SMALL DEFORMATION RHEOLOGICAL PROPERTIES OF MALTODEXTRIN-MILK PROTEINSYSTEMS

Small deformation dynamic oscillation was used to investigate the stru ctural behaviour of conformationally dissimilar maltodextrin and milk protein macro-molecules in a mixture, with the view of identifying the state of phase separation and the pattern of solvent distribution bet ween the two constituent phases. The enthalpic nature of the maltodext rin network produced a sigmoidal transition in the development of stor age modulus (G') during cooling and substantial thermal hysteresis upo n heating of the gel. By contrast, the entropically-driven build up of structure in milk protein samples yielded linear and overlapping cool ing and heating scans of G' with networks reverting into solutions at relatively low temperatures. These differences in the viscoelastic fun ctions of the two polymers in combination with theoretical analysis (i sostress-isostrain models, Kerner equation) have documented the reinfo rcing effect of strong and spherical maltodextrin inclusions on the we aker and continuous milk protein phase. However, at concentrations of maltodextrin beyond the phase inversion point, the binary assembly com prises a strong and continuous maltodextrin network surrounding the we aker milk protein inclusions. Finally, the sharp change in the pattern of water partition between the two polymeric components, as a result of phase inversion in the system, was rationalised on the basis of kin etically-influenced co-gels comprising phase separated networks which are trapped away from the state of thermodynamic equilibrium. Copyrigh t (C) 1996 Published by Elsevier Science Ltd