Method Optimization for Quantification of GABA and Isoflavone Aglycones in Germinated Soybean

Germinated soybean is rich in bioactive compounds such as gamma-aminobutyric acid (GABA), polyphenols, and flavonoids. Thus, quantification of these components is critical for assessing nutritional value of soybean after germination and processing. In the current research, methods for determination of GABA, daidzein, genistein, and glycitein in germinated soybeans using high-performance liquid chromatography with ultraviolet-visible detector (HPLC-UV-VIS) were optimized. Then, soybean germination time was optimized in 'DT84' and 'DT51', two Vietnamese soybean cultivars. These cultivars were soaked for 1 h, 2 h, 3 h, 4 h, and 5 h with water-to-bean ratio of 1:5 at 26 - 28 oC to initiate germination. After being soaked, the seeds were germinated, dried, and ground into powder for quantification of GABA and isoflavone aglycones. The highest concentration of GABA, daidzein and genistein were reached after 1 h of bean soaking. Further, germinated 'DT51' had higher GABA and lower genistein and daidzein content than germinated 'DT84'. Previous studies had reported the extraction and quantification of GABA and isoflavone aglycones in various food matrices. However, in this study we performed optimization of these procedures in a soybean matrix and showed potential of germination as a low-cost processing to boost the nutritional quality of soybean.