Towards multi-purpose valorisation of polyphenols from grape pomace: Pressurized liquid extraction coupled to purification by membrane processes

Champagne or sparkling wines elaborated through the same traditional method, which consists in two major yeast-fermented steps, typically hold about 10 to 12 g/L of dissolved CO2 after the second fermentation in a closed bottle. Hundreds of molecules and macromolecules originating from grape and yeast cohabit with dissolved CO2; they are essential compounds contributing to many organoleptic characteristics (effervescence, foam, aroma, taste, colour…). Indeed, the second alcoholic fermentation and the maturation on lees (which may last from 12 months up to several years) both induce various quantitative and qualitative changes in the wine through the action of yeast, as listed hereafter: development of aromas during aging on lees, release of nitrogen compounds during autolysis and release of macromolecules (polysaccharides, lipids, nucleic acids) in wine.

During the tasting of a fine, old wine, the aromas generated in the glass are intertwined in an intimate, complex manner, expressing the fragrance of the aging bouquet. This aging bouquet, which develops during bottle storage through a complex transformation process, may result in a broad palette of nuances. Among these, undergrowth, truffle, toasted, spicy, licorice, fresh red- and black-berry fruit and mint descriptors were recently identified as features of its olfactory representation for red Bordeaux wines. Although a targeted chemical approach focusing on volatile sulfur compounds revealed the role played by dimethyl sulfide, 2-furanmethanethiol, and 3-sulfanylhexanol as molecular markers of the typicality of the wine aging bouquet of red Bordeaux wines, its chemical transcription has only partially been elucidated.

A new process for vacuum evaporation was developed where evaporation takes place near the inner surface of a vortex produced by a rotor submerged in the liquid. Contrary to the state of the art the Vortex rotor process does not need a vacuum vessel but the rotating liquid creates a geometrically stable low pressure void surrounded by a vortex stabilized by the equilibrium between centrifugal forces and the pressure difference. First tests with water and sugar solutions at concentrations similar to grape must were conducted to verify the theoretical predictions, test the performance under different conditions and study the effect of various process parameters (Rösti et al 2015).

Grape phenolic compounds are very important constituents of red wine because, in addition to their antioxidant properties, they contribute to color, astringency and bitterness, oxidation reactions, interactions with proteins and ageing behavior of wines. The aim of our study was to assess the structural characteristics of grape and wine proanthocyanidins of Agiorgitiko variety and to evaluate the influence of the vintage year. Twelve vineyard locations were designated in the Nemea wine region. For three consecutive years (2012-2014), the grapes were harvested at technological maturity and the method of phloroglucinolysis was employed to determine the mean degree of polymerization (mDP) and subunit composition of the samples.

This study evaluated the levels of trans-resveratrol in commercial wines made from Cabernet Sauvignon grapes from different valleys of Chile stilbenes. The Cabernet Sauvignon is the most planted variety in Chile, being 38% of the total vineyard country. Chile is the fourth largest wine exporter in the world, so it is important to evaluate the Cabernet-Sauvignon wines in their concentration levels of trans-resveratrol and its relation to the benefits provided to human health in moderate consumption. Evaluation comprises commercial wines from different valleys of Chile and its relationship with climatic characteristics, soil and vineyard handling.