γ-aminobutyric acid (GABA) treatment alleviates off-flavor in postharvest waxed citrus fruit by enhancing peel gas permeance

Postharvest wax coating reduces water loss and enhances visual appeal but impairs gas exchange in citrus fruit, inducing anaerobic fermentation and off-flavor development. This study demonstrates that exogenous γ-aminobutyric acid (GABA) mitigates these physiological disorders. GABA enhanced peel gas permeance by 1.7- to 2.2-fold through suppression of C25-C31 cuticular alkane biosynthesis and enlargement of stomatal apertures, thereby alleviating internal hypoxia. This metabolic shift from anaerobic fermentation toward aerobic respiration was mediated by GABA shunt reprogramming and amino acid metabolic remodeling, which reduced ethanol accumulation by 57% while preserving key flavor compounds. Transcriptomic analysis revealed coordinated regulation of genes associated with wax synthesis, fermentation, and hypoxia responses. This simple amino acid treatment preserves citrus fruit flavor and nutritional quality under waxing-induced hypoxia by mitigating physiological disorders.