Processing and Formulation Strategies for PFAS-Free Food Packaging: Nanocellulose–Natural Wax Hybrid Coatings for Barrier Applications

The environmental impacts of fossil-based plastic food packaging and the use of grease-resistant coatings containing per- and polyfluoroalkyl substances (PFAS) are driving the development of bio-based and fluorine-free alternatives. Nanocellulose and natural waxes are promising components for PFAS-free barrier coatings, but their performance depends strongly on how they are produced, formulated, deposited, and dried. Nanocellulose provides excellent oxygen-barrier performance, particularly under dry conditions, whereas natural waxes contribute primarily to moisture and grease resistance. Their combination can therefore provide complementary barrier functions, while also introducing challenges related to dispersion, interfacial compatibility, crystallization, and coating uniformity. This review critically examines the replacement of PFAS-based coatings on food paper packaging with formulations derived from nanocellulose and natural wax. The material selection and processing strategies are addressed in relation to component structure, formulation, and performance. Key contributions, compared to previous studies, include an explanation of how the combination of nanocellulose, natural waxes, and complementary barrier materials meets the diverse functional requirements of food packaging. Likewise, the study examines how formulation parameters and processing conditions can determine interfacial compatibility, coating morphology, and barrier performance. Particular attention is given to natural wax processing, including dispersion and emulsion formation, and to formulation parameters that control interfacial interactions, coating structure, surface morphology, and barrier performance. Coating and deposition methods, drying and film formation, and the effects of processing conditions on oxygen, moisture, and grease resistance are evaluated. The review also addresses mechanical performance, sustainability and end-of-life considerations, process scale-up, economic aspects, and compatibility with industrial coating technologies. Overall, nanocellulose–wax hybrid systems offer a promising processing platform for application-specific PFAS-free barrier coatings, although further optimization and validation under realistic food-packaging conditions are required for industrial implementation.