Effect of process temperature on gluten film properties

Gluten has been proposed as raw material to develop edible film formulation. Gluten based edible films are characterised by good mechanical and gas barrier properties but poor water vapour barrier properties. Process conditions influence final film structure and performances. In particular, heating treatment is supposed to improve protein reticulation. In this study, different temperatures from 30° to 85°C were used to prepare film forming dispersions with the aim of studying the influence of temperature on mechanical and water vapour barrier properties of edible films. Differences in mechanical and barrier properties of films were observed only for samples prepared at 30° and 85°C. Size Exclusion-HPLC was performed to study the effect of temperature dispersion on molecular properties of gluten based films. Protein size distribution seemed not to change when dispersion temperature increased, suggesting the absence of modifications in protein chains. Therefore, the different behaviours observed for film prepared at different temperature are not due to changes in gluten fraction on the basis of molecular weight. Probably, heating leads to a more homogeneous gluten network caused by the protein unfolding, to the increase in hydrophobic interactions and a better plasticizer distribution.