Hot Air Drying Schedule Of Auricularia Auricular Under Varying Temperature And Humidity And Product Quality Control

Auricularia auricular is a kind of edible fungus that grows on rotten wood、cut-log or bags.Auricularia auricular is delicious and has high nutritional value and a certain medicine value. Because of its high moisture content, fresh auricularia auricular is difficult to store. Drying is an important method to process and store auricularia auricular. The traditional drying method of auricularia auricular is sun-drying, but this method has many disadvantages such as large cover area, long drying time and easily affected by weather, sandstorm and insect pests.With the fast development of the auricularia auricular industry in China, mechanical drying of auricularia auricular becomes necessary.Drying room is a kind of hot air convection drying equipment which has many advantages such as large production capacity, simple structure, easy operation, low operation cost, suitability for wide fuel sources. Drying room is widely applied in the rural area for drying of agricultural products. The aim of this project was to investigate a suitable hot air drying schedule for the auricularia auricular in the drying room by laboratory and pilot experiments, and to obtain the knowledge of the drying characteristic and the dried products’quality.The main work and findings of this work are as follows:(1) Carrying out Auricularia auricular drying experiments in constant drying air temperature and humidity. The drying curves and drying rate curves were plotted under various hot air temperatures (40℃、50℃、60℃) and relative humidity (40%、50%、60%、80%). On the base of analysis of the auricularia auricular drying characteristic and the quality of dried auricularia auricular, the auricularia auricular hot air drying process could be divided into four stages and the operating essentials in each stage were concluded:Temperature rise and accelerate stage:keeping the air temperature at about40℃and sustaining a high humidity, reducing the moisture content to90-92%. Low temperature and high humidity operation can raise the auricularia auricular temperature quickly and prevent surface hardening of auricularia auricular;The first falling-rate drying stage:keeping the air temperature at about50℃, lowering the air humidity and reducing the moisture content to85%. In this stage, free water in the fungus can be removed easily with higher temperature and lower humidity, and the shrinkage is small and so, has little effect on the product appearance;The second falling-rate drying stage:keeping the air temperature at about55℃lowering the humidity and reducing the moisture content to66%. In this critical stage, it is important to control the drying rate to ensure the shrinkage and product appearance; The third falling-rate drying stage:keeping the temperature at about60℃and reducing the moisture content to14%. The water removed in this stage is bound water, so it’s necessary to keep high temperature.(2) Drying experiment under varying air temperature and humidity were conducted in laboratory and pilot equipment respectively. The experimental results showed that the drying process under varying temperature and humidity can produce high quality dried auricularia auricular that had nice appearance, high levels of agaric polysaccharides and ratio of wet-and-dry. The product quality was close to the one produced by sun-drying.