Pre-harvest Influence of Gamma-aminobutyric Acid (GABA) on Post-harvest Quality and Shelf-Life of Bell Pepper (Capsicum annuum L.) During Cold Storage

The short shelf-life, sensitivity to cold temperature, and high perishable nature of sweet bell pepper (Capsicum annuum L.) have predisposed the crop to rapid deterioration and huge post-harvest loss. Research was conducted in the Department of Horticultural Sciences, Ilam University, Iran during 2022-2023 growing season to assess the efficiency of pre-harvest application of gamma-aminobutyric acid (GABA) on post-harvest quality and shelf-life of pepper fruits during cold storage at 4 degrees C. GABA at the concentrations of 0, 1, 5, 10, and 15 mM was sprayed at 3 and 6 days before harvest. Post-harvest quality was evaluated at harvest time (0, 12, and 24 days) after harvest. Results demonstrated that the pepper fruits treated with GABA at 5, 10, and 15 mM had lower chilling injury (CI, score 1.23, 1.3, and 1.33, respectively) and more extended shelf-life (38.33, 37.83, and 37.16 days, respectively) comparing to 1-mM-treated fruits (CI = score 2.53 and shelf-life = 30.66) and control (CI = score 3.73 and shelf-life = 28). Generally, extending storage duration led to a decrease in fruits radical scavenging activity, vitamin C, and total phenol content, but GABA treatments alleviated these reductions. The activity of ascorbate peroxidase and phenylalanine ammonia lyase enzymes on 24 days of storage decreased compared to that on harvest time. On all storage durations, the highest salicylic acid content of fruits was recorded in 5 mM treatment followed by 1 mM treatment. Exogenous application of GABA could considerably increase its endogenous content, so that on harvest time, treated fruits had higher GABA content than the control. Reduction of weight loss, electrolyte leakage, hydrogen peroxide and malondialdehyde content, and increasing tissue firmness, total soluble solid content, titratable acidity, radical scavenging activity, vitamin C content, total phenol content, and antioxidant enzymes activity were the most important positive effects of GABA treatment. Therefore, pre-harvest application of GABA at 5 mM concentration could be introduced as an efficient technique to extend maintainability of pepper fruits during cold storage at 4 degrees C.