Effect of heat and relative humidity treatment on γ-aminobutyric acid (GABA), other free amino acids, and quality characteristics of wheat flour

Abstract Heat and relative humidity (HRH) treatment was applied to increase γ-aminobutyric acid (GABA) content in wheat and evaluate its effects on free amino acids and quality properties. Following HRH treatment, the GABA levels in 35 wheat varieties across three colour categories increased from 0.76–6.87 to 11.93–31.12 mg/100 g DW. Analysis of the highest-GABA varieties from each category revealed that GABA was distributed throughout the kernel, with the highest concentration in the shorts, followed by coarse bran and flour. In flour, HRH treatment significantly increased all essential amino acids (EAAs) and semi-EAAs except for cysteine and histidine (p < .05). Additionally, HRH treatment increased flour yield by 1.15%–3.18%, induced protein denaturation and aggregation, elevated paste viscosity, and reduced dough stability. Notably, the purple wheat variety P1 (Jizi 439) demonstrated higher tolerance to HRH-induced dough softening compared to other wheat varieties. These findings provide a basis for developing GABA-enriched wheat products.