Effect of sugar and sorbitol on the formation of low methoxyl pectin gels

Pectin gels were made with amidated low methoxyl pectin using sucrose, glucose, fructose and sorbitol as sweetening agents. The adsorption of water at controlled activity was measured by determining sorption isotherms and by differential scanning calorimetry. These results were correlated with the gel formation mechanism. ¹H NMR spectra were measured for sugar with and without Ca²⁺ or La³⁺ cations. Results demonstrated no correlation between water adsorption on sugars and gel rigidity. The effects of the different sugars appear to be associated with the competition between each sugar and the pectin for calcium cations.