Influence of Degree of Protein Aggregation on Mass Transport Through Wheat Gluten Membranes and Their Digestibility—An In Vitro Study

ABSTRACT The influence of the network structure of wheat gluten on the barrier properties against enzymes was investigated in vitro. The changes in the network structure were introduced by different temperature treatments. The modifications were assessed with solubility studies of wheat gluten proteins in sodium dodecyl sulfate (SDS). The physical barrier properties of wheat gluten membranes were investigated with transport studies examining the transfer of a model protein with no enzymatic activity (BSA) through gluten membranes. The protein network was an effective barrier for BSA, although lightly cross‐linked films were mechanically instable. Membrane breaks occurred in function of the cross‐linking density (percentage of SDS‐insoluble proteins) after only 24 hr for lightly cross‐linked films (≈30% SDS‐insoluble proteins), while highly cross‐linked membranes (≈80% SDS‐insoluble protein) were tight up to more than 33 days. The digestion experiments of the gluten films with pepsin showed that the hydrolysis of wheat gluten films with >72% of SDS‐insoluble protein was significantly retarded. In conclusion, technological treatments to increase the cross‐linking density of gluten have the potential to slow the digestion of cereal‐based foodstuff and to reduce the degradation rate of composite biomaterials.