Quantifying liquid drainage in egg-white sucrose foams by resistivity measurements

• The drainage properties and stability of egg-white sucrose foams are quantified.
• A new high-resolution AC conductance meter enables very accurate resistance measurements.
• The resistance measurements have improved resolution as a function of foam height compared with previous data.
• High gas volume fraction foams made from egg-white sucrose mixtures are shown to be very stable.
• Little drainage is evident in these foams even after 200 min.

Free drainage in egg-white foams with a variety of gas volume fractions was investigated by an electrical resistivity technique. Changes in resistivity at different heights in the foam were monitored as a function of time thus giving information on the local liquid volume fraction (or content) and therefore the rate of foam drainage. The wettest egg-white foam was the most unstable, with changes in liquid volume fraction observed within minutes of foam aging. Because bubble sizes are very small, a huge effect of capillary forces confers egg-white foams with a very good stability to drainage. The complex nature of the egg-white liquid (bulk and interfacial properties), the likely presence of denatured-aggregate complexes in the Plateau borders, and very small bubble sizes are key parameters for understanding the stability of egg-white foams that makes them excellent foaming materials for food science and culinary purposes.

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