Carbohydrate content and composition of product from subcritical water treatment of coconut meal

Coconut meal, a by-product from coconut milk production, was treated with subcritical water at 100–200 °C for 30–240 min in a batch-type reactor. The analysis focused on the content and constituent neutral sugar of the soluble carbohydrate in the liquid products. The carbohydrate is composed of both monosaccharides and oligosaccharides. Treatments at 100–150 °C gave a small amount of a carbohydrate (3.5–5.1 g/100 g dry coconut meal). At 175 °C, the carbohydrate content increased from 4.9 to 9.6 g/100 g dry coconut meal (p < 0.05) for 30–240 min of treatment, but the value decreased from 10.6 to 6.1 g/100 g dry coconut meal for 30–240 min of treatment at 200 °C. The soluble carbohydrate contained mannose, glucose, galactose and arabinose. A response surface methodology study indicated that 13.9 g/100 g dry coconut meal of mannose in the soluble carbohydrate could be produced at 227 °C in 3 min.