Synergistic inactivation effect of ultrasound and nano-emulsified basil essential oil on the metabolic responses of Salmonella on sprouts

Abstract

This study investigated the effectiveness and mechanisms of ultrasound (US), nano-emulsified basil essential oil (NBEO), and their combination (NBEO_US) in inactivating Salmonella enterica cells inoculated on pea sprouts. The results demonstrated that the combined treatment was more effective than individual treatments in inactivating the target. This led to a decrease of 4.4 to 5.0 log CFU/g. Transmission electron microscopy showed that NBEO_US leads to the disruption of the bacteria morphology. Additionally, the leakage of cell constituents (proteins and nucleotide) demonstrated that NBEO_US disrupted the structural integrity of S. enterica cells. In addition, the metabolomics analysis using ¹H NMR showed that NBEO_US had a detrimental effect on energy and amino acid metabolism in bacterial cells, specifically affecting glycolysis and amino acid production. Also, NBEO_US affected the Embden-Meyerhof-Parnas pathway in S. enterica cells by decreasing the activity of hexokinase, phosphofructokinase, and pyruvate kinase. Finally, the application of NBEO_US resulted in a substantial (P < 0.05) increase in the hardness of the treated pea sprouts while simultaneously decreasing their lightness. The present investigation illustrated the synergistic antibacterial mechanism of NBEO_US against S. enterica strains using sprouts as a food model. By understanding the microbiological changes in metabolic pathways induced by the combined treatment, sanitization strategies can be optimized to specifically target critical vulnerabilities, thereby ensuring safer and more efficient production of fresh produce.