Relationship between the glass transition of soy protein and molecular structure

The change in molecular structure of the soy protein samples as a result of the microbial transglutaminase treatment was studied using solid-state (13)C NMR spectroscopy and circular dichroism (CD), and the relation to the glass transition temperature (T(g)) was examined. From NMR measurements, the structure of the local region of the C(alpha) methine was observed to change, and the region had relatively high mobility. From CD measurements, the structural change seemed to be caused by the change in the secondary structure (disintegration of the beta-structure). By comparison with the T(g) of another protein, the state of the secondary structure of a protein was suggested to be a key in determining its T(g).