45C-23 |
Photooxidation and chlorophyll photosensitized oxidation of the volatile compound formations from lard |
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-induced lipid oxidation can be either photooxidation or photosensitized oxidation depending on the absence or presence of photosensitizers in samples, respectively. Study of photooxidation on lipid is not easy due to the difficulty of removing photosensitizers completely in foods and model systems. A combination of adsorbents including activated silica gel, Celite, powder sugar, and activated charcoal has been used to remove the impurities from vegetable oils using solvent under nitrogen gas. The objectives of this work were to develop a photosensitizer-free lipid model system using lard and to study the volatile compounds in chlorophyll photosensitized lard. Chlorophyll was dissolved in the oils from lard to obtain 0 and 5 ppm in a 55 oC water bath while magnetic stirring. Samples of 0.1 g lard with 0 or 5 ppm chlorophyll were put in 10-mL serum bottles and sealed air-tight with Teflon-coated rubber septa and aluminum caps. Sample bottles of the lard were kept at 55 oC in a tungsten light box. One set of sample bottles was wrapped with aluminum foil to make a dark condition. Volatile compounds and headspace oxygen content in sample bottles were analyzed at 0, 6, 12, 24, 36, and 48 hr. Sample bottles were prepared in duplicate at each sample analysis. Total volatile compounds in lard with 5 ppm chlorophyll under light were 19 times more than that in samples with 0 ppm chlorophyll for 48 hr. Headspace oxygen content in lard with 5 ppm chlorophyll under light changed from 21 to 15% for 48 hr but that in lard with 0 ppm chlorophyll did not change significantly (P>0.05). Photooxidation mechanism on lipid seems to be a free radical chain reaction like autoxidation. Photosensitizer-free lipid model system was developed using lard, which can be used for the study of photosensitization and photooxidation on lipids. Singlet oxygen can explain the formation of volatile compounds and headspace oxygen depletion in photosensitized oxidation of lard.
Session 45C, Food Chemistry: Flavor and aroma chemistry
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