Phenolic Compound-Incorporated Sodium Caseinate Barrier Coatings for Paper Packaging

Abstract

Sodium caseinate (SC)-based barrier coatings containing tannic acid (TA) and ferulic acid (FA) were applied to paper substrates as biodegradable alternatives to synthetic polymer coatings. The objective was to evaluate the effects of phenolic compound type, phenolic compound loading, and coating weight on the structural, thermal, barrier, and mechanical properties of SC-coated papers and to establish suitable coating conditions for biodegradable paper-based packaging applications. FT-IR analysis indicated that TA and FA interacted with SC mainly through hydrogen bonding and other noncovalent intermolecular interactions, with no detectable evidence of ester bond formation under the investigated conditions. The addition of TA or FA shifted the thermal decomposition of the SC coating to a higher temperature range and improved air, grease, and water-related barrier properties. Barrier performance depended strongly on phenolic compound loading and coating integrity, with excessive TA loading causing surface cracking and reduced air resistance. All coated papers showed the maximum measurable oil resistance, and moderate increases in tensile strength were observed. These results suggest that TA- and FA-containing SC coatings are promising biodegradable barrier coatings for paper-based packaging, particularly for dry or grease-containing food applications requiring improved air and oil resistance.