A differential scanning calorimetric study of the stability of egg white to heat denaturation

The heat denaturation of egg white and its component proteins was studied by differential scanning calorimetry. At a heating rate of 10 °C/min, egg white at pH 7 shows two major endotherms, at 65 °C and 84 °C, produced by the denaturation of conalbumin and ovalbumin, respectively. The conalbumin endotherm is increased to 70 °C by raising the pH to 9.0, or 77 °C by addition of aluminium at neutral pH. Addition of sucrose stabilises all the proteins; at 10%sucrose, all endotherms are shifted 2 °C to higher temperatures. Within experimental error, the enthalpy of denaturation of egg white equals the sum of the enthalpies of denaturation of its component proteins, and is independent of pH over the pH range 7–9.