Effect of osmotic pretreatment and pulsed electric field on the viscoelastic properties of potato tissue

Compression stress relaxation of potato tissue exposed to pulsed electric field (PEF) treatment, with or without osmotic pretreatment, was measured and modelled with five parameter generalised Maxwell model. The changes in viscoelastic model coefficients were quantified as a response to applied field strength, pulse length, and pulse number and were correlated with conductivity changes. Using the same approach, additional effects of different osmotic treatments along with constant PEF treatment were also studied. As measured by the post-PEF conductivity, the residual elasticity was the parameter most affected at lower levels of PEF treatment. At high PEF levels, the longer of the relaxation times dropped from 10 to 2-3 s range. Maximal PEF treatment had a similar effect to 0.7 M hyper-osmotic treatment, implying that the effect of PEF on relaxation behaviour was dominated by loss of turgor. Neither hypo-osmotic nor hyper-osmotic pretreatment appeared to interact with the PEF treatment. (C) 2003 Elsevier Science Ltd. All rights reserved.