Effect of additives on the thermo-mechanical behaviour of dough systems at sub-freezing temperatures

Abstract

The aim of this study was to examine the effects of different additives, ascorbic acid, α-amylase, protease, hemicellulase, gluten, and gum guar, on thermo-mechanical dough properties at sub-freezing temperatures as measured by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMA). The DSC thermograms showed that dough with a combination of ascorbic acid and hemicellulase had greater amount of water unable to crystallize and a lower co-operativity in ice-melting transition, indicating more polymer–water interactions. DMA studies permitted identification of three peaks, which were related to the ice melting, α-relaxation and β-relaxation. α-transition occurred over a temperature range of ∼40 °C and the ascorbic acid and their combination with hemicellulase, amylase, protease and gum guar increased temperature transition. An increment of the matrix viscosity due to higher number of inter- and intra-molecular interaction caused by oxidation of gluten proteins (ascorbic acid), and the increment of aggregated solid or generated molecules in the unfrozen phase could explain the increment in this transition.