Improvement of structure and cooking quality of brown rice using ultrasonic and enzymatic treatments

Abstract

Brown rice (Oryza sativa L.) was subjected to ultrasonic treatment (UT) and three enzymatic treatments (ET) with cellulase, glucoamylase and α-amylase. All treatments changed pasting properties of brown rice flour and structure of brown rice grain surface, but only UT and α-amylase treatment (AT) significantly affected starch granules inside the grain. During cooking, water uptake and volume expansion of UT brown rice were higher than those of ET. Both UT and ET decreased hardness of the cooked brown rice from 206.05 N to 192.22–154.02 N in which the AT cooked rice was the softest. Although UT reduced hardness and increased volume expansion, the brown rice from AT had the highest liking score. Principle component analysis also visualized the preferable brown rice from AT. Therefore, AT was considered to potentially become a novel technology for development of high-quality brown rice. Practical applications Brown rice is normally soaked in water before cooking. Modifying the structure of brown rice by ultrasonic or enzymatic treatment could improve water uptake, volume expansion and texture of the cooked brown rice. Therefore, enzymatic treatment by α-amylase was recommended to produce the soften brown rice without soaking before cooking.