Effect of storage on the chemical composition of husked, undermilled and milled rice

Abstract

Raw husked rice, raw undermilled rice containing I-8 µg. of thiamine/g., parboiled rice and raw milled rice were stored in gunny bags for a period of one year. The samples were kept free from infestation. The changes in the grain during storage have been studied. The amylase activity in freshly harvested rice decreased rapidly; there was an improvement in the cooking quality, and in all the samples, except parboiled undermilled rice, a loss of thiamine of about 20-30% was observed. A decrease in nitrogen soluble in 3% sodium chloride solution was observed, and this may be due to denaturation of protein during storage. There was an increase in the acidity and the peroxide value of the fat present in the different samples of rice, the increase being at a maximum for husked rice. The storage lives for the various samples, as estimated by plotting the peroxide values of the fat against the storage period for all the samples in conjunction with organoleptic tests at the end of one year, are approximately as follows: raw husked rice, 7 months; raw undermilled rice, 12 months; parboiled undermilled rice, II months; and raw milled rice 13 months.