Optimization of rice bran stabilization by infrared‐vacuum process and storage stability

Abstract Hydrolytic rancidity seriously reduces the quality and limits the utilization of rice bran (RB) in foods. Thus, stabilization of RB has become of great interest to producers. This study proposes a new stabilization technique using infrared heat in combination with a vacuum (IR‐VC) to inhibit free fatty acids (FFA) and microbial growth as well as to preserve the phytochemical compounds in the RB. Optimization of the IR‐VC process was performed by Response Surface Methodology (RSM) and Central Composite Design (CCD) and found to be 999 W of infrared power, 650 mmHg of vacuum strength, and 562 s of treatment time. This level of IR‐VC treatment successfully reduced FA hydrolysis while still preserving the bran's beneficial components such as tocols, and essential fatty acids. The improved shelf life of thus stabilized rice bran (SRB) was 130 days (30°C), compared to only 35 days for the fresh rice bran. Slow rate increase in FFA was found in SRB over 8 weeks of storage at 35°C in a range from 1.50% to 3.24% with effective microbial growth control (<1 × 10 4 CFU/g TPC). Nutritional values, tocols and oryzanol in the SRB were well preserved with approximately four times longer shelf life than fresh rice bran. Practical applications The rice bran stabilization process by IR‐VC was optimized by RSM. IR‐VC process effectively inhibited lipase activity in the fresh rice bran by lowering the FFA to <5% suitable for oil extraction and consumption. IR‐VC process enabled the deactivation of undesired chemical changes in the rice bran while still maintaining nutrients and biochemicals such as tocols and oryzanol. The shelf life of stabilized rice bran was extended to ~4 months with acceptable qualities. Further development of a pilot‐scale, continuous stabilization process of rice bran using IR‐VC is carried out to meet the demand of rice bran and RBO manufacturers.