Amino acid metabolomic analysis involved in flavor quality and cold tolerance in peach fruit treated with exogenous glycine betaine

Glycine betaine (GB) has been reported to mitigate chilling injury of peach fruit during postharvest cold storage, but the effects of GB treatment on changes of fruit flavor and amino acid metabolism remain unclear. In this study, the changes of organic acids and amino acids in peach fruit treated with GB were analyzed through physiological and metabolomic methods. The results manifested that GB treatment reduced internal browning index and maintained higher contents of total soluble solids, titratable acidity, organic acids and total free amino acids. Electronic tongue analysis exhibited separation between GB-treated and control fruit. Additionally, GB treatment increased proline, polyamines and γ-aminobutyric acid (GABA) contents by higher enzyme activities and upregulated gene expressions of arginine metabolism, GABA shunt pathway and lower enzyme activities and downregulated gene expressions of polyamine degradation pathway. Thus, GB treatment could enhance flavor quality and cold tolerance of peach fruit during low temperature storage.