The impact of combination of pulsed electric field and ultrasound treatment on air drying kinetics and quality of carrot tissue

In the study, the impact of combined pulsed electric field (PEF) and ultrasound (US) pre-treatments on drying kinetics and quality of dried carrot was evaluated. Carrot samples were subjected either to US followed by PEF (US-PEF) treatment or to PEF followed by US (PEF-US) treatment. Afterwards material was dried using convective method at 70 degrees C. Drying time of the samples subjected to combined treatment ranged from 180 to 255 min, whereas in the case of untreated carrots the drying time was equal to 298 min. The highest water diffusion coefficient (11.5.10(-10) m(2)/s) was calculated for the samples subjected to PEF treatment followed by immersive sonication and it was 63% higher than reference ones. No significant differences were stated when comparing the rehydration properties of all investigated samples. However, samples pre-treated by combined method exhibited lower ability to adsorb water vapour from environment. Subjecting carrots to combined treatments resulted in a better carotenoids retention (60.5-80.6%). The material treated by PEF-US or US-PEF exhibited higher values of redness (a*) and lower of yellowness (b*) in comparison to untreated dried carrots.