Preliminary study on the interaction of gelatin-red wine components

Physico-chemical parameters of two oenological gelatins (G1 and G2) were examined to investigate the interaction of protein-wine components during the fining of red Sangiovese wine. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) was used to analyze the molecular weight distribution (MWD) of the two gelatins. The differences in the gelatins are primarily due to the manufacturing method. In particular, gelatin G2 showed the greatest reduction in MWD as a result of the atomization process. Moreover, G1 and G2 differed greatly in net charge density (0.94 and 0.12 meq/L, respectively) and Bloom strength (75 and 0 g, respectively). The implications of these observations on the mechanism of gelatin-wine components interaction in wine are discussed. Increasing amounts of gelatin were added to Sangiovese red wine at controlled temperatures and the efficacy of the fining treatment was evaluated in terms of turbidity and the amounts of precipitate developed. Both gelatins were able to interact with wine polyphenols and the amount of precipitate increased from 0degree>30degree>15degreeC. The amount of precipitate increased with gelatin dosage. We postulate that wine components other than polyphenols (e.g., tartrate microcrystals, protein and/or polysaccharides) may co-precipitate with gelatin during the coagulation process.