Insights Into Processing Properties of Germinated Brown Rice: Based on Physicochemical, Non-Volatile, and Volatile Metabolomics

Germinated brown rice is increasingly recognized for its physiological benefits. However, the effects of germination on its processing properties, as well as on the composition of its volatile and non-volatile metabolites, have not been systematically elucidated. In this study, the elongation of germination time may represent one of the contributing factors to the decline in brown rice integrity. Prolonged germination was associated with reduced hardness, chewiness, and resilience of the cooked brown rice, likely due to increased water infiltration during the germination process. Furthermore, non-volatile metabolomic analysis revealed the accumulation of 141 non-volatile metabolites in germinated brown rice. Germination significantly promoted γ-aminobutyric acid (GABA) accumulation in the cooked brown rice; however, disruption of the OsBADH2 gene significantly suppressed GABA accumulation. Volatile metabolomics analysis revealed that short-duration germination enhanced the formation of aldehydes, esters, and alcohols, while the levels of several undesirable metabolites, such as indole, decreased with prolonged germination time. These findings will contribute to the industrial production and promotion of germinated brown rice.