Ethanol Precipitation of Mannooligosaccharides from Subcritical Water-Treated Coconut Meal Hydrolysate

Subcritical water hydrolysis is an effective method for producing mannooligosaccharides from coconut meal, which is a by-product from coconut milk processing. In this study, the purification process to obtain mannooligosaccharides from coconut meal hydrolysate was investigated. The effects of adsorbent (activated carbon and bentonite), concentration (1–10% w / v ), and adsorption time (5–60 min) were studied for impurities removal. The activated carbon showed much higher efficiency for impurities removal. Mannooligosaccharides were precipitated using ethanol at different concentrations (0–90% v / v ) and initial carbohydrate contents (50, 100, and 200 g/L). The results showed that the ethanol concentration at 90% v / v and initial carbohydrate content of 200 g/L gave the highest recovery of saccharides (31 g/L). The obtained precipitate contained 9.7, 22.6, 12.9, 19.4, 19.4, and 16.1% w / w of saccharides with 1 to 6 degree of polymerization, respectively.