INTRODUCTION. G. Cherian,*,2 M. P. Goeger,* and D. U. Ahn

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1 Dietary Conjugated Linoleic Acid with Fish Oil Alters Yolk n-3 and Trans Fatty Acid Content and Volatile Compounds in Raw, Cooked, and Irradiated Eggs 1 G. Cherian,*,2 M. P. Goeger,* and D. U. Ahn *Department of Animal Sciences, Oregon State University, Corvallis, Oregon ; and Department of Animal Sciences, Iowa State University, Ames, Iowa ABSTRACT We investigated the effect of dietary conjugated 0.05). The yolk contents of cis-9 trans-11 CLA and transfatty linoleic acid (CLA) along with n-3 polyunsaturated acid (n-3 PUFA) on yolk fatty acid composition and 10 cis-12 CLA increased linearly (P < 0.05) as the dietary CLA supply increased. Total monounsaturates were reduced (P < 0.05) with an increase in saturates in yolk. No volatile compounds in eggs that were raw (RA), hardboiled (HB), or hard-boiled, irradiated (HBI, 2.5 kgy). difference was observed in the total PUFA content of Single Comb White Leghorn laying hens (n = 40) were eggs. Total volatiles were reduced in RA eggs from 1.0 and 2.0% CLA diets. 2-Propanone, hexane, and methyl randomly assigned to one of the four experimental diets cyclopentane were the major volatiles in RA eggs and containing 0, 0.5, 1.0, or 2.0% CLA. Menhaden oil was were reduced by dietary CLA at 1.0 and 2.0%. Acetaldehyde, pentane, propanol, acetic acid methyl ester, acetic used as the source of n-3 PUFA. Eggs collected after 6 wk of feeding were analyzed for fatty acids and volatile acid ethyl ester, propionic acid methyl ester, 2-methylmethyl propionic acid, 2-propanone, and octane were the compounds. The content of docosahexaenoic acid (C22:6 n-3) was reduced (P < 0.05) in eggs from hens fed the 2.0% major volatiles in HB eggs and were reduced by 2.0% CLA diet. Eggs from hens fed 0.5% CLA incorporated the highest concentration of docosahexaenoic acid (P < 0.05) with a concomitant reduction in arachidonic acid (P < CLA (P < 0.05). No difference was observed in the acetaldehyde, pentane, propanol, acetic acid ethyl ester, octane, or total volatile content of HBI eggs. (Key words: conjugated linoleic acid, egg, n-3 polyunsaturated fatty acid, irradiation, volatiles) 2002 Poultry Science 81: INTRODUCTION Conjugated linoleic acid (CLA) is the generic name for a group of positional and geometric conjugated dienomic isomers of linoleic acid and has received considerable attention for its anticarcinogenic, antiatherogenic, and hypocholestrolemic properties (Pariza et al., 2001). Other beneficial effects of CLA include body fat reduction, immuno-modulation, and antioxidant properties (Cook et al., 1993; Cantwell et al., 1999; DeLany et al., 1999). Humans cannot synthesize CLA; it is contributed to the human diet by food lipids of ruminant origin such as milk and beef. Current intake of CLA is estimated to be several hundred milligrams per day (Fritsche et al., 1999). However, considering the variation in CLA content of food products, these estimates are questionable. Based on ani Poultry Science Association, Inc. Received for publication December 4, Accepted for publication May 9, Journal paper number of the Oregon Agriculture Experiment Station, Corvallis, OR ; Project No To whom correspondence should be addressed: mal data, it is estimated that approximately 3 g/d of CLA would be required to produce beneficial effects in humans (Ha et al., 1989). However, as Americans are opting for low-fat dairy products and choosing more poultry foods than beef, it is likely that dietary contribution of CLA will further be reduced in a typical US diet. CLA, when associated with food, has been reported to have higher tissue retention and better anticancer effects than commercially available supplements (Ip et al., 1999). In this respect, CLA-enriched chicken poultry foods may be an alternative vehicle for delivering health-promoting fatty acids to consumers. Feeding CLA to hens can contribute substantially to the energy content (Sell et al., 2001) and also increase the CLA content of tissues and yolk (Ahn and Sell, 1999; Chamruspollert and Sell, 1999; Jones et al., 2000). These researchers used soy oil or canola oil along with CLA to feed laying hens. Recently, Cherian et al. (2001) used Abbreviation Key: CLA = conjugated linoleic acid; HB = hard-boiled; HBI = hard-boiled, irradiated; MUFA = monounsaturated fatty acids; PUFA = polyunsaturated fatty acids; SFA = saturated fatty acids; RA = Raw. 1571

2 1572 CHERIAN ET AL. fish oil [as source of n-3 polyunsaturated fatty acid (n-3 PUFA)] along with CLA in the diet of laying hens to produce n-3 PUFA-CLA-rich eggs. Incorporating PUFA and CLA into eggs may influence the stability of lipids and fatty acids and may change the volatiles of eggs. However, no information is available on the influence of PUFA and CLA on the volatile profiles of raw and cooked eggs. Irradiation of foods including eggs has gained as an effective tool for assuring food safety and controlling bacteria such as salmonella (Rajkowski and Thayer, 2000). However, one concern with irradiation is increased lipid peroxidation due to production of free radicals. Eggs high in PUFA may be more susceptible to lipid oxidation. Therefore, irradiation can lead to increased production of lipid peroxidation products and lower consumer acceptability. Feeding CLA has been reported to reduce PUFA in eggs (Du et al., 1999). Therefore, PUFA-CLArich eggs may be less susceptible to irradiation-induced lipid peroxidation. The hypothesis for the present study is that CLA may reduce the PUFA content of eggs, resulting in the formation of less lipid oxidation products. The consumer acceptability of PUFA-CLA-modified eggs also depends on odor and sensory quality characteristics. The objectives of the present study were to determine the influence of dietary PUFA and CLA on yolk fatty acids and CLA incorporation and to determine the volatile profiles of raw (RA), hard-boiled (HB), hard-boiled and irradiated (HBI) eggs. MATERIALS AND METHODS These experiments were reviewed by the Oregon State University Animal Care Committee to ensure adherence to Animal Care Guidelines. Birds and Diets A total of 40 Single Comb White Leghorn laying hens were kept in individual cages and were fed corn-soybean meal-based diets with added CLA at 0, 0.5, 1.0, and 2.0%. The control diet (0% CLA) contained 3% menhaden oil, and the CLA source was substituted for menhaden oil on a weight:weight basis. The composition of the diet is shown in Table 1. The CLA source, which contained 75% free fatty acid, was obtained from a commercial source and contained 34.9% cis-9 trans-11, and 35.9% trans-10 cis-12 CLA isomers. 3 The diets were prepared biweekly and kept at 4 C in airtight containers. Hens were fed the experimental diets for 42 d. Sample Collection Eighteen eggs per treatment, collected from Days 40 through 42 of feeding, were taken for fatty acid analysis, 3 Pharmanutrients, Lake Bluff, IL. TABLE 1. Composition and calculated analysis of the laying hen diets 1 Ingredients (% of diet) Corn Soybean meal Limestone Calcium phosphate Layer premix Fish oil CLA Salt DL-Methionine Calculated analyses Crude protein ME, kcal/kg 2, , , ,938.5 Calcium Available phosphorus All diets contained corn and soybean meal, with added CLA at 0, 0.5, 1.0, or 2.0%. 2 Supplied per kilogram of the diet the following: vitamin A, 8.25 KIU/kg; vitamin D, 2.64 KIU/kg; vitamin E, 16.5 KIU/kg; riboflavin, 5.28 mg/kg; niacin, 26.4 mg/kg; vitamin B 12, 8.91 MCG/kg; biotin, mg/kg; pyridoxine, 1.32 mg/kg; thiamine, mg/kg; selenium, mg/kg; manganese, 90.4 mg/kg; zinc, 92.4 mg/kg. cooking, and volatile compounds assay (six eggs per treatment per assay). Egg Cooking Prior to hard boiling eggs were maintained at room temperature for 24 h. Eggs (n = 6 per treatment) were cooked at 98 C for 30 min, cooled in ice water for 20 min, and equilibrated at room temperature for 15 min (Cherian et al., 1990). HB and RA eggs were shipped by overnight express to Iowa State University for volatile analysis. Lipid and Fatty Acid Analyses Total lipids were extracted from egg yolks by the method of Folch et al. (1957). One gram of yolk was weighed into a screw-capped test tube with 20 ml of chloroform:methanol (2:1, vol/vol) and was homogenized with a Polytron for 5 to 10 s at high speed. The homogenate was filtered through Whatman no. 1 filter paper into a 100-mL graduated cylinder, and 5 ml of 0.88% sodium chloride solution was added and mixed. After phase separation, the volume of the lipid layer was recorded, and the top layer was removed by siphon. Three milliliters of the lipid extracts was dried in a block heater under nitrogen atmosphere and used for fatty acid analyses. The dried lipids were redissolved in 2 ml borontrifluoride-methanol methylation solution (Cherian et al. 1996) and were incubated in a boiling water bath for 1 h at 90 to 100 C (Wang et al., 2000). After cooling to room temperature, the fatty acid methyl esters were separated by hexane and distilled water. Analysis of fatty acid composition was performed with a HP 6890 gas chromato-

3 CONJUGATED LINOLEIC ACID AND EGG VOLATILES 1573 graph 4 equipped with an autosampler, flame ionization detector, and SP-2560 fused silica capillary column (100 m 0.25 mm 0.2-µm film thickness). 5 Two microliters of sample was injected with helium as carrier gas (1.0 ml/min) onto the column. The initial column temperature was set at 110 C, held for 0.5 min, increased by 20.0 C/min to 200 C, and held for 50 min. The temperature was then increased by 10.0 C/min to 230 C and held for 5.0 min. Inlet and detector temperatures were 250 C. Peak areas and percentages were calculated using HP ChemStation software. 4 Fatty acid methyl esters were identified by comparison with retention times of authentic standards. 6 Fatty acid values and total lipids were expressed as weight percentages. Irradiation HB eggs were packaged in oxygen-permeable plastic bags and irradiated at 0 or 2.5 kgy using a Linear Accelerator. 7 The energy and power level used were 10 MeV and 10 kw, respectively, and the average dose rate was 89.0 kgy/min. To confirm the target dose, two alanine dosimeters per cart were attached to the top and bottom surfaces of the sample. The alanine dosimeter was read using a 104 Electron Paramagnetic Resonance instrument. 8 Volatile Compound Analysis A purge-and-trap apparatus 9 connected to gas chromatograph-mass spectrometer 4 was used to analyze the volatiles responsible for the off-odor in samples. A 2-g sample was placed in a 40-mL sample vial that had been flushed with helium gas (99.99%) for 5 s. The egg sample was then purged with helium gas (40 ml/min) for 15 min. Volatiles were trapped at 20 C using a Tenax column, 9 desorbed for 2 min at 220 C, focused in a cryofocusing unit at 100 C, and then thermally desorbed into a column for 30 s at 220 C. A combined column HP-624 column, 250-µm i.d. with 1.4 µm nominal; a 52-m HP-1 column, 250-µm i.d. with 0.25 µm nominal; and an 8-m HP-wax column 250-µm i.d. with 0.25 µm nominal combined using zero dead-volume column connectors were used for volatile analysis. Ramped oven temperature was used (0 C for 2.5 min, increased to 10 C at 2.5 C/min, to 45 C at 10 C/min, to 110 C at 20 C/min, to 180 C at 10 C/min, and held for 2.5 min). Inlet temperature was 180 C. Liquid nitrogen was used to cool the oven below ambient temperature. Helium was the carrier gas at constant pressure of 20.5 psi. The ionization potential of mass spectrometry was 70 ev and the scan range was 18.1 to 300 m/z. Identification of volatiles was achieved by comparing mass spectral 4 Hewlett Packard Co., Wilmington, DE. 5 SP-2560, Supelco, Bellefonte, PA. 6 Matreya Inc, Pleasant Gap, PA. 7 Circe IIIR, Thomson CSF Linac, Saint-Aubin, France. 8 Bruker Instruments Inc., Billerica, MA 9 Tekmar-Dohrmann, Cincinnati, OH. TABLE 2. Major fatty acid composition of egg yolk as influenced by hen diets containing different levels of conjugated linoleic acid 1 Fatty acids (%) SEM (% of total lipids) 16: b 33.8 a 34.7 a 35.3 a :0 8.7 c 16.2 b 19.7 a 20.7 a :1 n a 24.7 b 20.9 c 17.4 d :2 n :4 n ab 0.5 b 0.7 ab 0.8 a :6 n c 4.2 a 3.8 b 2.5 d 0.10 Cis-9 trans-11 CLA d 0.8 c 1.6 b 3.6 a 0.06 Trans-10 cis-12 CLA 0.0 c 0.16 c 0.8 b 1.6 a 0.08 Total CLA 0.0 d 0.97 c 2.4 b 5.3 a 0.13 Total SFA 38.3 c 51.3 b 55.5 a 56.8 a 0.67 Total MUFA 41.4 a 26.8 b 22.4 c 18.7 d 0.40 Total PUFA a-d Means within a row with no common superscript differ (P < 0.05); n = 6. 1 All diets contained corn and soybean meal, with added CLA at 0, 0.5, 1.0, or 2.0%. CLA was substituted for menhaden oil on a weight:weight basis. 2 CLA = conjugated linoleic acid; SFA = saturated fatty acids, MUFA = monounsaturated fatty acids; PUFA = polyunsaturated fatty acids. data of samples with those of the Wiley Library and standards when available. The area of each peak was integrated using the ChemStation software, 4 and the total ion counts (peak area s) 10 4 were reported as an indicator of volatiles generated from the egg samples. Statistical Analyses The effects of dietary CLA on yolk fatty acids and volatile compounds were analyzed by ANOVA using SAS software (SAS Institute, 1985). Student-Newmann- Keul s multiple-range test (Steel and Torrie, 1980) was used to compare differences among treatment means (P < 0.05). Means and SEM are reported. RESULTS AND DISCUSSION The CLA content of the egg yolk increased significantly in a dose-dependent manner with the dietary CLA content. At 2.0% CLA, yolks showed the highest incorporation of CLA. The total yolk CLA was 5.3% with the 2.0% CLA diet but was 0% with the control diet (P < 0.05) (Table 2). The major CLA isomer in the yolk lipids was cis-9 trans-11 isomer, which was 0, 0.8, 1.6, and 3.6% in the yolk lipids of hens fed 0, 0.5, 1.0, or 2.0% CLA diets, respectively. The content of trans-10 cis-12 CLA isomer constituted 0, 0.16, 0.8, and 1.6% of yolk lipids from hens fed diets containing 0, 0.5, 1.0, or 2.0% CLA, respectively. Addition of 2% CLA to diets resulted in greater than 50% reduction of monounsaturated fatty acids (MUFA) and was replaced by saturated fatty acids (SFA). These results also corroborate with those reported by Chamruspollert and Sell (1999) and Du et al. (1999). 9 -Desaturase is responsible for the conversion of stearic acid (18:0) to oleic acid (18:1). Dietary CLA may have inhibitory effect on desaturases, which may lead to reduction of MUFA.

4 1574 CHERIAN ET AL. TABLE 3. Volatile profiles of raw egg yolk as influenced by hen diets containing different levels of conjugated linoleic acid (CLA) 1 Volatiles SEM (total ion counts 104) Oxybis methane 120 d 338 c 534 b 770 a 40 1,1-Oxybis ethane 144 ab 113 b 147 ab 200 a 20 2-Propanone 1,368 a 1,071 ab 454 b 476 b 206 Hexane 1,470 a 1,159 a 623 b 329 b 162 Methyl cyclopentane 865 a 1,013 a 422 b 236 b 170 Total 3,966 a 3,694 a 2,180 b 2,011 b 314 a,b Means within a row with no common superscript differ (P < 0.05); n = 6. 1 All diets contained corn, soybean meal, and fish oil with added CLA at 0, 0.5, 1.0, or 2.0%. SEM = standard error of the mean. Choi et al. (2000) also reported that a decrease in mrna expression of steroyl coenzyme A in CLA-fed rats affected the synthesis of MUFA and accumulation of SFA. The SFA contents of eggs from hens fed 1.0 and 2.0% CLA were higher (P < 0.05) than hens fed 0 and 0.5% CLA diets. These results suggest an inhibitory effect of CLA on enzymes responsible for MUFA synthesis, resulting in accumulation of SFA. Dietary CLA did not alter the total n-6 and n-3 PUFA contents of yolk. The volatile profiles of raw eggs are shown in Table 3. No volatile unique to eggs from hens fed CLA diets were identified, indicating that the changes were quantitative. The total amount of volatiles was reduced (P < 0.05) in eggs from hens fed diets containing 1.0 and 2.0% CLA. Alkanes and ketones were the major volatiles in raw eggs and were reduced in eggs from 1.0 and 2.0% CLA eggs. The contents of 2-propanone, hexane, and cyclopentane were reduced (P < 0.05) as the diet concentration of CLA increased. Production of volatiles is closely related to oxidative changes in eggs. Irrespective of the higher total PUFA (n-6 + n-3) content of eggs from the 2.0% CLA diet, the reduction in volatile components may suggest that dietary CLA has a protective effect on lipid oxidation, thereby increasing the oxidative stability. Cooking resulted in a significant increase in volatile compounds in HB eggs. Formation of flavor compounds may be initiated in the lipid portion of food during heating, resulting in an increase in volatiles of HB eggs. A total of 25 volatiles were identified and quantitated in the HB eggs (Table 4). Those volatiles in the greatest concentrations in CLA-rich eggs (1.0 and 2.0% CLA diets) were pentane and hexane and were reduced (P < 0.05) by dietary CLA. Volatile classes such as sulfides, furans, esters and ketones, and total volatiles were reduced in eggs from hens fed 1.0 and 2.0% CLA diets. Dimethyl sulfide and other sulfur compounds are derived from degradation of amino acids and are associated with irradiated odor formation (Ahn et al., 2000). Brown et al. (1986) reported the odor of dimethyl sulfide as sulfurous, or bad eggs, and was associated with spoilage of egg com- TABLE 4. Volatile profiles of cooked egg yolk as influenced by hen diets containing different levels of conjugated linoleic acid (CLA) 1 Volatiles SEM / (total ion counts 104) 2-Methyl-1-propene 21 b 175 a 109 a 142 a 25 Butane 113 c 374 b 667 a 406 b 66 Acetaldehyde 1,362 a 0 c 760 b 801 b Butene 0 b 2,644 a 0 b 0 b 208 Pentane 3,545 b 5,229 b 10,329 a 6,659 b Pentene 0 b 462 a 452 a 569 a 68 Propanol 718 b 3,729 a 1,388 b 1,362 b Propanone 713 a 0 b 0 b 0 b 0 Thiobismethane 671 1, Acetic acid methyl ester 5,535 a 9,099 a 0 b 0 b 1,175 2-Methylpropanal 0 b 282 a 289 a 236 a 24 Hexane 708 c 1,417 c 5,322 a 3,304 b 510 Butanal 0 b 192 a 0 b 0 b 34 2-Butanone Acetic acid ethyl ester 3,712 17, ,437 Propionic acid methyl ester 842 ab 1,434 a 0 b 0 b 233 Benzene 147 a 0 b 0 b 0 b 3 3-Methylbutane 244 a 187 b 0 c 0 c 18 Heptane Methylmethyl propionic acid 1,237 ab 1,758 a 0 b 0 b Ethylfuran 729 a 447 b 229 c 302 c 25 Pentanal 181 a 142 a 0 b 0 b 22 Dimethyl disulfide 645 a 185 b 0 b 0 b 54 Toulene Octane 82 ab 185 a 158 a 0 b 38 Total 22,153 b 47,305 a 21,109 b 15,545 b 5,926 a-c Means within a row with no common superscript differ (P < 0.05); n = 6. 1 All diets contained corn, soybean meal, and fish oil with added CLA at 0, 0.5, 1.0, or 2.0%. CLA was substituted for menhaden oil on a weight:weight basis.

5 CONJUGATED LINOLEIC ACID AND EGG VOLATILES 1575 TABLE 5. Volatile profiles of cooked egg yolk from hen diets containing different levels of conjugated linoleic acid (CLA) after irradiation 1 Volatiles SEM (total ion counts 104) Cyclopropane Methyl propane Methyl-1-propene 9,670 8,972 8,243 10, Butane 9,921 6,771 8,087 9, Acetaldehyde 16,023 13,887 23,228 16,143 2,696 2-Butene 1,153 1,310 1,226 1, ,4 Pentadienone 0 b 78 a 0 b 0 b 3 1-Pentene 4,625 3,739 3,939 4, Pentane 31,993 a 13,563 b 21,171 ab 27,675 a 3,332 2-Pentene 1,232 b 898 b 249 b 20,567 a 4,157 Propanol 9,000 a 5,428 b 13,039 a 11,148 a 1,144 2-Propanone 6,161 11,649 12,513 8,810 1,530 Thiobismethane 3,729 2,231 1,191 1, Acetic acid methyl ester 442 c 12,590 a 7,002 b 562 c 1,570 2-Methyl propanal 2,150 2,089 1,781 2, Hexene 2,953 2,342 2,236 2, Hexane 18,901 a 4,299 c 7,683 bc 13,026 b 1,864 2-Hexene 0 b 0 b 195 a 200 a 21 Butanal 2,122 a 577 b 2,030 a 2,241 a Butanone 2,294 b 1,477 b 2,373 b 4,280 a 459 Acetic acid ethyl ester 609 6,521 2,937 10,246 4,424 Propionic acid methyl ester 0 c 1,331 a 509 b 0 c 127 Benzene Methylbutane 1,157 1,389 1,709 2, Heptene 4,358 4,036 3,927 4, Heptane 5,691 2,911 5,048 5, Methyl-methyl propionic acid 156 b 823 a 604 ab 233 b Ethylfuran 243 c 1,098 a 901 b 543 c 60 Pentanal 425 b 487 b 485 b 5,149 a Heptyne Methyl-1-4-cyclopentane 0 b 0 b 213 a 223 a 29 Dimethyl disulfide 240 b 571 a 307 b 292 b 71 Toulene Octene , Octane 1,718 ab 605 b 1,791 ab 2,206 a Octene 0 b 0 b 505 b 1,062 a Methyl-2-heptene 0 b 0 b 501 a 501 a 71 Octyne 0 b 0 b 374 a 360 a 34 Total 139, , , ,797 14,530 a-c Means within a row with no common superscript differ (P < 0.05); n = 6. 1 All diets contained corn, soybean meal, and fish oil with added CLA at 0, 0.5, 1.0, or 2.0%. CLA was substituted for menhaden oil on a weight:weight basis. ponents. Dimethyl sulfide is formed by degradation of sulfur-containing amino acids. The content of methionine or other sulfur containing amino acids in the CLA eggs is not known in the present study. The absence of dimethyl sulfide in eggs from 1.0 and 2.0% CLA eggs may suggest a protective effect of dietary CLA on the degradation of sulfur containing amino acids. The two ketones identified in cooked eggs were 2-propanone and 2-butanone and were reduced (P < 0.05) in 1.0 and 2.0% CLA-eggs. Ketones in foods have been implicated with off-flavors referred to as perfume rancidity (Stokoe, 1928). Propanol was the only alcohol detected in eggs and was higher in eggs from the 0.5% CLA diet when compared to other treatments. The reason is not known for low content of propanol in HB eggs from hens on 1.0 or 2.0% CLA in diet. The contribution of alcohols to flavors of foods has been reported to be minor (Heath and Reineccius, 1986). Aromatic compounds such as benzene were not detected in eggs from CLA-fed hens. The occurrence of lipid and fatty acid oxidation is often associated with deleterious changes in food flavors (Frankel, 1984). PUFA are more susceptible to lipid oxidation. Fatty acids of the n-6 family (linoleic and arachidonic acid) are suggested to be the precursors of hexanal (Meynier et al., 1999). Hexanal and pentanal contents in volatiles are suggested to be good indicators of oxidation (Ahn et al., 1998). Pentanal was not detected in HB eggs from 1.0 and 2.0% CLA diets when compared to eggs from 0 and 0.5% CLA diets. Irradiation is one of the most efficient methods available for ensuring microbiological food safety (Rajkowski and Thayer, 2000). However, irradiation has been reported to increase lipid oxidation and off-odor (Ahn et al., 1998, 1999). The effects of irradiation on PUFA-CLArich eggs are not known. In the present study, a total of 38 different volatiles were identified and quantitated in HBI eggs. Irradiation resulted in an increase (P < 0.05) in the ion counts of total volatiles in all eggs. No difference

6 1576 CHERIAN ET AL. was noted in the total volatiles of control or CLA-rich eggs. Alkanes, alkenes, and aldehydes were the major volatiles in HBI eggs (Table 5). As the content of CLA in the eggs increased, irradiation resulted in an increase in the ion counts of volatiles such as pentanal, pentane, 2-hexene, 2-butanone, 1-methyl-1,4-cyclopentane, octane, 2-octene, 3 methyl-2-heptene, and octyne (P < 0.05). When molecules absorb ionizing energy, they become reactive and form ions or free radicals, which further leads to an increase in oxidation products. Lipid oxidation byproducts are considered important volatiles related to the off-odor in irradiated meat (Jo and Ahn, 2000). The presence of dimethyl sulfide in HBI eggs from hens fed a diet containing 0.5% CLA was higher (P < 0.05) than all other treatments. The reason for this difference is not known. No significant changes in the amount of irradiation-sensitive compounds, such as 1-heptene and 1-heptyne, were observed in eggs. The absence of irradiationsensitive compounds in eggs with high PUFA and CLA may suggest lipid stability and increased sensory quality of n-3 PUFA-modified eggs. The ion counts of other volatiles related to irradiation, such as 2-methyl butanal was not different among treatments (P > 0.05). In conclusion, these studies support the theory that irradiation leads to high ion counts volatiles in cooked eggs. However, no specific volatile compounds unique to irradiation were observed in HBI eggs with high CLA content. Further elucidation of changes in volatile compounds associated with CLA and n-3 PUFA enrichment of eggs and their effects on product quality after cooking and or irradiation may be critical for maintaining overall flavor quality of eggs and egg products and consumer acceptability of such egg-based foods. ACKNOWLEDGMENTS The Ott Professorship awarded to G. Cherian is acknowledged. The CLA used in this study was kindly supplied by Pharmanutrients, Lake Bluff, IL. The assistance of the Oregon State University Poultry Farm staff is acknowledged. The generous donation of menhaden oil from Omega Protein Inc, Reedville, VA, is appreciated. Our sincere thanks are also extended to D. Holtan of the Department of Animal Sciences, Oregon State University, for gas chromatography help. REFERENCES Ahn, D. U., C. Jo, and D. G. Olson Analysis of volatile components and the sensory characteristics of irradiated raw pork. Meat Sci. 54: Ahn, D. U., and J. L. Sell Effect of dietary conjugated linoleic acid on the composition of egg yolk. Poult. Sci. 78: Ahn, D. U., C. Jo and D. G. Olson Headspace oxygen in sample vial affects volatiles production and lipid oxidation of raw and cooked meat during the automated purge-andtrap dynamic headspace/gc analyses. J. Agric. Food Chem. 47: Ahn, D. U., D. G. Olson, J. I., Lee, C. Jo, X. Chen, and C. Wu Packaging and irradiation effects on lipid oxidation and volatiles in pork patties. J. Food Sci. 63: Brown, M. 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