Salicylic acid and putrescine treatments reduce yellowing, decay and retain postharvest quality of bitter gourd (Momordica charantia L.) during cold storage

Abstract

Bitter gourd is a valuable cucurbitaceous vegetable rich in various beneficial phytochemicals such phenols, antioxidants, saponins, charantin etc. In spite of high medicinal value bitter gourd faces significant postharvest losses due to factors such as mass reduction, tissue softening, yellowing, and fungal contamination, especially when stored under ambient conditions. To combat these issues, immature green bitter gourd fruits (16 DAP) were subjected to different concentrations of salicylic acid (SA) at 5, 7.5, and 10 mM) and putrescine (PUT) at 1, 2, and 3 mM, through a 15-minute dipping process. In contrast, untreated fruits were dipped in distilled water and served as the control group. These treated and control fruits were subsequently stored at 10 ºC with a relative humidity range of 85–95 % for 20 days. Results showed that among all treatments, bitter gourd fruits treated with 10 mM SA exhibited the most noteworthy outcomes. They retained higher levels of total phenols (26.28 μg GAE 100 g-1), radical scavenging activity (27.95 %), ascorbic acid content (50.0 mg 100 g-1 FW), and total chlorophyll (0.32 mg g-1 FW) on the 20th day of storage. Additionally, the 10 mM SA treatment demonstrated the highest inhibition of α-amylase and α-glucosidase activity, as well as the lowest decay percentage when compared to the control. On the other hand, 3 mM PUT treatment resulted in greater fruit firmness (27.45 N), lower per cent postharvest loss weight (6.60 %), and reduced pectin methyl esterase (PME) activity (0.0075 µmol min-1 g-1 FW). These findings were further validated through principal component analysis (PCA), which highlighted that bitter gourd fruits could be effectively stored for up to 20 days at 10 ºC with pre-storage treatment involving 10.0 mM SA and 3.0 mM PUT. Overall higher quality and shelf-life of bitter gourd were obtained in bitter gourd treated with 10.0 mM SA. Consequently, it is recommended that the application of SA and PUT represents an environmentally friendly approach to preserve the quality of bitter gourd during storage, benefiting both retailers and consumers alike.