The turbidity of wine has an influence on the aroma of the ferment

As regards the sensorial implications of these findings, a wine-tasting session was carried out, with both filtered and unfiltered wines, after maturing between three and twelve months. The conclusion was that the filtered wines were more pleasant on the nose but more aggressive on the palate, while the unfiltered wines stood out for their qualities on the palate. In fact, the tasters were able to distinguish between filtered and unfiltered wines. The scientific literature coincides, effectively, in that the lees provide greater roundness and untuosity to the wine, which enhances the sensations on the palate of the consumer on drinking this product.

Biogenic amines

Another aspect related to the quality of wines that has sparked great interest over the past few years and that Ms Jiménez has studied for her research, is the presence of biogenic amines in this alcoholic drink. These nitrogenated compounds are mainly formed during the alcoholic and malolactic fermentations of the wine, their importance lying in the negative effects on human health that can arise with their ingestion. Consuming wine with high concentrations of these amines, principally histamine and tyramine, can cause headaches, allergic reactions, heart palpitations, high blood pressure, diarrhoeas, and so on.

Moreover, the presence of high concentrations of histamine in wines can give rise to export restrictions, as a number of countries are planning to place recommended limits on this histamine content in wines; in other countries, such as Switzerland, they have already imposed this limit. To this end, it is important to know the evolution of the biogenic amines during the cask maturing of the wine as their final concentration can determine its exportability.

In her PhD, Nerea Jiménez concluded that there exists a grand variety in the evolution of biogenic amines during the maturing process of the wine in the barrel. For example, histamine and tyramine, the most toxic, are formed at the beginning of the process and subsequently their concentration falls, possibly due to their degradation. Nevertheless, putrescine and cadaverine, both of which boost the toxic action of the former two amines, build up in the wine throughout the whole ageing process.

These findings are important in that they warn the enologist not to drop their guard in the control of these post-malolactic fermentation compounds, especially if part of the wine production is to be exported.