Postharvest application of hot water and ultraviolet light prolongs the marketable window of fresh grapes by maintaining physicochemical attributes during ambient storage

Abstract

The short shelf life of table grapes, mainly due to moisture loss, oxidative stress, and loss of quality during ambient storage conditions, is a significant limitation in regions that do not have cold-chain facilities. The current research addresses this challenge by comparing the performance of hot water treatment (HWT) + ultraviolet (UV-C) light as a non-chemical method of preservation to increase the market shelf life of Sultana grapes stored under room temperature (25 ± 1.5°C). Freshly harvested grape bunches were treated to HWT and subsequently exposed to UV-C and compared to untreated controls over a 7-day storage period. Changes in physicochemical attributes were quantified using a completely randomized design under two-factor factorial settings. The interaction between the treatment and storage time had a significant impact on all the attributes studied, excluding the juice pH. On day 7, the treated grapes had approximately 13.3% greater firmness and lower weight loss by 6.5% and electrolyte leakage by 11.3% than the control. Oxidative stress was significantly inhibited, exhibited by decreases of about 85% in levels of superoxide anions and 50.8% in levels of hydrogen peroxide with the application of HWT + UV-C. These were linked to the increased activities of superoxide dismutase, catalase, peroxidase and ascorbate peroxidase as well as the increased retention of phenolics, chlorophyll and ascorbic acid. Moreover, HWT + UV-C increased the marketable fruit by 19.7%. In conclusion, HWT + UV-C effectively postponed senescence and preserved the quality of grapes under ambient storage. Future studies are required to understand the molecular responses to facilitate its adoption on a large scale.