Ultrasonic mass transfer button mushroom after osmotic dehydration process

Button mushroom has sensible to mechanical blows and has low shelf life. The purpose of this project was determining of the optimum method of ultrasonic dehydration and the effect of osmotic processing conditions on mass transfers. In the first step, sodium chloride solution with concentrations 6, 9, 12 and 15%, for 20,40,60,90 and 120 minutes at 25°C and 45°C were used and in the second step, in the constant conditions of salt concentration (12%), immersion time (60 min) and temperature (45°C), the mushroom samples were subjected to ultrasonic wave in two levels (pulse duration time to pulse rest time of 1:1 and 1:4) at frequency of 20 KHz and constant power 400 w, to determine their effect on water loss, solid gain and water reduction. The results showed that, as the concentration of osmotic solution increased, mass transfer from the sample increased. When immersion time was increased to 60 min, solid gain and moisture diffusion increased. After this time, water loss was less increased and solid gain was more increased. Further solid gain created a resistant layer against permeability and solute movements on both sides of tissue. in this process, at temperature of 45 °C, greater the mass transfer rate achieved, mainly due to the increase in cell permeability and permeability coefficient. It was found that salt concentration of 12%, immersion time of 60 min and temperature of 45°C gave the minimum solid gain (2.83%) and maximum water loss (29.36%) and weight reduction (24.53%). Also, the use of ultrasound with pulse ratio of 1:1 in constant osmotic dehydration condition was conducted better results. At 40 min processing time, the solid gain, water loss and weight reduction were 2.93%, 41.23% and 40.30%, respectively.Moisture content of mushrooms after osmotic dehydration and ultrasound treatment reduced to 85 and 82 %, respectively.