Physicochemical and Functional Characterization of Dried Distiller’s Rice Spent Grain as a Function of Particle Size

Abstract

Dried distiller’s rice spent grain (DDRSG), a protein-rich by-product of the rice-based ethanol industry, has considerable potential as a sustainable food ingredient; however, its physicochemical and functional characteristics can vary with particle size. The present study investigated the influence of particle-size fractionation on the physico-chemical, and functional properties of DDRSG. Dried DDRSG was fractionated using a mechanical sieve shaker into seven particle-size ranges: < 125, 125 - 212, 212 - 300, 300 - 500, 500 - 850, 850 - 1000, and 1000 - 2000 μm. The fractions were evaluated for particle-size distribution, proximate composition, colour characteristics, bulk and tapped bulk densities, compressibility, Hausner ratio, wettability, water-holding capacity (WHC), and oil-holding capacity (OHC). The highest yields were recorded for the 1000-2000 μm (27.09 %), 300-500 μm (26.82 %), and 212–300 μm (24.17 %) fractions. Particle size significantly affected most evaluated properties. Crude protein decreased from 53.23 % in the < 125 μm fraction to 47.25% in the 1000-2000 μm fraction, whereas moisture increased from 9.92 to 12.40 %. Increasing particle size decreased L* value from 51.50 to 37.13, while a* and b* values increased. Bulk and tapped bulk densities decreased with increasing particle size. In contrast, WHC and OHC increased from 2.35 to 4.03 g/g and 1.36 to 2.45 g/g, respectively. Wetting time decreased from 30.00 to 11.37 s, indicating improved wettability in coarser fractions. Crude fat and ash were not significantly affected by particle size. Overall, particle-size fractionation effectively modified the physico-chemical and functional attributes of DDRSG, demonstrating its potential for tailoring this protein-rich by-product to specific food-processing and formulation requirements.