STRUCTURAL AND NUTRITIONAL CHANGES IN IRRADIATED FOOD PROTEINS (ANTIOXIDANTS, QUALITY, PROCESSING EFFECT TOXICOLOGY, RADIATION).
AuthorKRUMHAR, KIM CARLETON.
KeywordsIrradiated foods -- Nutrition.
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PublisherThe University of Arizona.
RightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
AbstractA two part study was designed to investigate radiation-induced structural and nutritional changes in food proteins. Model systems composed of 0.1-10% myoglobin, lactalbumin or BSA were used and the effects of propyl gallate, ascorbic acid, air or nitrogen, pH 5, 6 or 7 citrate or phosphate buffer, and addition of glucose and SDS were investigated. We found that 0.02-0.04% propyl gallate (PG), alone or in conjunction with other solutes, inhibited protein aggregation after irradiation to 0.5 and 1.0 megarad and subsequent -20 C storage for 3-6 months. PG alone at 0.04% yielded up to 90% retention of myoglobin after 0.5 megarad and up to 94% retention of lactalbumin after 1.0 megarad as compared to unirradiated controls. BSA appeared more radiation sensitive than other proteins, and use of 0.02% PG yielded retention of only 10% of the original protein after 1.0 megarad. Use of synergists such as glucose or SDS together with PG allowed up to a two-fold increase in protein retention, while use of 0.02% ascorbic acid led to lower retention compared to samples irradiated alone in control buffer. Irradiations at pH 5 and 6 yielded greater protein retention than at pH 7. Isoelectric focusing of myoglobin revealed acidic shifts in protein pI with new bands at pH 4.9-5.2 after irradiation at pH 6 with glucose and PG. A similar acidic shift was seen in focusing lactalbumin, with major new bands forming at pH 3.7-4.0 after irradiation in pH 6 phosphate with 0.04% PG. BSA showed a bipolar pattern of pI shifts after irradiation in pH 6 phosphate. Mice fed irradiated lactalbumin in factorial studies grew slightly faster and ate more than unirradiated controls, while those fed protein irradiated with 0.02% PG showed slightly decreased rates of gain and feed consumption. Amino acid analysis revealed a 35% decrease in lysine, as compared to control, in diets prepared with protein irradiated to 1.0 megarads in 0.05 M phosphate, pH 6 with 0.02% PG. The negative effects of PG on feeding and growth were reduced when protein was irradiated at 22.5% rather than 15% (w/v). Liver to body weight ratios among animals fed protein irradiated with PG were decreased by 18% in contrast to control animals fed identical, though unirradiated, diet. (Abstract shortened with permission of author.)
Degree ProgramNutrition and Food Science