Shellac, gelatin and Persian gum as alternative coating for orange fruit

Postharvest fruit coatings are an effective method to replace natural waxes lost during washing and handling. The coatings can reduce water loss and impart gloss to the fruit. Edible coatings, instead of synthetic waxes, are perceived to offer advantages with respect to human health concerns and environmental protection. In this research, edible coatings made from relatively inexpensive, easy to dissolve components that are suitable for increasing fruit gloss were studied on 'Valencia' oranges during storage. The coating materials included 5, 6 and 7% gelatin, 3.5, 4 and 4.5% Persian gum, 9, 10 and 11% shellac were compared to un-coated control, and fruit coated with a commercial wax. After coating, the fruit were stored for up to 60 days at 5 degrees C. Every 20 days fruit were removed from storage and evaluated. Scanning electron microscopy images of coated rind surfaces were also obtained. The results indicated that weight loss, fruit firmness, total soluble solids (TSS), titratable acidity (TA), pH, ascorbic acid content, total phenolic content (TPC), total antioxidant capacity (TAC) and respiration rate were affected by the coatings. Shellac coatings reduced weight and firmness loss. As the storage time was increased fruit TA and ascorbic acid content decreased, and pH, TPC and TAC increased. Glossiness was observed in all coatings, however, with increasing storage time, fruit coated by gelatin and Persian gum coatings, showed visible cracks. Shellac was the best coating as it dried quickly, forming a not sticky and odorless coating, and gave highest fruit gloss.