Effect of Postharvest Application of Gamma-aminobutyric Acid on Respiration Rate and Some Qualitative Characteristics of Peruvian Groundcherry (Physalis peruviana L.) Fruit During Storage

The Peruvian Groundcherry (Physalis peruviana L.) is a perennial plant that is native to the South American regions and belongs to the Solanaceae family. The harvested fruits are vulnerable to both biotic and abiotic stresses, which can trigger unfavorable physiological and biochemical changes. As a result, the quality and marketability of the product may decrease by the time it reaches the consumer. The fruit of the Peruvian Groundcherry has a high water content and is sensitive to ethylene, causing rapid ripening with a high respiration rate, making it highly perishable. To ensure quality maintenance after harvest, various postharvest treatments are being studied; however, some methods may not be practical due to low customer preference or lack of effectiveness verification. Therefore, alternative treatments need to be found to prolong shelf life and reduce postharvest losses. Currently, environmentally friendly technologies and treatments are recommended. The aim of this study was to investigate the effects of γ-Aminobutyric acid (GABA) postharvest treatment on the respiration rate, antioxidant activities, and fruit quality of the Peruvian Groundcherry during 21 days of storage, addressing a research gap in this area.

Handpicked Peruvian Groundcherry fruits were taken from a commercial greenhouse located in Fars province, Iran. The fruits were picked at two stages of maturity based on their color, which was either yellowish green or orange. Following the harvest, the fruits were taken to a horticulture laboratory where they were assessed for appearance, size, color, and any damages. The experimental design was factorial based on a completely randomized design with three replications, each containing 25 fruits. Experimental factors included the GABA concentration (0, 5, 10 and 15 mM), storage time (7, 14 and 21 days) and fruit maturity stage based on color at harvest (yellowish green and orange). Following dip treatments in GABA solutions, fruits were packed in plastic clamshells measuring 20×5×10 cm3 and with a hole ratio of 3%. Fruits were stored at a temperature of 15 ◦C for 21 days, and their quality characteristics and respiration rate were evaluated on a weekly basis.

The findings indicated that both groups of treated fruits had a slower increase in respiration rate and lower final respiration rate compared to the control group. The effect of different concentrations of GABA on the final respiration rate of fruits was similar for each stage of fruit maturity. During the storage period, the changes in total soluble solids and total acids of the treated fruits were less than the control group. At the end of the storage period, yellowish green fruits treated with 10 and 15 mM GABA had the lowest amount of total soluble solids; orange fruits had the lowest amount with 15 mM GABA treatment. GABA concentrations had a similar effect on total acids retention of yellowish green fruits, but 15 mM GABA treatment was more effective for orange fruits. Ascorbic acid content and phenylalanine ammonia-lyase enzyme activity were consistently higher in treated fruits than in the control group. In green fruits treated with GABA concentrations, the amount of ascorbic acid increased significantly and continuously, with no significant difference between treatments at the end of storage period. Orange fruits showed a significant increase until the second week of storage, followed by a non-significant decrease. Higher amounts of ascorbic acid in orange fruits were detected by applying higher GABA concentrations. Both groups of fruits had significantly higher amounts of total phenol, carotenoid, and antioxidant capacity in response to increasing GABA concentration, while the minimum amount of these compounds during the storage period was related to the control group. However, orange-colored fruits were more sensitive to treatments compared to yellowish green fruits.

The results of the present study indicate a positive effect of postharvest GABA treatment on reducing respiration rate, improving antioxidant activities, and maintaining the quality and nutritional value of Peruvian groundcherry fruit during a 21-day storage period. Considering the global preference and demand among governments and consumers to use environmentally-friendly treatments of biological origin that pose no risk to human health, we recommend the use of GABA treatment for optimal storage of Peruvian groundcherry fruit. Finally, it is recommended to assess the efficacy of GABA or other safe and environmentally-friendly postharvest treatments on the quality and shelf life of other valuable horticultural commodities.