Due to the high cost of energy, and in order to obtain a product with the high nulritional value, the aim is to reduce the time of freezing. The study was focused on the impact of sonication on the process of freezing of apple tissue. Apples (ldared) slices was subjected to ultrasound at a frequency of 21 kHz and 35 through 10, 20 and 30 minutes, and then sub- jected to freezing. The material was frozen by air chilling to -25°C. The use of ultrasound pre-treatment shortened the freezing time, in comparison to untreated sample, however, these changes were significant in the case of ultrasound of frequency 35 kHz.