Optimization of enzymatic production of fructooligosaccharides from longan syrup

Abstract

Fructooligosaccharides (FOS) are nutritive and low calorie sweeteners. They have been attracted and attributed to the expansion of healthy-sugar market due to prebiotic function. Longan is one of the traditional and economic fruits in the Northern of Thailand. In addition to its typical taste and floral flavor, it is a good source of sugars. In some years, over supply of longan is reported, consequently the extra produce was discarded. This research aimed to produce FOS from longan syrup and to optimize the yield of FOS using two enzymes of Pectinex Ultra SP-L and glucose oxidase from 60°Bx of the syrup. The sugar contents of the syrup consisted of sucrose (222.2±3.6 g L-1), glucose (120.3±0.8 g L-1) and fructose (104.7±1.7 g L-1), respectively. Response surface methodology using central composite design was applied to optimize three parameters of FOS production, including pectinase (2.7-7.2 U g-1sucrose), glucose oxidase (1022-4022 U g-1sucrose) and reaction time (7-25 h). Results showed that Pectinex Ultra SP-L concentration had a significant effect (p<0.05) on nystose and 1-kestose contents. Optimal values of Pectinex Ultra SP-L, glucose oxidase and reaction time were 3.3 sucrose, 1022 U g-1sucrose and 8 h 41 min, respectively which resulted in the highest amount of nystose (30.27 g L-1) and 1-kestose (123.36 g L-1). © 2012 Asian Network for Scientific Information.