Crosslinked starch-coated cellulosic papers as alternative food-packaging materials

In general, during the papermaking process or the production of cellulosic materials for food-packaging applications, lignin and other amorphous components are usually removed via the pulping and multilevel bleaching process to entirely separate them from the fiber. The aim of this work was to study the positive effect that can impart the residual lignin remaining in the alkali-treated fiber surface over bleached fibers to produce an alternative food-packaging cellulosic paper. Herein, cellulosic papers based on alkali-treated and bleached fibers obtained from the Alfa plant were successfully prepared using a compression process. The as-obtained papers were coated by crosslinked starch using a solvent-casting method to improve their mechanical and surface properties. The morphological and contact angle results showed that the residual lignin in the alkali-treated cellulosic papers strongly increased the interfacial adhesion by making the structure denser and more compact, resulting in an improved water resistance property over the bleached ones. On the other hand, it also promoted char formation, slowing down the burning process, resulting in better flame resistance. Additionally, the mechanical properties demonstrated that the presence of lignin contributed to the material rigidity improvement without compromising its flexibility (folding endurance). The as-developed cellulosic papers coated with crosslinked starch could be used for the production of high-quality materials for food-packaging applications using conventional industrial processes.