Transglutaminase as an Enzymatic Crosslinker of Protein-Based Thermoformed Bioplastics

Abstract The packaging industry needs to develop new materials to replace conventional plastics. This is where bioplastics, primarily derived from biopolymers such as proteins, come into play in addressing this problem. However, given their overall mechanical properties, cross-linking methods are needed to improve their performance compared to synthetic counterparts. Thus, this article proposes the development of bioplastics using pea protein as a biopolymer and glycerol as a plasticizer in different ratios (60/40 and 70/30), and incorporating transglutaminase as a natural cross-linking agent (0.25% and 0.50% concentrations), using compression molding as a processing technique for the development of prototypes. Therefore, the mechanical, thermal, optical, physicochemical, and functional properties were analyzed, demonstrating, first of all, the obtention of a material with a glass transition temperature of approximately 65–70 °C lower than that of conventional plastics such as PET. In this way, the materials showed an improvement in flexural properties (obtaining an elastic modulus of 1–2 MPa), at the expense of a deterioration in tensile tests (with a Young’s Modulus of 20–30 and 45–50 MPa for the 60/40 and 70/30 formulations, respectively). Similarly, opacity was increased by incorporating the enzyme into the formulation, highlighting its role in the 70/30 formulation with 0.50% of the enzyme. Moreover, this enzyme also reduced the water absorption capacity by approximately 13%. This demonstrates the potential application of this type of material in dry product packaging, which maintains its properties after a period of 125 min with a moisture content of 3–5%, highlighting its viability for the development of more environmentally responsible packaging solutions.