Composite Coating as a Carrier of Antioxidants Impr oves the Postharvest Shelf Life and Quality of Table Grapes ( Vitis vinifera L. var. Thompson Seedless)

Abstract

Composite edible coating comprising xanthan gum (0. 3%) and olive oil (0.1%) enriched with antioxidants (gallic acid 0.1%, ferulic acid 0 .1% and ascorbic acid 0.1%) enhanced the postharvest storability and nutritional quality of table grapes. The quality characteristics of table grapes were monitored duri ng storage at 10±2°C, (70–75% RH), at regular intervals of 6 days until 24 days of sto rage. Xanthan gum combined with olive oil reduced the weight loss, decay occurrence, accu mulation of total soluble solids and total sugars by reducing the rate of respiration an d metabolism in the coated fruit. Moreover, incorporation of antioxidants in coating enhanced the level of phenolics, ascorbic acid and total antioxidant activity in gra pes. The activities of cell wall modifying enzymes such as Polygalacturonase (PG) and Pectate Lyase (PL) were reduced in the fruits of treated sets as compared to that of the c ontrol set. These results suggest that the composite coating delayed the ripening and softenin g process in grapes and thereby extended their shelf life up to 24 days, while the control grapes were decayed on the 12 th day. Keywords: Composite edible coating, Nutritional quality, Phenolic compounds, Shelf life , Vitis vinifera L.