Germination Triggers Substantial Changes in GABA, Polyphenol, Sugar, and Organic Acid Content of Commonly Consumed Legumes

This study investigated the effects of germination on gamma-aminobutyric acid (GABA), free sugars, organic acids, polyphenols, protein content, and antioxidant activity in six legumes (mung beans, Dobrudzha beans, white beans, brown lentils, red lentils and chickpeas). Seeds were germinated for 5 days at room temperature, with or without an initial freezing pretreatment at -18 °C for 20 h. Daily analysis revealed significant increases in GABA across all legumes, especially chickpeas, which showed an 18-fold rise to 210.5 mg/100 g dry weight (DW), alongside elevated glutamate decarboxylase activity. Total polyphenols increased 3.4-fold in white beans and chickpeas by day five. Antioxidant activity (ORAC) rose in parallel, reaching 123.8 and 83.3 µmol TE/g DW in germinated white beans and chickpeas, compared to 68.4 and 45.4 µmol TE/g DW in non-germinated controls. While protein content remained stable, levels of free sugars (notably maltose) increased during germination. Organic acids rose across all samples as well, with quinic acid being the most abundant and showing the sharpest increase. Initial freezing had a clear effect on enhancing GABA accumulation compared to non-treated seeds, but generally exerted neutral effects on other bioactive components. Overall, germination triggered biochemical transformations in seeds, enriching them with bioactive compounds and enhancing their nutritional and functional properties, with chickpeas emerging as a particularly rich source of GABA, polyphenols, and organic acids, supporting their potential in functional food development.