The role of proteins on colloidal formation in Italian red wine

Until recently, the presence of protein colloids in red wines has been denied due to the belief that they precipitate during maceration. There is a noticeable gap in literature on this topic due to the challenges associated with red wine analysis. The current research aims to investigate the role of proteins in colloidal formation as well as their interaction with other macromolecules in red wine. The proposed method for studying protein aggregation is fluorescence correlation spectroscopy (FCS). Purified grape proteins will be labelled with fluorescent dye and added to deproteinated red wine samples for analysis. Colloidal aggregation kinetics are to be followed before, during and post fermentation using SDS-PAGE and FCS. The changes induced in the wine colloidal structures should affect the colloidal properties, thus increasing solubility of particles in the wine matrix. Research findings on the mechanism of protein aggregation will edify our knowledge of colloidal formation in red wines. These notions will be used to propose solutions to prevent and manage colloidal instabilities in red wines. Grape variety and ethanol concentration are expected to influence the aggregation activity and protein content in wine. Wine proteins may participate in the colloidal matrix as protein-phenol sub-aggregates, linked non-covalently to polysaccharides. The other colloidal entities expected to be present in red wine are of polysaccharides and phenols. These macromolecules are expected to change in quantity, pre and post fermentation. Findings will help in the better understanding of the mechanism of colloid formation in Italian red wines and allow new solutions to be proposed in the future for managing colloidal instability in wines. The main focus of the research is on red wine proteins, details on the involvement of tannins in colloidal formation will not be investigated.