Inactivation of Escherichia coli O157:H7 in tomato juice by combined treatment of ethanolic clove extract and mild heat

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The combination of plant extracts with mild heat treatment is a promising strategy for obtaining microbiologically and chemically safe food products. In this study, we evaluated the antimicrobial activity of ethanolic clove extract against Escherichia coli O157: H7 in nutrient broth, buffer, and tomato juice. Clove extract at 0.4% concentration showed significant E. coli O157: H7 population reduction in all media tested. E. coli O157: H7 was most sensitive to the ethanolic clove extract in nutrient-deficient media but demonstrated relative resistance in nutrient-rich media and tomato juice. Moreover, we evaluated the potential of clove extract as a preservative in tomato juice stored at cold storage temperatures of 4 °C and 15 °C. The clove extract exhibited stronger inhibitory effects against the pathogen in tomato juice stored at 15 °C than at 4 °C. Additionally, we assessed the antimicrobial efficacy of clove extract in combination with mild heat treatment against E. coli O157: H7 in tomato juice. The combined treatment of 0.05% clove extract with mild heat at 60 °C for 30 min achieved a 5-log reduction in the E. coli population in tomato juice. Our findings present a potential hurdle technology against E. coli O157: H7 in tomato juice processing by employing a combination of naturally sourced antimicrobial agents from clove and mild heat treatment. This approach can be effectively adopted by large-scale industries and small-scale local juice vendors to ensure the safety of tomato juice products.