A commercial whey protein concentrate (WPC65, supplied by ILAS S.A., Spain) was used as raw material to obtain an alpha-lactalbumin (alpha-La) enriched solution. Firstly, alpha-La was simultaneously precipitated with bovine serum albumin (BSA) and immunoglobulins (Igs) by adding lactic acid as Ca2+ ion sequestrant at a pH value around 4.0. The alpha-La precipitation process was observed to be reversible. Therefore, when the original pH was recovered the protein became soluble again. The proposed process consists of the following steps: (1) precipitation, (2) centrifugation (1), (3) precipitate washing (twice), (4) centrifugation (11) and finally (5) solubilization of the precipitate. Steps 1 and 2 were studied in a previous work by the same authors. Steps 3-5 were investigated in this work. These steps were performed and optimized at laboratory scale. The final alpha-La enriched solution obtained had a purity of about 74%, while the recovery of this protein was about 86%. More than 99% of the beta-lactoglobulin (beta-Lg) present in the WPC was removed in the process. This alpha-La enriched solution can be considered as a good base to prepare infant formulas. This product is very interesting because of its high water solubility and the very low beta-Lg concentration. The concentration of beta-Lg in the supernatant fractions was higher than 85% (on a dry basis); therefore these fractions could be further concentrated by membrane technology (ultrafiltration) to obtain a beta-Lg enriched concentrated product. (c) 2006 Elsevier B.V. All rights reserved.