Comparative study of brown rice and germinated brown rice for nutritional composition, in vitro starch digestibility, bioactive compounds, antioxidant activity and microstructural properties

Background and Objectives: Brown rice is rarely consumed as a staple food due to its dark appearance and hard texture. However, germination can improve the taste, nutritional composition, and phenolic content, of brown rice. Therefore, the aim of this study was to compare the pasting properties, thermal properties, nutritional profile, in vitro starch digestibility, bioactive compounds {particularly gamma -aminobutyric acid (GABA), and gamma-oryzanol}, morphological and antioxidant characteristics of ungerminated brown rice (UGBR) and germinated brown rice (GBR) of one of the most commonly consumed rice variety (Jhelum) of Northern Highland Himalayan regions. Findings: When compared with UGBR, GBR exhibited lower pasting viscosities but gelatinization temperatures were observed to be higher. Germination increased the total free amino acids, protein, total and reducing sugars, while resistant starch, apparent amylose content, and slowly digestible starch decreased. L* value minimized while a* and b* maximized upon germination. Scanning electron micrographs revealed that the continuous matrix structure of starch granules was severely damaged after germination. Total phenolic contents, GABA, gamma-oryzanol, and antioxidant properties (1,1-diphenyl-2-picrylhydrazyl and ferric reducing antioxidant power) were improved while phytic acid, pyridoxine, niacin, and thiamine contents were reduced in brown rice after germination. Conclusion: Germination caused significant changes in the nutritional profile of brown rice. Specifically, it improved GABA and y-oryzanol levels and lowered the phytic acid contents of brown rice. Novelty: Jhelum is one of the most commonly consumed rice variety in Northern Highland Himalayan regions. In the present study, germination significantly improved the biologically active compounds in Jhelum. Therefore, regular consumption of GBR of the said variety may help in preventing the various chronic disorders in Northern Himalayan regions where rice is a staple food.