title: Tribology of swollen starch granule suspensions from maize and potato.
abstract: The tribological properties of suspensions of cooked swollen starch granules are characterised for systems based on maize starch and potato starch. These systems are known as granule 'ghosts' due to the release (and removal) of polymer from their structure during cooking. Maize starch ghosts are less swollen than potato starch ghosts, resulting in a higher packing concentration and greater mechanical stability. In a soft-tribological contact, maize ghost suspensions reduce friction compared to the solvent (water), generate bell-shaped tribological profiles characteristic of particle entrainment and show a marked concentration dependence, whereas potato ghost suspensions exhibit lubrication behaviour similar to water. Microscopy analysis of the samples following tribological testing suggests that this is due to the rapid break-up of potato ghosts under the shear and rolling conditions within the tribological contact. A reduction in the small deformation moduli (associated with a weak gel structure) is also observed when the potato ghost suspensions are subjected to steady shear using parallel plate rheometry; both microscopy and particle size analysis show that this is accompanied by the partial shear-induced breakage of ghost particles. This interplay between particle microstructure and the resultant rheological and lubrication dynamics of starch ghost suspensions contributes to an enhanced mechanistic understanding of textural and other functional properties of cooked starches in food and other applications.
authors.affiliation: Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St. Lucia, Brisbane, QLD 4072, Australia; ARC Centre of Excellence in Plant Cell Walls, The University of Queensland, St. Lucia, Brisbane, QLD 4072, Australia. Electronic address: zhangb@scut.edu.cn.
authors.forename: Bin
authors.initials: B
authors.lastname: Zhang
authors.affiliation: School of Chemical Engineering, The University of Queensland, St. Lucia, Brisbane, QLD 4072, Australia.
authors.forename: Nichola
authors.initials: N
authors.lastname: Selway
authors.affiliation: Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St. Lucia, Brisbane, QLD 4072, Australia; ARC Centre of Excellence in Plant Cell Walls, The University of Queensland, St. Lucia, Brisbane, QLD 4072, Australia; School of Chemical Engineering, The University of Queensland, St. Lucia, Brisbane, QLD 4072, Australia.
authors.forename: Kinnari J
authors.initials: KJ
authors.lastname: Shelat
authors.affiliation: Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St. Lucia, Brisbane, QLD 4072, Australia; ARC Centre of Excellence in Plant Cell Walls, The University of Queensland, St. Lucia, Brisbane, QLD 4072, Australia.
authors.forename: Sushil
authors.initials: S
authors.lastname: Dhital
authors.affiliation: ARC Centre of Excellence in Plant Cell Walls, The University of Queensland, St. Lucia, Brisbane, QLD 4072, Australia; School of Chemical Engineering, The University of Queensland, St. Lucia, Brisbane, QLD 4072, Australia.
authors.forename: Jason R
authors.initials: JR
authors.lastname: Stokes
authors.affiliation: Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St. Lucia, Brisbane, QLD 4072, Australia; ARC Centre of Excellence in Plant Cell Walls, The University of Queensland, St. Lucia, Brisbane, QLD 4072, Australia. Electronic address: m.gidley@uq.edu.au.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Gidley
keywords: Granule ghosts; Maize; Potato; Rheology; Starch; Tribology