Glass transition of gluten. 2: The effect of lipids and emulsifiers.

The effects of lipids and emulsifiers on the glass transition temperature (Tg) of gluten have been studied as a function of water content, using differential scanning calorimetry, dynamic mechanical thermal analysis, a three point bend test and pulsed nuclear magnetic resonance. Lipids and emulsifiers were found to have little or no effect on Tg, with the exception of the lower molecular weight caproic and hydroxycaproic acids, which had a plasticizing effect. In the case of hydroxycaproic acid this was found to be in accordance with the Couchman-Karasz equation. The magnitude of the drop in modulus at Tg was increased in the presence of these additives at low water contents. The effect of lipids and emulsifiers on the Tg of gluten and their compatibility with gluten appears to depend both on their hydrophobicity and on their molecular weight.