Surface and foaming properties of potato proteins: Impact of protein concentration, pH value and ionic strength

Using a multiscale approach, potato protein isolate was characterized holistically in terms of its solubility and surface charge, surface activity and surface dilatational properties as well foaming properties and bubble structural attributes. By means of varying protein concentration (0.1-10.0%), pH (3.0-10.0) and NaCl concentration (0-200 mM), it was aimed to establish a better mechanistic understanding of potato protein functionality. Overall, surface activity was found to be rather unaffected by a modification of protein concentration and pH, whereas pH had a clear effect on surface dilatational elasticity. Likewise, foam stability was affected by pH, yielding a maximum around the isoelectric point, which is due to an enhanced network formation at the air/water interface imparting an increased surface film stability. Coarsening exponents were found to reflect the results on foam stability. By comparison, NaCl presence clearly had an enhancing effect on surface activity and led to increased protein-protein interactions within the surface film. More compact surface films in turn resulted in a better foamability and foam stability as well as lower coarsening exponents. Comparison of findings to mechanisms known for beta-lactoglobulin-stabilized surfaces revealed their principal applicability also to potato proteins' functional properties. Overall, by means of the obtained knowledge, foam structures based on potato proteins can be controlled more specifically.