COMBINING PULSED ELECTRIC FIELD (PEF) PRE-TREATMENT AND ULTRASOUND ASSISTED CONVECTIVE DRYING TO OBTAIN POTATO SNACKS
Résumé
Pulse electric fields (PEF) technology can modify the structure of foods affecting further mass transport processes such as drying. On the other hand, the effects of airborne ultrasound when applied during drying depends on product structure. This work evaluated the combination of PEF pretreatment and ultrasound-assisted convective drying of potato slices to obtain oil-free snacks. Potatoes were cut in 3 mm slices and blanched in boiling water for 60 s. Then, PEF pretreatment up to 150 pulses of 25 μs at 10 Hz, 0.6 kV/cm and specific energy input up to 1525.5 J/kg were applied. After, convective drying (50°C and 1 m/s) was applied, without or with ultrasound (20.5 kW m−3, 21.8 kHz) assistance. PEF affected the potato structure: the more intense this pre-treatment, the higher were the cell disintegration index and the lower the cell wall elasticity. Both technologies, PEF pre-treatment and ultrasound-assisted drying, individually applied increased the water transport. However, it was the combination of both the strategy more efficient to enhance the process, increasing the effective diffusivity in 46% and the convective coefficient of mass transfer in 41%. The combined approach also resulted in sample twisting and bending, with higher deformation. Drying reduced the potato antioxidant activity about 20% (both ABTS and FRAP methodologies), with more impact in the combined strategy. Consequently, although the combination of both technologies improved the potato slices drying, further studies are needed to obtain the conditions that reduce the impact on product quality.