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

Abstract

Combination of plant extracts with mild heat treatment is a promising strategy to provide a microbiologically and chemically safe food product. In this study, we evaluated the antimicrobial activity of ethanolic clove extract against Escherichia coli O157:H7 in nutrient broth, buffer, and tomato juice. E. coli O157:H7 was most sensitive to ethanolic clove extract in nutrient-deficient media, while demonstrating 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 compared to 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 minutes achieved a 5-log reduction to the E. coli population. Our findings present a potential hurdle technology against E. coli O157:H7 in tomato juice processing, employing a combination of naturally sourced antimicrobials from clove and mild heat treatment. This approach can be effectively adopted by large-scale industries to small-scale local juice vendors to ensure the safety of tomato juice products.