INFRARED-SPECTRA AND DIELECTRIC-PROPERTIES OF THERMALLY TREATED SOYBEAN PROTEINS

The infrared spectra of protein, heat-treated at various temperatures and times in the atmosphere were recorded. The temperature-induced cha nges in the absorbance of the bands at 1660, 1530 and 2950 cm(-1) were determined. The data revealed that soybean protein exhibits significa nt breakdown on heating at 90 degrees C as indicated by the marked dec rease in the absorbances of C-O and C-H stretching vibrations and the N-H bending vibration, in addition to the significant decrease in the permittivity epsilon' and dielectric loss epsilon''. The decrease exhi bited after heating above 100 degrees C can be attributed to the NH gr oups and a decrease in the amount of amide groups. Moreover the degrad ation of soybean protein molecules to lower molecular weight substance s takes place on heating above 160 degrees C.The effect of water conte nt on epsilon' and epsilon'' of soybean protein was also investigated. It was concluded that the DC conductivity depends upon water content while there is no detectable dependency on increasing temperature.