Combinations of three types of inulin differing in the degree of polymerization, that is, short, medium, and long chained (010%), and modified starch (0-3%) with different composition ratios were prepared according to the D-optimal design of experiments. The microstructural and rheological characteristics of the prepared samples were analyzed to study the effect of the inulin composition on the low-fat mayonnaise. Rheological characterizations, including oscillatory frequency sweep tests, transient creep, and stress relaxation analysis, were carried out on the samples. An optical microscope was used to observe the microstructure. According to the results, the effects of all types of inulin were precarious in the presence of starch (>= 1.5%). In fact, a relationship was found between the inulin type and concentration and also the starch content in all of the prepared samples; with increasing starch content (>= 1.5%), inulin chain length, and concentration of long-chain inulin (>5%), the elastic properties of the emulsion were improved and showed a higher resistivity against deformation. Furthermore, a more packed structure with a larger average particle diameter and dominant monodispersity were observed under such conditions. (C) 2013 Wiley Periodicals, Inc.