|Satsuma mandarin (Citrus unshiu Marc.) is an important citrus commodity grown in the Gulf Coast area of Alabama. Mandarins are regarded as a valued part of a nutritious diet and health benefits are attributed to vitamin C, folate, dietary fiber, minerals as well as many phytochemicals including flavonoids, carotenoids and phenolic acids. However, mandarin fruit are highly perishable with a potential storage life of 2-4 weeks. Currently, little is known about the optimal postharvest practices for these fruit and there is an extensive need to develop advanced postharvest treatments to maintain high quality fruit during the storage and marketing period. Despite numerous advances achieved in postharvest biotechnology in ameliorating commodity losses associated with
postharvest decay, much of the nutritional value as well as the sensory quality of mandarin fruit can be lost as a result of current postharvest handling practices, which were developed primarily to maintain acceptable visual appearance with less regard to other quality aspects such as flavor and nutritional value. Although synthetic fungicides are effective in suppressing postharvest pathogen decay, public concerns regarding fungicide residue and development of pathogen resistance have stimulated the need for reduction of postharvest chemical use and for developing alternative non-chemical technologies. This led to the identification of trans-resveratrol (3,4’,5-trihydroxystilbene), which is responsible for resistance of grapevines to fungal diseases, as a possible candidate in this regard.
In order to identify the most efficient means of providing nutritious and visually appealing fruit, a postharvest study was conducted to determine optimal dosage of trans-resveratrol (1.6x10-3M, 1.6x10-4M and 1.6x10-5M) and to compare its efficacy with a mixture of wax and Imazalil or tap water. Studies were conducted on external color attributes, total phenolics, total flavonoids, vitamin C, total carotenoids and free radical scavenging properties. Results from this study indicated that resveratrol treatment not only improved shelf life of fruit but also enhanced nutritional quality. Resveratrol (1.6x10-5M) had a significant effect on the total phenolic, ascorbic acid and total carotenoid content of fruit. A high correlation was also found between vitamin C content and antioxidant capacity determined by ABTS. Therefore, use of resveratrol as a natural fungicide offers a new simple and safe method to improve the shelf life and postharvest quality of mandarin fruit.