In order to prevent direct contact with a liquid medium, the 100 g carrot slices were hermetically packed in BOPA/PE 1540 FF foil, removing the 90% of the air out of the packages by using a vacuum packaging machine (TEPRO, Koszalin, Poland).
Material was weighed with accuracy of ±0.01 g and then it was immersed in 1 L of distilled water, which was used as a medium in both ultrasonic baths. Moreover, the temperature of the water surrounding
the immersed sample was measured. To prevent flowing out samples from the bag, packages were locked up in metal net.
After pre-treatment the material was weighed with an accuracy of ±0.01 g and the temperature of the medium was measured once again.