GLUTEN VISCOELASTICITY IS NOT LIPID-MEDIATED - A RHEOLOGICAL AND MOLECULAR FLEXIBILITY STUDY ON LIPID AND NON-PROLAMIN PROTEIN DEPLETED GLUTENS

Wheat flours differing in their lipid and non-prolamin protein (NPP) c ontents were obtained by chloroform or Lubrol PX extraction. Starch wa s hand-washed out of the flour, and the resulting glutens were studied by dynamic theology and electron spin resonance spectroscopy (ESR) sp in probing and spin labeling. Compared to control gluten, the storage modulus of NPP-including lipoprotein-depleted gluten is unchanged, and the loss modulus is not significantly different. The mobility of spin probes differing in size in the gluten aqueous phase suggests the exi stence of at least two compartments: a network with a mesh size of abo ut 0.8 nm and larger water pockets. These compartments are present in all glutens. The spectra resulting from ESR spin labeling experiments are composite, reflecting the contribution of at least two types of po lypeptides differing in flexibility. The population of mobile spin lab els linked to the lysine residues is much larger in control gluten com pared to NPP depleted gluten, indicating the lysine residues of these proteins are in a less flexible environment. On the contrary, only a s light difference is observed between the various samples when cysteine residues are labeled. These results suggest that NPP and lipids behav e only as fillers in the prolamin network.