Effect of soaking time, pre-germination time and parboiling processes on chemical and physicochemical properties of paddy and brown rice
2011
Praopen Rattanadee(Kasetsart University, Bangkok (Thailand). Faculty of Agro-Industry. Department of Food Science and Technology) | Onanong Naivikul(Kasetsart University, Bangkok (Thailand). Faculty of Agro-Industry. Department of Food Science and Technology) E-mail:[email protected]
Aim of this study was to investigate effects of germination on the chemical and physicochemical properties of paddy and brown rice, one variety of Thai rice (Chai Nat 1) was selected. In a pre-germination process of rice grains, the effect of soaking time at 30 percent moisture content 30 deg C was investigated , the results showed that the optimal soaking times for pre-germination were 12 h for paddy rice and 4 h for brown rice, and the pre-germination time at subsequent embryo growth lengths of 3 stages, 0.5-1 mm (minimum), 1-2 mm (optimum) and 2-3 mm (maximum) at 30 deg C were 16, 20 and 24 h respectively for paddy rice, and 12, 16 and 20 h, respectively for brown rice. After both ungermination and pre-germination of all 3 stages from paddy and brown rice were steamed at 121 deg C for 8 min were analysed for chemical and physicochemical properties. The amount of crude protein (percent dry basis), reducing sugar (percent dry basis), and alpha-amylase activity in the pre-germinated brown rice (PGBR) and parboiled pre-germinated brown rice (PPGBR) from paddy rice were significantly higher (p LT 0.05) than those of PGBR and PPGBR from brown rice and ungerminated brown rice. The pasting properties (peak viscosity, trough, breakdown, final viscosity and setback) of the PGBR and PPGBR from paddy rice were lower than those of PGBR and PPGBR from brown rice and ungerminated brown rice.
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