Free α-amino acids, γ-Aminobutyric acid (GABA), phenolic compounds and their relationships with antioxidant properties of sorghum malted in different conditions

Abstract

Two cultivars of sorghum were germinated at 25 or 30 °C for 1, 2, or 3 days to investigate the evolution of γ-Aminobutyric acid (GABA), total free phenolic compounds (FPC), hydroxycinnamic acid derivatives, free amino acid (FAA) profile, and antioxidant activity during malting. Results showed time–temperature interaction had significant influence on GABA accumulation, increasing over time at 25 °C, but keeping constant after first day at 30 °C. Free amino acid profile changed during malting with time and temperature, increasing until the third or second day at 25 and 30 °C, respectively. Content of hydroxycinnamic acid derivatives depended on time, temperature, and cultivar; ferulic was the phenolic acid found in greater amount. Pearson correlation analysis suggested malting generated not only FPC responsible for antioxidant activity, but also other bioactive compounds like FAA, particularly sulfur-containing ones. Germination for 3 days at 25 °C was the most suitable condition to obtaining functional sorghum malt.