Effect of superheated steam heating on quality and antioxidant activities of riceberry bran
Riceberry is known for its health-promoting properties and it has increased in popularity as a pigmented rice. Rapid degradation in terms of enzyme hydrolysis is a major problem in the further utilization of rice bran. Rice bran and pigmented rice bran must be stabilized before use. Superheated steam heating (SSH) could be an effective method to inhibit enzymatic activities as well as rancidity as this method involves high temperature and a short process. This study investigated the SSH conditions influencing the physical, chemical and antioxidant properties of freshly milled riceberry bran (FRB) and 5-month-frozen stored riceberry bran (5M SRB) and the influence of sample handling. Riceberry bran was subjected to SSH at 275−375°C for 5−20 s. Stabilized samples were determined for color, moisture content, peroxide value (PV), free fatty acids (FFA) content, lipase activity and antioxidant activities. All SSH conditions could reduce the moisture content, PV and FFA in riceberry bran. SSH conditions at 275°C ≥ 15 s, 325°C ≥ 10 s and 375°C ≥ 10 s had PVs lower than the maximum acceptable level (15 mg equivalents/kg oil). The total phenolic content of FRB was maintained, while the antioxidant activity of diphenyl-picrylhydrazyl radical scavenging activity increased. SSH significantly reduced lipase activity, compared to the untreated control under both tested conditions of handling. SSH could be potentially used to retard rancidity and to promote antioxidant activities in riceberry bran even with bran stored for a prolonged period (up to 5 mth).