NEW ANTIMICROBIALS BASED ON SYNERGISTIC INTERACTIONS BETWEEN PHYSICAL AND CHEMICAL STRESSORS

Abstract

Produce microbial contamination remains a U.S. food safety concern. Chlorine is widely used to clean produce, but has limited efficacy and poses health risks. This research therefore investigates two alternative antimicrobial treatments. First, inactivation of Listeria innocua using a combined zinc oxide (ZnO) and low-frequency ultrasound treatment was quantified. 40 mM ZnO sonicated for 8 minute reduced Listeria innocua populations 100,000-fold. The mechanism appeared to be Reactive Oxygen Species-mediated, and enhanced interactions between ZnO and bacteria facilitated by lowering of ZnO nanoparticle size by sonication. Second, medium-chain fatty acid (MCFA, C6, C8, C10) and mild heat (30-50 °C) treatment against Escherichia coli O157:H7 was observed. The combined treatment achieved more than 100,000 fold reduction in E. coli in solution and no significant impairment of sensory (texture, color) qualities was observed on tomatoes. Spinach treated using this treatment showed 100-fold less bacterial cross-contamination compared to treatment with water.