BACKGROUND:
The physical stability of several food systems depends strongly on their interfacial properties, which may be modified by adding proteins and low-molecular-weight surfactants to their formulation. This study deals with the possibility of using wheat gluten to alter the surface and interfacial properties of an aqueous system, considering the effects of protein concentration, pH and the presence of monostearin. RESULTS: It was generally found that the surface tension decreased as the protein concentration increased, reaching a minimum value at 0.5 g kg -1 . The influence of protein concentration on surface tension was much greater than the effect of pH owing to the low ionic character of wheat gluten protein. At acidic and alkaline pH values the interfacial viscosity of the protein system underwent a significant increase with time. The addition of monostearin either promoted the displacement of protein molecules at the interface or generated an interfacial mixed film with surface tension values lower than those of both single components, depending on the pH.
CONCLUSION:
The results obtained indicate that gluten can contribute to the stabilisation of air/water and oil/water interfaces in some food systems (emulsions, foams, etc.).