Drying kinetics, physicochemical properties, antioxidant activity and antidiabetic potential of Sargassum fusiforme processed under four drying techniques

Sargassum fusiforme has been consumed as a healthy seaweed for thousands of years. To maximally maintain its quality after harvest, the drying kinetics, physicochemical properties, as well as antioxidant capacity and anti-diabetic potential of S. fusiforme were compared, after undergoing sun drying (SD), hot air drying (HD), mi-crowave drying (MD) and freeze-drying (FD). Results showed that FD created a porous honeycomb-type structure, provided the highest retention of chlorophyll a, total phenolics, p-hydroxybenzoic acid, hyperoside and cinnamic acid, and maintained the highest FRAP, DPPH and ABTS free radicals scavenging activities, as well as inhibitory effects against alpha-amylase, alpha-glucosidase and lipase. Sample dried by MD demonstrated the highest polysaccharide and gallic acid contents, and showed the highest hydroxyl radicals scavenging and DNA damage protective activities. The SD and HD processes produced dense structure, and caused the additional loss of color, bioactive compounds and biological activity. These findings implied that FD could be a best drying technique for S. fusiforme, however, MD could be a promising alternative method thinking to the long time and high cost of FD procedures.