THERMAL AND SPECTRAL PROPERTIES OF TRANSGLUTAMINASE‐CROSSLINKED WHEAT GLUTEN IN TRIS‐HCl*

Abstract

ABSTRACT Wheat gluten (10 g) was crosslinked (XL) using 10 units of transglutaminase (TG) in 2 L 0.1 M TRIS‐HCl, pH 7.5. The suspension was stirred for 24 h at 40C and freeze‐dried as‐is or dialyzed and then freeze‐dried. The XL material was tested using modulated differential scanning calorimetry (MDSC), where 25–30 mg was placed in a stainless steel pan and heated from 20 to 200C at 7C/min. The samples were subjected to three heating and cooling cycles. The MDSC data of the undialyzed sample showed two endothermic transitions during the first cycle and an exothermic followed by an endothermic transition on the second cycle. Further analysis showed that the two transitions of the first cycle are the melting of the TRIS. The first cycle of the dialyzed sample displayed two glass transitions at 46.0C with 0.11 J/g/C and 130.0C with 0.29 J/g/C, followed by an exothermic transition at 120.7C onset, 150.6C peak with 14.8 J/g ΔH. The second cycle of the dialyzed material showed one broad glass transition at 97.3C and 0.495 J/g/C. Fourier transform infrared spectra showed differences between crosslinked and uncrosslinked gluten and provided spectral evidence of molecular interaction between gluten and TRIS.