Effects of cooking conditions on the concentrations of extractable tocopherols, tocotrienols and γ‐oryzanol in brown rice: Longer cooking time increases the levels of extractable bioactive components

Abstract

This study aimed to examine the effects of cooking conditions on the extractable content of bioactive compounds, namely tocopherols (Toc), tocotrienols (T3), and γ‐oryzanol (GO) in brown rice. The results showed that cooked brown rice possessed significantly higher sum of Toc and T3, total Toc, total T3 and GO concentrations than uncooked brown rice. The highest concentrations of these bioactive compounds were noted after the cooking time of 64 min. Among the different vitamin E homologs, α‐Toc, α‐T3, and γ‐T3 were the major three homologs present in cooked brown rice; although δ‐Toc and β‐T3 were not detected, a longer cooking time was observed to increase α‐Toc, β‐Toc, α‐T3, and γ‐T3 level. Compared with untreated brown rice, cooking brown rice with a pre‐soaking step significantly enhanced the levels of Toc, T3, and GO. This study concludes that cooking and pre‐soaking increases the extraction yield of Toc, T3, and GO, and hence improves the quality and functionality of brown rice.Practical application: Tocopherols (Toc), tocotrienols (T3), and γ‐oryzanol (GO), major bioactive components of brown rice, are known to provide various health benefits. Cooking can help release them from the food matrix and increase their extraction recovery. This study shows how the cooking process can enhance the extractable Toc, T3, and GO concentrations. A longer cooking time led to an increase in α‐Toc, β‐Toc, α‐T3, and γ‐T3 levels.Cooked brown rice showed higher extractable content tocopherols (Toc), tocotrienols (T3) and γ‐oryzanol concentrations than uncooked brown rice. The major vitamin E homologs in cooked brown rice were α‐Toc, α‐T3 and γ‐T3, of which the yields were enhanced with a longer cooking time.