THE FLOW PROPERTIES OF NATIVE, HEAT-MOISTURE TREATED, AND ANNEALED STARCHES FROM WHEAT, OAT, POTATO AND LENTIL

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Abstract
The effect of heat‐moisture treatment (30% moisture, 100C, 16 h) and annealing (75 % moisture, 50C, 72 h) on the flow behavior of gelatinized starch pastes from wheat, oat, lentil and potato starches were studied at a concentration of 6% starch with a cone and plate viscometer (Wells Brookfield RVTDV II CP 200). The power law rheological model (σ=Kγn) was used to describe the flow behavior of the above starch pastes. All native starches exhibited a non‐Newtonian shear thinning behavior. A thixotropic loop was evident only in oat starches and native potato starch. Among native starches, the magnitude of the shear thinning index (n) followed the order: oat > wheat > lentil > potato, while the corresponding order for the consistency index (K) was: potato > lentil > wheat > oat. Heat‐moisture treatment decreased the K value of all starches. On annealing, K decreased in wheat and lentil starches, but increased in potato and oat starches. Heat‐moisture treatment and annealing increased the n value of wheat, lentil and potato starches, but decreased that of oat starch. In all starches, the modification to the flow behavior was more marked on heat‐moisture treatment than on annealing.