Abstract:

Polysaccharide in fresh longan pulp was extracted with the assistance of enzymatic hydrolysis. Cellulase gave relatively higher polysaccharide yield than pectinase and neutral protease, and was chosen for further study. The effects of cellulase concentration, the ratio of water to material, and extraction temperature and time on the yield of polysaccharide was investigated by single factor experiments. Subsequently, a quadratic regression rotational combinational design involving the above four factors at five levels was employed, and data obtained were analyzed with response surface methodology. Polysaccharide yield was most significantly affected by cellulase concentration, followed by extraction time, temperature and water-tomaterial ratio. An optimum polysaccharide yield of (12.23 ± 0.15) mg/g (on the basis of dried longan biomass weight) was obtained when longan pulp was treated with 1.2% cellulase at 45.0 ℃ for 187.0 min in a water-to-material ratio of 6:1, which was much higher than that obtained by conventional hot extraction.

Key words: longan, polysaccharide, enzymatic extraction, response surface methodology, process optimization