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The swelling of native starches and modified starches at moderate range of temperatures has a large effect on the rheological properties of starch suspensions and thus to their processing characteristics because the heating of these systems often involves non-isothermal regimes. The main objective of this work was to develop a model that is able to predict the swelling of modified starch granules under non-isothermal conditions using data collected from heating at isothermal conditions. Swelling of crosslinked corn starch granules suspended in distilled water was measured at several uniform temperatures between 50 and 70 °C. The results were fitted with the Weibull model log10 Y = −b (T)tn(T), where Y is defined as (De − Dt)/(De − D0), and Dt, D0 and De are the granules’ momentary, initial and equilibrium mean diameters, respectively, t is the time, and b(T) and n(T) are the two temperature dependent parameters of the model. Mathematical expressions were found to describe the temperature dependence of b(T) and n(T) and were used to construct a dynamic rate model able to predict the changing mean size of starch granules during non-isothermal heating. Comparisons of the predicted changes in granule size with those measured under a non-isothermal heating test were in good agreement. This demonstrated that isothermal swelling data could be used to predict swelling patterns under non-isothermal conditions. The findings of this research will have a broad impact on industrial applications because the model is able to predict starch granule swelling for heating conditions that are commonly encountered in industrial starch processes. |
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