Foaming of aqueous solutions of protein plus propylene glycol alginate

Volumes of foams produced by sparging have been determined as a function of pH for dilute aqueous solutions containing a mixture of propylene glycol alginate (PGA) and a food protein (beta-casein, beta-lactoglobulin, gelatin or soy protein) in the ratio 10: 1 by weight. At a concentration insufficient to give significant foaming on its own, each protein gives an enhancement in the foaming capacity of PGA at pH 7. The order of effectiveness of the proteins is: beta-casein > beta-lactoglobulin > gelatin> soy protein. The results are consistent with the formation of a weak electrostatic complex between protein and polysaccharide at the air-water interface under neutral pH conditions.