Extrusion-induced changes to the chemical profile and viscosity generating properties of citrus fiber

Each of 8 variants in extrusion conditions was applied to a commercially available citrus fiber. Extrusion under conditions where the specific mechanical energy (SME) exceeded 400 kJ·kg(-1) was able to solubilize up to 30% of the fibers. Where the SME was ～200 kJ·kg(-1) the degree of fiber solubilization was between 8 and 12%. All extruded fibers showed a loss of water-retaining capacity compared to the reference fiber, and this was attributed to the disruption of the integrated cell wall structure during the extrusion process. Nevertheless, within the 8 extruded variants there was a wide range of viscosity generating capacity which depended on the level of SME to which the fibers were subjected. The SME also had a pronounced effect on the nature of the solubilized fibers in terms of both their monosaccharide composition and their molecular weight profile. Both pectic and hemicellulosic polysaccharides were solubilized. It is concluded that extrusion has promise as a physical process for manipulating both the technological functionality and the health promoting properties of dietary fibers.