Development and characterization of bio-based composite films with matcha powder: Impact of matcha concentration and glutaraldehyde crosslinking on properties

The growing demand for sustainable packaging solutions has led to the development of biodegradable materials with improved functionality. In this study, polyvinyl alcohol (PVA) and sodium caseinate (NaCAS) were blended with glycerol as a plasticizer to produce a biodegradable film matrix. Matcha tea (MT) powder was then incorporated into this matrix at varying concentrations (1%, 2%, 5%, 10 wt%) as a natural antioxidant and antimicrobial agent. To enhance structural performance, glutaraldehyde (GLA) was used as a cross-linking agent. The non-crosslinked and GLA cross-linked PVA/NaCAS/MT films were then evaluated based on their morphological, mechanical properties (tensile strength, elongation at break, Young’s modulus), water solubility, antioxidant capacity (DPPH and ABTS assays), and antibacterial activity against Escherichia coli and Staphylococcus aureus . The results showed that increasing the MT content enhanced the antioxidant capacity of the films, while GLA cross-linking suppressed this. Additionally, both MT incorporation and GLA cross-linking resulted in a decrease in mechanical strength and flexibility. On the other hand, the cross-linking effect of GLA was proven through a water solubility test. According to the antibacterial activity test, PVA/NaCAS/MT films didn’t exhibit bacterial inhibition under test conditions. After the GLA cross-linking, all films showed antibacterial activity thanks to GLA. This study, which is the first investigation on the direct incorporation of MT into a polymer matrix, has generally proven the usability of MT as an antioxidant in food packaging films.