SEQUENCE-DEPENDENT KINETIC TRAPPING OF BIPHASIC STRUCTURES IN MALTODEXTRIN-WHEY PROTEIN GELS

The structural properties of maltodextrin in mixtures with native whey protein have been investigated using dynamic oscillation and a sequen ce of experimental time-temperature, frequency and strain sweeps. Cool ing of the binary system results in a gelled maltodextrin matrix surro unding the liquid whey protein inclusions. Subsequent heating denature s the protein and the formation of a gelled filler changes the viscoel astic functions of the mixture dramatically. Modelling of the two dist inct microstructures shows a clear transition from an isostrain condit ion with a solid-like maltodextrin matrix to an isostress arrangement where the protein filler forms the strongest phase. Estimation of the pattern of solvent partition between the two phases suggests that ther e is a linear, positive dependence between the relative amount of solv ent kept in the liquid inclusions of whey protein and its polymer conc entration. However, gelation of the protein immobilizes the mixed syst em and prevents, within the experimental timescale, solvent diffusion into the maltodextrin network, thus creating a constant value for the relative solvent distribution between the two phases. (C) 1997 Elsevie r Science Ltd.