Effect of Power Ultrasound Pretreatment on Edamame Prior to Freeze Drying

Immersion freezing with the aid of power ultrasound prior to freeze drying of edamame was investigated. The effect of power ultrasound on the freezing rate was influenced by ultrasonic power, exposure time to ultrasound field, and the pulse duration of the ultrasound that was applied. The higher the ultrasound power and the longer the exposure time, the stronger the ultrasonication effect on edamame was. However, the ultrasound power, ultrasound intermittency, and exposure time need to be chosen with consideration of the thermal effect of ultrasound. Response surface methodology (RSM) was adopted for optimization. The hardness and the water-holding capacity of edamame after thawing were 6050g and 92%, respectively, when 58-W ultrasound power was applied for 0.7min, 50% pulsed at the coolant temperature of-20C.