Development of a sprayable antimicrobial formulation using hydrophobic yeast for one-step deposition on plastic surfaces and prevention of bacterial cross-contamination of baby spinach

Microbial cross-contamination of fresh produce poses a significant safety risk in both pre and postharvest environments. In this study, a sprayable, bio-based antimicrobial formulation was developed using hydrophobic yeast cells (hYC) to reduce the surface-mediated cross-contamination of fresh produce with bacteria. The results illustrated that chlorinated hYC (hYC@Cl) particles were uniformly distributed on plastic surfaces using the one-step spray-coating method, and hYC@Cl-coated surfaces exhibited strong antimicrobial activities against both Gram-negative (Escherichia coli O157:H7) and Gram-positive (Listeria innocua) bacteria (> 5 log reductions in 5 min). The antimicrobial activities are attributed to the formation of stable N-halamine in the hYC. In addition, hYC@Cl-coated surfaces exerted significantly (p < 0.05) enhanced mechanical resistance against dry abrasion compared to plastic surfaces coated with less hydrophobic yeast-based formulations, and the antimicrobial activities were retained on the surfaces even after 30 dry abrasion cycles (480 single passes with a dry sponge). Based on the simulated cross-contamination test, hYC@Cl-coated surfaces effectively inhibited the surface-mediated cross-contamination of baby spinach leaves, and no E. coli O157:H7 cells were transferred to fresh spinach leaves (detection limit: 0.4 log CFU/cm²). The novel antimicrobial formulation developed in this study can be easily deposited without the use of extrinsic binders or extensive modification of the food contact surfaces. Overall, findings in this study suggest the potential of hYC-based antimicrobial formulation in reducing the microbial cross-contamination of fresh produce, thereby enhancing the microbial safety of fresh produce handling environments.