Role of seaweed (Ulva flexuosa Wulfen) extract in improvement of postharvest quality of Washington navel orange fruits

Seaweeds are rich sources of bioactive natural products, which have been considered as potential biotic agents. Ulva flexuosa Wulfen is a species of seaweed which is endemic to the Persian Gulf. In this study, the effect of different concentrations of U. flexuosa extract on the antioxidant activity of Washington Navel orange (Citrus sinensis L. cv. Washington Navel) fruits (measured as free radical scavenging activity; FRSA) and postharvest quality of the fruits were evaluated under cold storage (5±1°C) conditions and 85-90% relative humidity up to 60 days. Results indicated that prolonging the storage time increased fruit weight loss, fruit decay and total soluble solids (TSS) contents of the fruits, while prolonging the storage time reduced the percentage of juice and ascorbic acid contents of the fruits. Postharvest quality and antioxidant activity of Washington Navel orange fruit improved significantly when they were immersed in seaweed extracts. The most effective treatment was 3.76 g L-1 concentration of Ulva flexuosa extract, which maximized the improvement of antioxidant capacity, ascorbic acid content and TSS during days of storage (DS). The results of this study indicated that the seaweed extract could be used as a new bioactive agent for maintaining the postharvest quality of orange fruit through enhancing the antioxidant activity.