Abstract
Freezing technique is a very useful method for food preservation, although it sometimes produces damages in the product. The distribution of temperatures of raw potato was measured during the freezing operation by using an infrared thermographic camera Thermal Imager Optris PI160. Moreover, volume, moisture and water activity were measured before and after the freezing process. Cryo-SEM was also used to analyze the microstructure of fresh, frozen and thawed potato. The dielectric spectra of potato samples were measured before freezing and after defreeze, using an Agilent 85070E Open-ended Coaxial Probe connected to a network analyzer Agilent E8362B in the frequency range from 500 MHz to 20 GHz. The aim of this work was to monitor the temperature of potato surface during the freezing operation and to determine the water chemical potential and the structural changes of potato during this process, in order to determine the water motion throughout the freezing. The results showed important relations between the heat flux, water chemical potential gradients and structural changes. The paper demonstrated that infrared thermography and dielectric properties can be considered very important nondestructive tools for monitoring the freezing process of potato.
