Question

Why As the pH of a pectin solution is lowered, the highly hydrated and charged carboxylate groups are converted into uncharged, only slightly hydrated carboxylic acid groups ???

Answer 1

The formation of high methoxyl gels needs the existence of sugar and acid. As acid is added, the highly charged and hydrated carboxyl groups are transformed into uncharged, only slightly hydrated carboxylic acid groups. The loss of charge and hydration permits the pectin molecule to associate with other chains and junction zones to form. The formation of junction zones is supported by the addition of sugar, which strives for the water and thus lowers the solvation of the polymer chain, which stimulates chain to chain connections.