Quality attributes of paddy rice as affected by frozen storage

Abstract

ABSTRACT After harvest, paddy rice may encounter frozen conditions during the storage and transportation periods. However, the effect of frozen storage on quality of paddy rice remains unclear. In this research, two moisture contents of paddy rice (13.5% and 15.1%) were stored at two frozen temperatures (−18°C and −30°C) for two months and then evaluated for quality attributes, including germination rate, peroxidase and polyphenol oxidase activities, fat acidity, milling quality, pasting property, cooking property, and texture of the cooked rice. The results showed that the frozen storage generally decreased the germination rate, activities of peroxidase and polyphenol oxidase, husked rice yield, head rice yield of paddy rice, reduced the water uptake ratio and volume expansion rate of milled rice during cooking, and lowered the hardness of cooked rice. At frozen condition, the decrease of temperature and the increase of moisture content led to a more pronounced reduction in germination rate and peroxidase activity. Frozen treatment of paddy rice did not significantly affect the pasting temperature of milled rice flour, but decreased the peak viscosity. Fat acidity of paddy rice slightly increased after frozen storage.