| Fructose is the sweetest natural nutritive sweetener. Nowadays, fructose has been widely used in food production for its good sensory characters such as great sweet, sweeter in lower temperature, and flavor enhancement as well as its metabolic advantages such as insulin-independence and low glycemic effect. Time-consuming, low-yield and bad crystal size distribution are the common problems existing in domestic crystalline fructose production. In this thesis, cooling and solventing-out crystallization method is applied to preparing crystalline fructose which shows high yield and better granulometric distribution.Ethanol--ultrasonic Nucleation approach was employed to prepare fructose seeds. The obtained optimal conditions are: supersaturation degree 1.25, ethanol concentration 0.4 ml/g, electric current 0.3 A, ultrasonic treating-time 1min. The consequently prepared seeds present smooth surface and uniform size.Part of fructose crystallization properties have been studied. The viscosity variation of water-ethanol solutions of fructose (different v/v ratio) and the metastable zone widths of fructose in water and in ethanol concentration 0.2 solution was measured. The effect of sucrose ester S-570 and surfactant Span 60 on crystals was studied and the results show that the crystals are uniform and the viscosities of massecuite are decreased by 16.4% and 9.7% when adding 50 mg/kg S-570 and 50 mg/kg Span 60, respectively. The CV of crystals decreased by 51.5% when adding 100 mg/kg Span60. Optimax glucoamylase is untilized to hydrolyze oligosacchrides in fructose syrup, with the optimal conditions are: pullulanase 234 ASPU/kg,glucoamylase 156 GAU/kg and hydrolysis time 20 h, pH 4.0, temperature 55℃, concentration of fructose syrup 60%.Based on the studies on fructose crystallization properties, the optimized cooling-crystallization conditions are: seeds amount 2% (wt), initial supersaturation degree 1.02~1.08, cooling rate before adding ethanol 0.4℃/h, ethanol concentration 0.2 (v/v), cooling rate after adding ethanol: 0.28℃/h (52~ 46℃), 0.55℃/h (46~43℃), 0.8℃/h (43~35℃), 0.9℃/h (35~25℃).Crystallization kinetics studies demonstrate that the order ratio between nucleation and growth reaches 2.766 under the experimental parameters, unfavorable for crystal growth. The crystal growth rate increases with the increasing of supersaturation degree when it is below 1.160 and decreases rapidly after 1.160 because of the uncontrolled spontaneous nucleation. Temperature shows no apparent influence on crystal growth rate. Crystal growth rate is relatively high at 40℃and 45℃and is very low bescause of spontaneous nucleation at 50℃. The optimal cooling programme was calculated and the timetable for cooling rate was obtained while the result is not ideal which indicated that this programme is not suitble for fructose crystallization and the optimal cooling opration should be developed on the basis of experiment.In comparison with the purchased crystallied fructose, the self-produced crystallized fructose presents higher purity but smaller size and wider size distribution, which may be attribute to the contact nuclearation.
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