Amaranth proteins foaming properties: Film rheology and foam stability – Part 2

Abstract

In this work the influence of pH and ionic strength on the stability of foams prepared with amaranthprotein isolate was analyzed. The behaviour observed was related to the physico-chemical and structuralchanges undergone by amaranth protein as a result of those treatments. The results obtained showthat foams prepared at acidic pH were more stable than the corresponding to alkaline pH. At pH 2.0the foams presented higher times and more volumes of drainage. This behaviour is consistent with thecharacteristics of the interfacial film, which showed a higher viscoelasticity and a greater flexibility atacidic pH than alkaline pH value, which in turn increased by increasing the concentration of proteins inthe foaming solution. It is also important to note that the presence of insoluble protein is not necessarilydetrimental to the properties of the foam. Detected changes in the characteristics of the interfacial filmas in the foam stability have been attributed to the increased unfolding, greater flexibility and net chargeof amaranth proteins at acidic conditions.