Assessment of pasting characteristics of size fractionated industrial parboiled and non-parboiled broken rice

Background and objectives Rice flour generated from broken rice (brokens) has inconsistencies in functional properties. This may be due to differences in size and composition of brokens used for the flour. It is postulated that size classification of brokens can improve flour functionality. Parboiled brokens generated at 12.5% (aged rice) and 18% (fresh rice) moisture content (MC, wet basis) and non-parboiled (regular) brokens were obtained from commercial milling streams. Broken rice was also generated from six cultivars (two long-grain pureline, two long-grain hybrids, and two medium-grain) of freshly harvested rough rice that were dried at 25 degrees C in the laboratory. The brokens were classified into large, medium, and small, using US sieve size 10, 12, and 20 respectively. Comingling of the brokens based on size was done. Pasting property of the broken rice flour was determined using the Rapid Visco Analyzer. Findings Conclusions The results indicate that the MC of rice before parboiling affects the pasting property of the parboiled broken rice flour, thus rice parboiled at 12.5% MC (aged rice) had higher peak viscosity and final viscosity than rice parboiled at 18% MC (fresh rice). Larger brokens had better pasting properties than smaller brokens. Smaller brokens had higher protein content than large brokens. Whole kernels had higher peak and final viscosities than brokens across all cultivars. These differences may be due to variations in starch distributions across the rice kernel. Comingling of large and small brokens produced flour that has pasting property like either the medium or small brokens. Size classification of brokens is important in maintaining consistency in the pasting properties of the broken rice flour and resulting products. Significance and novelty Size fractionation of brokens provides the opportunity to better understand the functionality of brokens, to direct them to the right end-use processes and to maximize the potential of this by-product in producing premium and high-quality products.