Chemical and Physicochemical Changes of Rice cv. Khao Dok Mali 105 during Storage at Different Temperature

Abstract

Changing of rice qualities during storage are affected by physical conditions such as temperature, moisturecontent and storage time. The objectives of this study were to study the changes in chemical and physicochemicalproperties of post-harvested rice and stored for 7 months at temperatures of 25 ÌC with 40-50% relative humidityand 37 ÌC with 30% relative humidity. In this study, the newly harvested paddy cv. Khao Dok Mali 105 was driedto reduce the moisture content to 15.12% and packed in polypropylene bags. The bags were stored at 25 ÌC and37 ÌC for 7 months. It was found that analysis of the reducing sugars of the starch of the milled rice duringstorage at 37 ÌC was found to have increased from 0.19 % to 0.62% while the reducing sugars of the starch ofthe milled rice stored at 25 ÌC, decreased from 0.19% to 0.14%. The total sugars and amylose contents wereanalyzed and found no significant changes were found during storage at 25 ÌC and 37 ÌC. α -Amylase activity inthe brown rice was found to be 0.9-7.8 and 0.9-9.6 U/100g during storage at both 25 ÌC and 37 ÌC, respectively.The viscosity property by RVA of the milled rice starch was found to have increased during storage under thestudy conditions. From the results, it might be shown that the relationship between the increase of the reducingsugars when the rice was stored at high temperature and this condition tended to cause the higher viscosityproperty of the rice starch during storage.

Keywords : Rice cv. Khao Dok Mali / Storage / Temperature / Chemical / Physicochemical