Protein instability of white wines and oenological tannins
Protein instability of white wines: origin and prevention strategies
Fernanda COSME, CQ-VR, Food and Wine Chemistry Laboratory, Utad
The protein instability of white and rosé wines is a problem associated with the presence in wine of chitinases and thaumatins (PR proteins) with molecular weight between 10-40 kDa and an isoelectric point lower than 6. At present, the most effective process to avoid this instability is through the elimination of these unstable proteins with sodium bentonite. However, many alternative products and solutions (proteolytic enzymes, rapid pasteurization, zirconium oxide, natural zeolites, chitin and chitosan, carrageenan and mannoproteins) have been studied in recent years. More recent studies have also shown that k-carrageenan reduces the pathogen-induced protein (PR) content and, consequently, the instability of wine proteins, being even more efficient than bentonite.
Oenological tannins: origin, properties and their applications in oenology
Filipe RIBEIRO, Technical Director of SAI Enology
Oenological tannins from various plant species are widely used in oenology due to their antioxidant and antioxidase properties, reactivity with wine proteins, sensory impact, among others. Antioxidant activity is extremely important, and it is essential to distinguish the different types of tannins according to this characteristic, so that winemakers can choose the most appropriate solution depending on the objective. The presentation will briefly review the chemical structure of tannins and their properties, focusing especially on the antioxidant activity of tannins from different plant origins. In this work, developed by SAI Enology’s R&D team, it was observed that gallic tannins have the highest antioxidant activity, followed by ellagic tannins and, finally, with lower antioxidant capacity, condensed tannins.
