Effects of temperature on sorption of water by wheat gluten determined using deuterium nuclear magnetic resonance

The effects of lipids and residual starch components of wheal flour gluten on gluten hydration properties were investigated using nuclear magnetic res onance (NMR) and Fourier transform infrared (FTIR) techniques. Whole or nat ive, lipid-free, starch-free, and lipid- and starch-free gluten samples wer e prepared from wheat (Triticum aestivum) cv. Mercia. H-2 NMR relaxation on gluten samples hydrated with deuterium oxide (D2O) was measured over a 278 -363 K temperature range. FTIR spectra were recorded in dry and fully hydra ted material. Transverse relaxation (T-2) results indicated that all four g luten samples were hydrophilic in nature. There was little difference in re laxation behavior of whole and lipid-free gluten samples. T-2 values and po pulations of the relaxation components were very similar in each. The FTIR spectra of both samples showed an increase in extended beta-sheet secondary structures on hydration. These results suggest that lipid binding in glute n, if it occurs, has little effect on wheat gluten properties. Adding starc h to the gluten matrix results in an increase in water sorption on heating that may be attributed to the effects of starch gelation. However, the whol e water uptake of the gluten cannot be accounted for by the contribution of the residual starch, as estimated by the effects of added starch. Extracti on of residual starch required solubilization of the protein, including bre aking of the disulfide bonds. This process altered the gluten structure and properties. Light microscope investigation showed that glutens with residu al starch extracted were unable to form fibrillar strands on hydration. NMR and FTIR results showed greater water sorption in both samples with extrac ted starch than in the unextracted samples.