REACTIVITY OF SULFITE DURING THE DEHYDRATION OF A GLUCOSE-GLYCINE-SULFITE-AGAR-MICROCRYSTALLINE CELLULOSE GEL

This paper considers the extent to which sulphite species, S(IV), react with intermediates in the glucose-glycine reaction, when a gel matrix consisting initially (on a wet weight basis) of cellulose (22% w/w), agar (1% w/w), glycine (0.19% w/w), and variable amounts of glucose (0.14-9.0% w/w) and sodium disulphite Na2S2O5 (0.012-0.24% w/w) is dehydrated in air at 80 degrees C. The amount of S(IV) which undergoes reaction increases with S(IV) and glucose concentration when (on a dry weight basis) S(IV) is 2 g SO2/kg and glucose is <10% (w/w). At higher concentrations of S(IV) and glucose, the amount of S(IV) which reacts is independent of the concentration of these reactants. It is suggested that high concentrations of glucose give rise to an increase in the viscosity of the medium thereby causing the extent of reaction to be limited by the rate of molecular diffusion. On the other hand, specific interactions involving S(IV) may be responsible for its concentration behaviour.