Variation in Polyphenols, Tocols, γ-Aminobutyric Acid, and Antioxidant Properties in Whole Grain Rice (Oryza sativa L.) as Affected by Different Germination Time

Dynamic alterations in the polyphenols, tocols, antioxidant activities (AOA), and gamma-aminobutyric acid (GABA) contents of white, red, and black germinated rice upon different germination periods were studied. The results indicated that the contents of the free, bound, and total phenolics and AOA steadily increased during germination, even though the free part of colored germinated brown rice (GBR) showed a notable decline at the earlier stages, but still higher than the white rice. The compositions of the nine phenolic acids and six tocols generally accumulated in a time-and variety-dependent manner during the germination process. However, the contents of p-coumaric, ferulic, and sinapic acids displayed a pronounced increase with the duration of germination in all cultivars. The GABA in white, red, and black GBR accumulated to the highest content at the end of germination, which was 4.7, 14.2, and 6.7-fold of their respective nongerminated counterparts. Interestingly, the total anthocyanin content in black GBR displayed a constant drop at earlier stages and then a rise at the later stages. These results suggest that prolonged germination may further increase the functional properties of GBR.