| The mechanism of inactivation on spores and its application have always been a severe challenge and an important topic faced by the food industry.Non-thermal sterilization technology has become the focus of research and development of new sterilization technology.B.cereus are reported to be seriously polluted in cereals,dairy products and other foods,while the B.cereus spores are highly resistant to harsh conditions.Therefore,it is necessary to develop effective,non-toxic and environmentally friendly sterilization methods to reduce or even inactivate spores.In recent years,the application of cold plasma in non-thermal sterilization has developed rapidly and plasma activated water(PAW)has the advantages of high sterilization efficiency and convenient operation.Therefore,in this study,the inactivation effect and mechanism of plasma activated water on B.cereus spores was investigated,as well as the application of this technology in rice sterilization by using the knowledge of mathematical model,electron microscope imaging technology,fluorescence imaging technology and other fields,and the effects of PAW on the texture quality and sensory quality characteristics of rice(Oryza sativa L.ssp.japonica)by using texture analyzer and sensory evaluation methods.The main research results are as follows:(1)The inactivation effect of PAW on B.cereus spores under different conditions such as temperature,initial spore concentration,organic matter(BSA)content and activated volume was studied through inactivation curves and kinetic models.The inactivation curves were fitted by Linear,Weibull and Log-logistic models,respectively.The results showed that PAW obtained by treating sterile water with plasma equipment at 650 W power for 1min could achieve a killing effect of 2.96 log10CFU/m L by treating on B.cereus spores for 60 min.Treatment temperature,initial spore concentration,organic matter content and activated volume would significantly affect the inactivation efficiency of PAW on B.cereus spores.Log-logistic model was suitable for fitting the inactivation curve of PAW to B.cereus spores under different conditions.(2)To study the mechanism of inactivation of B.cereus spores by PAW,the changes of spore structure were investigated via the changes of the concentration of DPA,nucleic acid and protein,as well as electron microscope images and fluorescence images of B.cereus spores.The results showed that the structure of spore outer wall,outer membrane,inner membrane could be destroyed in the process of inactivation of B.cereus spores by PAW.The destruction of B.cereus spore inner membrane might directly lead to the death of spores,and the degree of destruction increased with the increase of treatment temperature.(3)The inactivation effect of PAW on B.cereus spores that inoculated the rice under different solid-liquid ratio and temperature conditions was studied.At the same time,the influence of PAW on the tasty of rice was studied according to the texture and sensory indexes.The results showed that PAW obtained by treating sterile water for1 min with plasma equipment at 650 W power could achieve a killing effect of 2.11log10 CFU/m L by treating rice inoculated with B.cereus spores for 60 min,and the killing rate reached more than 99.9%.The ratio of material to liquid and temperature had significant effects on the inactivation of B.cereus spores on rice of PAW(p < 0.05).Therefore,appropriate sterilization parameters should be selected in practical application to obtain better sterilization effect.The results of texture and sensory analysis of rice treated with PAW were close to those of the control group.It could be seen that PAW treatment had no significant effect on the texture and sensory quality of rice suggesting that PAW has a great potential in inactivation of B.cereus spores in rice. |
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