4. Conclusion
This work has shown the positive effect of pulsed electric field
(q ¼ 32 kJ/kg) as an intensification method for improving yield,
nutritional value and sensory attributes of juices. Combining
a continuous electric treatment module and a continuous pressing
system on an industrial scale the juice yield increased from 711 g/kg
to 763 g/kg. The increase of juice yield and the decrease of water
quantities in pomace were positive factors for economic balance of
this process because drying the pomace requires less energy. The
effects of the electrical treatment on the mash composition before
pressing were very limited. However the mechanical expression of
juice led to an improvement of the solutes extraction from mash.
Indeed, the chemical composition (sugars, and native polyphenols)
of treated pomace was lower than the control. Furthermore, the
concentration of total native polyphenol of the juices increased due
to PEF treatment. The presence of oxidation products of polyphenol
was also significantly higher in the treated juices resulting in
a modification of the hue and the saturation in the yellow range.
This browning intensified by the PEF and the higher content of 5-
caffeoylquinic and epicatechin in treated juice requires additional
research on the modification of PPO activity and the formation of
oxidation products. Finally, PEF treatment had a positive impact on
the sensory attributes of the raw juices that had a higher intensity
of typical odour of apple. Further experiments should include the
seasonality and diversity of varieties of cider apples, in order to
prove the feasibility and the economic and environmental benefits
of this technology in industrial conditions.