A collaboration between Institute of Vine and Wine Sciences (ICVV) and Turin University (Italy) shows the impact of oenological tannins in red wine according to phenolic, antioxidant, and sensory traits

The main aim of the present research is to evaluate the chemical, antioxidant, colour, and sensory properties of seventeen selected oenological tannins (OETs), and to compare their effects in a red wine. OETs are winemaking processing aids used to facilitate stabilization and fining, to increase the antioxidant capacity, and to promote colour stability of grape juice and wine. A wide variability of pure or mix formulates are available for winemaking purposes, including hydrolysable tannins (gallotannins and ellagitannins), proanthocyanidins from grape skins and seeds (prodelphinidins and procyanidins), and from exotic wood (prorobinetinidins and profisetinidins).

The evaluated OET formulations were very heterogeneous and this was particularly evident in phenolic content, which strongly influences their antioxidant capacity and sensory properties. Antioxidant capacity was particularly high for hydrolysable tannins, ellagitannins owing the highest antioxidant ability. Also, ellagitannins favoured the formation of long polymeric pigments in red wine after one-month of storage. Aromatic descriptors were not highly discriminant in the differentiation of OET formulations whereas in-mouth perceptions were more influenced by the total phenolic content of the formulates than their origin and chemical characteristics. In fact, very few differences were highlighted in terms of astringency and bitterness when tannins were compared, even though quebracho was characterized by the highest intensity in the two in-mouth properties studied when tasted in water.

This study highlighted the importance of knowing the characteristics of OETs before the addition of a given formulate and its dosage, taking into account that the OET phenolic content together to antioxidant capacity were well correlated with those of the added wines in a short storage period whereas the sensory properties were dependent on wine features and composition. Future studies on different types of wine will be useful for better understanding the influence of the wine matrix on the modification of chemical and sensory parameters of OETs. This study was supported through a contract with the AEB company.

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