Viscoelasticity of inulin-starch-based dairy systems.: Influence of inulin average chain length

Inulin is a natural component of several fruits and vegetables with beneficial effects on health and interesting technological properties, which are linked to its average chain length. The objective of this work was to study how the addition of different types of inulin (average long-chain, native and average short-chain inulin) at four concentrations (0%, 2.5%, 5% and 7.5% w/w) may affect the viscoelastic properties of semisolid dairy systems formulated with either skimmed or whole milk and two modified tapioca starch concentrations (3.25% or 4% w/w). The mechanical spectra obtained for most of the samples were typical of gelled materials. A significant effect of the interactions between the inulin type, the inulin concentration and the starch concentration on the storage and loss moduli (G' and G ''), on the loss tangent angle (tan delta) and on the complex viscosity (eta*) values at 1 Hz was observed in both whole- and skimmed-milk samples. The effect of the different types of inulin on the viscoelastic properties of the systems was dependent not only on the inulin concentration added to them but also on the sample composition. The most remarkable effects were observed when adding 7.5% of long-chain inulin, which significantly increased G', G '' and eta* values, and significantly decreased tan delta values in both types of milk and both starch concentrations. (C) 2007 Elsevier Ltd. All rights reserved.