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Crystalline amylose complexes were prepared with decanal, 1-butanol, menthone and alpha-naphtol. Their crystalline structure and the related helical conformation, determined by wide angle X-ray diffraction (WAXD) and 13C CPMAS solid state NMR, were assigned to V6I, V6II, V6III and V8 types, respectively. It was possible to propose some hypotheses on the possible nature of interactions and especially intra-/inter-helical inclusion. Some shifts in the NMR C1 carbon signals were attributed to the presence of ligand in specific sites inside the structure for a same type of V6 helical conformation. Moreover, the crystallinity and polymorphic changes induced by desorption/rehydration were studied. A general increase of the carbon resonances sharpness upon rehydration has been observed, but also a V6II-V6I transition when decreasing the water content. Differential scanning calorimetry (DSC) experiments were also performed to approach the thermostability of the four types of complex and also the way they form again after melting/cooling sequences.

Cellulose microfibrils extracted from lemon and maize were studied by solid state NMR, Wide Angle X-ray Scattering, Fourier Transform Infrared Spectroscopy and Transmission Electron Microscopy. Some structural characteristics such as the allomorphic composition, the degree of crystallinity and the lateral or longitudinal crystal size were determined. These depended on the processing conditions, especially grinding, and determined the texturising properties of the microfibrils for liquid food product. Hydrolysed tunicin and Avicel were also studied as reference systems in terms of crystallinity and texturising properties in water. Lemon cellulose was shown to have a higher crystallinity or crystal size and a better texturising behaviour than maize microfibrils. Nevertheless, lemon microfibrils are more sensitive to grinding which decreases systematically the crystallinity and increases the amount of Iβ allomorph. Solid state NMR was also used to probe the mobility of the different regions of microfibrils by measuring T 1ρ which was well correlated to crystallinity. The presence of both surface and internal amorphous areas was discussed with respect to the NMR and X-ray scattering data. Some possible hypotheses for discrepancies observed between lemon and maize microfibrils in terms of texturising properties are expressed. Finally, these various properties were studied in the presence of polysaccharides such as carboxymethyl cellulose, scleroglucan or xanthan.

15 ref.; International audience