Comparison of the Functional Properties of Egg White Protein and Whey Protein Isolate in Aerated Food Systems

Abstract

This study investigated the static and dynamic physical properties of protein foams and cake batters made from egg white protein and whey protein isolate. A method of rheological evaluation (vane method) initially employed in the study of soils was used to evaluate protein foam rheology. The method was shown to be a reliable method for determining large-scale rheological properties of protein foams. Egg white protein produced foams with higher yield stress at lower concentrations and shorter whip times than did whey protein isolate. Short lifetime decreases in yield stress were observed in foams of higher protein concentration of both types, which were both concentration and whip time dependent. This is considered to be the result of a restructuring of the system as opposed to collapse of the foam. Cakes made from foams of both types showed different performance properties as well. Cakes produced from egg white protein exhibited a minimum concentration of protein (between 5 and 10% w/w of foam) necessary to form a cake of satisfactory volume. Whey protein isolate was unable to form a satisfactory cake regardless of the concentration studied. Phase contrast microscopy, fluorescence microscopy and differential scanning calorimetry studies suggested that the difference in behaviors might be due to a high degree of phase separation between egg white protein and soluble starch that was not seen in whey protein containing systems. This phase separation appears to allow significant matrix development in egg white protein containing cakes that can support the volume of the final product.