Martine Mietton-Peuchot

Structural and biochemical changes induced by pulsed electric field treatments on Cabernet Sauvignon grape berry skins: impact on cell wall total tannins and polysaccharides.

Pulsed electric field (PEF) treatment is an emerging technology that is arousing increasing interest in vinification processes for its ability to enhance polyphenol extraction performance. The aim of this study was to investigate the effects of PEF treatment on grape skin histocytological structures and on the organization of skin cell wall polysaccharides and tannins, which, until now, have been little investigated. This study relates to the effects of two PEF treatments on harvested Cabernet Sauvignon berries: PEF1 (medium strength (4 kV/cm); short duration (1 ms)) and PEF2 (low intensity (0.7 kV/cm); longer duration (200 ms)). Histocytological observations and the study of levels of polysaccharidic fractions and total amounts of tannins allowed differentiation between the two treatments. Whereas PEF1 had little effect on the polyphenol structure and pectic fraction, PEF2 profoundly modified the organization of skin cell walls. Depending on the PEF parameters, cell wall structure was differently affected, providing variable performance in terms of polyphenol extraction and wine quality.

Effect of Wine Properties and Operating Mode upon Mass Transfer in Micro-Oxygenation

All along wine-making and during its ageing, oxygen plays an important role for the evolution of the wine. Solubilization of oxygen into musts or wines occurs when gaseous oxygen is brought into contact with the liquid. In this work, the specific technique of wine micro-oxygenation is addressed through the evaluation of transfer capacity for oxygen solubilization. This was done considering the parameters likely to influence the saturation concentration of dissolved oxygen and the conventional volumetric mass transfer coefficient kLa, which quantifies the efficiency of the oxygen transfer. The study has shown that the sugar concentration in the must induces a viscosity enhancement which leads to a significant decrease of the kLa value. Surprisingly, it was also observed that a very low quantity of ethanol in the liquid phase (0.05 percent volume) strongly favours the oxygen transfer. Conversely, the presence of dissolved carbon dioxide in the wine, which desorbs and dilutes the oxygen in the micro-bubbles, dramatically decreases the transfer of oxygen. The presence of anti-oxidant compounds (SO2) or oxygen consumer compounds (polyphenols) was shown to have no effect upon the efficiency of oxygen transfer. Operating parameters such as gas flow rate or geometrical aspect of the tank have also been considered.

Membrane Technologies in Wine Industry: An Overview

Membrane processes are increasingly reported for various applications in wine industry such as microfiltration, electrodialysis, and reverse osmosis, but also emerging processes as bipolar electrodialysis and membrane contactor. Membrane-based processes are playing a critical role in the field of separation/purification, clarification, stabilization, concentration, and de-alcoholization of wine products. They begin to be an integral part of the winemaking process. This review will provide an overview of recent developments, applications, and published literature in membrane technologies applied in wine industry.

Extraction and purification of high added value compounds from by-products of the winemaking chain using alternative/non-conventional processes/technologies.

ABSTRACT Grape byproducts are today considered as a cheap source of valuable compounds since existent technologies allow the recovery of target compounds and their recycling. The goal of the current article is to explore the different recovery stages used by both conventional and alternative techniques and processes. Alternative pre-treatments techniques reviewed are: ultrasounds, pulsed electric fields and high voltage discharges. In addition, nonconventional solvent extraction under high pressure, specifically, supercritical fluid extraction and subcritical water extraction are discussed. Finally alternative purification technologies, for example membrane processing were also examined. The intent is to describe the mechanisms involved by these alternative technologies and to summarize the work done on the improvement of the extraction process of phenolic compounds from winery by-products. With a focus on the developmental stage of each technology, highlighting the research need and challenges to be overcome for an industrial implementation of these unitary operations in the overall extraction process. A critical comparison of conventional and alternative techniques will be reviewed for ethe pre-treatment of raw material, the diffusion of polyphenols and the purification of these high added value compounds. This review intends to give the reader some key answers (costs, advantages, drawbacks) to help in the choice of alternative technologies for extraction purposes.