Effect of drying process and long-term storage on characterization of Longan pulps and their biological aspects: Antioxidant and cholinesterase inhibition activities

Abstract

Impacts of the drying process (DP) and long-term storage (LTS) of longan pulp products were evaluated for fresh longan pulp (FLP), golden dried longan pulp (GDLP), dried whole longan pulp (DWLP) and dried whole longan pulp after one-year storage (DWLP_1Y) by assessing physicochemical properties against glycosylation reaction and bioactivities. All dried longan pulp products were defined as intermediate moisture food (IMF). GDLP containing sulfur dioxide had a lower browning index, whereas DWLP attained light brown to intense brown color after the storage period. Interestingly, DWLP_1Y exhibited a remarkable increase in rare sugars and monosaccharides especially D-allose, D-allulose and D-mannose. Reduction of total amino acid content and free α-amino groups in DWLP_1Y and SDS-PAGE results confirmed the occurrence of glycosylation (Maillard reaction) between amino acids and reducing sugars in pulps after DP and LTS. DWLP_1Y had the highest potential for antioxidative capacity and inhibition activity on acetylcholinesterase and butyrylcholinesterase enzymes, with potential use as a functional food and/or bioactive ingredient for treating Alzheimer's disease. This research paved the way for increasing the economic value of longan pulp products containing potent bioactivities.