Production and Characterization of Collagen-Based Film with Natural Oil and Zinc Oxide

The leather sector generates substantial quantities of protein-rich residues, and converting these residues into value-added products is crucial for sustainability, environmental and human health, and the circular economy. For this purpose, collagen hydrolysate (CH) was produced from trimming residues of the leather sector via bromelain-mediated enzymatic hydrolysis, and films incorporating nano zinc oxide (ZnO) and Calendula officinalis L. (CO) essential oil were fabricated and subsequently characterized. In this study, prior to enhancing the functional properties of CH-based films, one of their primary limitationswater barrier performancewas addressed by producing CH/ZnO films containing 0–4% ZnO nanoparticles, identifying CH/ZnO(2%) as the optimal formulation; at this fixed ratio, CH/ZnO(2%) films were enriched with CO essential oil at 2%, 4%, 6%, and 8% to prepare CH/ZnO/CO films, which were subsequently characterized. In general, the results show that CH/ZnO/CO-based environmentally friendly and sustainable films obtained from leather industry trimming wastes are promising in terms of applicability to packaging materials.