Exploring the Effect of Microparticles in Enhancing the Functional Properties of Dairy Protein‐Based Coatings for Kraft Paper and Biodegradable Plates

ABSTRACT This study investigates the potential of microparticle‐reinforced dairy protein coatings for sustainable packaging applications, focusing on sodium caseinate and whey protein‐based coatings. Initial experiments on handmade lotus‐based paper identified optimal formulations: sodium caseinate with 1.5% microcellulose and whey protein with 1.5% casein microparticles. These coatings were then applied to biodegradable plates and kraft paper for comprehensive evaluation. Results showed significant improvements in key properties. For biodegradable plates, contact angles increased from 69.9° to over 90°, indicating enhanced hydrophobicity. Water absorption at room temperature decreased from 112.27% (uncoated) to 79.14% (casein coated) and 87.43% (whey coated). Oil absorption reduced from 15.05% to 10.69% and 14.66% for casein and whey coatings, respectively. Kraft paper samples demonstrated improved flame resistance, with burn rates decreasing from 5 (uncoated) to 2.027 (casein coated) and 1.923 mm/s (whey coated). Biodegradable plates showed excellent flame resistance, failing to propagate flames under standard testing conditions. Thermal analysis revealed slight alterations in degradation behaviour, while SEM imaging confirmed the formation of continuous coating layers. XRD analysis showed a reduction in crystallinity index from 77.996% to 73.415% (casein coated) and 72.582% (whey coated) for kraft paper. Importantly, soil burial tests demonstrated substantial biodegradation of all samples within 60 days, with kraft paper samples degrading to ~4%–5% of their original weight and biodegradable plates to ~15%–18%. This study highlights the potential of microparticle‐reinforced protein coatings in developing sustainable packaging solutions with enhanced performance and maintained biodegradability.