The effect of instant green tea on the foaming and rheological properties of egg albumen proteins

Abstract

AbstractThe effects of three varieties of instant green tea (from China, Japan and Kenya) on the foaming and thermal properties of 1% (w/v) egg albumen and the gelation properties of 5 and 15% (w/v) egg albumen were investigated. All varieties produced similar effects on the foaming and gelation properties of egg albumen, but to different extents depending on the tea constituents. Mixtures of 1% (w/v) egg albumen and 0.25–0.4% (w/v) instant green teas in distilled water showed the greatest foam expansion (800–1140%) and foam stability (97–100%) at 10 min after whipping compared with 1% (w/v) egg albumen alone (226% for foam expansion and 34% for foam stability). Addition of instant green teas at levels above 0.5% (w/v) decreased foam expansion and stability. Small‐deformation rheology of mixtures of 5% (w/v) egg albumen and 1 or 2% (w/v) instant green teas showed an initial increase in elastic modulus (G′) and viscous modulus (G″) followed by a small, broad peak, indicating that the binding of tea constituents (polyphenols) with proteins may be reversible between 20 and 54 °C; this peak was not seen for 5% (w/v) egg albumen on its own. Large‐deformation rheological tests also indicated increased strength of mixed egg albumen/green tea gels with increasing levels of instant green teas. Differential scanning calorimetry thermograms showed that for the same instant green tea a higher concentration decreased the onset and peak (Tm) temperatures and enthalpy change values of all egg albumen protein peaks. Copyright © 2007 Society of Chemical Industry