Analytical and Chemometric Investigation of Phenolic Content of South African Red Wines

Context and purpose of the study ‐ Phytopathogenic diseases impact the development and yield of grapevines, resulting in economical, social and environmental losses.

The sustainability of vineyards is a major issue. The choices proposed to date have major flaws such as the lack of scientific bases or the use of dangerous products such as copper. GiESCO has published a charter of best practices for the environment and for people adapted to various environments. The use of sustainably resistant grape varieties that produce quality wines plays a central role here. Often innovative cultivation systems associated with new technologies and based on scientific bases, guarantee respect for people and the environment. These proposals are brought together in a charter which is part of a meta-ethical approach to seeking consensual measures to ensure the sustainability of vineyards.

Controlling the speed of alcoholic (AF) and malolactic (MLF) fermentations in wine can be an important challenge for the production of certain short rotation wines for entry-level market segments. Immobilization techniques for Saccharomyces cerevisiae and Œnococcus œni, the microorganisms responsible for these fermentations, are widely studied for industrial applications. Indeed, these processes allow to accumulate biomass and thus to increase cell densities inducing high fermentation velocities. Recent works have shown the performance of MLF carried out with biofilms of O. œni, immobilized on various supports in a rich medium (MRSm: modified MRS broth with malic acid and fructose).

Eugenol, widely spread in various plants notably cloves, basil and bay, was identified too in wines from hybrid grapes without contact with oak wood. This aromatic molecule presents a strong spicy note of clove and also antifongic properties. Eugenol was described as an endogenous compound of Baco blanc, from the grapes to the spirits of Armagnac area. Moreover, this compound is a chemical marker of Baco blanc products quality.
Influences of harvest time and different winemaking processes (settling, use of enzymatic preparations, lees content and stock time before distillation) on Baco blanc wine eugenol contents were explored using a two-levels full factorial Design of Experiments (DoEs).

Grapevine is grown grafted in most of the world largely because of Phylloxera. Rootstocks not only provide tolerance to Phylloxera, but also ensure the supply of water and mineral nutrients to the scion. Rootstocks are an important means of adaptation to environmental conditions if we want to conserve the typical features of the currently used scion genotypes. To aid this adaptation, we can exploit the large diversity of rootstocks used worldwide. To fully explore this existing rootstock diversity, this work benefits from the unique GreffAdapt vineyard, in which four scion genotypes were studied onto 55 commercial rootstocks in three blocks. The aim of this study was to characterise rootstock regulation of scion mineral status and how it relates to scion development.