Recovery of Proteins from Raw Sweet Whey Using a Solid State Sulfitolysis

A simple, efficient method to recover functional proteins from cheese whey was developed. It involves partial sulfitolysis of disulfide bonds in whey proteins using sodium sulfite and solid state copper carbonate catalyst. About 25 to 40% of the initial disulfide bonds were modified within 15 to 30 min at pH 7.0. When treated whey was adjusted to acidic pH, about 70 to 80% of the whey proteins precipitated below pH 5.0. The protein precipitate contained some copper as protein-copper complex. However, extraction of the precipitate with EDTA at pH 4.5 completely removed the copper. The uncomplexed protein showed a U-shaped pH-solubility profile with 100% solubility below pH 3.0 and above 6.0. About 90% of the proteins precipitated in the pH range 4.0 to 5.0. The method could be used on an industrial scale to recover highly functional and nutritional whey protein for use in a variety of products.