Oenological Tannins' Effect On Wine Composition And Sensory Properties

The wine industry has been exploring new and innovative ideas for the vinification process for a number of years. The role that these methods will play on the wine sensory and analytical composition is of specific importance. Finding alternative methods allows the industry to evolve over time ensuring higher volumes can be processed at better quality and at cost effective prices. Included in these are the use of oak maturation (Botha, A. , 2015), oxygenation (Coetzee et al. , 2013), and sulphur supplements including ascorbic acid and glutathione (Makhotkina et al. , 2014).

Sulfur dioxide is one example of a substance which has been used in the industry for an extremely long period of time. Its primary function in the winemaking industry is that of a preservative, this is true for many different food related industries. The function which is of interest to this specific research project is its ability to safeguard wine against the loss of phenols through oxidative effects(Sonni, F. et al. , 2009). SO2 is able to restrict endogenous oxidases, it also plays a role in the suppression of microbial activity in wine or must which could lead to undesirable fermentation. The trend is however still against SO2 use in the industry mainly due to possible toxic effects, there is also a allergic reaction found in a select few. Generally there is a strong questioning of the health implications(Sonni, F. et al. , 2009).

All though possible alternatives do exist they must be able to cater for a large industry, they must also accomplish the same and more than the previously available options do. Taking into account such factors, oenological tannins are found to be amongst the possible future alternatives. A number of research trials have been completed in an attempt to better understand the effects of oenological tannins on redox control, protein-enzyme control, structure and mouthfeel as well as on colour stability (Versari et al. , 2013). Oenological tannins, specifically ellagitannins, functions as an oxygen scavenger in must and wine. In wine a certain amount of oxygen is necessary for volatile aromas. Gee ‘n voorbeeld- spesifiek van die manier hoe toile gevorm word. Die oksidasieproses van hexenal om die aldehied te vorm wat dan uiteindelik die tiool vorm. Kyk vir die artikel van Carien Coetzee. Oxygen scavengers reduce the amount of oxygen available in the matrix to a lower and more favourable level. This means that that production of fresh and fruity aromas in wine takes place, while not having issues with oxidative effects. gee voorbeelde van die oxidative effects met ‘n referenceTannins do not only have an effect on the aromatic potential of a wine but also contributes to the structure and mouthfeel of the wine. This is due to chemical interactions which cause a sensation of weight on the palate and also by softening and rounding off grape tannins. (reference) Ellagitannins and gallotannins are able to bind to anthocyanins which allow a more stable colour environment (Louw, M. , 2017).

Previous research on the role and efficiency of tannins in wine were more commonly conducted on red wines. The sensorial effect of tannins have been reported on by (Puech et al. , 1999), however not much research has been completed on the effect of tannins on the sensory and analytical characteristics of wine over time. Wines, especially white wines, lose a large amount of aromatic compounds during maturation. The preservation of oxygen sensitive fermentation aromas and sulphur in addition with oenological tannins is not known, particularly under South African conditions. Sulphur dioxide, all though being well known and commonly used as an antioxidant and antimicrobial agent, is becoming less popular amongst consumers due to possible negative health impacts (Contanigro et al. , 2013).

There are sulphites which have been found to form during fermentation as a natural occurrence. However, most winemakers who do not follow organic winemaking would typically add around 30-90ppm of additional sulfites to obtain a free sulphur concentration of 35-40ppm. Additionally the idea of canned wine is becoming more common and acceptable, unfortunately it has been found that the cans do not react well to wines containing sulphites due to can degradation and negative aromatic compounds being formed (Rademeyer, M. , 2017). Oenological tannins have been found to impact the final products quality to some degree. The effect that tannins have on the redox potential can influence the colour stability and amount of sulphur that is needed to preserve the wine and fermentation aromas. The use of oenological tannins became popular with South African winemakers, especially bulk producers, due it being a cost-effective way to add to wine complexity. The main aim of this study was to investigate the influence of extraneous oenological tannins on the wine volatile composition and sensory properties of Sauvignon Blanc wine.