Studies On Drying Of Lycium Barbarum L. In Hot Air And Vacuum Far-Infrared Environment

Lycium Barbarum L. is a medicinal and edibleplant fruit with high nutritional value and strong pharmacological activity. The demand of health food (like Lycium Barbarum L.) is increasing with the improvement of people’s living standard. China is the main production and export country for Lycium Barbarum L. Lycium Barbarum L. contains a lot of water, it must be dried to safety moisture content for store and transport. Industry drying methods can overcome these problems. Lycium Barbarum L. is a kind of thermal sensitive and oxygenoussensitive material. The nutritional and commercial value of dried product is greatly influenced by the industry drying process.Nowadays, the main industry drying technology of drying Lycium Barbarum L. is hot air drying. Its advantages are:large throughput, simple equipment structure, low cost. But the drying time is longer and the color of product is poor under this processing, so new and more sophisticated drying technologies must be studid. Vacuum far-infrared drying is a kind of combined drying method, the heat is transferred to the wet material is in a vacuum environment. It has many advantages like short drying time, high efficiency of heat utilization, and is particularly suitable for drying thermal sensitive and oxygenous sensitive material. This project of this stidy is to obtain a optimal conditions for drying Lycium Barbarum L. by hot air and vacuum far-infrared. The content of agaric polysaccharide, color and rehydration rate of the dried products are quality index which were measured. The results of this study have a guiding significance on drying of Lycium Barbarum L.The main conclusions of this thesis are as follows:(1) Thermostatical experiments, poikilothermic experiments, poikilothemic and pretreatment experiments were done to dry fresh Lycium Barbarum L. The Lycium Barbarum L. drying curves and drying rate curves of different conditions are getten. The hot air drying characteristics and qualities of Lycium Barbarum L. are analyzed. Concrete contents were divided into three steps:a:thermostatical experiments (40℃,50℃,60℃). When the temperature was 40℃ and 50℃, the drying time were too long and the material was going to metamorphism. When the temperature is 60℃, the product discolored seriously before it got to the safety moisture content. So a conclusion is drawn that thermostatical condition can’t abtain preferabla quality product. b:poikilothermic experiments (40℃-60℃,50℃-60℃,40℃-50℃-60℃). Drying processing was completed. However, the quality of product was poor. c:poikilothermic and pretreatment experiments (40℃-60℃+Lye soaking,50℃-60℃+Lye soaking,40℃-50℃-60℃+Lye soaking). After soaking in 3% Na2CO3 solution for lmin, the drying drying time of Lycium Barbarum L. was shortened. The product quality by poikilothemic and pretreaement drying was good. The best process after comprehensive assessment was 40℃-50℃-60℃+Lye soaking.(2) The multivariate experimental studies of vacuum far-infrared drying in thermostatic and isobarically environment were taken. Drying and drying rate curves of Lycium Barbarum L. under different temperature (50℃,55℃,60℃) and pressure (4kpa, 5kpa,6kpa,7kpa) obtained obtained. The vacuum far-infrared drying characteristics and qualities of Lycium Barbarum L. were analyzed. Based on the multivariate experimental studies, the best vacuum far-infrared drying process were 60℃,4kpa, water soaking. Meanwhile, after comparing hot air drying and vacuum far-infrared drying with vacuum freeze drying and natural drying, it is found that vacuum far-infrared drying of Lycium Barbarum L. is potential.