THE PHYSICAL, OPTICAL AND RECONSTITUTION PROPERTIES OF APPLES SUBJECTED TO ULTRASOUND BEFORE DRYING

The purpose of the study was to present the influence of ultrasound pre-treatment on the physical, optical and reconstitution properties before convective drying of apple slices. The apples were subjected to ultrasonic treatment (35 kHz) for 10, 20 and 30 minutes and dried at a temperature of 70°C and at an air velocity of 2 m/s. The ultrasonic waves reduced the drying time by 5-13% and affected the properties of dried apples. The longest pre-treatment resulted in colour changes and increased the porosity of dried apples. It also decreased the density, hardness and hygroscopic properties of dried apples.