Influence of different commercial fining agents on proanthocyanidin fraction and antioxidant activity of a red wine from Baga grapes

Aims: Evaluate the impact of different commercial fining agents (egg albumin, bentonite, gelatine, potassium caseinate and isinglass) and their concentration on proanthocyanidin fraction content (monomeric, oligomeric and polymeric) and antioxidant activity of a red wine from Baga grape variety. Additionally establishment of correlations between the antioxidant activity and the different proanthocyanidin fraction content were also an other aim of this work. Methods and results: The fractionation of wine proanthocyanidins was made according to their polymerisation degree: catechins (monomers), oligomeric (degree of polymerisation ranging from 2 to 12-15) and polymeric (degree of polymerisation > 12-15). For antioxidant activity of red wine, two analytical methods were used: the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay and the ABTS radical cation scavenging assay. In general the different commercial fining agents applied induced a decrease of the wine total phenols and the different proanthocyanidin fraction content studied. The monomeric flavanols were significantly depleted by egg albumin and isinglass (specially using the highest concentration), while for oligomeric fraction only the highest egg albumin, gelatine and isinglass concentration induced a decrease on the values. Conclusion: The commercial fining agents analyzed in the present study affected the monomeric and the oligomeric proanthocyanidin. At same time some fining agents (specially in high concentrations), such as egg albumin, isinglass and gelatine induced a reduction of antioxidant activity of red wines too. Significant and impact study: The knowledge of the impact of the commercial fining agents in proanthocyanidin content and antioxidant properties of red wines is important for red wine fining optimisation and consequently for the red wine quality. This study is particular important when the « antioxidant power » of the foods, in this case in red wine, is an expression of its capability both to defend the human organism from the action of the free radicals and to prevent degenerative disorders deriving from persistent oxidative stress.