Research On Freeze Concentrated Of Lychee Juice

Freeze concentration technology,based on the solid-liquid phase equilibrium principle between ice and aqueous solution, can remove water as solid state from solution. Suspension freeze concentration was applied on lychee juice in this project,which can maintain the unique flavor and aroma of lychee juice well, prevent it from discoloration, and solve the"cooked flavor", the processing technology of lychee juice is improved.Suspension crystallization method can form a lot of tiny ice crystal in the mother liquor, resulting in the large surface area in unit volume of ice crystal. The pure ice crystal can be formed rapidly and the final concentration could be enlarged. So, this technology is being widely applied in the industry. The research includes:(1)Effects of four factors including the freezing temperature, the concentration of solution , the viscosity of solution, as well as the different crystallization patterns were investigated. The appropriate operation conditions and parameters of freeze concentration lychee juice were set up. The results show that the most influencing effect was the freezing temperature, and then followed by the concentration of solution, the viscosity of solution, and the different crystallization patterns. As the experiments showed, when the initial concentration of lychee juice is 17°Brix, the temperature of coolant between -5～-6℃, was suitable for lychee juice concentration and the concentration of solute trapped in ice was less than 0.5%.(2) By studying the mass and concentration changes of fruit juice, ice crystal over time, the kinetic model of ice crystal growth was developed for the lychee juice freeze concentration. And the result showed the growth rate of ice crystal was directly proportional to the mass of ice, by carrying out the simulation through mathematical model and searching method to get the results, the experimental data was compared with calculated data. The validity of simulation model and the reliability of experiments were validated. This model could preferably control the growth of ice crystal macroscopically and provide refer to large scale production of freeze concentration lychee juice.