Spectroscopic studies on hydrocolloid water interactions

The behaviour of gelatin and xanthan gum when hydrated to levels in the range of 0 to 1 g of H2O per g of dry solid has been compared using different spectroscopic techniques (NMR, FTIR and WAXS). For both biopolymers an increase in molecular mobility and order was observed with increasing hydration. C-13 CP-MAS NMR results suggested the appearance of a helical form during the first stages of hydration of xanthan (similar to 50 % water w/w dry basis). FTIR spectra of gelatin films, after deconvolution of the amide bands, showed a general increase in order as the biopolymer hydrated. A long range order was detected by WAXS for both biopolymers. The proton spin-spin relaxation NMR result suggested that xanthan and gelatin had similar mobilities for water contents below 15 %. However, gelatin displayed a higher mobility at the high moisture contents. This correlated with the appearance of very sharp peaks in the C-13 FT-MAS spectra describing the mobile component and suggesting a possible solubilisation of the low molecular weight components.