Influence of pulse width on polyphenol extraction from agricultural products by pulsed electric field

Abstract

Effect of a pulsed electric field (PEF) on polyphenol extraction from grape skins in water was investigated experimentally. The grape skins were immersed in the distilled water between plate-to-plate electrodes in a rectangular shaped reactor. The pulsed voltage was generated by pulse forming network (PFN) to control a pulse width of the high-voltage applied to the plate electrode. The total polyphenol extracted from the grape skins was evaluated as gallic acid using the Folin-Ciocalteu method. The grape skins were observed by a microscopy to clarify the cell morphological change. The experimental results showed the polyphenol extraction from the grape skins was enhanced with increasing pulse width in the PEF treatment. The energy consumption required for the polyphenol extraction decreased with increasing pulse width of the applied voltage. A microscopic measurement clearly showed that many anthocyanoplasts in cells were collapsed and the red color pigments were extracted from anthocyanoplasts into the cell. © 2013 The Institute of Electrical Engineers of Japan.