| Yam nutrient-rich, with a high nutritional value and health effects, rich in a variety of nutritional and physiological active ingredient, is a medicine, food, nourishing the three functions as one of the health food products. In order to improve the level of deep processing of yam to meet the domestic and foreign markets for high-quality Yam powder needs. Vacuum freeze-drying method produced a yam powder can be better to retain the nutritional components and physiological active ingredients, you can also Yam powder added to other foods, it will expand the application of yam. In this study, fresh yam as experimental materials, vacuum freeze-drying wet ultrafine powder Hill conducted a systematic research process. Determined by studying the vacuum freeze-drying powder mountain color-protecting technology, ultra-fine powder technology and vacuum freeze-drying process, and mountain powder quality during storage stability were studied. Main research contents and conclusions were as follows: (1) The technology of color maintain:First, a single-factor test for color retention agent citric acid, Vc, phytic acid and calcium chloride concentration of the appropriate color protection was discussed, followed by use of L9 (34) orthogonal analysis of variance test results and multiple comparison results to determine process conditions for protecting color: citric acid concentration of 0.6%, phytic acid concentration of 0.4%, calcium chloride concentration of 1.25%, in this condition can be a very good control of yam browning.(2) The technology of ultra-fine pulverization by wet processing : First, add water through research on the nutritional composition, drying rate and Sieving Rate to determine the optimum water content of 1:1; too plastic grinding times on the nutrient composition and sift yam paste the impact of the rate to determine the appropriate number of times over rubber mill three times, this time, a good yam paste particle size uniformity, and high nutrient retention. And then add the yam paste to help dry agent to improve the vacuum freeze-drying process, from the L9 (34) orthogonal test results analysis of variance and multiple comparison results to help determine the dry agent is maltodextrin, CMC andβ-cyclodextrin, dosage, respectively yam pulp soluble solids content of 50%, 0.4% and 5%. (3) The eutectic and co-melting temperature:The use of resistance determination of yam in the region of the eutectic point temperature of﹣14℃～-16℃, melting point temperature region for a total of -13℃～-15℃.(4)The technology of prefreezing: Yam eutectic point temperature of the region of﹣14℃～-16℃, due to color-protecting agents and agents to help stem the accession of solute will lower the eutectic point temperature of 5℃～10℃, with tests taken together, to determine the final pre-freezing temperature of﹣24℃. Choose the thickness of material loading, pre-freezing time factor, for 5×5 two-factor cross-test experiment to determine the filling thickness 8 mm, the pre-freezing time of 5 h.(5) The technology of vacuum freeze drying: According to the surface of ice crystals at different temperatures under saturated steam pressure gauge to determine the drying chamber working pressure range of 66.65～4.00 Pa, select the work of drying chamber pressure, sublimation temperature and analytical temperature factors for L9 (34) orthogonal test, the test results by analysis of variance and multiple comparisons to determine the freeze-drying process for the better: working pressure 40 Pa, sublimation temperature of 50℃, parsing the temperature 60℃.(6) Determination of yam polysaccharide:Phenol-sulfuric acid method's retrieving rate was up to 98.13%, anthrone-sulfuric acid method's retrieving rate was 74.33%, so phenol-sulfuric acid method was established.(7)The study on the qualitative stability of dehydrated Yam powder: The quality of vacuum freeze-drying powder mountain Stability Study: Determination of through regular vacuum-packed freeze-dried powder nutritional ingredients Mountain, indicating that the vacuum freeze-drying powder mountain yam better able to retain the original nutrients, better product quality , especially in the first four months of storage, mountain powder nutrient levels remained generally stable. The study also identified the dispersed powder to the mountains to add 0.15 g / kg of SiO2, can guarantee that freeze-dried powder has a good anti-Hill junction and mobility.(8)The technology of ultra-fine pulverization by wet processing vacuum freeze drying yam 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 yam powder has been determined: fresh yam, peeled, cleaning,color retention, ultra-fine pulverization by wet processing (smash, concoction, colloid mill), vacuum freeze drying, scatter, packing.
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