Evaluation of structural characteristics determining surface and foaming properties of β-lactoglobulin aggregates

Due to its structural versatility and remarkable surface activity, beta-lactoglobulin (beta-Lg) is a prominent food structuring agent in both its native state and in the form of heat-induced aggregates. In this study, we considered the properties of soluble aggregates of pure beta-Lg having a median diameter of 50 nm. The behavior of the aggregates at the air/water interface has been probed as a function of pH, with the aim of evaluating the controversial role of surface charge in connection with the functionality of particle stabilized foams. Based on these new experimental results, it would appear that charge shielding around the isoelectric point (pI) leads to significantly increased foam stability as compared to samples having a significant positive or negative zeta potential. Against expectations, however, maximum foam stability was not linked to minimum foam drainage. High foamability and foam stability have been found to correlate with maxima in the rates of initial surface pressure increase and with interfacial dilatational properties. Evidence for efficient stabilization of the air/water interface was also reflected in a small average bubble size and a low rate of mean bubble area increase for aggregates with pH similar to pI. Information from additional comparative experiments on systems with native beta-Lg enabled an evaluation of the significance of surface hydrophobicity and aggregate particle size in relation to the foaming properties. (C) 2016 Elsevier B.V. All rights reserved.