Two-Step PEF Processing for Enhancing the Polyphenol Concentration and Decontaminating a Red Grape Juice

Abstract

This study’s aim is to evaluate Pulsed Electric Fields (PEF) technology as an alternative method for the processing of red grape juice. For this purpose, two PEF treatments were applied: first to grapes for polyphenol enrichment of the juice, and subsequently for microbial decontamination of the obtained juice. Juice obtained from PEF-treated grapes (5 kV/cm, 63.4 kJ/kg) had the polyphenol content 1.5-fold higher and colour intensity two times higher of control juices by spectrophotometric measurement (p ≤ 0.05). A subsequent decontamination treatment by PEF (17.5 kV/cm and 173.6 kJ/kg) achieved inactivation of the present microbiota (yeasts, moulds, and vegetative mesophilic bacteria) below detection level (<30 CFU/mL). Furthermore, PEF-treated juices were microbiologically stable up to 45 days, even at abusive refrigeration storage temperatures (10 °C). PEF juice quality and sensory characteristics were similar to a fresh juice; they were neither affected by the PEF decontamination treatment, nor by storage time and temperature. Results obtained in this study demonstrate the considerable potential of PEF for the production of a polyphenol-enriched and microbially stabilized red grape juice as a unique and sustainable alternative for the juice industry, while avoiding enzymatic and heat treatments.