Studies on the Suitability for Storage of High Moisture Rough Rice : IV. Effect of self-heat production and air temperature the deterioration of high moisture rough rice on

Abstract

1. Relation between the self-heat production and the deterioration in stored paddy. When the rough rice of six grades of moisture, from 17% to 22%, was stored in insulated wooden boxes of 43 l capacity, the paddy of above 19% did heat produce. The paddy which self-heated 3°C higher than the normal condition began to deteriorate (Figs. 1, 4). When the high and low moisture content rough rice were stored in either mixed or stacked conditions in a box, they heated to higher temperatures and showed more deterioration than the paddy of homogeneous moisture which was equal to the mean moisture of the mixed or the stacked paddies (Figs. 2, 4). The seal-stored paddy was lower in temperature and the density of gas (light-reflect) was higher than that in the open box. The spotted grains were fewer in the sealed box than in the open one (Figs. 3, 4). But the cooked rice was smelled. 2. Effect of controlled temperature in self-heating paddy. The newly threshed rough rice of 28% moisture was stored in wire mesh tanks (5701). The paddy that was self-heated to 40°C and that kept at 18-24°C by periodically forcing air began to deteriorate to spot grains the next days, and deteriorated 40-60% of the grains after 5 days; the latter had somewhat fewer deteriorated grains than the former. The paddy which was constantly forced by room air was dried to 17% within 6 days, and it was not deteriorated (Figs. 5, 6). 3. Effect of storage temperature on the deterioration of stored paddy. When the high moisture rough rich which was controlled at several grades of moisture content from 18% to 25% was stored at 32°C, room temperature, and then at 8°C, the high moisture rough rice deteriorated earlier and grater at 32°C; while in the temperature, deterioration was later and less. The relation between the moisture content of paddies (X) and the storable terms (Y) are shown in the following formulas, (1) log Y=4.47-0.17X in the high temperature. (2) log Y=5.01-0.18X in the room temperature (10-30°C). (3) log Y=5.31-0.18X in the low temperature. When a significant difference was recognized between (1) and (2) or (2) and (3) at these storable terms in equal moisture rough rice; the difference of storage temperature was above 10°C (Table 2). From above facts, the storage of rough rice which was higher than 19% and partial deflection of moisture was danger. If the self-heated rice was cooled there are no effect for control of deterioration.