Active coatings for paper-based food packaging: A review of bioactive compounds from agro-industrial by-products and marine algae

Packaging plays a crucial role in food preservation by protecting products throughout processing, distribution and storage. Although petroleum-based plastics dominate the sector due to their functionality and convenience, their persistence in the environment has intensified the search for sustainable alternatives. Paper-based packaging has gained attention owing to its biodegradability, recyclability, and versatility; however, its hydrophilic nature and limited barrier properties remain significant constraints for broader food-related applications. To address these limitations, bio-based surface coatings have emerged as an effective strategy to enhance barrier performance while maintaining the sustainability profile of paper substrates. This review examines advances in bio-based active coatings for paper-based food packaging, with a particular focus on bioactive compounds derived from agro-industrial by-products and marine resources. Agro-industrial residues such as peels, pomace, and seeds provide polysaccharides, proteins, pigments, and phenolic compounds that support circular economy strategies through waste valorisation. Marine organisms, especially seaweeds and microalgae, offer sulphated polysaccharides, amino acids, and metabolites with antioxidant and antimicrobial activities that can further strengthen functional performance. By integrating these terrestrial and marine-derived compounds into coating formulations, promising opportunities arise to enhance barrier, antioxidant, and antimicrobial functions in paper packaging. This review synthesises current knowledge on coating materials, bioactive incorporation strategies, functional outcomes, and regulatory considerations. Overall, it highlights the potential of bio-based active coatings to overcome key limitations of paper substrates while contributing to more sustainable and environmentally responsible food packaging systems.