Résumé
To enhance the viscoelastic properties of Feruloylated Water Extractable ArabinoXylan (F-WEAX) gels, F-WEAX were covalently linked by a laccase in the presence of cellulose nanocrystals (CNC). The CNC/ F-WEAX weight ratios varied from 0 to 1.5 at a constant F-WEAX concentration of 1 % (w/v). The resulting CNC/ F-WEAX gels became stiffer with increasing CNC content with the elastic modulus scaling as [CNC]3. CNC also altered the relaxation spectrum of the CNC/ F-WEAX gels: the loss factor increased at low frequencies while remaining constant at high frequencies. The strong affinity between F-WEAX and CNC was demonstrated by in situ QCM-D analysis which showed that F-WEAX adsorb spontaneously and irreversibly onto CNC. Following laccase oxidative gelation, the rate of recovered ferulic acid (FA) in di-and trimer forms was twice as high when oxidation occurred in the presence of CNC. Due their higher covalent cross-link density, the swelling capacity of F-WEAX-CNC gels slightly decreased. The increased elasticity of the F-WEAX-CNC gels can thus be attributed to 3 factors: a higher volume fraction of CNC leading to increased entanglement, a greater number of di- or tri-ferulic acid covalent cross-links between F-WEAX chains, and the formation of multiarm physical junctions between F-WEAX and CNC.