Protein recovery and quantification in wine: development of a new procedure

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 pro- tein-potassium dodecyl sulfate complexes (KDS method) were used to recover BSA from protein-free wine. Re- covered BSA was then quantified by three colorimetric assays: Bradford, Lowry, and Smith. The KDS method fol- lowed by the Smith assay obtained the best match between actual and measured BSA quantities. When this pro- cedure was used for quantification of wine proteins, the results were in accordance to those determined by densi- tometric 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.