Effect of inulin and pectin on rheological and thermal properties of potato starch paste and gel

• Inulin of various degree of polymerization was used in starch based paste and gel.
• An increase in inulin addition does not increase enthalpy of gelatinization.
• An increases in inulin addition increase significantly enthalpy of retrogradation.
• Decrease in paste viscosity with increasing pectin and inulin contents was found.
• Viscoelastic properties of starch gel depend on average DP of inulin.

The aim of the study was to analyze properties of pastes and gels obtained from potato starch with the addition of pectin and inulin. It was observed that the partial replacement of starch by pectin and inulin with varying degrees of polymerization (average DP: <10, ⩾10, and ⩾23) significantly modified thermal and rheological properties of starch gels. In most cases, the increase in pectin concentration resulted in a drop of consistency coefficient and both moduli. Inulin exerted different effects, depending on its average DP and concentration, which could be explained by the presence or formation of low molecular weight sugars. A slight increase of moduli was observed for a DP < 10, a drop for a DP ⩾ 10, and for a DP ⩾ 23 the values of G′ and G′′ initially increased (at low concentration) and then diminished. Statistical analyses proved the significance interactions between inulin and pectin molecules on properties of starch pastes and gels, and their character was controlled by average DP of applied inulin preparation. Addition of inulin and pectin significantly reduced starch transition enthalpy after retrogradation, and consistency indices. The gels prepared with inulins of medium and high DP were characterized by low storage and loss moduli in comparison to standard, while the addition of low DP inulin caused a slight increase in their value.