The interaction of bovine serum albumin and lysozyme and its effect on foam composition

The composition of foams formed from mixtures of bovine serum albumin and lysozyme has been analysed by a spectroscopic method. The assay is based on differences in the UV absorption spectra of the proteins and the results compare favourably with quantitative electrophoresis. The incorporation of lysozyme in the foam is maximal at an ionic strength of 0.025. At higher ionic strength the interaction between the proteins is reduced and this may explain the reduction in lysozyme present in the foam. At ionic strengths lower than 0.025 the level of incorporation of lysozyme is also reduced. It is possible that the large protein aggregates present under these conditions are not incorporated in the foam or alternatively destabilize the foam. Dilution studies reveal that the aggregates are more stable at an ionic strength of <0.025. The turbidity of the protein mixtures is temperature sensitive and this accounts for the observed temperature dependence of the composition of the generated foam.