Effect of vacuum and atmosphere pressure pre-treatments times on physical properties of hot air dried slices of button mushroom

Fresh mushrooms have low durability. Therefore, use of practical solutions to increase their shelf-life, is necessary for improvement of production. The aim of present research is study the effects of salt fortification by vacuum impregnation on physical characteristics and some qualitative characters of hot-air dried mushrooms. At first, the condition of salt fortification by vacuum impregnation was used at 5, 15 and 25minute process times for mushroom samples. Then, pre-treated and control mushroom samples dried by warm air at 60 C. Finally, shirinkage, porosity, Re-hydration percent of dried textures, color and hardness were determined. The results indicated that vacuum time had significant effect on shirinkage, porosity, re-hydration percent of dried samples, hardness and color change. By increasing vacuum time, hardness and shirinkage decreased, their color improved and porosity increased. Also increasing vacuum time had similar changes on traits with lower amounts. Re-hydration percent of textures, decreased by increasing vacuum time and increased via increasing atmospheric pressure time. Finally, it is revealed that, optimal vacuum time and atmospheric pressure time for dried mushroom quality conservation, were 20-24 and 22-25 minutes, respectively.