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Bracken as a traditional exports wild mountains, unique flavor, delicate taste, known as the \In this paper, Hunan produced fresh bracken as raw material, generally in the bud for Bracken soon after picking, strong seasonal, when the hot and humid season, fern quickly browning, aging, can not eat, and its decline in quality , bracken serious waste of resources, the present experiment by choosing different color protection and color protection solution concentration, the use of blanching, room temperature dip green color saturation and vacuum infiltration measures discussed fern green color process conditions to optimize bracken green color and crispness technology to better exploitation of the wild resources. Through the fresh bracken color protection and crispness process study results showed that zinc gluconate 3.5mg / L, zinc lactate 50mg / L, sodium 300mg / L, sodium sulfite 300mg / L, zinc acetate 250mg / L composition The composite solution can achieve the best color protection. Calcium lactate 100mg / L, calcium chloride 50mg / L, magnesium chloride 150mg / L Mixtures consisting best crispness. Paul crisp color protection agent solution and the best ratio of 1:2. Through the above solution and the concentration of color protection agent mixture crispness on Paul Bracken to protect color and crisp handling, processing of fresh bracken color, taste crisp, fresh bracken can be better to keep the original flavor. Up to 92% moisture content of fresh bracken, and by the impact of the production season, place two days or so appearance and quality will deteriorate. In order to extend shelf life and maintain the appearance of the test uses low-temperature vacuum freeze-drying technology to dry bracken test, using three factors and three levels of response surface analysis method optimizes the drying process parameters. Bracken by tests shelf vacuum freeze drying process the heating temperature, drying chamber pressure, material thickness and the drying time between quadratic regression model, the significant test and analysis of variance, that the model fit is high, the model reasonable and reliable, able to better predict the drying time. Validation test, validate and determine the optimal bracken vacuum freeze-drying conditions when the pre-freeze freezing rate of 1.5 ℃ / min, end temperature of -25 ℃ ~ 27 ℃, freezing time was 90min; vacuum freeze-drying when resting plate heating temperature 42 ℃, drying chamber pressure 48Pa, material thickness 14.5mm, dried bracken this condition can greatly reduce energy consumption and improve economic efficiency. The vacuum freeze-dried bracken test physicochemical characteristics were analyzed and compared with hot air drying bracken compare two kinds of drying process of dried bracken obtained in rehydration, water activity and other differences, and with fresh The nutrient composition of bracken comparison study its nutrients in case of loss, the test results show that the vacuum freeze-drying of fresh bracken fern maintaining the inherent color and texture, flavor and aroma with bracken, bracken and hot air drying the color becomes dried up, organized crime, aroma light; vacuum freeze-drying moisture content is low bracken, bracken higher than the hot air drying drying rate and lower water activity, and thus has better preserved nature; vacuum freeze-drying Bracken rehydration rate was 91.8% after recovery with fresh fern color, smell, taste, shape, taste fresh, and hot air drying bracken in the case of heating water recovery was 77%, with bracken aroma only after recovery ; vacuum freeze-drying bracken nutrients stored higher than air drying bracken, wherein the amino acid, vitamin C, vitamin E, carotene, respectively, compared with hot air drying bracken by 10%, 63.4%, 61% and 7.7%.
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