Study of Application of Composite Coating of Guar Gum-Garlic Oil on Grapes

Prevailing high temperature during harvesting to consumption of grapes in India results in accelerated water loss, faster respiration, physiological weight loss, rachis browning, berry shattering, poor shelf life and finally leads to significant post-harvest losses. Fruit surface is protected by the application of coating to maintain its freshness and shelf life for longer duration. Present experiment was designed to determine the effectiveness of guar gum (GG)/Garlic Oil (GO) composite coatings for maintaining the quality of Thompson Seedless grapes while stored at 10°C and 60-65 per cent relative humidity. Coating emulsions were formulated using guar gum (0.5 per cent) with different GO concentrations viz., 0.125, 0.5 and 1 per cent as T1, T2, T3, respectively and uncoated grapes were used as a control (T4). The recorded data showed that coated berries were registered with delayed changes in total soluble solids and titratable acidity in comparison to control. Physiological loss in weight in coated treatments were effectively lowered. Antioxidant activities and total phenols were increased in treated berries during the storage. Microbial load and total plate counts were decreased in coated berries. Among four treatments, T2 and T3 showed better results than other treatments. Results of present study indicated that treatment T2 was effective in maintaining quality of Thompson Seedless grapes when stored at 10° and 60-65 per cent RH.