Impact of kernel thickness on parboiled rice properties

Background and objective Approximately 15% of the rice produced in the world is parboiled. Parboiling, a hydrothermal process involving soaking, steaming, and drying, is conventionally utilized to improve milling quality, nutritional value, and shelf life of rice. Because rice is composed of kernels of varying thickness, rice kernel thickness may impact parboiled rice properties. This study investigated the milling and color properties of parboiled rice prepared from two rice cultivars with different kernel thickness distributions and chemical compositions by subjecting them to different soaking temperatures and durations. Findings RoyJ was composed of a greater proportion of thinner kernels, whereas XL756 was composed of a greater proportion of thicker kernels. The head rice yield (HRY) of the resultant parboiled rice was strongly affected by rice cultivar and thickness fraction, but was not impacted by their chemical compositions. RoyJ had a greater HRY than XL756 for the same thickness fraction under the same soaking conditions. Lightness (L*) and yellowness (b*) appeared to be greatly affected by cultivar with RoyJ displaying greater L* and b* values than XL756 for most conditions. Conclusion Kernel thickness and soaking duration were important factors affecting the HRY of parboiled rice for both rice cultivars. Rice cultivars composed of a greater percentage of thinner kernels would be more susceptible to severe parboiling conditions and thus produce more variation in the HRY of parboiled rice. Significance and novelty The distribution of kernel thickness is different for different rice cultivars and should be taken into consideration when choosing parboiling conditions to maximize the HRY of parboiled rice.