Effect of Physical Processing of Commercial De-oiled Rice Bran on Particle Size Distribution, and Content of Chemical and Bio-functional Components

Rice bran is a rich source of nutrients and nutraceuticals, which has bio-functional properties. De-oiled rice bran, a major byproduct of rice bran oil industry, is not yet efficiently utilized for human consumption due to its poor edible quality. Various physical processing methods like sieving, pin milling and air classification were applied to upgrade the quality of bran and also to investigate its effect on particle size distribution, content of ash, protein, total dietary fiber, insoluble fiber, soluble fiber and oryzanol as well as total antioxidant activity in bran fractions. Sieve separation resulted in an increase in the content of protein and bio-functional components like soluble fiber and oryzanol as well as total antioxidant activity. Pin milling and sieving resulted in smaller particle size fraction without loss in the content of protein and other bio-functional components and antioxidant activity. Air classification of this material resulted in significant decrease in ash content with moderate increase in protein content and significant increase in the contents of oryzanol and soluble fiber and the total antioxidant activity. This resulted in quality improvement of commercial de-oiled bran viz., reduction in coarse bran fraction (>250μm size particles) from 65% to 0%, content of ash from 14.3 to 13.1 g/100 g, and insoluble fiber from 49.3 to 46.1 g/100 g, and increase in the content of protein from 13.7 to 17 g/100 g, soluble fiber from 2.75 to 4.35 g/100 g, oryzanol from 13.6 to 18.1 mg/100 g, and total antioxidant activity from 61 to 96 mM α-tocopherol equivalent/g. About 30% edible and nutrient rich rice bran, which can be used as an ingredient in the bakery products and health food formulations, was obtained from unutilized commercial de-oiled bran by this process.