Casein films crosslinked by tannic acid for food packaging applications

Natural proteins are good candidates for producing food packaging films due to their excellent functional properties. However, some deficiencies as their poor water resistance need to be addressed before films can be used in daily applications. This article explores the use of a low-cost plant-derived phenolic compound, tannic acid, as crosslinking agent for producing plasticized casein films. FTIR, high-resolution NMR, and rheological measurements confirmed the crosslinking reaction between casein amine groups and tannic acid. The influence of crosslinking agent concentration on the mechanical and viscoelastic properties, thermal stability, swelling behavior, water vapor permeability, cytotoxicity and degradation in composting conditions were investigated. The obtained results showed that tannic acid was an effective crosslinking agent for casein protein, so the yielded films which exhibit improved physicochemical properties, can be employed for food packaging applications.