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Multiple-Particle Tracking Study of Microheterogeneity of Nutrim-10 Suspensions

¹National Center for Agricultural Utilization Research, Agricultural Research Service, U.S. Department of Agriculture, 1815 North University Street, Peoria, IL 61604. ²Corresponding author. Phone: 309-681-6359. Fax: 309-681-6685. Email: xuj@ncaur.usda.gov ³Department of Chemical Engineering, The Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218. Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by the USDA implies no approval of the product to the exclusion of others that may also be suitable.

Nutrim is a newly developed food product containing dietary soluble fiber β-glucan. The microstructural heterogeneities of Nutrim-10 suspensions were investigated by monitoring the thermally driven displacements of well-dispersed microspheres through video fluorescence microscopy. By comparing the distribution of the time-dependent mean-square displacement (MSD) of polystyrene microspheres embedded in three concentrations of Nutrim-10 suspensions, we found that the degree of heterogeneity of suspensions increased dramatically within a narrow range of Nutrim-10 concentrations. The ensemble-averaged MSD of 5.5% Nutrim-10 suspension exhibited a power-law behavior scaling linearly with time, which was similar to the behavior for a homogeneous aqueous glycerol solution. But the MSD distribution was wider and more asymmetric than for glycerol. Increasing Nutrim-10 concentration rendered the MSD distribution much more asymmetric and skewed. This study provided a quantitative method to characterize the organization of Nutrim-10 in suspension.