Producing High Fructose Syrup from Longan Juice

High fructose syrup was produced from raw longan juice. Optimizations on the deproteinization, enzymatic hydrolysis and isomerization of the process were performed. The results showed the optimized deproteinization to be executed with a soluble solid content of 30% and an addition of 0.12% citric acidat a heating temperature of 70℃ for 60 min to reach a theoretical fructose and glucose content of 42.19%. For the enzymatic hydrolysis, 1.5% sucrose hydrolase was added to the juice at 60℃ for 2 h to obtain a fructose content of(18.34±0.75)% with more than 80% sucrose hydrolyzed. The isomerization was carried out with an addition of 0.1 mg·g^-1 glucose isomerase at 60℃ for 60 min to arrive at a fructose content of (27.71±0.67)%. The resulting high fructose longan syrup had no less than 65% dry matters, of which 97.90% were fructose and glucose and no less than 67.20% were fructose, meeting the national standard for the product category.