Optimisation of Pulsed Electric Field Strength for Electroplasmolysis of Vegetable Tissues

Two experimental methods are proposed for the determination of the optimal field strength E in the case of pulsed electric field treatment of different plant tissues: apple (Golden Delicious), potato (Agata), cucumber (Straight Eight), aubergine (Black Beauty), pear (Conference), banana (Dwarf Cavendish) and carrot (Nantaise). One of the methods is based on estimation of the characteristic damage times τ and the total energy consumption factor during treatment τE2. Another approach is based on estimation of the maximal change of the sample disintegration index caused by the energy input during each pulse. The maximal energy input efficiency is observed in the first phase of electroplasmolysis when the disintegration index Z is not less than 0·5 for all the investigated food materials. Both proposed methods give consistent results. The optimal electric field strength Eopt depends on the type of tissue and is higher for cells having developed secondary cell wall: aubergine (Eopt=500–600 V cm−1), pear and banana (Eopt=900–1100 V cm−1), whereas for apple, potato, carrot and cucumber, the value of Eopt falls in the range from 200 to 400 V cm−1.