Effect of solution conditions on protein damage in foam

In this study we investigated the conditions under which protein damage during foaming could be reduced. We used bovine serum albumin (BSA), immunoglobulin G (IgG), pepsin, catalase and lysozyme. The parameters examined were ionic strength, pH, protein concentration and the addition of sugars (trehalose and sucrose). Results showed that protein damage can be reduced by operating at optimal ionic strength and pH, and to a lesser extent, by the addition of sugars. Solution conditions under which the native structure of the protein was stabilised in solution favoured a reduction in the amount of damage, due to lower surface adsorption. The actual quantity of protein damaged in foaming was found to be relatively insensitive to changes in the bulk protein concentration, provided that the concentration was near to, or greater than, the apparent CMC value. (C) 2000 Elsevier Science S.A. All rights reserved.