CHANGES IN PROPERTIES OF PARBOILED RICE DURING AGING

Five non-waxy varieties of paddy were parboiled under two conditions, milled, stored for 40 months in the laboratory, and analyzed for various properties at intervals. A waxy variety was partially tested. original raw paddy was also stored, and then parboiled at the same Intervals as above and analyzed as control. In both sets, hydration, Brabender viscosity and slurry viscosity increased over a period of 6-10 months, and then decreased steadily until the end of the experiments. Solubility of amylose and mobility of alkaline gel decreased steadily, while firmness of cooked rice Increased steadily. The changes with time were strikingly similar to those undergone by raw rice during ageing, thereby showing that ageing changes occurred in parboiled rice just as in raw rice. The results suggested that neither amylases, free fatty acids, nor carbonyl compounds are responsible for the storage changes in rice. Firmness of cooked rice was well correlated with water-insoluble amylose content in all samples, regardless of parboiling or ageing.