Effect of a Pulsed Electric Field Treatment on Expression Behavior and Juice Quality of Chardonnay Grape

This work discusses the effects of pulsed electric field (PEF) application on low-pressure mechanical expression (the pressure maximum was 1 bar) and characteristics of juice produced from Chardonnay white grape. The experiments were carried out using a texture analyzer equipped with a PEF-treatment compression chamber operated at moderate electric field strength E = 400 V/cm. Two regimes of extraction were compared: expression at constant pressure (0.5 or 1 bar) and expression at progressive pressure increase (from 0 to 1 bar). This last one was chosen for the scale-down modeling of industrial grape pressing process. It was shown that PEF treatment at the electric field E = 400 V/cm and the total time of treatment t (PEF) a parts per thousand aEuro parts per thousand 0.1 s allowed reaching of a high level of cell disintegration, Z a parts per thousand aEuro parts per thousand 0.8. The energy consumption of PEF treatment corresponding to this level of disintegration was rather low and equal to W a parts per thousand aEuro parts per thousand 15 kJ/kg. The PEF pretreatment resulted in juice yield increase from 67% to 75% (1 h of pressing at constant pressure of 1.0 bar). PEF treatment accelerated development of grape deformation. Decrease of difference between deformations of untreated and PEF-treated samples at high pressure and long-pressing time was observed. Statistical analysis showed no significant effect of PEF treatment on turbidity and content of polyphenols for the constant pressure regime. However, PEF treatment application resulted in elevation of the content of polyphenols (more than 15%) for the progressive pressure-increase regime.