Glass transition temperatures of a ready to eat breakfast cereal formulation and its main components determined by DSC and DMTA

摘要

The effect of water content on the glass transition temperatures of a ready to eat cereal formulation was determined, as well as for its major components, oat flour, rice flour and an oat-rice flour blend, in the same ratio as they are present in the formulation. All samples were compression moulded at high temperature and were moisture conditioned in a 10-22% interval (dry basis). Glass transition temperatures (T_g) were measured by differential scanning calorimetry (DSC) and the main mechanical relaxation temperatures (T_(alpha)), measured by dynamic mechanical thermal analysis (DMTA). The relaxation temperatures taken at tan delta peaks, were found 20-30 °C larger than T_g. Besides the plasticizing effect of water adequately described by the Gordon-Taylor equation, no differences of T_g (and T_(alpha)) values between the major components were obtained at a constant moisture content. The T_g and T_(alpha) values of the RTE formulation were found to be about 30 °C lower than its components, a result which was attributed to the plasticizing effect of the minor components in the formulation (sugar and malt extract).