Effect of Bubble Velocity and pH Step Changes on the Foam Fractionation of Sporamin

Foam fractionation can be employed to concentrate and separate sporamin (ipomoein) from a sweet potato protein−water extract. In this foam fractionation study, the bulk solution pH and the air superficial velocity, V 0, were the two primary control variables. It was determined that the protein separation ratio is strongly dependent on the bulk solution pH, with the highest sporamin recovery occurring at pH 3. Two types of experiments were conducted here. The first was to hold the air superficial velocity constant and step down the pH in small increments, with 10 mL of foamate collected at each pH level. The second was to hold the pH constant and step up the air superficial velocity, V 0, in small increments, again with 10 mL of foamate collected at each V 0 level. The lowest feasible air superficial velocity generally corresponds to the maximum protein recovery at a given pH. One strategy for separating β-amylase from sporamin in the sweet potato extract is to first foam the bulk solution at pH 5 to concentrate the sporamin, followed by foaming at pH 3 to collect the concentrated β-amylase.