The physiochemical and nutritional properties of high endosperm lipids rice mutants under artificially accelerated ageing

Abstract

High lipids in rice endosperm can lower the digestibility of rice starch. However, as lipids tend to oxidize and hydrolyze, whether the high lipids rice is easily deteriorated during storage is unknown. In this study, artificially accelerated ageing was adopted as a fast way to investigate the changes of endosperm lipids and the physiochemical properties of high lipids rice mutants (i.e. ALK3 and RS4) during storage. Ageing treatment did not affect total lipids content, but NSL and γ-oryzanol in aged ALK3 (2.30%, 113.6 μg/g) and RS4 (2.10%, 72.2 μg/g) significantly decreased. Aged ALK3 had a lower pH of cooking solution (6.92) and lower Tp (64.04 °C) of the second endothermic peak in DSC compared to untreated ALK3 (7.04, 65.86 °C, respectively), suggesting the hydrolysis of lipids and damage of amylose-lipids complex. After ageing treatment, all varieties had lower proportion of unsaturated fatty acid in NSL and lower breakdown, indicating an inferior lipids quality and rice eating and cooking quality. However, no more serious quality deterioration was observed in high lipids rice compared to common rice. The high-lipid mutants had better nutritional quality in terms of higher γ-oryzanol content and lower initial digestion rate (IRR20) even after storage.