Impacts of size fractionation, commingling, and drying temperature on physical and pasting properties of broken rice kernels

Abstract

AbstractBackground and objectivesInconsistencies in rice flour produced from broken rice (brokens) may be due to differences in size, composition, and processing methods of the brokens. This study sought to investigate the effect of size fractionation, drying temperature, and commingling practices on the physical and pasting properties of broken rice. Broken rice was generated from rice (cultivar XP753) dried at 25, 45, and 60°C. The brokens were classified into large, medium, and small sizes using US sieve size 10 (2.00 mm), 12 (1.68 mm), and 20 (0.84 mm), respectively. Commingling of the brokens based on size was done. Physical and pasting properties of broken rice flour were analyzed.FindingsDrying temperature and size of brokens had significant impacts on protein content, starch damage content, bulk density, peak viscosity, trough viscosity, breakdown viscosity, final viscosity, and peak time of brokens. Comingled samples were not significantly different from at least one of the individual constituents of the comingled flour for most of the properties measured. Developed models predicted large brokens obtained from drying at 60°C as the most suitable for products requiring high peak and final viscosities and short peak time. Small brokens obtained from drying at 60°C were predicted as the most suitable for high protein and low starch damage products. The impact of size, drying temperature, and commingling on the physical and pasting properties of brokens may be due to variations in rice composition across the length of the rice kernel, variations in kernel thickness, differences in degrees of milling of different parts of the rice kernel, modifications in the starch structure during drying, and differences in protein content and functionality of the brokens.ConclusionsDrying temperature and size fractionation of brokens are important in maintaining consistency in the cooking properties of broken rice and resulting products.Significance and noveltySize fractionation of brokens and control of drying temperature provides the opportunity to better understand the functionality of brokens, control commingling practices, direct brokens to the right end‐use processes, and maximize the potential of this by‐product in producing premium products.