8-3 |
Lipid oxidation: A problem in multiple phases |
J. B. GERMAN, S. Watkins, and E. Frankel. Dept. of Food Science & Technology, Univ. of California, Davis, 212 Food Science & Technology, Davis, CA 95616 The oxidation of polyunsaturated fatty acids remains a major problem in the deterioration of food quality and is now recognized to be an important source of damage to living biological tissues. As lipid oxidation is a thermodynamically spontaneous process it can be slowed, but not stopped and in biology, repair is as important as prevention. Antioxidants provide kinetic hindrance to lipid oxidation and though this has been well described, traditional approaches largely treat lipid containing foods and biological tissues as homogeneous. In fact, lipids function in biology as structural elements forming discrete phases in water and cells. Therefore the partitioning of substrates, catalysts and antioxidants into these phases is an important aspect of both the rate, and types of products formed as a result, of lipid oxidation. For example, in foods, the partitioning of antioxidants into different phases can have a dramatic impact on their activity in slowing oxidation, and the ability to transport insoluble antioxidants in water affects their activity in emulsions. Within cells, the importance of structure is even more apparent. docosahexaenoic acid is accumulated selectively into the mitochondrial inner membrane phospholipid cardiolipin. The replacement of oleic acid by docosahexaenoic acid in the mitochondria of cultured human cells causes a significant increase in the leakage of reactive oxygen species from the mitochondria. Therefore, future directions for designing stability into foods and living tissues must specifically define the phases and subcellular location of lipid oxidation and focus protection there.
Session 8, Oxidation in heterogenous foods and biological tissues: Impact on food quality and health
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