New molecular evidence of wine yeast-bacteria interaction unraveled by untargeted metabolomic profiling

Copper and iron are known to substantially impact wine stability through oxidative, reductive or colloidal phenomena. However, the binding of metal ions to different wine components under wine conditions, and the impact of this binding on the ability of the metal ions to induce spoilage processes, is not well understood. This study surveyed a range of red and white wines for an understanding of the variability of broad metal categories within the wines. The techniques utilized included an electrochemical constant current stripping potentiometry technique (ccSP), and solid phase extraction (SPE) fractionation of wine with subsequent analysis of the metal content of each fraction by inductively coupled plasma – optical emission spectroscopy (ICP-OES).

Those previous years, pesticides are often brought to the forefront by media. Questions arose about their toxicity for growers and consumers. Even if a downward trend is underway, the use of pesticides is required to ensure steady quality and quantity of harvests. A large number of active ingredients are authorized but regarding viticulture, mainly insecticides and fungicides are applied, to control pests and diseases and to increase crop yield. Some phytosanitary products, principally fungicides, applied close to the harvest date may frequently be detected in wines.

Polysaccharides and more specifically pectins, make up a significant portion of the cell wall material of the plant cells including the grapes. During the fruit ripening the associated softening is related to the breakdown of the cell wall polysaccharides. During this process, it is expected that polysaccharides that are soluble in red wine will be formed influencing its texture. Anthocyanins are responsible for the wine color and tannins for the astringency, body and bitterness of the wine. In the skins, these compounds are located in the cell vacuoles and the barrier that conditions their extractability is the skin cell wall that may determine the mechanical resistance, the texture and the ease of processing berries. The aim of this work was study the evolution of the polysaccharides and the anthocyanin and tannin extractability during the ripening period in Cabernet Sauvignon grapes, trying to correlate these variables.

The use of next-generation sequencing (NGS) has helped understand microbial genetics in oenology. Current studies mainly focus on barcoded amplicon NGS but not shotgun sequencing, which is useful for functional analyses. Since the high percentage of grapevine DNA conceals the microbial DNA in must, the majority of sequencing data is wasted in bioinformatic analyses. Here we present capture depletion of grapevine whole genome DNA.

In partnership with a Bordeaux property wanting to improve the quality of its second wine, the effects of two factors, American oak barrels and mannoproteins were studied. Their impact on the attractiveness and sweetness of wines were characterized during two successive vintages (2012 and 2013). Vinification took place with a homogeneous batch of Cabernet Sauvignon. The wine was then divided up into various groups of five barrels of French and American oak, new or reused. Analyses of volatile and non-volatile wood compounds were undertaken at four months and eight months of wood ageing, by LC-MS and GC-MS.