Dynamic rheological and thermal study of the heat-induced gelation of tomato-seed proteins

The structural aspects of proteins prepared from tomato seeds were studied by dynamic rheology, modulated differential scanning calorimetry (MDSC) and Fourier transform infrared (FTIR) spectroscopy. The critical gel point was determined from storage (G') and loss (G '') moduli as functions of time and frequency. The findings indicate that tomato-seed proteins can create gels during heat treatment at 90-95 degrees C. Mechanical spectra of the tomato-seed protein gels were classified as weak gels based on the frequency sweep, complex viscosity (eta(*)) and tan delta results. Moreover, G' and G '' changes were found to be dependent on both concentration and frequency. MDSC showed two peaks, with gelation temperatures (T-d) of 70 and 87 degrees C, which we attribute to starch and globular protein fractions, respectively. The FTIR spectra show an increase in the absorbance of amides I and II after increasing the solid content from 1 to 10% w/w, indicating mostly beta-sheet and alpha-helical conformations. (C) 2012 Elsevier Ltd. All rights reserved.