Developing eco-friendly coatings from natural materials for water-repellent and antimicrobial kraft paper

Moisture can lead to microbiological growth in paper packaging, which is commonly used in the packaging industry. To enhance its performance, especially in corrugated board for food packaging, microbial growth inhibition is crucial. This research focused on coating kraft paper with three natural components: chitosan (CS)-mixed styrene-acrylate resin, carvacrol (CAR)-mixed styrene-acrylate resin, and CS and CAR-mixed styrene-acrylate resin. The objective was to evaluate the coating's physical and mechanical properties, moisture level, and water resistance, as well as its antimicrobial effectiveness. A central composite design (CCD) with a D-optimal design was employed to determine the optimal coating composition. The results revealed that kraft paper coated with CS demonstrated better water resistance than CAR, while the mixture of CS and CAR showed the lowest water resistance. Microbial analysis demonstrated a reduction in total plate count from 240 CFU/g in uncoated kraft paper to 150 CFU/g with CS coating, further decreasing to 30 CFU/g with CAR coating. Antimicrobial resistance revealed that kraft paper coated with CAR demonstrated the strongest antimicrobial activity, while chitosan provided superior water repellency. The combination of both CS and CAR, mixed with resin, offered a balanced barrier against moisture and microbial contamination.