Studies on some comparative milling properties of raw and parboiled rice.

Abstract

Parboiled rice required greater abrasive force and/or longer period of milling than raw rice tor milling to the same degree of polish in a laboratory McGill polisher. Breakage increased slowly during millina' of both raw or parboiled rice up to 7-8 per cent polish; at higher percentages of polish, breakage increased rapidly. Breakage was lower in parboiled rice than in raw rice both during shelling and milling. The sticking of bran to rice while polishing of parboiled rIce is caused by the 'oiliness' of the surface. It can be overcome by using a moderate abrasive force and increasing the milling time. The use of a sievlng-cum-brushing device helps in eliminating the bran. Bran from parboiled rice contains a certain proportion of large particles and this contributes to the clogging of sieves while polishing. Bran from parboiled rIce can be removed with little 10S1il of endosperm. Colour eJl:tracdon studies using a red variety of rice showed that for equal weight of bran removed during polishing, a greater amount of aurface bran can be removed from parboiled rice than from raw rice.