Characterization of Oat (Avena nuda L.) β-Glucan Cryogelation Process by Low-Field NMR.

Low-field nuclear magnetic resonance (LF-NMR) is a useful method in studying the water distribution and mobility in heterogeneous systems. This technique was used to characterize water in an oat β-glucan aqueous system during cryogelation by repeated freeze-thaw treatments. The results indicated that microphase separation occurred during cryogelation, and three water components were determined in the cryostructure. The spin-spin relaxation time was analyzed on the basis of chemical exchange and diffusion exchange theory. The location of each water component was identified in the porous microstructure of the cryogel. The pore size measured from the SEM image is in accordance with that estimated from relaxation time. The formation of cryogel is confirmed by rheological method. The results suggested that the cryogelation process of the polysaccharide could be monitored by LF-NMR through the evolution of spin-spin relaxation characteristics.