Study On Purification Of Fructose Esters

Fructose esters was one important kind of the non-biosurfactants. Fructose esters were used in foodstuff, cosmetics, pharmaceuticals, detergents, fibers and so on. Synthesis of the sugar esters by enzyme had the advantage of mild reaction conditions, high efficiency, high speciality.In this paper, the thin layer chromatography (TLC) to qualitatively analyze fructose esters was developed. The optimal conditions of TLC were as follows: The solid phase was silical gel G, the mobile phase was toluene—ethyl acetate—methanol -water (10: 5: 4.5: 0.2, V/V/V/V) . The Rf of fructose monopalmitate was 0.46. The Rf of fructose dipalmitate was 0.66.A method of HPLC-ELSD quantitative analysis of fructose esters was developed. The HPLC conditions were as follows: Prevail C18 column as the stationary phase, 1mL/min of flow rate, 30℃ of column temperature, A solution(99% ethyl acetate and 1% water (V/V)) -B solution (75% ethanol and 25% water (V/V)) (60: 40, V/V) as the mobile phase. The temperature of the ELSD detector drifting pipe was 73.8 ℃, flow rate of carrier gas was 2 mL/min. For the fructose monopalmitate, the calibration equation was y=985604x - 52298 , R2 = 0.998 ; For the fructose dipalmitate, the calibration equation was y=720236x—26324, R2 = 0.998.According to the characteristic of chemical constitutes, in the systems of enzymatic synthesis of fructose esters, a separation process of fructose esters was submitted. Firstly removed fructose by extraction with salt effect, then purified fructose monopalmitate by extraction with mixed organic solvents, and last purified fructose dipalmitate by crystallization.Separation of the fructose esters by water-organic extract with salt-effect was studied. The optimal process conditions were: 2% NaCl aqueous solution, 60℃, the removal rate of fructose was 99.1%.The fractionation separation of fructose monopalmitate and fructose dipalmitate by extraction with mixed organic solvent were performed. The optimal conditionswere as follows: cyclohexane—ethanol—water(2: 2:1, V/V/V), initial concentration of fructose monopalmitate was within the limits of 0.48-0.6mg/mL, the optimal temperature was 60°C. The yield of fructose monopalmitae was 92.5%, and the purity of the fructose monopalmitate obtained was 93.8%.After removed of the fructose and fructose monopalmitate, the solution was distilled under reduced pressure, the residue was solved in mixed solvents (ethyl acetate—methanol—water (24: 1: 0.5, V/V/V)), stirred and stood in ice brine, after 8 hours, the fructose dipalmitate was crystallized from the solutions, and the palmitic acid remained in solutions. The yield of fructose dipalmitate was 84.7%, and the purity of the fructose dipalmitate was 92.2%.The products were identified by FT-IR and ESI-MS..