The gelatinization behaviour of potato starch in an excess of water or solutions of sugars, other organic hydroxy compounds, or various inorganic salts was studied. The distribution of water and solutes between the external phase and the starch granules was measured by refractometry and a dye exclusion technique. When the limited water uptake of native starch granules is taken into account, the cooperative nature of gelatinization and the effect of water content on gelatinization behaviour can be explained solely on the basis of the Flory theory of polymer melting. Following the same argument, the effect of many solutes can be approximately described by the derived relationship between initial gelatinization temperature, water activity of the system and volume fraction of water in the granules.

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.

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