Theoretical and experimental study of one-dimensional syneresis of a protein gel

Abstract

Gels formed by macromolecules or solid particles in a solvent by physical aggregation may show syneresis, because such a gel is usually very inhomogeneous and many additional cross-links or points of contact may be formed after gelation. This causes a stress in the gel matrix which may lead to syneresis, i.e. shrinkage of the gel matrix and expulsion of solvent. The syneresis can be described by applying Darcy's law, but syneresis pressure and permeability of the gel both change with time and with spatial location. Moreover external pressure (caused by gravity for example may enhance syneresis. A numerical mathematical model was developed which takes these complications into account for one-dimensional syneresis. The results of the calculations were compared with those of experiments on gels formed from skim milk by renneting. Good agreement was obtained. The syneresis pressure was found to be very low, of the order of 1 Pa.