Rheology of Gelatinised Starch Suspensions

Abstract

When starch powders are mixed with water and heated at or above the gelatinisation temperature, the granules absorb large quantities of water and form a viscous paste. The gelatinised pastes are shear‐thinning fluids, whose flow curves fit the expression n̈=kγm over a wide range of shear rates. Behaviour at very low shear rates indicates the existence of a yield stress. Under oscillatory shear the elastic moduli of the pastes considerably exceed the loss moduli, and both show only weak dependence on frequency over the range 0.002‐2.5 Hz. The apparent viscosities, pseudoplasticity constants, yield stresses and elastic moduli of the pastes are all concentration dependent, assuming significant values only when the starch level exceeds a minimum concentration. In many cases this threshold concentration corresponds closely to the point at which the volume of flocculated swollen starch granules just fills the total volume of the system.

Network development during shear-thickening in semidilute solutions of gently solubilized starches

“…For each solution an oscillatory shear experiment was first conducted using frequencies from 0.01 to 10 The starch solutions were prepared at a concentory shear experiment was conducted to probe the tration of 0.020 g/mL. This concentration is suffistructure formed during the thixotropic loop exciently high to place the solutions into the semidiperiment.…”

Rheological behaviour of low moisture molten maize starch

“…The rheology of starch in solution or in the presence of a large amount of water has been well studied: coaxialcylinder rheometers are often used to define the viscosity of aqueous dispersions of native [6,7] or transformed products [8]. The theological behaviour of cereal doughs (over 50% water content, at low temperature) has been determined using capillary rheometry or viscometer dies [9,10].…”

Effect of hydrothermal treatment on the physical and rheological properties of maize starches

“…These flow curves are typical of a non-newtonian shear-thinning fluid with a yield stress as described by Evans and Haisman (1979) and Doublier …”