Date of Award

1996

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

First Advisor

Joseph A. Liuzzo

Abstract

While brown rice is nutritionally superior to white rice, it is not shelf stable, becoming rancid in a matter of weeks. Preservation by refrigeration or freezing is expensive and not universally available. Therefore, other preservation methods, such as aqueous ethanol extraction of lipids, have been studied to overcome this problem, but these methods also have limitations. The effects of gamma-irradiation on the physicochemical properties and lipase activity in brown rice has been well documented. Gamma-irradiation has been shown to reduce lipase activity, presumably preserving sensory quality. A sensory study of 2 Louisiana grown varieties (Mars and Lemont) of irradiated brown rice performed at monthly intervals over a period of 6 months was conducted to provide the definitive data to assess this method of preservation for sensory effects. Rough rice was de-hulled, irradiated at 0, 1, and 2 kGy, and stored for a period of up to 6 months at ambient temperature in sealed plastic bags. Duplicate samples were taken at monthly intervals starting with time 0 and evaluated for thiamine and riboflavin status using reverse phase HPLC and sensory quality using an experienced 8-person panel, respectively. These procedures were replicated 3 times to ensure scientific and statistical validity. The 2 kGy treatment level produced the worst hedonic rating for both varieties. The 1 kGy radiation level did not significantly affect the sensory quality of either rice variety. Storage negatively affected nutty and milky attributes, which were stable to irradiation treatment. The rancidity attribute of brown rice samples, as perceived by the sensory panel, was negatively affected by irradiation treatment. The effect of treatment and storage on thiamine and riboflavin levels of the rice samples was significantly different from the control only at the 2 kGy level Mars variety at 6 months of storage. However, treated samples of the Mars variety stored for a period of 6 months retained nearly 50% of original thiamine and riboflavin levels. Thiamine and riboflavin were essentially unaffected by storage or treatment in Lemont rice samples.

ISBN

9780591289084

Pages

111

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