Feasibility of using pulsed electric field processing to inactivate enzymes and reduce the cutting force of carrot (Daucus carota var. Nantes)

• PEF can induce enzyme inactivation in carrot pieces
• PEF can reduce the cutting force of carrots
• PEF can improve the accuracy of cutting surface
• Fibre direction of carrot pieces affects the resulting cutting force

The aim of this research was to investigate the feasibility of using pulsed electric fields (PEF) to inactivate selected enzymes, namely ascorbic acid oxidase (AAO) and peroxidase (POD), and to reduce the cutting force of carrots (Daucus carota var. Nantes). The effect of PEF processing parameters (i.e. pulse frequency, electric field strength and specific energy inputs), pre-conditioning temperature and the direction of carrot fibre (parallel and vertical) to the PEF electrodes on enzyme inactivation and texture was studied. The positioning of carrot in the chamber significantly (p < 0.05) affected the enzyme inactivation. Increasing energy inputs up to 166 kJ/kg at electric field strength of 0.8 kV/cm enhanced enzyme inactivation. Pre-conditioning the carrots at 20, 30 and 40 °C prior to PEF processing had further enhanced AAO and POD inactivation for at least 20% to 50% when compared to carrots pre-conditioned at 10 °C. Additionally, significant cutting force reduction up to 60% (on average up to 70–75 N decrease in cutting force) was found after PEF treatment (162 kJ/kg/80 Hz/3000 pulses/0.6 kV/cm). The carrot cells at epidermis and xylem region were softened after PEF. The reduction of cutting force was enhanced not only with increasing energy input, electric field strength and pulse frequency, but also when placing the carrots so that the direction of fibre was parallel to the electrodes. Due to PEF treatment, the resistance towards cutting became less and it resulted in a smoother cutting surface and higher cutting accuracy, compared to untreated carrots.Industrial relevancePEF processing enhanced tissue softening that could reduce the cutting force and improve the cutting quality (better cutting accuracy and smoother cutting surface) of carrots. Due to partial enzyme inactivation obtained after PEF processing, the intensity (temperature-time combination) of sequential blanching to achieve complete enzyme inactivation could be reduced.