Study Of Combined Vacuum Microwave And Air Puffing Drying Pleurotus Eryngii

Pleurotus eryngii, as nutrition and health green food, are very popular at home and abroad. The traditional drying ways of Pleurotus eryngii were mainly solarization and hot-air drying, which make the product quality poor. This paper, screened appropriate drying method of Pleurotus eryngii with the comparative study of four different drying methods on the quality and microstructure of Pleurotus eryngii dry products, researched the pretreatment conditions, vacuum microwave drying characterister and optimized the best drying technology of combination drying. The main results were such as:Pleurotus eryngii were processed by four different drying methods, freezing drying, hot air drying, vacuum microwave and combination hot air+vacuum microwave+air puffing drying. With the comparison of the energy consumption of different drying methods and sensory evaluation and property characters of Pleurotus eryngii dry products, the results showed that hot air+vacuum microwave+air puffing drying was suitable for processing Pleurotus eryngii. The drying time length and unit energy consumption of different drying methods were freezing drying>hot air drying> hot air+vacuum microwave+air puffing drying> vacuum microwave. Freezing drying products were the most bright (L*88.98), basicly kept the Pleurotus eryngii original structure, hot air drying products appeared serious browning contraction phenomenon, and hardness was the greatest, vacuum microwave drying appeared JiaoHu phenomenon, joint dry product quality was best.Effects of pretreatments including slicing, steam blanching and infusing of moisture content, color, hardness cripness on the dry products were researched. Results showed that the slicing shape was beveling, slicing thickness was7mm, the time of steam blanching was90s, and the concentration of maltodextrin infusing was4%. The crosscut product had large hardness, inclined cut products were crispy, longitudinal cut products easy appeared edge horn effects. With the increase of slice thickness, moisture content, hardness and cripness were increasing trend. Hot bleaching time increased more, the smaller the hardness was, L*reduced. When the concentration of maltodextrin was4%,6%and8%, moisture content, hardness, dawolong differences were not significant.The Pleurotus eryngii vacuum microwave drying process was divided into three stages that were accelerated phase, constant-speed phase and decelerated phase. Based on the rule of water changes during vacuum microwave drying process, the kinetics model of vacuum-microwave drying was established, which was appropriate for Page equation. MR=exp(-KtN), K=e0.265+0.00.LXI-(1.000E-5)X2.002X3,N=1.010+0.003X3. It was proved that predicted date and experimental date were nearly accordant and the model could be used for describing the change of moisture during vacuum microwave drying.The process of vacuum microwave+air puffing drying Pleurotus eryngii was optimized by response surface method, with the parameters of the moisture content, microwave power density and microwave treating time and the indicator of the expansion ratio and the sensory quality of Pleurotus eryngii dry products. Regression equations were Y1=1.46-0.16x1+0.10x2+0.093x3-0.13x12Y2=6.45+1.22x1+0.41x2+0.36x3+1.01x1x2+0.74x1x3-0.94x12-0.85x32The optimum processing conditions were as follows:the moisture content as75%, microwave power density at20W/g and microwave treating time at105s. Under this condition, the quality of Pleurotus eryngii dry products was best.