Widely targeted metabolomics analysis of nutrient changes in a new black rice variety ‘Huamoxiang No.3’ (Oryza sativa L. var. Glutinosa Matsum) under different cooking modes

Background

Black rice is rich in various nutrients, such as anthocyanins, which may undergo some changes during cooking. However, previous studies have been mainly focused on a single substance and paid less attention to the changes in overall nutrient components. Here, we performed widely targeted metabolomics analysis on the chemical compositional changes in a new black rice variety (‘Huamoxiang No.3’) under three cooking modes, including bottom heating (BH), induction heating (IH), and IH + pressure.

Results

Among the detected 1458 metabolites, 276 and 108 metabolites were differential metabolites after cooking and in three cooking modes, respectively. Cooking increased the contents of most peptides, phenolic acids, and organic acid compounds but significantly decreased those of lipids and flavonoids, particularly anthocyanins. However, phenolic acids such as chlorogenic acid, erucic acid, and p-coumaric acid increased significantly, possibly due to the release of bound phenols and degradation of flavonoids to phenolic acids, such as thermal degradation of C3G to protocatechuic acid and among the three heating modes, the IH + pressure mode resulted in the most significant changes.

Conclusion

Although cooking reduced the content of flavonoids and anthocyanins, the increase in phenolic acids and other substances contributed to the healthy effect of cooked black rice, and the content of these active substances increased more significantly in the IH + pressure mode.