Effect of Carboxymethyl Chitosan and Genipin on the Structural, Water Uptake, and Thermomechanical Properties of Zein‐Based Biodegradable Materials

Zein is an insoluble prolamin protein extracted from different by‐products of the corn industry. More recently, the thermoplastic behavior and ability to melt when heated displayed by zein/glycerol blends (zein/Glycerol) have highlighted its use in versatile plastic thermal processing techniques. In this study, the effect of additives that may reinforce the resulting materials is examined. A water‐soluble chitosan derivative, carboxymethyl chitosan (CMCH), was included in zein/CMCH/Glycerol systems to assess the feasibility of complexation between zein and CMCH as a way to tune the hydrophilicity and mechanical properties of the material. Additionally, genipin (GNP), a natural cross‐linker, was added either to zein/Glycerol or zein/CMCH/Glycerol systems to reinforce the mechanical properties. In this context, Young's modulus ( E ) increased from around 16 to 40 MPa when GNP was added at 0.5 mM, while maintaining its water uptake (WUC) around 170%. The joint role of CMCH and GNP was only synergistic at low GNP concentrations (0.01 mM). However, at high GNP concentrations (0.5 mM), no enhancement of the mechanical properties was observed, despite the greater thermal resistance. Thus, the properties of zein‐based materials can be improved by selecting a suitable GNP concentration, which facilitates the development of bioplastics with specific applications.