Reductions in polycyclic aromatic hydrocarbon (PAH) concentrations have been observed during frying. However, transformation mechanisms of PAHs remain unclear. We hypothesize that PAHs may be oxidized into oxygenated polycyclic aromatic hydrocarbons (OPAHs) and other derivatives during frying. First, the levels of 24 PAHs and 12 OPAHs during frying stinky tofu were evaluated. Among the OPAHs, 9,10-anthraquinone exhibited the greatest increase in frying oil, with an increase rate of 55 %. The transformation of anthracene into 9,10-anthraquinone was further confirmed through stable isotope tracing. Targeted and untargeted mass spectrometry analyses suggested that anthrone, heavy PAHs, and alkyl derivatives were also produced from anthracene. Theoretical calculations revealed that radical addition was kinetically and energetically more favourable than hydrogen abstraction in the initial reaction of anthracene. This study systematically elucidates, for the first time, the transformation mechanisms of anthracene in frying oil, paving the way for reducing health risks associated with PAHs.
Lactiplantibacillus plantarum X7021 is a novel strain originated from the brine of stinky tofu. In order to investigate the application potential of the strain in food industry, the genomic characteristics as well as some metabolic features were studied using comparison genomics and transcriptional assay. The complete genome of X7021includes a 3,407,054 bp chromosome with 3259 protein coding sequences, and 6 plasmids. L. plantarum strains, WCFS1, JDM1, and ST-III were selected for comparative genomic analysis. Results revealed that X7021 is safe for the application in foods with less antibiotic resistance and virulence genes. The strain has 25 complete phosphotransferase system transporters and strong proteolytic system for its adaptability to various foodstuffs. The strain containes a complete purine metabolic pathway incorporating 4 permeases, resulting in the reductions of 38.9% guanine, 26.1% hypoxanthine and 70.2% xanthine during the soymilk fermentation. Soy isoflavone glycosides could be converted to corresponding aglycones by two β-glucosidases. The strain could grow in 700 mg/L nitrite and entirely degrade 100 mg/L nitrite during 24 h based on highly active nitrite transporter and nitrite reductase. Accordingly, the results suggest that L. plantarum X7021 is a prospect starter candidate for the fermentation of plant foodstuffs.
危险品化学品经营许可证（带存储）