Chemical Synthesis And Separation And Purification Of D-tagatose

D-tagatose, a rare natural hexoketose, is one of the rare sugars, which are defined as monosaccharides and their derivatives that rarely exist in nature. Tagatose is a C-4 fructose epimer, with 92% of the sweetness of sucrose. It has an excellent sucrose like taste, no aftertaste or potentiation of off-flavour, and can be considered as a possible alternative bulking sweetener. It has been tested that D-tagatose can be used in food industry GRAS. D-tagatose has low caloric value, and no effect on plasma glucose levels. In addition, it can control dental caries, improve healthy bacterium and so on.Lactose was hydrolyzed by enzyme, and catalyzed hydrolysis yielding a mixture of D-galactose and D-glucose. The lactose enzyme activity was measured by the method of ONPG, and the enzyme activity reached 3000 U/ml. Glucose Assay Kit tested lactose hydrolyticl rate, and the result showed the hydrolyticl rate was over 90% in the optimum condition.This paper researched the processes for the conversion from galactose to isomeric tagatose with chemical catalyzer. The effect of different calcium chloride concentration, reaction time and neutralized acid on yield of tagatose was investigated by single factor tests. Results showed that the condition, such as calcium chloride (0.01～0.03 mol/L), reaction time(20～40 min), acetum, carbon dioxide, phosphate acid to synthesize tagatose was suitable. Through the orthogonal experiment, the optimum condition for tagatose synthesization was determined to be 0.02 mol/L calcium chloride, 30 min, acetum neutralization. The yield of tagatose was 49.05%. As calcium acetate can be dissolved, and make some difficulty for desalt, thus usually phosphate acid replaced it.The technology of separation and purification of D-tagatose was established according to the methods of DTF-01Ca2+ cation exchange chromatography, ion exchange resin desalting and bleaching. The optimal Ca2+ cation exchange chromatography conditions: column temperature of 70℃, the input volume of 20 ml and the flow velocity of 1.0 ml/min, in which the recovery of D-tagatose was 83% and its purity reached 90%. Desalting and bleaching with anion and cation exchange resin in series once, 93% salt was desalinized and the recovery of D-tagatose was 87%.The technology of crystallization of D-tagatose was established, which using the compositive process of vacuum concentrate, cooling, ethanol crystallization, separation and desiccation. The result showed crystallization rate reached 52%, the optimal conditions is vacuum concentrate of 70-80°Bx with 55℃, ethanol of double volume, staying of 24 h in 4℃. From the infrared spectroscope data, it showed that the crystal was D-tagatose.