl disulfide, DMTS = dimethyl trisulfide.
"tr = Trace.
TABLE 4. Volatile sulfur components in pasteurized egg yolk allowed to deteriorate at 14 to 22 C
Can 1
Sample no.
Storage time
Odor category 2
DMS 3
DMDS
4 Sat/1 E 4 Sat/1 E 4 E / l SS 1 S S / 2 S/2 SP 5P 5P
tr" tr 15.0 19.4 17.1 11.6
(ppu) tr tr .8 .8 1.4 1.0
(hr) 25N
1 2
2 4 5 6 9 10
13 24 36 40 63 92
DMTS
0 0 .3 .6 .6 .6
B,C,N,S = Processing plants. Sat = Satisfactory; E = eggy; SS = slightly sour; S = sour; SP = slightly putrid; P = putrid. Five panelists.
3
DMS = Dimethyl sulfide, DMDS = dimethyl disulfide, DMTS = dimethyl trisulfide.
4
tr = Trace.
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22S
DMTS
INDICATORS OF DETERIORATION IN LIQUID EGG PRODUCTS 5
1931
18
8.5
5 6 o o o lii 3 _l
< >
I 3
o o DC W 3 0.
O
11
3
i
n
IB~5
T*
is!
15
si
is
2T.5
RETENTION TIME IN MINUTES FIG. 2. Chromatogram of pasteurized, whole egg allowed to deteriorate at 14 to 22 C. Sample 1B5, 36 hr, slightly sour. FID, attenuated 1 x 8; FPD, attenuated 104 x 1. Peak identifications: 1, methanol; 2, acetaldehyde; 4. ethanol; 5, acetone; 6, dimethyl sulfide; 7, 1-propanol; 8, 2-butanone; 10, 3-methylbutanol; 11, ethyl propionate; 13, dimethyl disulfide; 14, hexanal; 15, impurity in decanol; 17, impurity in decanol; 18, decanol.
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21.5 9.5 11 12.5 14 ta.5 715.5 s" Y so RETENTION TIME IN MINUTES FIG. 1. Chromatogram of pasteurized, whole egg allowed to deteriorate at 14 to 22 C. Sample 1B4, 24 hr, satisfactory. FID, attenuated 1 x 8; FPD, attenuated 104 x 1. Peak identifications: 1, methanol; 2, acetaldehyde; 4, ethanol; 5, acetone; 6, dimethyl sulfide; 7, 1-propanol; 8, 2-butanone; 10, 3-methylbutanol; 11, ethyl propionate; 13, dimethyl disulfide; 14, hexanal; 15, impurity in decanol; 17, impurity in decanol; 18, decanol.
nr
1932
BROWN ETAL.
T"
15.5 18.5 21.5 Is" so IF I RETENTION TIME IN MINUTES FIG. 3. Chromatogram of pasteurized, whole egg allowed to deteriorate at 14 to 22 C. Sample 1B9, 63 hr, putrid. FID, attenuated 1 x 8 ; FPD, attenuated 10 x 1. Peak identifications: 1, methanol; 2, acetaldehyde; 4, ethanol; 5. acetone; 6. dimethyl sulfide: 7, 1-propanol; 8. 2-butanone; 9. ethyl acetate: 10. 1-methylbutanal; 11. ethyl propionate; 12, methyl thioacetate; 13, dimethyl disulfide; 14, hexanal; 15, impurity in decanol; 16, dimethyl trisulfide; 17, impurity in decanol; 18, decanol.
3 4
6
8,9
o o o o
*
lii _l
< > 2 2 X
< s
T
IF
RETENTION TIME IN MINUTES FIG. 4. Chromatogram of pasteurized, whole egg allowed to deteriorate at 14 to 22 C. Sample 1B14, 183 hr, putrid. FID, attenuated 1 x 8; FPD, attenuated 104 x 2. Peak identificatons: 1, methanol; 2, acetaldehyde; 3, methanethiol; 4, ethanol; 5, acetone; 6, dimethyl sulfide; 7, 1-propanol; 8, 2-butanone; 9, ethyl acetate; 11, ethyl propionate; 12, methyl thioacetate; 13, dimethyl disulfide; 14, hexanal; 15, impurity in decanol; 16, dimethyl trisulfide; 18, decanol.
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Ti
INDICATORS OF DETERIORATION IN LIQUID EGG PRODUCTS REFERENCES
Bullard, R. W., T. J. Leiker, J. E. Peterson, and S. R. Kilburn, 1978. Volatile components of fermented egg, an animal attractant and repellent. J. Agric. Food Chem. 26:155-159. Cronin, E. E, and G. Beswick, 1974. Volatile sulphur compounds produced on the heat treatment of the hen's egg. Proc. 4th. Int. Congr. Food Sci. Technol .1:17-21. Flanders, A., G. Beswick, and D. A. Rosie, 1981. The isolation of volatile sulphur compounds from cooked hen's eggs using two novel trapping methods. Pages 153-162 in Quality of Eggs. Spelderholt Inst. Poult. Res., Beekbergen, Netherlands. Flanders, A., G. Beswick, and D. A. Rosie, 1983. Volatile sulphur compounds produced on the heat treatment of hen's eggs (Gallus domesticus) and egg components. Proc. Int. Congr. Food Sci. Technol. 6th. 1:172-173. Germs, A: C , 1973. Hydrogen sulphide production in eggs and egg products as a result of heating. J. Sci. Food Agric. 24:7-16. MacLeod, A. J., and S. J. Cave, 1975. Volatile flavour components of eggs. J. Sci. FoodAgric. 26:351-360. MacLeod, A. J., and S. J. Cave, 1976. Variations in the volatile flavour components of eggs. J. Sci. Food Agric. 27:799-806. Maga, J. A., 1982. Egg and egg product flavor. J. Agric. Food Chem. 30:9-14. Parkinson, T. L., 1966. The chemical composition of eggs. J. Sci. FoodAgric. 17:101-111. Rayner, E. T , H. P. Dupuy, M. G. Legendre, W. H. Schuller, and D. M. Holbrook, 1980. Assessment of egg flavor (odor) by unconventional gas chromatography. Poultry Sci. 59:2348-2351. Sato, Y., K.Watanabe, andR. Ishihara, 1973. Further studies on amines and neutral compounds in egg white smell. Jpn. J. Zootech. Sci. 44:232-240. Suzuki, J., and M. E. Bailey, 1985. Direct sampling capillary glc analysis of flavor volatiles from ovine fat. J. Agric. Food Chem. 33:343-347. Westendorf, R. G., 1981. Development and application of a semiautomatic purge and trap concentrator. Am. Lab. 13:88-95.
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DMTS. It is thought that some DMTS decomposes to DMDS in the 250 C stainless steel transfer line between the GC/MS interface and the ion source of the MS. The purge and trap technique was not satisfactory for H2S analysis because the Tenax trap did not retain H2S during a 30-min purge. However, use of the direct GC method with an inlet temperature of 50 to 55 C, i.e., below the temperature where H2S would be formed in egg products, did not reveal any H2S in the sour, slightly putrid, or putrid whole egg or the putrid albumen samples examined. This is consistent with the results of Germs (1973), who detected no H2S in egg yolk or albumen held at room temperature for 4 days. Classes of compounds reported by Bullard et al. as contributors to the odor of fermented, dried whole egg product were organic sulfur compounds, amines, esters, and volatile fatty acids. Although some esters were identified in the present investigation, they were not useful as indicators of unacceptability. The methodology was not appropriate for analysis of amines and fatty acids. The DMS detected in the egg products as they were first judged unacceptable may or may not have contributed to the perceived odor. However, the correlation between the presence of significant amounts of DMS and the perception of a slightly sour odor in most of the samples examined suggests that measurement of DMS may serve as an objective method for determining acceptability of liquid or frozen egg products for human consumption.
1933
1986 Poultry Science 65:1925-1933 INTRODUCTION
MATERIALS AND METHODS
In the US, the acceptability of liquid egg products for human consumption is based partly on the odor of the product as perceived by trained and licensed US Department of Agriculture (USDA) egg product inspectors. The volatile components formed during deterioration of uncooked egg products have not been extensively investigated. A number of studies on egg volatiles have been reported, but in most cases, the eggs were either boiled before analysis (Cronin andBeswick, 1974; Flanders et al., 1981; 1983) or were heated during the process of volatiles extraction or analysis (MacLeod and Cave, 1975, 1976; Rayner et al., 1980). Sato et al. (1973) identified amines, alcohols, aldehydes, and ketones in the volatiles from unheated, fresh egg whites but did not investigate volatile components of deteriorated products. Additional studies of egg volatiles are discussed in a review by Maga (1982). The present investigation was undertaken to determine whether one or more volatile components of liquid egg products, heated only during pasteurization (52 to 61 C), could be correlated with the detection of an unacceptable odor and serve as a marker of initial product deterioration.
Egg Products. Batches of fresh, pasteurized, liquid egg products (whole, yolk, and albumen) obtained from four egg processing plants (designated as B, C, N, and S) were placed in 30-lb lacquered tins. Headspace was provided to enhance odor detection. Each batch was stirred and smelled by a panel of five trained USDA inspectors. Egg odor was characterized as satisfactory, eggy, slightly sour, sour, slightly putrid, or putrid. (Only products judged satisfactory or eggy would be acceptable for human consumption .) After evaluation of odor, one or more 6-oz. samples were withdrawn into sterile plastic cups, capped, and stored in a freezer at -20 to -23 C for subsequent analysis. Batches of egg product were then allowed to deteriorate over a period of days, during which time they were moved to a warmer or cooler environment as deemed necessary to accelerate or retard spoilage. Cans 1 to 25 were maintained at product temperatures ranging from 14 to 22 C. Products in Cans 26 to 35 were maintained at 7 to 16 C. Products were periodically evaluated for odor and sampled after storage times ranging from 13 to 183 hr. The original sample numbering system is retained, although only selected samples were analyzed by the methodology described here. Purge and Trap. Initial purge and trap analyses were conducted with a simple system in which volatiles were purged at room temperature from a sample in a 25-ml impinger (Supelco, Inc.3) into a glass tube packed with about .3 gTenax GC. Desorption of the volatiles was accomplished by heating the trap in the inlet
Poultry Division, Agricultural Marketing Service. Washington, DC 20250. 2 Poultry Division, Agricultural Marketing Service, Gastonia, NC 28054. Reference to a brand or firm name does not constitute endorsement of the brand by the USDA over others of a similar nature not mentioned.
1925
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ABSTRACT Pasteurized, liquid egg products were allowed to deteriorate over a period of days. Products were periodically evaluated for odor and sampled for analysis of volatile components by combined purge and trapgas chromatography. Peaks were identified by mass spectrometry. In general, first detection of unacceptable odor in whole egg, albumen, or yolk samples was accompanied by the appearance of significant amounts of dimethyl sulfide. Concentrations of dimethyl disulfide, dimethyl trisulfide, and ethanol increased on further deterioration of the products. (Key words: liquid egg product, odor, volatile components, gas chromatography, dimethyl sulfide)
1926
BROWN ET AL.
the same retention time as the one observed from the purge and trap concentrator. Flow rates for nitrogen, hydrogen, and air were 35, 60, and 100 ml/min, respectively. The GC column was 2.44 m x 3.2 mm o.d. (8 ft X 1/8 in) stainless steel, packed with Tenax GC 80/100 mesh, coated with 6% poly-m-phenoxylene (polyMPE). The column temperature was increased from ambient to 60 C within less than a minute, then programmed to 200 C at 10/min. A Hewlett Packard Lab Automation System 3356 was used for data acquisition and analysis. Calibration of Flame Photometric Detector. Calibration curves were made for dimethyl sulfide (DMS), dimethyl disulfide (DMDS), and dimethyl trisulfide (DMTS),. Standard solutions of DMS and DMDS (ICN Pharmaceuticals, Inc.) in ethanohmethanol (1:1) were prepared. Five microliters of solution were injected into a plug of glass wool placed in a glass liner, which was then inserted in the heated inlet of the GC (Rayner et al., 1980). Carrier gas passing through the liner transferred the volatiles to the GC column, which was then programmed as previously described. The log-log curves of peak area vs micrograms of sample were straight lines with slopes of 1.74 and 1.81 for DMS and DMDS, respectively. The response and the efficiency of the purge and trap/GC procedure were checked by analyzing standard solutions of DMS and DMDS added to 3 ml water. Essentially the same calibration curves were generated as by the direct GC method. The DMTS curve was prepared by purge and trap/GC analysis of technical grade DMTS (Columbia Organic Chemical Co., Inc.). Corrections were made for the presence of about 20% DMDS in the sample. The slope of the log-log curve was 1.87. Gas Chromatography-Mass Spectrometry. Selected egg samples of 3 to 7 g, placed in a 25 ml sample holder, were purged for 1 hr on the purge and trap concentrator and the volatiles collected on a removable Tenax trap inserted in the purge line between the sampler and the standard trap in the instrument. To prevent breakthrough on the first trap when large samples of putrid products were purged, the trap was surrounded by a plastic sleeve packed with dry ice (Suzuki and Bailey, 1985). Subsequent desorption of the standard trap and GC analysis indicated that all volatiles were retained on the removable trap. The trap with adsorbed volatiles was placed in the external inlet of a GC interfaced with a mass spectrometer (MS), the Finnigan 4000 GC/MS/DS. Volatiles were desorbed
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of a gas chromatograph (GC) at 225 C for 20 min. The trap was then removed and analysis carried out. ATekmar semi-automatic purge and trap concentrator, Model LSC-3 (Westendorf, 1981), interfaced with the GC, was used for the majority of the analyses. A 152.4 x 6.4 mm (6 x 1/4-in) stainless steel trap packed with 5A molecular sieve was installed in the purge gas line just before the sampler assembly to remove traces of a sulfur-containing contaminant that comes from the concentrator and has a retention time very near that of dimethyl sulfide. The 5-ml needle sparge sampler supplied with the instrument was modified to eliminate leaks by replacing the cap and plastic connector to the conical test tube with a 27.2-mm long glass tube and appropriately sized Swagelok fitting with Teflon ferrules. A few grams of frozen sample were drilled out of the cup with an electric drill and 4.8 mm (3/16-in) steel bit and allowed to thaw in a small, capped vial. The thawed samples were treated as follows: 1 g of whole egg was weighed into a sample holder; .5 ml deionized water was added as diluent and 10 (xl decanol were added as antifoam agent. One gram of albumen was weighed into a sample holder and 10 (xl decanol were added. Two grams of yolk, which is a stiff paste after freezing and thawing, were mixed thoroughly with 5 g deionized water in a 50 ml Erlenmeyer flask; 1 g of the mixture was weighed into the sample holder and 10 (JL! decanol were added. Nitrogen was bubbled through the sample at 14 ml/min for 30 min at room temperature. The volatiles were trapped on a 203 X 6.4 mm (8 X 1/4 in) stainless steel trap packed with .6 g Tenax GC, 60/80 mesh. Initially, volatiles were desorbed from the trap for 20 min at 225 C onto the head of the GC column, maintained at ambient temperature. During the course of the work, it was determined that desorption from the trap and temperature programming of the GC column could be done simultaneously, which shortened analysis time and resulted in better definition of early peaks. Gas Chromatography. The gas chromatograph was aTracor Model 222. The detector was a Tracor Model 100AT, a combination flame photometric detector (FPD) used in the sulfur mode and flame ionization detector (FID). A molecular sieve 5A trap was installed in the carrier gas line just past the flow regulator/meter to remove a sulfur-containing contaminant with
INDICATORS OF DETERIORATION IN LIQUID EGG PRODUCTS
at 225 C onto aTenax-poly MPE column, which was then heated from ambient temperature to 200 C at 5/min. Peak identities were assigned by comparing mass spectra and retention times of the sample volatiles with those of known compounds, with the exception of the methanethiol peak, which was identified by computer match of its spectrum with the MS library spectrum for methanethiol. RESULTS AND DISCUSSION
bles 1 to 4. In batches of whole egg maintained at temperatures between 14 and 22 C, a slightly sour odor was first detected between 20 and 40 hr (Table 1). Commercial source of the batches did not appear to be a factor in the rate of deterioration. In the batches maintained at somewhat lower temperatures, a slightly sour odor was first detected after 67 hr (Table 2). With one exception, Sample 7C2, the DMS concentration was negligible in whole egg samples drawn before a slightly sour odor was observed by any panelist. (Traces of DMS and DMDS are probably due to contaminants not completely removed from the purge and trap concentrator.) In all samples judged unacceptable by two or more panelists, DMS was above 20 ppb. Sample 12C6, with a DMS concentration of 13.3 ppb, was judged unacceptable by one panelist. Albumen fractions, held at 14 to 22 C, deteriorated more slowly than whole egg or yolk products; organoleptic indications of poor quality appeared after 120 or 136 hr (Table 3). Slower decomposition would be expected because of the differences in protein composition of egg yolk and albumen (Parkinson, 1966). Sample 22S11 is the major exception to the correlation between detection of the slightly sour odor and large increase in DMS. The five panelists judged the odor as eggy, while the GC data would indicate a poorer quality. In Can 23S, sulfur components were beginning to increase in Samples 11 and 11(1), although none of the panelists detected a slightly sour odor. The batch of egg yolk held at 14 to 22 C showed the first organoleptic sign of spoilage and an increase in DMS from trace amounts to 15 ppb after 36 hr (Table 4). Concentrations of DMS were, in general, lower in unacceptable yolk samples than in unacceptable whole egg or albumen samples. The additional handling required in preparation of the yolk samples for analysis may have resulted in loss of DMS. To determine the reproducibility of the DMS analysis, duplicate analyses were run on each of 15 cups of frozen, whole egg having significant DMS concentrations. Deviation from the mean ranged from 1.7 to 15.8%. However, in each case, the DMS concentration was lower in the second aliquot drilled from a sample cup than in the first and continued to decrease when third and fourth aliquots were analyzed. For some samples, replicate cups were available. Analysis of DMS in first aliquots taken from two, three, or four replicate cups of seven differ-
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The first approach to analysis of egg product volatiles was essentially that of Rayner et al. (1980), where .1 g sample was heated in the GC inlet at 100 C and the volatiles were swept by carrier gas onto the GC column. Analysis by this "direct GC" technique of 50 samples, drawn from 17 cans of whole egg product, showed that the ethanol content tended to increase as the samples deteriorated-from .3 ppm in satisfactory to 300 ppm in putrid samples. Ethanol also increased with deterioration of albumen and yolk fractions. For whole, albumen, and yolk samples of the same odor category, ethanol was highest in albumen and lowest in whole egg samples. However, there was no significant difference in ethanol concentration between the eggy (nine samples judged eggy by at least four of the five panelists) and slightly sour (nine samples judged slightly sour by at least four of five panelists) categories, i.e., between an acceptable and an unacceptable product. Additionally, heating the sample at 100 C generated some volatile compounds not originally present, the most obvious being hydrogen sulfide and methanethiol. With the purge and trap technique, volatiles were removed from the egg products at room temperature. Larger samples could be used and, because little water is retained on Tenax, it did not interfere with chromatographic separation of the volatiles. In preliminary experiments with the simple purge and trap system, consecutive pairs of eggy/slightly sour samples drawn from five cans of whole egg were analyzed. Concentrations of DMS were below 1 ppb in the eggy samples and ranged from 28 to 60 ppb in the slightly sour ones. Samples from 16 other cans of egg product were analyzed on the commercial purge and trap concentrator, which permitted use of a larger trap and eliminated its handling between analyses. Sample history, odor evaluation and concentrations of DMS, DMDS, and DMTS for these samples are summarized in Ta-
1927
1928
BROWN ETAL. TABLE 1. Volatile sulfur components determined in pasteurized whole egg products allowed to deteriorate at 14 to 22 C
Can 1
Sample no
Storage time
Odor category 2
DMS 3
DMDS
5 Sat 1 E / 4 SS 5P 5 P
tr 4 84.9 80.5 81.4
tr
(hr) IB
7C
11B
12C
14S 17C 18N
1
sppu;
4 5 9 14
24 36 63 183
1 2 3 4 5 6 7
0 13 20 24 36 40 45
5 Sat 4 Sat/1 E 5 SS 2 SS/3 S 1 SS/2 SP/2 P 1 SP/4 P 5P
tr 14.1 55.0 34.1 40.1 40.4 49.3
tr
4 5 6 7 8 9
24 36 40 45 50 63
5 Sat 1 Sat/4 E 2 E/3 SS 1 SS/3 S / l SP 2 SP/3 P 5P
tr tr 32.5 26.4 38.4 38.0
tr
1 2 3 4 5 6 7 9
0 13 20 24 36 40 45 63
5 Sat 5 Sat 5 Sat 5 Sat 5SS 1 E / l SS/1 S/2 SP 2 SS/3 SP 5 P
tr tr tr tr 78.5 63.6 54.5 58.6
tr
1 4 5 6 7 8 9
0 24 36 40 45 50 63
4 Sat/1 E 4 Sat/1 E 1 Sat/4 E 4 E / l SS 2E/3S 2 S / l SP/2 P 5 P
tr tr 1.4 13.3 41.5 54.3 56.4
tr tr
3 4
20 24
5 Sat 2 E/l SS/2 S
tr 72.1
tr
4 5
24 36
4 Sat/1 E 1 E/3 SS/1 S
tr 45.6
tr
4 5
24 36
5 Sat 2 SS/3 S
0 55.8
tr
.4 18.5 >86s .4 .4 .4 .8 1.2 2.0 .5 .6 .7 1.3 2.5 .4 .4 .3 .4 .4 .8 5.7
.4 .4 .5 1.3 2.0 .4
0 0 2.6 >58s 0 0 0 0 .3 .3 1.1 0 0 0 .3 .5 .8 0 0 0 0 0 0 .2 .7 0 0 0 0 0 .4 .6 0 0 0
.8 .5
.2 0 0
B,C,N,S = Processing plants.
2
Sat = Satisfactory; E = eggy; SS = slightly sour; S = sour; SP = slightly putrid; P = putrid. Five panelists.
3
DMS = Dimethyl sulfide, DMDS = dimethyl disulfide, DMTS = dimethyl trisulfide.
*tr = Trace. 5
Electrometer saturated at selected attenuation.
ent samples, showed the average deviation from the mean ranged from 3.6 to 9.5%. For comparison with the samples frozen in a freezer after sensory evaluation, a few random samples were frozen in liquid nitrogen within 5 min and then stored in the freezer. For those
samples with significant amounts of DMS, DMS concentration in the "liquid nitrogen" samples averaged about 40% lower than in the ' 'freezer'' samples, indicating that some microbial/enzymatic action continued during slower freezing of the product. Ethanol, determined by both di-
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8N
DMTS
INDICATORS OF DETERIORATION IN LIQUID EGG PRODUCTS
1929
TABLE 2. Volatile sulfur components determined in pasteurized whole egg products allowed to deteriorate at 7 to 16 C
Can 1
Sample no.
Storage t i m e
Odor category 2
DMS3
DMDS
(hr) 28B
31B
35B
1
sPpo;
1 8 9 10 11 12 13 15
0 52 67 70 76 79 91 100
5 5 5 5 1 5 3 5
Sat E SS SS SS/4 S S SP/2 P P
tr4 tr 69.1 56.7 56.7 91.2 74.2 70.6
tr tr
1 7 8 9 10 11 12 13 15
0 47 52 67 70 76 79 91 100
4 Sat/1 E 5E 5 E 3 E / 2 SS 5 SS 1 SS/4 S 5 S 1 S/4 SP 5 P
tr tr tr 39.6 50.6 49.2 23.6 37.9 57.7
tr tr tr 1.0 .7 .8 1.0 1.1 2.0
0 0 0 0 0 0 0
1 6 7 8 9 10 11 12 13 15
0 42 47 52 67 70 76 79 91 100
4 Sat/1 E 1 Sat/4 E 5 E 5 E 5 SS 5 SS 1 SS/4 S 5 S 1 S/4 SP 5P
tr tr tr tr 23.0 45.6 49.3 43.0 49.1 54.8
tr tr
0 0 0 0 0 0 0 0
8 9
52 67
5 E 2 E / 3 SS
0 72.7
.4 .5 .4 .8 1.1 2.9
.4 .4 .5 .9 .8 1.0 1.5 2.2 .4 .3
0 0 0 0 0 .4 .5 .7
.3 .5
.3 .6 0 0
B,C,N,S = Processing plants.
2
Sat = Satisfactory; E = eggy; SS = slightly sour; S = sour; SP = slightly putrid; P = putrid. Five panelists.
3
DMS = Dimethyl sulfide, DMDS = dimethyl disulfide, DMTS = dimethyl trisulfide.
"tr = Trace.
rect GC and purge and trap/GC, was also significantly lower in liquid nitrogen samples. Concentrations of DMDS and DMTS tended to increase as the egg products deteriorated but exhibited no sharp increase with the first detection of unacceptable odor. Methyl thioacetate was detected in putrid whole egg samples 1B9, IB 14, and 12C9 and in putrid albumen 22S15. Methanethiol was detected only in IB 14 and 22S15. Chromatograms obtained on analysis of whole egg samples from Can IB by the commercial purge and trap/GC method, with simultaneous desorption of the trap and temperature programming of the GC column, are shown in Figures 1 to 4. The significant difference between
the volatile profiles of the satisfactory and slightly sour samples is the size of the DMS peak. Amount of ethanol purged from the samples increased as the products deteriorated but, as was observed on direct GC analysis, there was no sharp increase in ethanol with the first detection of an unacceptable odor. In the GC/MS analysis of samples containing DMTS, the mass spectrum of the peak with the retention time (ca 15 min) of DMTS was, in some instances, identical with that of the DMDS peak, having the molecular ion 94 of DMDS and not the molecular ion 126 of DMTS. In egg samples high in DMTS and in the commercial preparation of DMTS, spectra for both DMDS and DMTS were obtained at the position of
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30B
DMTS
1930
BROWN ETAL. TABLE 3. Volatile sulfur components determined in pasteurized egg albumen allowed to deteriorate at 14 to 22 C
Can1
Sample no.
Storage time
Odor category 2
DMS3
DMDS
0 0 0
0 0 0 0
(hr) 21S
23S
1
i.ppu,i •
1 10 11(1) 12 12(2) 13 13(2) 14
0 92 120 136 144 164 169 183
5 Sat 1 Sat/4 E 5E 2 E/3 SS 1 E/2 S S / 2 S 2 SS/3 S 4S/1 P 5 S
tr 4 tr .5 17.0 29.7 36.3 36.2 31.8
tr .5 .5 .9 1.1 1.5 1.5 1.5
1 8 9 10 11 11(1) 12 13 14 15
0 50 63 92 116 120 136 164 183 351
5 Sat 3 Sat/2 E 2 Sat/3 E 2 Sat/3 E 5E 1 E / 4 SS 4 SS/1 S 1 SS/4 S 5S 5P
tr tr tr tr 58.2 32.9 44.1 23.9 17.0 9.8
tr .5 .3 .3 1.2 .8 .8 1.3 1.8 62.7
1 10 11 11(1) 12 12(1) 12(3) 13 14
0 92 116 120 136 139 148 164 183
5 Sat 1 Sat/4 E 5E 5E 3 E / l SS/1 S 1 E/3 SS/1 S 2 SS/3 S 1 SS/4 S 5S
tr tr 3.1 9.9 75.0 43.6 33.2 30.1 19.4
tr .5 .6 .8 1.6 1.5 1.1 1.2 1.0
.2 .3 .4 .4 .4
.4 .3 .3 .4 .6 10.6 0 0 0 .3 .4 .5 .3 .4 .3
B,C,N,S = Processing plants.
2
Sat = Satisfactory; E = eggy; SS = slightly sour; S = sour; SP = slightly putrid; P = putrid. Five panelists.
3
DMS = Dimethyl sulfide, DMDS = dimethyl disulfide, DMTS = dimethyl trisulfide.
"tr = Trace.
TABLE 4. Volatile sulfur components in pasteurized egg yolk allowed to deteriorate at 14 to 22 C
Can 1
Sample no.
Storage time
Odor category 2
DMS 3
DMDS
4 Sat/1 E 4 Sat/1 E 4 E / l SS 1 S S / 2 S/2 SP 5P 5P
tr" tr 15.0 19.4 17.1 11.6
(ppu) tr tr .8 .8 1.4 1.0
(hr) 25N
1 2
2 4 5 6 9 10
13 24 36 40 63 92
DMTS
0 0 .3 .6 .6 .6
B,C,N,S = Processing plants. Sat = Satisfactory; E = eggy; SS = slightly sour; S = sour; SP = slightly putrid; P = putrid. Five panelists.
3
DMS = Dimethyl sulfide, DMDS = dimethyl disulfide, DMTS = dimethyl trisulfide.
4
tr = Trace.
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22S
DMTS
INDICATORS OF DETERIORATION IN LIQUID EGG PRODUCTS 5
1931
18
8.5
5 6 o o o lii 3 _l
< >
I 3
o o DC W 3 0.
O
11
3
i
n
IB~5
T*
is!
15
si
is
2T.5
RETENTION TIME IN MINUTES FIG. 2. Chromatogram of pasteurized, whole egg allowed to deteriorate at 14 to 22 C. Sample 1B5, 36 hr, slightly sour. FID, attenuated 1 x 8; FPD, attenuated 104 x 1. Peak identifications: 1, methanol; 2, acetaldehyde; 4. ethanol; 5, acetone; 6, dimethyl sulfide; 7, 1-propanol; 8, 2-butanone; 10, 3-methylbutanol; 11, ethyl propionate; 13, dimethyl disulfide; 14, hexanal; 15, impurity in decanol; 17, impurity in decanol; 18, decanol.
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21.5 9.5 11 12.5 14 ta.5 715.5 s" Y so RETENTION TIME IN MINUTES FIG. 1. Chromatogram of pasteurized, whole egg allowed to deteriorate at 14 to 22 C. Sample 1B4, 24 hr, satisfactory. FID, attenuated 1 x 8; FPD, attenuated 104 x 1. Peak identifications: 1, methanol; 2, acetaldehyde; 4, ethanol; 5, acetone; 6, dimethyl sulfide; 7, 1-propanol; 8, 2-butanone; 10, 3-methylbutanol; 11, ethyl propionate; 13, dimethyl disulfide; 14, hexanal; 15, impurity in decanol; 17, impurity in decanol; 18, decanol.
nr
1932
BROWN ETAL.
T"
15.5 18.5 21.5 Is" so IF I RETENTION TIME IN MINUTES FIG. 3. Chromatogram of pasteurized, whole egg allowed to deteriorate at 14 to 22 C. Sample 1B9, 63 hr, putrid. FID, attenuated 1 x 8 ; FPD, attenuated 10 x 1. Peak identifications: 1, methanol; 2, acetaldehyde; 4, ethanol; 5. acetone; 6. dimethyl sulfide: 7, 1-propanol; 8. 2-butanone; 9. ethyl acetate: 10. 1-methylbutanal; 11. ethyl propionate; 12, methyl thioacetate; 13, dimethyl disulfide; 14, hexanal; 15, impurity in decanol; 16, dimethyl trisulfide; 17, impurity in decanol; 18, decanol.
3 4
6
8,9
o o o o
*
lii _l
< > 2 2 X
< s
T
IF
RETENTION TIME IN MINUTES FIG. 4. Chromatogram of pasteurized, whole egg allowed to deteriorate at 14 to 22 C. Sample 1B14, 183 hr, putrid. FID, attenuated 1 x 8; FPD, attenuated 104 x 2. Peak identificatons: 1, methanol; 2, acetaldehyde; 3, methanethiol; 4, ethanol; 5, acetone; 6, dimethyl sulfide; 7, 1-propanol; 8, 2-butanone; 9, ethyl acetate; 11, ethyl propionate; 12, methyl thioacetate; 13, dimethyl disulfide; 14, hexanal; 15, impurity in decanol; 16, dimethyl trisulfide; 18, decanol.
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Ti
INDICATORS OF DETERIORATION IN LIQUID EGG PRODUCTS REFERENCES
Bullard, R. W., T. J. Leiker, J. E. Peterson, and S. R. Kilburn, 1978. Volatile components of fermented egg, an animal attractant and repellent. J. Agric. Food Chem. 26:155-159. Cronin, E. E, and G. Beswick, 1974. Volatile sulphur compounds produced on the heat treatment of the hen's egg. Proc. 4th. Int. Congr. Food Sci. Technol .1:17-21. Flanders, A., G. Beswick, and D. A. Rosie, 1981. The isolation of volatile sulphur compounds from cooked hen's eggs using two novel trapping methods. Pages 153-162 in Quality of Eggs. Spelderholt Inst. Poult. Res., Beekbergen, Netherlands. Flanders, A., G. Beswick, and D. A. Rosie, 1983. Volatile sulphur compounds produced on the heat treatment of hen's eggs (Gallus domesticus) and egg components. Proc. Int. Congr. Food Sci. Technol. 6th. 1:172-173. Germs, A: C , 1973. Hydrogen sulphide production in eggs and egg products as a result of heating. J. Sci. Food Agric. 24:7-16. MacLeod, A. J., and S. J. Cave, 1975. Volatile flavour components of eggs. J. Sci. FoodAgric. 26:351-360. MacLeod, A. J., and S. J. Cave, 1976. Variations in the volatile flavour components of eggs. J. Sci. Food Agric. 27:799-806. Maga, J. A., 1982. Egg and egg product flavor. J. Agric. Food Chem. 30:9-14. Parkinson, T. L., 1966. The chemical composition of eggs. J. Sci. FoodAgric. 17:101-111. Rayner, E. T , H. P. Dupuy, M. G. Legendre, W. H. Schuller, and D. M. Holbrook, 1980. Assessment of egg flavor (odor) by unconventional gas chromatography. Poultry Sci. 59:2348-2351. Sato, Y., K.Watanabe, andR. Ishihara, 1973. Further studies on amines and neutral compounds in egg white smell. Jpn. J. Zootech. Sci. 44:232-240. Suzuki, J., and M. E. Bailey, 1985. Direct sampling capillary glc analysis of flavor volatiles from ovine fat. J. Agric. Food Chem. 33:343-347. Westendorf, R. G., 1981. Development and application of a semiautomatic purge and trap concentrator. Am. Lab. 13:88-95.
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DMTS. It is thought that some DMTS decomposes to DMDS in the 250 C stainless steel transfer line between the GC/MS interface and the ion source of the MS. The purge and trap technique was not satisfactory for H2S analysis because the Tenax trap did not retain H2S during a 30-min purge. However, use of the direct GC method with an inlet temperature of 50 to 55 C, i.e., below the temperature where H2S would be formed in egg products, did not reveal any H2S in the sour, slightly putrid, or putrid whole egg or the putrid albumen samples examined. This is consistent with the results of Germs (1973), who detected no H2S in egg yolk or albumen held at room temperature for 4 days. Classes of compounds reported by Bullard et al. as contributors to the odor of fermented, dried whole egg product were organic sulfur compounds, amines, esters, and volatile fatty acids. Although some esters were identified in the present investigation, they were not useful as indicators of unacceptability. The methodology was not appropriate for analysis of amines and fatty acids. The DMS detected in the egg products as they were first judged unacceptable may or may not have contributed to the perceived odor. However, the correlation between the presence of significant amounts of DMS and the perception of a slightly sour odor in most of the samples examined suggests that measurement of DMS may serve as an objective method for determining acceptability of liquid or frozen egg products for human consumption.
1933