Reduction of phenolic profiles, dietary fiber, and antioxidant activities of rice after treatment with different milling processes

Abstract Background and objectives Milling, polishing, and color selection are the basic unit operation steps during rice processing, which may remove much amounts of nutritional components, such as phenolics and dietary fiber. And for a long time, rice is often overprocessed which results in a serious loss of nutrients. However, the reduction of the nutritional components during rice milling process has not been evaluated. The aim of this study was to investigate the effect of different milling processes during industrial rice processing on the free and bound phenolic content, composition, dietary fiber, and antioxidant activity (DPPH, ABTS, T‐AOC) of two kinds of rice (Dao Huaxiang and Jiangxi Indica). Findings As the milling degree increased, the loss percentages of total phenolics, flavonoids, and anthocyanins of Dao Huaxiang rice were 52.8%–76.4%, 43.3%–72.9%, and 100.0%, respectively; it was similar for the reduction percentages of total phenolics, flavonoids, and anthocyanins for Jiangxi Indica rice, which were 56.5%–77.4%, 58.7%–87.7%, and 87.5%–100%, respectively; the amounts of total dietary fiber were also decreased from 5.87 to 2.03 g/100 g DW for the Dao Huaxiang rice and from 5.14 to 2.84 g/100 g DW for Jiangxi Indica rice, respectively. Correspondingly, the content of individual phenolic, flavonoid, and anthocyanin compositions in both rice varieties decreased with the increase in milling degree during the rice processing. Antioxidant activities of T‐AOC, DPPH, and ABTS showed a same trend with phenolic profiles for the two rice varieties. Conclusions The phenolic profiles, dietary fiber, and antioxidant activities for Dao Huaxiang and Jiangxi Indica rice decreased significantly with milling degree increase during rice processing. Therefore, it is recommended that the milling and polishing degree should be reduced during rice grain processing, in order to achieve the purpose of not only satisfying the edible quality of rice but also retaining the nutritional characteristics as much as possible. Significance and novelty The rice samples in this study were from the actual industrial production industry, and the Dao Huaxiang rice and Jiangxi Indica rice were from northeast China and south China, respectively, which were representative and could provide specific and practical data for reducing milling degree in rice industry and reducing the removal of bran layer. These findings indicate that the milling degree should be reduced or controlled for retention of nutrients and acceptable sensory quality in rice.