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Tham khảo tài liệu 'waste water treatment and reutilization part 13', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Low-Value Maize and Wheat By-Products as a Source of Ferulated Arabinoxylans 349 The rheological differences between FAXN FAXMB and FAXWB gels might have its origin in the structural and or conformational characteristics of these macromolecules. Clearly further studies on the distribution of arabinose and feruloyl groups along the polymer chain backbone of these different arabinoxylans are needed to establish relationships between the molecular structure gelling ability and gels properties. The equilibrium swelling of FAXN FAXMB and FAXWB gels was reached between 15-20 h. The swelling ratio q g water g polysaccharide in FAXN FAXMB and FAXWB gels were 40 22 and 20 respectively Table 4 . AX Source Swelling ratio q g water g AX Mc a x103 g mol pc b x10-6 mol cm3 8 c nm FAXN 40 1.5 95 0.1 9.0 0.01 183 4 FAXMB 22 1.9 20 0.1 75 0.01 48 1 FAXWB 20 1.7 29 0.1 59 0.01 58 1 a Molecular weight between two cross-links b Cross-linking density c Mesh size Table 4. Structural characteristics of FAXN FAXMB and FAXWB gels. The lower swelling ratio values obtained for FAXMB and FAXWB can be related to the more compact polymeric structure that limits the water absorption in comparison to the FAXN gels. The higher water uptake of gels made from FAXN can be explained in terms of a decrease in ferulic acid content and therefore the existence of longer un-cross-linked polysaccharide chains sections in the network. Uncross-linked polymer chains sections in the gel can expand easily conducting to higher amounts of water uptake. The molecular weight between two cross-links Mc the cross-linking density pc and the mesh size values of the different gels are presented in Table 3. Higher Mc and Ẹ and lower pc values have been reported in laccase induced water soluble arabinoxylan gels from wheat at similar AX concentrations Carvajal-Millan et al. 2005b . The latter could be related to a high molecular weight in arabinoxylans from wheat endosperm 400-600 kDa in comparison to alkali-extracted .
