The effect of pH on the bubble size distribution, void fraction, and enrichment ratio of a continuous foam fractionation column containing ovalbumin was investigated. The bubble size and void fraction were measured using a photoelectric capillary probe for different solution pHs (3.5, 4.5, 6.5, and 9.7). The bubble diameters for pH 3.5 and 4.5 were the largest of the four pHs studied. At these two pHs, the foam was less stable and formed aggregates, leading to lower enrichment and mass recovery. For the nearly neutral pH 6.5 or the more basic pH 9.7, the bubble size was smaller and the foam was more stable, resulting in both high enrichment and high mass recovery. The void fraction was smallest for pH 6.5, but the effect of pH on void fraction was not significant. In the lower foam phase, the calculated specific area increased as the pH increased from 3.5 to 9.7, which may partially contribute to the higher enrichments at pH 6.5 and 9.7.