Basic Studies on Parboiled Rice (1)

Processing Methods and Hydrating Characteristics of Paddy during Soaking

Abstract

Parboiled rice has been known for a long time in some countries of Asia and of Africa, where the people prefer parboiled rice.
The advantage of parboiling treatment comes from the fact that the treatment gelatinizes the rice starch and thus hardens the rice grains. consequently the milling loss is decreased.
The conventional parboiling process consists of soaking of the paddy in cold or lukewarm water for 48 to 72 hours, steaming for 10 to 30 minutes and then drying in the sun. The process has not been standardized to any extent and the produced rice has many disadvantages. Parboiled rice prepared under primitive conditions, has a very dark yellow color, undesirable flavor, aroma, lack of uniformity. Research should be undertaken to study the problems of industrializing and mechanizing the conventional methods for the purpose of improving productions, obtaining products of high quality and increasing commercial value.
This investigation was carried out to produce parboiled rice with a comparatively simple method and to study the effects of parboiling conditions on physicochemical properties by measuring certain changes in rice grains when they were parboiled.
The results of experiments in this report were as follows,
(1) Since soaking paddy in cold or lukewarm water for a long time not only decreased hydrating effects of paddy but made disagreable chnages such as a fermentation in rice grains, soaking should be finished within 24 hours.
(2) Raise of the soaking temperature increased the rate of hydration and kept hydrating effects comparatively long time.
(3) Soaking temperature should be set up below gelatinization temperature of rice starch in order to avoid changes of properties in rice grains.
(4) Prope use of either raw paddy of dried paddy as occasion required had good effects on saving resources and cutting down expenses of processing.