Antimicrobial coating for reusable produce-handling cardboard containers using clay complexed with a quaternary ammonium compound (QAC)

Bacterial cross-contamination of porous, reusable food packaging materials, such as cardboard, presents significant food safety challenges. Here, a novel antimicrobial coating system was developed using a combination of kaolin and benzalkonium chloride (BAC) for reusable cardboard boxes. A stable kaolin and BAC complex (kaolin@BAC) was formed through methoxylation of kaolin, followed by interactions between methoxylated kaolin and BAC, and uniformly deposited on the cardboard surface via a one-step paint-coating method. The kaolin@BAC-coated cardboard surface exhibited strong antimicrobial activities against bacterial cells and achieved > 4-log reductions of Listeria innocua and Escherichia coli O157:H7 cells within 15 min. The storage test revealed that the antimicrobial activity of the kaolin@BAC coating was retained for at least two weeks. Furthermore, the kaolin@BAC-coated cardboard significantly reduced the risk of produce-mediated cross-contamination, and only ca. 1.3 (detection limit) – 1.6 log CFU/cm² of L. innocua cells were enumerated from the coated surface after repeated exposure to contaminated cherry tomatoes, whereas ca. 3.8–4.4 log CFU/cm² of L. innocua cells were enumerated from non-coated cardboard surfaces. These findings highlight the potential of kaolin@BAC coatings as an effective strategy for reducing the bacterial cross-contamination of reusable food packaging materials, thereby enhancing the microbial safety of the food supply chain.