Consumers are driving food production toward the use of more organic antimicrobial agents such as essential oils (EOs) by demanding more natural and clean-label food products. Due to the strong aromatic and flavor properties of EOs, their use is often precluded, or limited to concentrations below the flavor threshold. However, adding EOs at concentrations this low often renders their biocidal activity ineffective. An opportunity exists for low concentrations of EO antimicrobial agents to be combined with mild heating (e.g., 42 to 55°C) for short treatment times to use the hurdle concept for additive or synergistic effects on foodborne pathogens such as Escherichia coli O157:H7, Salmonella, or Listeria monocytogenes; norovirus; and surrogate organisms. In some cases, especially with fruit juices, this intervention combination is described as antimicrobial-assisted pasteurization. Used below the organoleptic quality threshold, EOs, which otherwise would have little effect on the inactivation of foodborne pathogens, are effective antimicrobial agents when used in conjunction with mild thermal processes. Thermal processes combined with antimicrobial agents can be used for processing liquids, eggs, juices, drinks, and fresh produce. This review highlights research literature where antimicrobial agents and mild heating have been combined to increase the inactivation of foodborne pathogen populations. Commodities and testing substrates reviewed include buffers and nutrient broths, juices, liquid egg, mangoes, cut lettuce, cut and shredded cabbage, shredded carrot, baby spinach leaves, and salsa. Opportunities exist for the application of this hurdle technology to a whole array of food products, which could benefit from pathogen reduction or elimination, and to prevention of aqueous cross-contamination and/or internalization during the washing of fresh produce.
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