Antioxidant activities of longan (Dimocarpus longan var. obtusus Leenh.) seeds and their application in longan jam

Abstract

The objectives of this study were to investigate total phenolic compounds and antioxidative activities of crude extract of Dimocarpus longan var. obtusus Leenh. (longan) seeds. Development of longan jam supplemented with longan seeds, their proximate composition, antioxidant capacity and sensory characteristics were also evaluated. The longan seeds were extracted using 95% ethanol and water. Total phenolic content and antioxidative activities were evaluated using Folin-Ciocalteu assay, diphenyl-1-picrylhydrazyl (DPPH) scavenging and Ferric reducing ability power (FRAP) methods, respectively. The results of total phenolic contents of longan seed ethanol and water extracts were 93.12±58.88 and 554.16±42.83 mg GAE/g dry weight of longan seed. Longan seed water extract showed the highest antioxidative activities (p≤0.05). Longan jam (control) and longan jam supplemented with 1%, 3% and 5% longan seed powder were prepared. Proximate analysis indicated that the addition of 1%, 3% and 5% longan seed powder could increase protein, fat and fiber in longan jam, when compared to control. The quantification of total phenolic content and antioxidant using Folin-Ciocalteu and DPPH methods in longan jam samples were performed. The results found that longan jam supplemented with 5% longan seed powder showed the noticeable source of antioxidant and phenolic compounds (p≤0.05). Consumer acceptability using 9-point hedonic scale indicated that 90% of consumers accepted longan jam supplemented with 1% longan seed powder. Therefore, there is some potential in longan seeds to use as food fortification and dietary supplements.