Abstract
In the present study, the effects of longan peel and seed on the quality of longan cake were determined, and the effects of longan peel extract (LPE) and longan seed extract (LSE) on the physicochemical properties of wheat starch were also measured. Furthermore, the phenolic profile and antioxidant activities of these extracts were observed. The results showed that both longan peel and seed could improve the color, texture, and volatile flavor compounds of longan cake. In addition, the properties of wheat starch, including gelatinization characteristics, thermogravimetric analysis, rheological properties, solubility, swelling power, water/oil-holding capacity and iodine binding ability, were all affected by LPE and LSE significantly. Both LPE and LSE had high contents of total phenols (LPE: 71.05 ± 2.57 mg/g, LSE: 78.49 ± 5.21 mg/g) and total flavonoids (LPE: 286.27 ± 6.04 mg/g, LSE: 423.21 ± 7.69 mg/g). Gallic acid, ellagic acid, and ellagic acid 4-O-α-l-arabinofuranoside were identified as the main phenolic compounds of LPE, while those of LSE were gallic acid, ellagic acid, ellagic acid 4-O-α-l-arabinofuranoside and (-)-epicatechin. Furthermore, LPE and LSE both exhibited good antioxidant activities to scavenge free radicals and showed high reducing power. All results suggest that longan peel and seed are rich in phenols and can improve the properties of starch so as to enhance the quality of starch product, which shows their potential application in food and chemical industries.