Chemical and Functional Properties of Food Saccharides

© 2004 by CRC Press LLC
FIGURE 14.2 Typical 1 H-NMR spectrum (300 MHz) of solutions of a depolymerized chitosan
with F A 0.43 (10 mg/ml) in D 2O at pH 3 and 90∞C. The resonance at 0 ppm is the
internal reference TSP [sodium-(trimethylsilyl)-propionate-d 4], whereas the resonances at 4.8
and 4.6 ppm are H-1 of D-units and A-units, respectively. For further assignments of the
resonances in the spectrum, see Vårum, K.M. et al., Carbohydr. Res., 211, 17, 1991.
14.2.2 SEQUENCE
High-field 1 H and 13 C NMR spectroscopy has been used to determine sequences of
the monomers in chitosans. However, it should be noted that high-resolution spectra
are required to obtain information on sequence parameters of chitosans. 7,8 The units
in the chitosan chain have been found to be randomly distributed in water-soluble,
partially N-acetylated chitosans prepared from chitin by alkaline de-N-acetylation. 7,8
14.2.3 MOLECULAR MASS
As polysaccharides in general, chitosans are polydisperse with respect to molecular
weight. Because of this, the “molecular weight” of a chitosan is an average over the