Influence of the year and the environmental factors on condensed tannins from Cabernet franc grapes

Constitue une appellation d’origine “la dénomination géographique d’un pays, d’une région ou d’une localité servant à désigner un produit qui en est originaire, et dont la qualité ou les caractères sont dus exclusivement ou essentiellement au milieu géographique, comprenant les facteurs naturels et les facteurs humains …”

Aims: In previous work, five indigenous Pichia kluyveri strains, GS1-1, FS-2-7, HS-2-1, C730 and C732, were isolated and selected from spontaneous fermented wines from Ningxia and Gansu. The aims of this study were to 1) evaluate resistance of these strains to environmental stressors that may restrict their growth and the progress of alcoholic fermentation; 2) Investigate their fermentation dynamics; 3) Characterise aroma profiles of Cabernet Sauvignon wines made from mixed cultures of P. kluyveri and Saccharomyces cerevisiae.

AIM: Vine diseases are still responsible for economic losses. Previous study in our laboratory, have shown effects of oenological tannins against Botrytis cinerea1,2. According to this, the aim was to evaluate the wine protection by oenological tannins against an another disease, the downy mildew. METHODS: During the 2020 vintage, infected grapes by downy mildew (Vitis vinifera cv. Merlot) were collected from the dispositive ResIntBio. The 100 kg were crushed, destemmed and dispatch into 10 aluminium tanks. SO2 was added at 3 g/hL. Oenological tannins (grape, quebracho, ellagitannin or gallotannin) were added at 100 g/hL into eight different tanks (4×2 tanks). The two last tanks were considered as control without addition of oenological tannins. Alcoholic fermentation was achieved with Actiflore 33® at 20 g/hL. Malolactic fermentation was achieved with Lactoenos B7at 1 g/hL. Finished wines were sulfited to obtain 45 mg/L of total SO2.

Under the pressure of global warming, several wine grape growing regions around the world are increasingly suffering from advanced and compressed phenology; endangering wine character while also creating serious logistic problems. From a physiological standpoint, the issue of delaying ripening is not simple as, in several instances, only a few processes must be delayed (i.e. sugar accumulation into the berries) while other events such as pigmentation and accumulation of other important phenolic compounds should proceed at a normal rate. Thus, the issue of decoupling technological maturity from phenolic maturity is another important consideration. Over the last decades, several research groups have endeavored to establish alternate cultural practices aimed at addressing this decoupling. In some cases, special applications of quite robust and well known practices regarding physiological principles have been utilized, however some completely new techniques are also being studied. In figure 1 of the review, we offer a panorama of the available tools and in the text we elaborate on those having provided most reliable and consistent results under an array of genotypes and environmental conditions. Among these, primary focus is given to post‐veraison—apical to the cluster—leaf removal (that can also be suitably replaced by applications of anti‐transpirants); the use of kaolin against multiple summers’ stresses; and a drastic version of late winter pruning having the potential to postpone ripening into a cooler period with improved grape composition and a limited negative impact on yield and storage reserves replenishment. 

Insufficient acidity in grapes from warm(ing) climates is commonly corrected through addition of tartaric acid during vinification, and less so with other organic acids. One alternative approach involves bio-acidification with certain strains of Lachancea thermotolerans (LT) via lactic acid production during fermentation.