Kinetics of thermally-induced conformational transitions in soybean protein films

The thermally-induced conformational transitions of soybean protein films were studied as the films were heated under isothermal conditions in the range 40–100 °C. By comparing the kinetics of protein–water interactions as a function of temperature using time-resolved Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and dynamic mechanical thermal analysis (DTMA) measurements on soybean protein films, we have shown that simply evaporating water from the film (TGA) is insufficient to explain the rate of conformational changes (FTIR and DMTA). We suggest that an elastic instability condition of denaturation or glass transition events in water-amide interactions is the governing mechanism for conformational changes that allows the evolution of disordered structures into more ordered secondary structures, thereby controlling the changes in physical properties such as stiffness and water sensitivity.