Changes in Grain Quality of Stored Brown and Milled Rice

Abstract

Changes in the cooking and eating quality, and some physiochemical characteristics of stored brown and milled rice were monitored monthly over a 12 month period using different storage tochniques. Using the variety Khao Tah Haeng 17 storage containers compared were jute bags, ceramic jars, plastic bags and vacuum sealed plastic bags; all were kept under warehouse conditions.
Storage of both brown and milled rice in vacuum sealed plastic bags was the most satisfactory storage technique; the us eof ceramic jars was the least satisfactory. Brown rice stored in the ceramic jars was weverely damaged by insects and developed an off-aroma on cooking after seven months storage. A deterioration in the aroma of cooked rice was also detected from brown rice stored in plastic bags and milled rice stored in jute bags; on cooking the rice also developed a darker colour. With prolonged storage, fat acidity increased in both the brown and milled rice; this was thought to be responsible for the off-aroma. The effect of milling was generally to reduce the level of the removal of the removal of the acidic fat from teh grain surface during milling. Prolonged storage tended to decrease the tenderness, stickiness and glossiness of teh cooked rice. Other changes detected with storage time included a decrease in total solids suspended in water used for cooking and an increases in the volume expansion and water absorption during cooking; however, there was no apparent change in teh elongation ratio of the grain. Gel consistency of teh grain became harder with age. Changes in amylose and protein contents, and alkali spreading value were negligible.