Cationic balance in skim milk during bipolar membrane electroacidification

Bipolar membrane electroacidification (BMEA) technology has been applied to skim milk protein, in order to produce high purity casein isolates. BMEA u ses a property of bipolar membrane to split water and the action of monopol ar membranes for demineralization. When the H+ are generated at the bipolar membrane, one cationic charge inherent to the solution being acidified mus t cross the cation exchange membrane (CEM) to keep the solution electricall y neutral. The purpose of this study was to monitor the migration of charge through th e CEM to counterbalance H+ generated at the bipolar membranes. K+ ions were identified as being the predominant ions that electromigrate f rom the skim milk solution until pH 5.0 is reached, at which point its conc entration becomes insufficient to counterbalance H+. The other cations part ially replaced K+ to assure the electroneutrality of the solution, It appea rs that K+ is a necessary ionic species to ensure the best efficiency of th e BMEA and to limit the non-desired migration of H+ across the CEM. Therefore, the electrical efficiency of BMEA is decreased by a loss of elec trogenerated H+ due to a lack of sufficiently mobile ions such as potassium . Consequently, the enrichment of the skim milk with some potassium would b e required in order to obtain a better electrical efficiency. (C) 2000 Else vier Science B.V. All rights reserved.