A new study of starch gelatinization under shear stress using dynamic mechanical analysis

A new technique for studying starch gelatinization under shear stress using dynamic mechanical analysis (DMA) with shear sandwich mode is reported. Rice starch was used as the model material in the experimental work. The physical meaning of storage modulus G^′, loss modulus G^′′ and tangent of the phase angle tan δ, measured during starch gelatinization, is discussed. The effects of various factors, such as sample preparation and measurement conditions, on the measured results are discussed. A sharp peak of tan δ was detected during heating starch, which well represents the starch gelatinization process under shear stress. Comparison between the results detected by DMA and differential scanning calorimetry was used to interpret the processes and mechanisms of starch gelatinization. Results showed that variations in physical properties occurred both before thermal transition started and after thermal transition was complete. DMA has proved to be a convenient technique to study starch gelatinization under shear stress. One of the important advantages of this technique is it can be used to study starch gelatinization at low moisture contents (≤50%) under shear stress.