NA-23 NMR MOLECULAR MOBILITY STUDIES OF HYDROCOLLOID NACL SOLUTIONS AS INFLUENCED BY SODIUM CONCENTRATION

Na-23 NMR molecular mobility studies were per-formed to investigate th e interaction between sodium ions and various hydrocolloid-water syste ms as affected by the nature of the hydrocolloid (ionic and non-ionic) and the concentration of added NaCl (0-5000 mg/100 ml). At low amount s of added NaCl (20-100 mg/100 ml) the transverse relaxation rates (R2 ) for the ionic gums, kappa-carrageenan and xanthan, rapidly decreased and were larger than those for the non-ionic gums, guar and locust be an. At higher concentrations of added NaCl (> 100 mg/100 ml), R2 for t he ionic gums gradually levelled off, approaching the R2 values for th e non-ionic gums. For the xanthan-water system, the R2 for the endogen ous Na+ concentration and very low added NaCl concentrations (<15 mg/1 00 ml) were also measured. This research suggests that gum type, NaCl and endogenous cation concentrations affect the binding of Na+ to the gums.