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

Carlota Delso,Javier Raso,Alejandro Berzosa,Ignacio Álvarez,Jorge Sanz

doi:10.3390/foods11040621

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.

Highlights

Over the last decade, healthy foods have become one of the strongest trends among consumers, who want to adopt their diet as a lifestyle [1]
In order to detect the outcome of the electroporation of grape cells by Pulsed Electric Fields (PEF), Table 1 compares pH, ◦ Brix, Acidity, Colour Intensity (CI), Total Polyphenol Index (TPI), Total
Electroporation of the grape skin cells facilitated the release of the polyphenols located in the cytoplasm; Color Intensity (CI), TPI, TAC, total polyphenols, and antioxidant capacity of the juice obtained from PEF-treated grapes were significantly higher (p ≤ 0.05)

Summary

Introduction

Healthy foods have become one of the strongest trends among consumers, who want to adopt their diet as a lifestyle [1]. Grapes are one of the most widely harvested fresh fruits worldwide, and their by-products (wine, grape juices, vinegar, herbal teas, etc.) are widely consumed [3] (Venkitasamy et al, 2019). Their singular organoleptic properties, high nutritional value, and versatility of processing make them one of the most highly appreciated fruits. The most important phytochemicals in red grapes are polyphenols, which include anthocyanins, flavanoids, flavonols, stilbenes (resveratrol), and phenolic acids These molecules have many useful biological properties: antioxidant, anti-inflammatory, anti-diabetic, antiplatelet, hepatoprotective, cardioprotective, and neuroprotective, many of which contribute to the prevention of certain serious diseases [4,5,6]

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