Valorization of Food Industry Waste: Synthesis and Fabrication of an Antibacterial and Barrier Paper Coating from Pomegranate Polyphenol-Grafted Silane

Functional coatings are crucial for enhancing the performance of paper-based packaging materials. Unlike petroleum-based or conventional biobased coatings, which face environmental or performance limitations, this study presents a high-performance, sustainable paper coating that utilizes industrial byproduct pomegranate peel extract (PPe), KH-560, and oxidized starch (OS). A biobased silane coupling agent (PK) was synthesized via a ring-opening reaction between PPe and KH-560, as confirmed by FT-IR, ¹H NMR, and ¹³C NMR analyses. The resulting PK was compounded with OS to create a multifunctional coating (OS&PK). This coating endows paper with exceptional mechanical strength, outstanding barrier properties (against water, vapor, and oil), high thermal stability (>200 °C), and significant antibacterial activity (77% inhibition against S. aureus). Remarkably, the coating can be effectively removed, enabling paper repulping with minimal mechanical strength loss. Thus, this work offers a green, cost-effective coating strategy that combines enhanced performance with repulpability, while promoting the valorization of industrial byproducts.