This study investigated the fungicidal efficiency and mechanism of action of dielectric barrier discharge cold atmosphere plasma (DBD-CAP) in inactivating Aspergillus niger ( A. niger ) spores. The disinfection efficacy and quality of dried jujube used as the processing application object were also studied. The results indicated that the Weibull + Tail model performed better for spore inactivation curves at different voltages among various treatment times, and the spore cells were reduced by 4.05 log (cfu/mL) in spores suspension at 70 kV after 15 min of treatment. This disinfection impact was further supported by scanning electron microscope (SEM) and transmission electron microscopy (TEM) images, which showed that the integrity of the cell membrane was damaged, and the intracellular content leaked out after DBD-CAP treatment. Elevated levels of reactive oxygen species (ROS) during the treatment increased the relative conductivity of cells, and leakage of nucleic acids and proteins further supported the disinfection impact. Additionally, the growth and toxicity of surviving A. niger spores after treatment were also greatly reduced. When DBD-CAP was applied to disinfecting dried jujube, the spore number exhibited a 2.67 log cfu/g reduction after treatment without significant damage observed onto the quality ( P > 0.05 ).
Yuhang Du,Shuna Mi,Huihui Wang,Fangwei Yang,Hang Yu,Yunfei Xie,Yahui Guo,Yuliang Cheng,Weirong Yao
Fresh wolfberry is a super fruit with excellent nutritive and medicinal values, but highly perishable and difficult to store. In this research, dielectric barrier discharge plasma (DBD) was used to control the spoilage and mycotoxin of Alternaria alternata ( A. alternata ), which frequently and heavily contaminated fresh wolfberries. Results showed that DBD treatment could inactivate A. alternata with a maximum reduction of 2.26 log CFU/mL (700V,480s). Its spore inactivation behavior most fitted the Log-logistic model (R 2 > 0.993). DBD disrupted A. alternata cell membrane integrity, oxidized membrane-associated substances and increased membrane permeability. The reactive oxygen species produced by DBD caused the accumulation of reactive oxygen metabolites in the spores and the inhibition of antioxidant enzyme activity. The average content of four mycotoxins on wolfberries could be reduced by 62.84% after the 60s treatment and storage for 6 days, while the decay rate decreased by 30.66%, and the firmness, TSS and DPPH free radical scavenging increased by 11.07%, 5.88% and 19.20%, respectively. Therefore, DBD could be used as a new technology to inactivate A. alternata , reduce its mycotoxin, and improve agricultural product quality.
Qing Wang,Rongxue Sun,Ning Jiang,Haojie Ren,Haibo Luo,Cheng Wang,Qianyuan Liu,Zhiqiang Li,Xingna Wang
Bacterial spores in food exhibit strong resistance to conventional processing methods, posing a significant challenge to food safety. This scientific aim of the study was to compare the antimicrobial effects of organic acids and plasma-activated lactic acid (PALA) on the specific spoilage bacteria (SSB) spores in cooked crayfish ( Procambarus clarkii ), and further explored the antimicrobial mechanism of PALA against Bacillus cereus spores. Plasma activation enhanced the antimicrobial efficacy of lactic acid (LA), as 1 % PALA showed equivalent antimicrobial efficacy to 1.5 % LA against spores. Microstructural changes and leakage of core contents indicated that PALA treatment caused damage to the inner membrane (IM) of B. cereus spores. Then, the spore germination experiments further revealed that PALA treatment disrupted the function of SpoVA proteins in the IM, leading to a significant decrease in spore germination capacity. Furthermore, inactivated spores did not regain viability after treatment with lysozyme or Ca-DPA, and no mutants were detected among the surviving spores. These results demonstrated that the inactivation effect of PALA on B. cereus spores is closely related to the structural disruption and dysfunction of the spore IM. Additionally, PALA treatment extended the shelf life and maintained the product quality of cooked crayfish, supporting PALA as a promising measure for controlling microbial safety.
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