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.

The presence of S-ovalbumin, a more heat-stable form of ovalbumin formed on storage of eggs, can be determined by differential scanning calorimetry of egg white. At a heating rate of lO"C/min, at pH 9, the characteristic denaturation temperature of ovalbumin is 84.5"C, that of S-ovalbumin, 92.5"C. The formation of S-ovalbumin proceeds through a previously unrecognised intermediate species having a denaturation temperature of 88.5"C. The kinetics of the conversion on storage of eggs at 4,22 and 37°C have been determined. Differential scanning calorimetry is a rapid and convenient method of determining the quality of eggs held in storage. Freeze-dried preparations of ovalbumin stored in the cold for 20 years showed partial conversion to the intermediate, but not to S-ovalbumin.

At temperatures above that required for gelatinization, an order‐disorder transition is observed for wheat, maize, waxy maize and potato starches. This transition is the melting of the crystallites in the granules. A second, higher temperature, transition occurs in wheat and maize starches. This also appears to be a melting transition. Potato starch Nägeli amylodextrins show increased thermal stability of the crystalline regions with increasing hydrolysis of the amorphous regions. Extensive hydrolysis lessens the destabilizing effect of the amorphous regions on the crystallites sufficiently that the gelatinization transition occurs to only a small extent, the crystalline regions melting, instead, at temperatures above the gelatinization temperature.

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