Effect of Whey Protein Isolate and Carnauba Wax Bilayer Coatings on the Barrier Properties of Cellulose-Based Materials for Food Packaging Application

Paper-based food packaging materials offer the advantages of renewability and biodegradability. However, their inherent porous structure and the hydrophilic nature of cellulose limit their resistance to water, water vapor, gas, and grease. This study presents a novel solution: a bio-based bilayer coating using whey protein isolate (WPI) and carnauba wax (CW), successfully applied to standard paper substrates using a rod coater. We investigated the effects of WPI and CW to determine their impact on the barrier and mechanical properties of the coated paper. Results demonstrated a significant improvement in grease/oil resistance, as measured by a 99.7% increase in hydrophobicity. Additionally, water vapor permeability was reduced by an impressive 97.7%, and air permeability reached 0 mL/min. To enhance flexibility, glycerol was added as a plasticizer within the WPI formulation, resulting in improved elongation at break values for the coated papers. The viscosities of both the WPI and CW coating solutions exhibited good processability, suggesting potential suitability for scaling up to industrial processes. Finally, scanning electron microscopy and contact angle measurements confirmed the uniformity of the paper’s coated layer and strong interlayer adhesion, which are crucial factors for effective barrier performance.