Submitted to: North American Thermal Analysis Society Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 10/6/2004
Publication Date: 10/6/2004
Citation: Mohamed, A., Gordon, S.H. 2004. Thermal properties of transglutaminase-crosslinked wheat gluten. (Abstract) North American Thermal Analysis Society Meeting. 2004 CDROM.
Technical Abstract: Wheat gluten (10 g) was crosslinked (XL) using 6 units of transglutaminase (TG) in 1L 0.1 M Tris-HCL pH 7.5. The suspension was stirred for 18 hours at 40 degrees C and freeze-dried as is or dialyzed and then freeze-dried. The XL material was tested using MDSC where 31.00 mg were placed in stainless steel pans and heated from 20 to 250 degrees C at 7 degrees C/min. The samples were subjected to two heating and cooling cycles. The MDSC data of the un-dialyzed sample showed two endothermic transitions during the first cycle and an exothermic and an endothermic transition on the second cycle. Further analysis showed that the two transitions of the first cycle are the TRIS-HCL melting. The dialyzed sample first cycle displayed a glass transition at 88.5 degrees C and 0.017 J/g/degrees C, where an exothermic transition appeared at 120.7 degrees C onset, 150.6 degrees C peak, and 14 J/g deltaH. The second cycle of the dialyzed material showed one broad glass transition at 119 degrees C and 0.147 J/g/degrees C. Crosslinked gluten in aqueous gel was examined by FT-Raman spectroscopy. The vacuum dried gel was also examined in KBr by FTIR transmission spectroscopy. Because TRIS'HCL buffer and the crosslinking enzyme, transglutaminase, were present in the test sample the gel was dialyzed to remove the buffer. The aqueous gel and the freeze-dried crosslinked gluten were examined by FT-Raman and FTIR transmission spectroscopy. Infrared spectra in the gel and dry states were compared with corresponding spectra of a control sample of purified gluten. Both FT-Raman and FTIR transmission spectroscopy revealed significant differences between the crosslinked gluten and the purified gluten. As would be expected in any transamination reaction, the spectral differences were not attributable to differences in the types of covalent bonds present in the crosslinked gluten versus the purified gluten. However, the spectral differences, which appeared as noticeable broadening or intensification of bands mainly in the carbohydrate regions, did indicate changes to the physical state of the gluten due to crosslinking. These infrared methods, especially when based on spectral de-convolution strategies, have potential applications for distinguishing between levels of crosslinking in gluten for studies in flour or dough rheology.