Combining pulsed electric fields (PEF) pre-treatment and ultrasound assisted convective drying to obtain coloured potato snacks rich in anthocyanins

Abstract

This study evaluated the use of pulsed electric field (PEF) technology as a pre-treatment to modify the structure of potato slices, for further addition of anthocyanins. Furthermore, this pre-treatment was combined with ultrasound-assisted convective drying for stabilization, therefore obtaining coloured potato snacks rich in anthocyanins. PEF application affected the potato structure: the more intense the PEF pre-treatment, the higher the cell disintegration index and the lower the cell wall elasticity. The pre-treatments with PEF enhanced the anthocyanin addition by 26–86 %, and the antioxidant capacity of the potato samples by 56–63 %. The added anthocyanins turn the natural colour of potato to reddish tones (increase in a*). The combination of the more intense PEF pre-treatment (1525.5 J/kg) and ultrasound-assisted convective drying (20.5 kW m⁻³; 21.8 kHz) increased the water effective diffusivity (D_eff) by 22 to 46 %. After drying, the retention of anthocyanins in PEF pre-treated and ultrasound-assisted treatment was in the range of 69–100 % and the antioxidant activity was 29–51 %. Furthermore, the antioxidant capacity of those samples was 25–43 % higher than the control. Therefore, the addition of anthocyanins into potatoes was enhanced by PEF pre-treatments, being necessary to find the balance among the processing parameters (pre-treatment and drying) to optimize the bioactive compounds retention in the final product.