A new method for the recovery of wine proteins allowing their quantification and electrophoretic analysis

Proteins have been recognised since a long time as important components affecting wine quality. However, the currently available methods for protein quantification and analysis are not completely reliable. In particular, the measurement of the exact amount of protein present in wine with colorimetric methods is particularly difficult because of the presence of strongly interfering substances of non-protein nature. We have developed a simple method to recover all proteins from untreated wine, which can be used for both protein quantification and electrophoretic analyses. The method is based on the possibility of precipitating the proteins as insoluble protein-Potassium-Dodecyl Sulphate complexes. After a washing procedure, which results in the complete removal of the interfering substances, the precipitate can be easily solubilised and protein determined colorimetrically by the bicinchoninic acid (BCA) method. The described method is much more rapid and simple than the classical methods of dialysis and concentration/liophylisation and is more reliable and simple compared to both acetone and ethanol precipitations when wine proteins are quantified by BCA. Moreover, the samples obtained in this way show excellent electrophoretic protein patterns. Densitometric analysis of the wine electrophoretic protein profiles, using known amounts of bovine serum albumin electrophoresed in the same gel as reference, were performed. The quantitative data were in optimal agreement with the results obtained with BCA and confirmed the superiority of the described procedure in comparison with other methods of wine protein precipitation. The quantitative and qualitative results obtained by this method with 13 samples of Prosecco (an Italian sparkling white wine) of different origin were presented.