Hydrophobic Interaction in the Gelation of High Methoxyl Pectins

ABSTRACT The role of hydrophobic interaction between the ester methyl groups in the gelation of high methoxyl pectins was investigated by using temperature and different cosolutes to modify hydrophobic interaction in a controlled manner. Both rupture strength and gel threshold were found to be partly proportional to the free energy of hydrophobic interaction between CH 3 ‐groups in model systems. The size of junction zones and the standard free energy of gelation were proportional to the square of the degree of methoxylation, i.e. to the probability of ester methyl groups being opposed in contiguous lengths of polymer. The contribution from hydrophobic interaction to the free energy of gelation was about half that from hydrogen bonds.