Study On The Preparation Of A Syrup Containing D-tagatose

D-tagatose is a new functional monosaccharide, and has been widely used in foreign countries. But there are still no industrial productions and applications of D-tagatose in China. In the domestic market, D-tagatose has a very high price, which greatly limits its wide applications. Arabic gum has a low price, a wide source and the high safety performance. Besides, when the Arabic gum is hydrolyzed, there are high contents of galactoses in the hydrolysate. This paper used Arabic gum as materials for synthesizing D-tagatose, studied the process of chemical synthesis of D-tagatose, and developed a kind of mix syrup containing the functional D-tagatose. This research optimized the process of synthesis and refining, and analyzed the final produce’s characteristics.This research used dilute acid to hydrolyze Arabic gum, and used the galactose’s content in the hydrolysate as the index, which measured the hydrolysis degree of Arabic gum. When the hyfrolysis degree of Arabic gum was very large, the galactose in the hydrolysate was isomerized to genetate D-tagatose, using sodium aluminate as the catalyst. Response Surface method was used to optimize the synthesis process. The dependent variable was the conversion rate of D-tagatose. When the mass fraction of sulfuric acid solution was 1.5%, the content of galactose in the hydrolysate was at a high level, totally up to 8.9 g. When adding 4.93 g sodium aluminum in 100 m L hydrolysate and reacting 3.5 h under the temperature condition of 45 ℃, the conversion rate of D-tagatose reached the maximum, 66.18% of galactose was isomerized to generate D-tagatose.The mix syrup had a darker color. The existence of coloured substances affected application and further research of the mix syrup, so the syrup decolorization was particularly important. Two kinds of flocculants, chitosan and γ-polyglutamic acid, were used together to study the decolorization of mix syrup. Factors of chitosan’s content, p H, temperature, time and γ-polyglutamic acid’s content were studied. Orthogonal experimental design was used to optimize the process. 0.25 g/L chitosan solution was added to 100 m L 25 °Bx mix syrup, under the condition of p H 4.5 and temperature 30 ℃, and the mix syrup was decolorized for 6 min, then added 0.07 g/L γ-polyglutamic acid solution to the mix syrup. After mixing and filtering, the syrup decolorization rate reached to 65%.The method of HPLC-ELSD was applied to analyze the composition of the refined mix syrup. Quality indicators were also determined, which were measured with reference to the national criterion of high fructose syrup. The results showed that the mix syrup was mainly composed of D-tagatose, L-arabinose and L-rhamnose. Their concentrations were respectively 58.9 g/L, 51.4 g/L, 17.5 g/L. The mix syrup was a transparent liquid, which was colorless or slightly yellow. The taste of mix syrup was pure and had no bad flavor. Other quality indexs also conformed to the national criterion of high fructose syrup.