Study On Freeze Drying Technology Of Wild Fiddlehead

There are rich wild fiddlehead resources in Fujian Minbei. Vacuum freeze drying can increase the economic value for fiddlehead. Under the backdrop of China entered WTO. the study of fiddlehead freeze drying is very important and there are good application prospect. In this work, color protection, vacuum freeze drying technology were studied, and the process parameters were optimize. Then, the dynamic characteristics of freeze drying were analyzed and the quality of freeze dried and air dried product were compared. Main conclusions are as follows:(1) Zinc acetate solution was selected as color protecting liquid. Based on the full-factorial experiments, blanching temperature of 85℃, citric acid concentration of 2.50% and blanching time of 4min, the results of orthogonal experiment showed that pH value has the most significant effect on protecting effect, the second was the zinc acetate concentration and the last was treating time. Optimized condition of color protection was a zinc acetate concentration of 30mg/100g, pH value of 6.5, treating time of 20 min.(2) Under the condition of pre-freezing temperature at -25℃, the suitable load for fiddlehead freeze drying process was 8.5kg/m2 and the best freezing speed was 1.5℃/min. The relative freeze-drying curves of fiddlehead were obtained according to the experimental data. The prepared freeze-dried fiddlehead was pale green, slightly bent and have the natural aroma.(3) The three factors of freezing temperature, vacuum degree and load, had different effect on fiddlehead drying effect. The fiddlehead freeze drying kinetic model was established and was verified that predicted value was similar to experimental value. The comparison of the sensory, moisture content, water activity, rehydration characteristics and main nutrition compositions of freeze dried fiddlehead to that of air dried showed that freeze dried fiddlehead had better physical characteristics, good flavor and plentiful nutritional components.(4) The fiddlehead vacuum freeze drying was determined by the hazard analysis critical control points as follows:hot drift and metal detection. Through the analysis for fiddlehead HACCP plan in the process of vacuum freeze drying processing, has been clear about the process, critical limit, monitoring measures, corrective measures, records and validation.