title: Using particle tracking to probe the local dynamics of barley β-glucan solutions upon gelation.
abstract: The sol-gel transition of aqueous barley β-glucan solutions which undergo gelation with ageing has been studied by conventional bulk rheology, phase contrast microscopy and particle tracking microrheology. Characterisation of the primary structure of the β-glucan isolate was carried out by enzymic methods and HPLC. The Brownian diffusion of fluorescent microspheres (0.75 μm diameter, carboxylate-coated particles) was used to probe the spatial mechanical properties of the gelling systems at the scale of microns; the potential use of passive particle tracking to study biopolymer gelling systems that present spatial heterogeneities is thus explored. For the β-glucan gels cured at 25°C both microrheology and bulk rheology revealed that with increasing the polysaccharide concentration the gelation time decreased, while the gelation rate and gel strength of the barley β-glucan gels increased. The particle tracking method had higher sensitivity and could map molecular ordering and structural heterogeneities in the evolving polysaccharide network at a micro-level. That is, different size pores were generated upon ageing with regions of depleted or less amount of β-glucan molecules. Furthermore, this method could detect changes in the fine structure of the system before such events can be registered by bulk rheological measurements; i.e. microheterogeneity and aggregation of β-glucan chains were revealed by particle tracking at earlier temporal stages of the experiment.
authors.affiliation: Department of Food Science and Technology, School of Agriculture, Aristotle University of Thessaloniki, Thessaloniki, Greece. tmoschak@agro.auth.gr
authors.forename: Thomas
authors.initials: T
authors.lastname: Moschakis
authors.forename: Athina
authors.initials: A
authors.lastname: Lazaridou
authors.forename: Costas G
authors.initials: CG
authors.lastname: Biliaderis
mesh_terms: D002236:Carbohydrate Conformation; D004058:Diffusion; D005456:Fluorescent Dyes; D005782:Gels / Q000737:chemistry*; D001467:Hordeum / Q000737:chemistry*; D007700:Kinetics; D008856:Microscopy, Fluorescence; D008858:Microscopy, Phase-Contrast; D008863:Microspheres; D009038:Motion; D044367:Phase Transition; D012212:Rheology; D012996:Solutions / Q000737:chemistry*; D013696:Temperature; D014783:Viscosity; D014867:Water / Q000737:chemistry; D047071:beta-Glucans / Q000737:chemistry* / Q000302:isolation & purification
chemical_list: D005456:Fluorescent Dyes; D005782:Gels; D012996:Solutions; D047071:beta-Glucans; D014867:Water