45C-20 |
Light-induced headspace volatile compound formations in milk |
J. H. LEE and D. B. MIN. Dept. of Food Science & Technology, Ohio State Univ., 2015 Fyffe Ct., 110 Parker Food Science Bldg., Columbus, OH 43210-1007 Light exposure can decrease the nutritional value and the flavor quality of dairy products and this light-induced off-flavor makes the dairy products less acceptable to consumers. Light exposure in milk can induce two distinctive off-flavors. One is sunlight flavor and the other is cardboard-like or metallic flavor. However, the formation mechanisms of light-induced volatile compounds in milk are not fully understood. The objectives of this work were to study the effects of riboflavin and fat content on the fluorescent light-induced volatile compounds in milk and to determine the formation of light-induced volatile compounds using singlet oxygen quencher and free radical scavengers. Five mL of whole milk with the added 5, 10 or 50 ppm riboflavin was put in a 20-mL serum bottle and sealed air-tight with a Teflon-coated rubber septum and an aluminum cap. To evaluate the effects of fat contents in milk, 0.5 to 1.0, 2.0, and 3.4% milk were used. To study the formation mechanisms of light-induced volatile compounds, ascorbic acid, sodium azide, or BHA was used. Sample bottles were kept at 4 oC in the dark and under light in a light box for 8 hr. Volatile compounds of samples were measured at 0, 1, 2, 4, and 8 hr by solid phase microextration method. Samples were prepared in triplicate at each sample analysis. Pentanal, dimethyl disulfides, hexanal, and heptanal were formed only in the light stored milk and increased significantly as the riboflavin concentration increased from 5 to 10, 50 ppm (P<0.05). As the fat contents in milk increased from 0.5 to 1.0, 2.0, and 3.4%, pentanal, hexanal, and heptanal increased significantly (P<0.05) but dimethyl disulfide concentration did not change (P>0.05). BHA and ascorbic acid, hydrogen donating free radical scavengers, reduced hexanal and heptanal formation. Sodium azide, a singlet oxygen quencher, prevented dimethyl disulfide formation. Formation of pentanal is different from that of hexanal and heptanal in milk. Singlet oxygen and free radicals play important roles in the formation of the light-induced volatile compounds in milk.
Session 45C, Food Chemistry: Flavor and aroma chemistry
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