Development of a new procedure for protein recovery and quantification in wine

In order to develop a procedure for protein recovery and quantification in wines, known amounts of bovine serum albumin (BSA) were added to samples of protein-free wine. Dialysis followed by lyophilization, precipitations with ethanol, acetone, trichloroacetic acid, and by a new method that precipitates proteins as protein- potassium dodecyl sulfate complexes (KDS method) were used to recover BSA from protein-free wine. Recovered BSA was then quantified by three colorimetric assays: Bradford, Lowry, and Smith. The KDS method followed by the Smith assay obtained the best match between actual and measured BSA quantities. When this procedure was used for quantification of wine proteins, the results were in accordance to those determined by densitometric quantification of the protein bands separated by sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE), indicating that the proposed method allows a reliable determination of the protein content of wine.