Effects of Temperature, pH and Steeping Time on the Extraction of Starch from Pakistani Rice

Abstract

Broken rice such as KSK-133 is processed due to low quality and economic reasons. The effects of temperature, pH and steeping time on rice starch extraction from low quality rice KSK-133 investigated. Starch was extracted from rice by alkaline extraction technique. The main objective is to obtain high starch content from KSK-133. The independent variables are temperature, pH and steeping time. Rice starch was extracted at five different temperatures (22, 25, 30, 35 and 40C). As well as rice starch was also extracted at five different pHs (7, 8, 8.5, 9.0 and 9.5). In a steeping process distilled water used with 0.1M caustic soda for required pHs, kept the steeping hours (18, 22 hrs.) in every trial for each pH and temperature. Maximum rice starch has been recovered that is (85-95.4) % for five different temperatures in both steeping hrs. at 9.5pH. At the higher temperatures and pH, starch damage was higher. At low temperature and pH, the percentage of starch recovery was low although the starch damaged was less. By increasing the steeping time, the starch recovery was increased. By taking all factors into consideration, 9.0pH at 30C was selected as a best rice starch extraction condition for 18 hours steeping time. In case of 22 hours steeping time, 8.5pH at 35C was selected best rice starch extraction condition.