| Strawberry is highted "The Queen of Fruit" for it's alluring colour, pleasant aroma and excellent taste, furthermore it has higher nutritional value and healthful efficacy. But it is difficult to storage and the harvested strawberry is liable to blet because of damnification or infection by bacterium. The storage life can be extended and the nutrient content can be retained more by vacuum freeze drying to strawberry powder. The strawberry powder also can be appended in other foodstuff to extend the application of strawberry. So strawberry was chosen as the experimental material, and the freeze drying technology of strawberry powder with ultra-fine pulverization by wet processing was systematically studied in the paper. The technology of pretreatment and hydro-ultrastructure shatter, and the technology of prefreezing have been determined by experiments. And the parameters of vacuum freeze drying of strawberry powder and the qualitative stability of dehydrated strawberry powder have also been studied. The main aspects and the results were represented as follows:(1) The technology of color maintain: Scalding and adding additive were two parts of the technology. The scalding could restrain the activity of POD and PPO to prevent the browning of enzyme. It could increase the stability of the pigment in strawberry, and decrease the losing of the pigment because of oxidation and iron by adjusting the pH and appending EDTA-2Na. The technology of scalding has been determined through the relationship of scalding with the retain of sugar, Vc, and the activity of POD: thickness 2.5 cm, scalding time 3 min. Through the L16(45) orthogonal design, it was made that the better technology of color maintain was: adding 0.04 % EDTA-2Na and pH 7.5.(2) The technology of ultra-fine pulverization by wet processing : First of all, it has been confirmed that colloid mill twice was beneficial to retain sugar and Vc, and increase the homogeneous of granularity. Through the result of L9(34) orthogonal analysis, it was made that the better technology of ultra-fine pulverization by wet processing was: adding 50%～75% malt dextrin and 0.4%～0.6% CMC.(3) The technology of sterilization: The pasteurism has been used in strawberry powder processing in order to sterilization and decreasing the destroy of nutrient. It has been confirmed that the temperature of sterilization was 70℃, by compared the strawberry physical state with different temperature condition. Through the total of bacterium and coliform of strawberry powder, it was confirmed that sterilization lasting 15 min.(4) The technology of prefreezing: The technology included the prefreezing temperature, the prefreezing time and the loading thickness. The eutectic temperature of strawberry is—15℃. Through the U12(121×61×41) uniform design the technology of prefreezing has been determined that: loading thickness 11 mm, prefreezing lasting 5 h, refreezing temperature—26℃.(5) The technology of vacuum freeze drying: According to the saturated vapor pressure of ice surface in different temperature, it has been made that the pressure of the hothouse was 66.65～4.00Pa. And the optimal vacuum freeze drying technology has been obtained through L9(34) orthogonal design were pressure 45 Pa, tempterature of sublimation 55℃, temperature of resolution 65℃.(6) The study on the qualitative stability of dehydrated strawberry powder: It has been showed that the vacuum freeze drying strawberry powder packaged with vacuum could retain nutrients and color more by measureing various nutrients and color in the storage, especially in the first three months. It has also been proved that appending 0.1 g/kg SiO2 in the dehydrated strawberry powder could increase the fluidness and decrease the agglomeration.(7) The technology of ultra-fine pulverization by wet processing vacuum freeze drying strawberry powder: According to the technology of ultra-fine pulverization by wet processing and vacuum freeze drying of other fruits, and adjusting the parameters of every period in the technology, the technology of ultra-fine pulverization by wet processing vacuum freeze drying strawberry powder has been determined: strawberry, launder, destroy mildew, slice up, scalding by vapor, ultra-fine pulverization by wet processing (smash, concoction, colloid mill), sterilization, vacuum freeze drying, scatter, packing.
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