Biochemical changes and quality characterization of cold-stored ‘Sahebi’ grape in response to postharvest application of GABA

Abstract In this study, the effect of γ-aminobutyric acid (GABA) at 0 (control), 20 and 40 mM on maintaining postharvest quality, chilling tolerance and fungal decay of ‘Sahebi’ grapevine (Vitis vinifera L.) was investigated during 60 days storage at 1°C. GABA- treated fruits especially at 40 mM showed less weight loss (35%), rachis browning (30%) and decay incident (63%) compared to the control. GABA- induced abscisic acid was linked to lower membrane electrolyte leakage (13%) in treated grapes. Moreover, at the end of 60 days, GABA treatment at 40 mM resulted in higher activities of antioxidant enzymes including superoxide dismutase (50%), catalase (35%), guaiacol peroxidase (65%), and ascorbate peroxidase (47%) and lower malondialdehyde (21%) compared to control samples. The highest soluble sugars and organic acids were related to 40 mM GABA- treated grape clusters. Phenolic compounds (phenolic acids, stilbenes, flavonoids and anthocyanidins) and antioxidant capacity increased in 40 mM GABA-treated grape due to lower polyphenol oxidase activity. Therefore, GABA is recommended for maintaining internal quality and reduction in fungal decay and chilling injury of grapes during postharvest storage.