2-hexenal--z-isomer and carvacrol

The aim of this work was to investigate the modifications of cell membrane fatty acid composition and volatile molecule profiles of Listeria monocytogenes, Salmonella enteritidis, Escherichia coli, during growth in the presence of different sub-lethal concentrations of thyme and oregano essential oils as well as carvacrol, thymol, trans-2-hexenal and citral. The results evidenced that the tested molecules induced noticeable modifications of membrane fatty acid profiles and volatile compounds produced during the growth. Although specific differences in relation to the species considered were identified, the tested compounds induced a marked increase of some membrane associated fatty acids, particularly unsaturated fatty acids, trans-isomers, and specific released free fatty acids. These findings can contribute to the comprehension of the stress response mechanisms used by different pathogenic microorganisms often involved in food-borne diseases in relation to the exposure to sub-lethal concentrations of natural antimicrobials.

Topics: Acyclic Monoterpenes; Aldehydes; Anti-Infective Agents; Cell Membrane; Cymenes; Dose-Response Relationship, Drug; Escherichia coli; Fatty Acids; Listeria monocytogenes; Monoterpenes; Oils, Volatile; Origanum; Plant Oils; Principal Component Analysis; Salmonella enteritidis; Thymol; Thymus Plant

The ability of trans-2-hexenal, carvacrol and eugenol to control F. verticillioides was explored in vitro and in artificially infected kernels. The effect of the trans-2-hexenal fumigation on F. verticillioides control, fumonisin production and kernel germination was also investigated in naturally infected kernels. Trans-2-hexenal, carvacrol and eugenol vapour showed fungicidal activity against F. verticillioides, in in vitro trials. Trans-2-hexenal was the best pathogen inhibitor, followed by carvacrol and eugenol. In maize kernels, fumigations with trans-2-hexenal provided a high inhibitory effect on F. verticillioides growth and its efficacy depended on concentration and time of incubation. The most effective dose of trans-2-hexenal was 369 microL/L, but this concentration induced off-odour in maize. The exposure to 246 microL/L trans-2-hexenal provided the best control of F. verticillioides and no phytotoxic symptoms or off-odour in kernels was observed. In contrast trans-2-hexenal fumigations were ineffective in the reduction of fumonisin concentration and high concentration (369 microL/L) stimulated fumonisin levels. Reduction or delay in the germinability of the kernel was observed after trans-2-hexenal exposure. The results showed that trans-2-hexenal postharvest fumigation is effective in F. verticillioides control also in asymptomatic maize kernels, but cannot reduce fumonisin production.

Topics: Aldehydes; Antifungal Agents; Cymenes; Eugenol; Food Contamination; Food Microbiology; Food Preservation; Fumonisins; Fusarium; Germination; Monoterpenes; Zea mays