Impact of soluble dietary fibre on the characteristics of extruded snacks

• Inulin influences greatly dough viscoelastic properties.
• Mechanical properties and expansion of snacks depend on fibre degree of polymerisation.
• Short-chain inulin influences snack quality more than long-chain inulin.
• Extrusion-cooking is not too severe for the stability of inulin.

The aim of this experimental work was to evaluate the effect of inulin addition on dough rheological properties, texture and sensory quality of extruded snacks. Two commercial fructan products of different degree of polymerisation (DPn) were used at levels from 2% to 7% (DPn = 10 for inulin GR; DPn = 23 for inulin HPX). Dough rheological properties were investigated using dynamic measurements in the linear viscoelastic range (frequency sweep and time cure tests) and farinograph test. Colour, specific volume (Vs), mechanical and sensory properties of snacks were evaluated. Fibre enrichment lowered dough consistency due to a reduction in water absorption. Large differences in elastic properties of samples were observed between 25 and 95 °C due to incompatibility between inulin and starch and different kinetics of starch gelatinization. The magnitude of G′ decreased with the increase in fibre content and GR had a greater effect than HPX. Inulin GR increased product expansion and hardness compared with the reference. No significant differences in Vs and mechanical properties were observed between reference and inulin HPX enriched samples up to 5%, while lower values were observed at 7%. Short-chain inulin lowered the extent of non-enzymatic browning. Snacks made with 5% inulin HPX can be used to enhance the fibre content without impacting negatively on product quality.

Storage modulus (G′) vs. temperature at 1 Hz for flour blend dough enriched with inulin GR at levels of 0 (a), 2% (b), 5% (c) and 7% (d).Figure optionsDownload as PowerPoint slide