Contribution of Disulfide Bonds to the Characteristics of Casein Micelles

Drainage in foam was analyzed by the capillary model proposed by Haas and Johnson. Foam was produced by introducing air into an ovalbumin solution through a spinneret. The electric conductivity at selected positions in the foam and the drained liquid height below the foam were measured at constant intervals. The measured electric conductivity was converted to the liquid volume fraction by Prager’s equation. The capillary model described well not only the liquid leakage rate from foam but also the liquid volume fraction in foam. The ratio of the liquid volume fraction in foam to the volume fraction of the Plateau border was much larger than the value estimated from Haas and Johnson’s result. It was confirmed that a time constant, T, involved in the model was suitable for estimating foam stability only by one parameter. However, T is affected not only by material characteristics but also by the foam height. On the other hand, since the ratio of the liquid volume fraction in foam to the volume fraction of the Plateau border reflects the material characteristics, it may be used for comparing the foam stability between materials with the same viscosity and density.