Effect of temperature on flow and viscoelasticproperties of dairy custard model systems

The rheological behaviour of dispersions of cross-linked starch in full fat milk, taken asmodels of custard model systems, was analysed at the two common consumptiontemperatures, 5°C and 25°C by both static and dynamic methods. All samples showedshear thinning behavior at both temperatures tested. Thixotropy was quantified bymeans of one empirical equation (Weltmann model). Flow of samples, after eliminatingthixotropy, were analysed by employing two different rheological models; Carreau andHerschel–Bulkley, and both of them fitted reasonably well the experimental data at alltemperatures (R2 > 0.998). The mechanical spectra obtained for most samples wastypical of gelled materials, at both temperatures, with Storage modulus (G´) higher thanLoss modulus (G˝), both moduli showing little variation with frequency. Although theextent of the differences varied among samples, in general, time dependence, plasticityand consistency were lower and pseudoplasticity was slightly higher at the highertemperature.

Keywords:

Custard , Viscoelasticity , Flow behavior , rheological models