Here we will review the wine’s texture and physical sensations in the mouth. Wines can vary from light and silky to full-bodied and creamy. Mouthfeel may also include aspects like astringency, viscosity, and overall texture.
The details regarding the tannins will be further developed on the dedicated page.
Residual sugar refers to the natural grape sugars that remain in the wine after alcoholic fermentation. Wines with higher residual sugar levels tend to have a sweeter mouthfeel.
Alcohol and glycerol produced during fermentation have been considered for years to contribute to the sweetness and unctuosity of wine. These assertions, linked to the properties of the pure compounds (the sweet taste of ethanol and the high viscosity of glycerol), are increasingly controversial due to the levels found in wine.
Even if we cannot exclude specific synergism with other components or mechanisms, a recent study carried out by Prof. Axel Marchal at the University of Bordeaux validated older studies and clearly reported the non-significant effect of ethanol or glycerol even with the addition of 1.5% of alcohol and 5 g/L of glycerol in a classical red wine.
Mannoproteins released during alcoholic fermentation can have a strong impact on mouthfeel and the reduction of astringency. This impact can be observed right after alcoholic fermentation, without any lees ageing, demonstrating the varying ability of yeast to directly contribute to volume in the mouth.
We usually characterise Fermivin® yeast strains by their ability to release mannoproteins during fermentation, and the difference is huge, directly linked to the perception in the mouth. Mannoproteins are involved in the tannin-aggregation mechanism, preventing their formation or reducing their size while increasing their stability.
The release of mannoproteins during ageing is dependent on yeast autolysis, and differences between yeast strains can be observed. Hanseniaspora vineae (Fermivin VINEAE) presents a very fast autolysis, making it well adapted for fast-release wine or barrel-fermented wines.
Recently, five sweetening compounds have been identified in grape seeds and red and white wines (Cretin et al., 2018). The starting point of the research was the increase in sweetness in wine with post-fermentation maceration. Among the five compounds tested in hydro-alcoholic solution, in white and red wine, compound five, epi-dihydrophaseic-β-D-glucopyranoside acid, had the highest sweetness level. The metabolism of this compound is related to that of abscisic acid (ABA), so it could build up during maturation. It balances wines, especially reds, and may contribute to “the sweetness without sugar”. Many aspects of these chemicals need further study, but their detection shows the importance of grape maturation to wine mouthfeel.
The choice of yeast strain and lactic acid bacteria (LAB) can influence the mouthfeel. As said, some yeast strains produce more polysaccharides, while others may enhance fruity and floral esters that impact the wine’s perceived body and texture.
The malolactic fermentation obviously influences the texture and perception of it because of the conversion of malic acid into lactic. This process can soften wine’s acidity and lead to a creamier mouthfeel.
Indirect effects of fermentation can also be considered, such as the production of metabolites that are involved in the evolution of polyphenols (additions, polymerisation, and interactions with other compounds). These indirect effects could also partly explain the impact of malolactic fermentation and especially of Anchor® DUET Soft bacteria blends for co-inoculation. The decrease in acidity and in lactic acid itself contribute to increased mouthfeel perception after malolactic fermentation.
The aroma impact of yeast strains can also indirectly contribute to mouthfeel. Some cognitive effects have been reported and are observed on a daily basis by winemakers. For instance, the decrease in green aroma due to the degradation of pyrazine, either by thermic degradation or by using an appropriate yeast such as Anchor Alchemy IV or Alchemy III, can contribute to a better appreciation of tannins, which would have been perceived as harsher.
Similar consideration can be given to increased fruitiness (especially mature fruit notes) due to the use of specific yeast strains such as Anchor Legacy NT 50, Fermivin VR5, or MT48.
The addition of yeast cell walls or yeast-derived nutrients can also modulate mouthfeel in wine, likely due to the presence of mannoproteins in these yeast components. In the Feel safe range, we have developed Natuferm Intense, formulated with a specific inactivated yeast which increases the fullness of mouth.
A similar observation has been made with Extraferm D’fend in which the inactivated yeast component allows for increased fullness in addition to its antioxidant properties.
Even if autolysis is a natural phenomenon occurring after alcoholic fermentation, it can be accelerated using β-glucanase enzymes. These enzymes can degrade the yeast cell wall since they are able to hydrolyse β-glucans that are constitutive of the cell wall. The effect of glucanase addition such as Rapidase Batonnage on mannoprotein release can be observed. The release of mannoproteins during lees ageing contributes to decreased wine astringency, increased unctuosity and mouthfeel, but also to tartaric, protein and colloidal stabilisation.
Another way to take advantage of mannoproteins in wine is the addition of mannoproteins extracted from yeast and proposed as ready-to-use products, such as Claristar and Final touch which contribute to tartaric stabilisation and present a strong organoleptic impact. A full range of products are available with different applications depending on the yeast strain and extraction process used. A good example of the impact of such a mannoprotein is illustrated by the effect of Final touch GUSTO addition on tannin perception.
With a highly qualified team of experts in many fields, Oenobrands strives to offer winemakers’ novel and scientifically sound solutions, as well as to highlight the positive synergies between its products.
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