45C-22 |
Off-odor study in gamma irradiated orange juice by sensory and volatile compound analyses |
S. R. YOO1, D. B. Min1, A. Prakash2, and J. H. Lee1. (1) Dept. of Food Science & Technology, Ohio State Univ., 2015 Fyffe Ct., 110 Parker Food Science Bldg., Columbus, OH 43210-1007, (2) Dept. of Food Science & Nutrition, Chapman Univ., 1 University Dr., Orange, CA 92866 Ionizing radiation is a non-thermal technique and has been used to preserve foods, due to the effective inactivation of human pathogens. However, irradiation treatment can develop distinctive off-odor in foods. These off-odor from irradiation treatment makes the food products less or unacceptable to consumers. The qualitative differences of volatile compounds in irradiated and non-irradiated orange juice have not been reported. The objectives of this work were (1) to determine the volatile compounds generated by gamma irradiation in orange juice, (2) to identify the off-odor volatile compounds in the irradiated orange juice, and (3) to study the chemical mechanisms for the formation of off-odor volatile compounds in orange juice by irradiation. Single-strength unpasteurized orange juice from Valencia oranges was gamma irradiated at 0, 0.5, 1.0, 2.0, and 3.0 kGy. The 75 mm Carboxen/divinylbenzene solid phase microextraction (SPME) fiber was used to isolate volatile compounds in 10-mL sample bottles for 30 min at 40°ĘC. The identification of compounds was made by a combination of GC mass spectrum and gas chromatographic retention times of standard compounds. The orange juice samples irradiated at 0, 0.5, 1.0, 2.0, and 3.0 kGy were evaluated by 15 sensory panels. As the dosage of irradiation increased from 0 to 0.5, 1.0, 2.0, and 3.0 kGy, the total volatile compounds in irradiated orange juice increased by 12, 15, 24, and 54%, respectively, in GC electronic counts, compared to that of the control sample. Dimethyl sulfide, dimethyl disulfide, and 2-butanone, which were not present in the non-irradiated samples, were present in irradiated orange juice. Dimethyl disulfide and dimethyl sulfide, which come from the radiolysis of sulfur-containing amino acids, were increased in irradiated orange juice. Sensory evaluation showed that non-irradiated orange juice was significantly different from orange juice irradiated from 0.5 to 3.0 kGy (P<0.05) with burning rubber, chemical, and alcohol odor. Dimethyl sulfide, dimethyl disulfide, and possible other sulfur compounds, which could be formed in orange juice by gamma irradiation, may play an important role in the off-odor formation in irradiated orange juice.
Session 45C, Food Chemistry: Flavor and aroma chemistry
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