Does UV-C Irradiation Help in Suppression of Anthracnose and Maintain Quality of Stored Papaya Fruit?

Papaya, a climacteric fruit, undergoes rapid ripening and softening, resulting in a shortened shelf life, notable quality deterioration and vulnerability to post-harvest diseases. UV-C irradiation is an environmentally conscious approach towards sustainable postharvest fruit preservation. The in vitro and in vivo effectiveness of UV-C against anthracnose and its impact on the quality of cold-stored papaya fruit were investigated. For the qualitative study, papaya fruits were subjected to UV-C irradiation at varying doses (1.2, 1.6, 2.0 kJ∙m⁻²) and subsequently stored at 13 ± 1°C for 20 days. Potent in vitro germicidal effects on anthracnose were demonstrated by UV-C doses (> 2.0 kJ∙m⁻²) doses during 7 days of incubation. However, complete prevention of in vivo disease incidence was not achieved, as UV-C light induced scalding and damage to the peel, causing latex to ooze out and creating a conducive environment for fungal colonization. The peel damage following UV-C exposure was attributed to the enhanced accumulation of MDA and H₂O₂ in the fruit peel. Conversely, lower doses (1.2 kJ∙m⁻²) of UV-C irradiation were effective in reducing weight loss and respiration rate, retaining higher firmness, and maintaining better phenols and antioxidant activity. However, a loss of glossiness and patchy discoloration on the fruit peel were observed, which reduced its visual appeal. Severe stress caused by UV-C light, even at the lower dose, led to higher oxidative damage, and thus least practical utility is found for UV-C in postharvest disease management and quality retention of stored papaya fruit.