Effects of pulsed electric fields and preliminary vacuum drying on freezing assisted processes in potato tissue

The effects of pulsed electric field (PEF) treatment and preliminary vacuum drying (VD) on freezing assisted processes for the potato tissue were studied. The PEF treatment was done at 600 V/cm using the protocol to insure the high level of potato disintegration. The VD was done at sub-atmospheric pressure of p = 0.30 bar. Such conditions allowed relatively fast dehydration accelerated by PEF treatment at low or moderate temperatures inside sample (<50 °C). Impacts of PEF and VD on freeze-thawing (FT) and freeze-drying (FD) processes were tested. The duration of the freezing and thawing processes noticeably increased with increasing of the moisture ratio. The PEF treatment also accelerated the FD and affected the final level of dehydration after prolonged FD for 24 h. It was demonstrated that application of VD and VD combined with FT deteriorated the rehydration, whereas VD combined with FD facilitated the rehydration of deeply dried potato tissue. The obtained regularities can be useful in future practical implementations of freezing assisted processes with fine control of deterioration of product quality and reduced operating and maintenance costs.