Exogenous Melatonin Treatments Maintain Berry Quality and Bioactive Compounds of Minimally Processed Table Grapes ('Crimson Seedless') During Cold Storage

Global market demand for minimally processed (fresh cut) table grapes is increasing due to the premium product quality and easiness in consumption as they are ready-to-eat. However, fresh table grapes necessarily deteriorate after harvest due to their delicate tissue and preparation operations. Therefore, innovative technologies for the postharvest quality maintenance of minimally processed fresh grapes are required. In this study, berry quality, biochemical features and bioactive compounds of minimally processed (berry pedicel detached) grapes (Vitis vinifera cv. 'Crimson Seedless') as affected by postharvest immersing the berries in melatonin at different concentrations (0, 0.1, 1 and 10 mmol L-1) were investigated with a 7-day interval during storage at 1.0 +/- 0.5 degrees C for 35 days. Melatonin dips at all doses significantly extended the physical and biochemical quality of minimally processed (stem excised) grapes by restricting polygalacturonase activity and retarding the losses in berry weight, skin rupture force and visual quality. Melatonin treatments also effectively delayed the changes in berry skin color, phenol content, antioxidant activity and many other biochemical components in berry must. For a sustainable storage of the minimally processed table grapes, a 1-mmol L-1 melatonin concentration can be recommended due to its relatively higher effectiveness over other doses as well as cost-effectiveness of the lower doses.