Effect of edible coatings on the postharvest quality of eggplant (solanum aethiopicum l.) Fruits during low temperature storage

Abstract

Eggplant is an important fruit with numerous health benefits, but it has a relatively short postharvest life. Edible coating in combination with low temperature storage can improve quality and extend shelf life but they are normally imported and are costly. This work, therefore, sought to study the effect of edible coatings prepared from inexpensive, locally available materials on the quality of eggplant fruits during storage. Fruits were coated with beeswax, Aloe vera or cassava starch solution (with or without citric acid pre-treatment) and stored at 10 °C. Beeswax coating was the most effective in minimizing fruit weight loss, maintaining firmness and delaying colour deterioration. Aloe vera coating also improved the fruit quality but starch coating was not very effective. Total phenolic content generally decreased during storage while ascorbic acid levels increased except for beeswax-coated fruits. Total antioxidant capacity was unaffected, irrespective of the coating treatment. Citric acid pre-treatment before starch coating minimized weight loss at 10 °C and in shelf life. The coating conditions for beeswax, starch and Aloe vera were then optimized using Response Surface Methodology Box Behnken Design. The optimized coating conditions were 4.6 % (w/v) coating concentration, 1 % (w/v) citric acid concentration and 3 min coating duration for beeswax coating; 4.99 % (w/v) coating concentration, 2.98 % (w/v) citric acid concentration and 10 min coating duration for starch coating; and 96.92 % (v/v) coating concentration, 1.07 % (w/v) citric acid concentration and 10 min coating duration for Aloe vera. Verification experiment gave a good correlation coefficient (R2) of 0.87 between the predicted and measured physicochemical properties of eggplant fruits coated with beeswax, cassava starch and Aloe vera.