Fungal contamination imposes threats to agriculture and food production and human health. A method to safely and effectively restrict fungal contamination is still needed. Here, we report the effect and mode of action of (E)-2-hexenal, one of the green leaf volatiles (GLVs), on the spore germination of Aspergillus flavus, which can contaminate a variety of crops. The EC 50 value, minimum inhibitory concentration (MIC), and minimum fungicidal concentration (MFC) of (E)-2-hexenal were 0.26, 1.0, and 4.0 μL/mL, respectively. As observed by scanning electron microscopy (SEM), the surface morphology of A. f lavus spores did not change after treatment with the MIC of (E)-2-hexenal, but the spores were shrunken and depressed upon treatment with the MFC of (E)-2-hexenal. The MIC and MFC of (E)-2-hexenal induced evident phosphatidylserine (PS) externalization of A. flavus spores as detected by double staining with Annexin V-FITC and propidium iodide, indicating that early apoptosis was potentially induced. Furthermore, sublethal doses of (E)-2-hexenal disturbed pyruvate metabolism and reduced the intracellular soluble protein content of A. flavus spores during the early stage of germination, and MIC treatment decreased acetyl-CoA and ATP contents by 65.7 ± 3.7% and 53.9 ± 4.0% (P < 0.05), respectively. Additionally, the activity of mitochondrial dehydrogenases was dramatically inhibited by 23.8 ± 2.2% (P < 0.05) at the MIC of (E)-2-hexenal. Therefore, the disruption of mitochondrial energy metabolism and the induction of early apoptosis are involved in the mechanism of action of (E)-2-hexenal against A. flavus spore germination.

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Plasma-activated liquid is a novel non-thermal antibacterial agent against a wide spectrum of foodborne bacteria, yet fewer studies focused on its disinfection of meat spoilage bacteria. In this study, the antibacterial properties of plasma-activated lactic acid (PALA) on Pseudomonas lundensis, isolated and identified from spoilage beef, were investigated. A plasma jet was used to treat lactic acid (0.05–0.20%) for 60–120 s. The results presented that the 0.2% LA solution treated with plasma for 120 s caused a 5.64 log reduction. Additionally, the surface morphology, membrane integrity and permeability were altered slightly and verified by scanning electron microscopy, double staining of SYTO-9 and propidium iodide, and a K+ test kit. The intracellular organization of the cells, observed by transmission electron microscopy, was damaged significantly. Increased intracellular reactive oxygen species (ROS) levels exceeded the antioxidant ability of glutathione (GSH), leading to a reduction in the activity of malate dehydrogenase (MDH), succinic dehydrogenase (SDH) and intracellular ATP levels. Metabolomics analysis indicated that the energy and synthesis of essential components, such as DNA and amino acid-related metabolic pathways, were disturbed. In conclusion, this research established a theoretical basis for the use of PALA in refrigerated beef preservation by shedding light on the bacteriostatic effect of PALA against Pseudomonas lundensis.