Functional bioplastic films from cocoa shell cellulose and natural waxes: Toward sustainable active packaging

The development of sustainable packaging materials from agro-industrial by-products supports the transition to a circular bio-economy and offers a viable alternative to petroleum-based plastics. Cocoa shells (CS), a by-product from the chocolate industry, are an abundant source of cellulose with limited industrial use. In this study, cellulose was extracted from CS and chemically converted into carboxymethyl cellulose (CS-CMC), which was then used to formulate bioplastic films plasticized with glycerol or sorbitol. To overcome the intrinsic hydrophilicity of CS-CMC-based materials and enhance their functional performance for food packaging, natural waxes (beeswax and carnauba wax) were applied to the film surface via spray coating in different ratios. Structural and morphological analyses (FTIR, SEM) confirmed wax deposition and modification of surface properties. The coated films showed significantly improved water resistance (contact angle >125°), mechanical strength (up to 3.58 MPa), and reduced water vapor transmission. The optimal wax ratio (25:75 beeswax/carnauba) preserved the film biodegradability and cytocompatibility (HaCaT cells), and enhanced antioxidant activity, supporting their potential for active food contact applications. This work demonstrates a sustainable and scalable approach to valorize cocoa shell waste into biodegradable packaging films. The use of natural, food-safe waxes enables the design of active barrier films suitable for protecting moisture-sensitive food products, aligning environmental performance with practical packaging requirements.