The results obtained suggest that polysaccharides generallyplay the role of fillers, which are able to interact with the pro-tein molecules in different manners depending on the proteincharge and their aggregation degree after bioplastic thermomoulding. However, biopolymers MC and CMC have a synergistic effect on the elongation properties of the protein based bioplastic materials,which suggests that polysaccharides might also play a plasticiserrole. Interestingly, polysaccharide incorporation not only enhances elongation but also leads to higher Young’s Modulus.Nevertheless, pH is the most relevant parameter that affectsthese protein-based materials. Their properties (e.g. Young’s Modu-lus, elongation, water absorption) strongly depend on the resultantprotein microstructure after being prepared at different pH values.Thus, low pH hinders protein cross-linking and leads to mate-rials with small moduli, high water absorption and enhanced elongation capability. A pH value of 6 leads to materials withhigh cross-linking degree (due to disulphide bonds formation)with high moduli and low elongation and water absorption abil-ity. Finally, alkaline pH induces negative charges on proteins and also promotes the formation of lysinoalanine, lanthionineand dehydroalanine-derived cross-links stimulated at the selected moulding temperature (130◦C). Both of them influence protein aggregation and lead to materials with high moduli as well as lowerelongation at break and lower water absorption than pH 3 but higher than those obtained at pH 6.In addition, polysaccharide incorporation slightly affects mate-rial hydrophilic character. As a result, bioplastic formulation at pH 3 and pH 9 would lead to materials to be used in application srequiring enhanced water absorption capacity and suitable end-usemechanical properties.