Effects of acetic acid on the rice gelatinization and pasting properties of rice starch during cooking

The mechanism of the textural changes such as increase in stickiness of rice cooked with acetic acid was studied focusing on the gelatinization and rheological properties of both rice starch and rice flour. The results of swelling power and solubility of rice starch indicated that acetic acid promoted water absorption of amylopectin in rice starch. It was shown by DSC measurements that rice starch heated with acetic acid was easy to gelatinize compared to that without acetic acid. The pasting properties measured by an RVA and rotational viscometer suggested that the structure of rice starch became more fluid by addition of acetic acid. Biochemical analysis using α-amylase indicated that the spaces which allowed the enzyme reaction were formed more in the structure of rice starch cooked with acetic acid. It was suggested that these changes in rice starch contributed to the textural properties of rice cooked with acetic acid.