Structural features and potential texturising properties of lemon and maize cellulose microfibrils

Abstract

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.