Intensification of Low-Temperature Drying of Mushroom by Means of Power Ultrasound: Effects on Drying Kinetics and Quality Parameters

The aim of this study was to assess the effects of ultrasonic assistance on low-temperature drying of mushroom. For this purpose, mushroom caps slices drying kinetics at 5, 10, and 15 degrees C without and with ultrasound application (at 20.5 k W/m(3)) were analyzed, together with the dried product microstructure and some quality parameters (ergosterol and total polyphenol contents, antioxidant activity, color, hydration properties, and fat adsorption capacity). Ultrasound application promoted drying time reductions of 41% at 5 degrees C, 57% at 10 degrees C, and 66% at 15 degrees C, compared with drying without ultrasound. After drying at each temperature, mushroom microstructure presented remarkable tissue shrinkage. Moreover, when ultrasound was also applied, micro-channels were observed. When drying was carried out with ultrasound application, no significant (p >= 0.05) differences or significantly higher (p<0.05) figures of quality parameters were observed, compared with drying without ultrasound application. Thus, mushroom drying process intensification was achieved by using ultrasound, particularly when drying at 15 degrees C since drying kinetics was enhanced and significantly (p<0.05) smaller changes in all quality parameters were observed, compared with drying without ultrasound.