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Microbial pathogens e.g., S. aureus can survive and spread in food cold chain. Under low temperature, microbes develop resistance to common antibacterial agents. Thus, it is important to identify alternative strategies to control pathogens in food cold chain. In present study, we discovered that thymol, different from other tested essential oils, displayed improved ability to kill S. aureus under frozen condition (−20 °C). Time-killing kinetics showed that 99.99% S. aureus were killed after exposure to 100 μg/mL thymol within 6 h, and such bactericidal activity was maintained even after multiple cycles of freezing and thawing. In contrast to the ROS-dependent bactericidal mechanism at 37 °C, thymol killed S. aureus in a ROS-independent mode at −20 °C. The proteomic analysis supported that thymol killed S. aureus by directly destroyed the stability of cell membrane without intracellular biological responses. Under frozen condition, thymol efficiently prevented bacteria contamination in low-lipid foods without affecting the foods' hardness, chewiness, resilience, adhesiveness, springiness and cohesiveness. These findings uncovered a new mechanism of thymol-mediated bactericidal activity under frozen condition and suggested an alternative efficient strategy to control bacterial contamination in cold chain food. • Identified the best bactericidal ability of thymol at −20 °C. • Revealed the mechanism of thymol to eradicate S. aureus in a ROS-independent manner under low temperature. • Provided new insights into the strategy to combat S. aureus contamination in cold chain food. [ABSTRACT FROM AUTHOR]

The contamination of food with Aspergillus flavus has caused serious economic losses and posed a great threat to human and animal health. Cumin, a condiment and flavoring in many dishes, was showed to have great potential to prevent A. flavus contamination in the present study. By using cumin essential oil (CEO), the occurrence of A. flavus contamination on peanuts was prevented during the storage period even up to 9 months. We further identified cuminaldehyde as the predominant component in CEO with great inhibitory activity to both the growth of A. flavus and aflatoxin B 1 (AFB 1) biosynthesis. The data showed that the minimum inhibitory concentration (MIC) of cuminaldehyde to conidial growth was 0.64 μL/mL, and the mycelia exposed to 0.80 μL/mL cuminaldehyde reduced AFB 1 production by more than 99% in comparison to the control. RNA-Seq profiles showed that some genes, involving the synthesis pathway of ergosterol and AFB 1 , were significantly down-regulated in the transcription by cuminaldehyde. Further investigation confirmed a significantly reduced cellular ergosterol content in the presence of cuminaldehyde, and the qRT-RCR results were also in agreement with that by RNA-Seq, indicating down-regulated expressions of those genes involving ergosterol and AFB 1 synthesis. Taken together, our study strongly supported cuminaldehyde as a potential agent for the prevention of A. flavus contamination. • Cumin essential oil (CEO) prevented A. flavus contamination on peanuts. • Cuminaldehyde in CEO was responsible for its anti- A. flavus activity. • Cuminaldehyde induced A. flavus necrosis by reducing ergosterol content. • Cuminaldehyde directly turned down the gene expression involving AFB 1 biosynthesis. [ABSTRACT FROM AUTHOR]