The influence of 11 kinds of oxygen-containing sulfur flavor molecules was examined on β-carotene stability under UVA irradiation in ethanol system. Both the effects of sulfides on dynamic degradation of β-carotene and the relation between structure and effect were investigated. The oxidation products of β-carotene accelerated by sulfides under UVA irradiation were also identified. The results indicated that the disulfides had more obvious accelerative effects on the photodegradation of β-carotene than mono sulfides. The degradation of β-carotene after methyl (2-methyl-3-furyl) disulfide (MMFDS), methyl furfuryl disulfide (MFDS) and bis(2-methyl-3-furyl) disulfide (BMFDS) exposure followed first-order kinetics. Furan-containing sulfides such as MMFDS and BMFDS showed more pronounced accelerative effects than their corresponding isomers. The oxidation products were identified as 13-cis-β-carotene, 9,13-di-cis-β-carotene and all-trans-5,6-epoxy-β-carotene. These results suggest that both the sulfur atom numbers and the furan group in oxygen-containing sulfides play a critical role in the photooxidation of β-carotene.
Vibrio parahaemolyticus is a food-borne pathogenic microorganism that commonly exists in aquatic products. In this study, the antibacterial activities of benzyl isothiocyanate (BITC) against V. parahaemolyticus were investigated by both transcriptomic analysis and morphological verification. Treatment with 1/8 minimum inhibitory concentration (1/8 MIC) BITC resulted in 234 upregulated genes and 273 downregulated genes. We selected six virulence genes that were significantly downregulated and verified them using quantitative real-time reverse transcription-polymerase chain reaction. The verification results revealed that the relative expression levels of the six genes VP0820, VP0548, VP2233, VPA2362, fliA and fliG were only 31.0%, 31.1%, 55.8%, 57.0%, 75.3%, and 79.9% of the control group, respectively. Among them, genes VP2233, fliA and fliG are related to flagella and VP2362 can regulate a protein relevant to biofilm formation. Morphologically, we verified that the swimming diffusion diameter of V. parahaemolyticus was significantly reduced by 14.9%, and biofilm formation was significantly inhibited by treatment with 1/8 MIC BITC. These results indicated that 1/8 MIC BITC had antibacterial effect on V. parahaemolyticus by inhibiting virulence gene expression related to flagella and biofilm. These findings are helpful to further elucidate the bacteriostatic mechanism of BITC on V. parahaemolyticus and other food-borne pathogens.
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