Finding robust descriptive features for the characterization of the coarsening dynamics of three dimensional whey protein foams

Hypothesis: Understanding the coarsening behavior of foams is of great interest for their deliberate design. In order to systematically quantify the influence of surfactants and other chemical parameters, identifying robust descriptive features of observed foam aging dynamics is essential. Existing coarsening theories for both wet and dry foams provide concise models with respective descriptive parameters. Experiment: Multiple micro computed tomography scans of moderately wet polydisperse beta-Lactoglobulin foam are recorded over a period of 15 min. The growth behavior of a large fraction of about 5 x 10(4) pores that constitute the imaged volume is individually observed and statistically analyzed as a function of pore radius as well as number of neighboring pores. Findings: The three-dimensional analog of von Neumann's law for dry foams by Glazier is confirmed as a suiting empirical model, whereby a critical number of 13 +/- 7 neighbors and a diffusion coefficient of (1.8 +/- 0.8) x 10(-11) m(2)/s are found for an exemplary sample. The pores growth can as well be related to their radius by means of Lemlich's coarsening model for wet foams though, whereby a critical radius marking the transition between shrinkage and growths is found to be R-c = (300 +/- 85) mu m. Although different, both models fit similarly well given the broad variance of the observed growth rates. (C) 2016 Elsevier Inc. All rights reserved.