过热蒸汽对熟制小龙虾优势腐败菌的杀菌动力学及其机理

【目的】研究过热蒸汽杀菌对熟制小龙虾优势腐败菌的杀菌效果。【方法】从腐败熟制小龙虾中分离腐败菌,根据16S rDNA基因序列信息鉴定其种属,研究过热蒸汽温度、流量和杀菌时间等的处理参数对小龙虾优势腐败菌的杀菌效果,并利用Weibull模型拟合其杀菌动力学过程。通过研究过热蒸汽处理对优势腐败菌菌悬液的电导率和紫外吸收的影响,以及通过扫描电子显微镜对菌体的微观结构进行观察,初步探讨其杀菌机理。【结果】熟制小龙虾优势腐败菌为短小芽孢杆菌(Bacillus pumilus)、解淀粉芽孢杆菌(Bacillus amyloliquefaciens)、蜡样芽孢杆菌(Bacillus cereus)和赖氨酸芽孢杆菌(Lysinibacillus macroides)。在过热蒸汽杀菌初期阶段,优势腐败菌的残活率迅速下降,随着杀菌时间延长,残活率下降速率变得缓慢,最后趋于稳定,说明过热蒸汽能完全杀灭小龙虾优势腐败菌。Weibull模型能较好拟合过热蒸汽对4种优势腐败菌的杀菌动力学,其R2≥0.935。Weibull模型得到的预测值与实测值接近程度较高。通过对模型的分析,提高过热蒸汽温度和增大流量,更容易到达灭活腐败菌的效果。过热蒸汽杀菌后,菌悬液的电导率值和吸光度迅速上升,之后趋于平缓;通过对微观结构的观察,发现杀菌后腐败菌的细胞膜完整性遭到严重破坏。【结论】过热蒸汽杀菌技术应用于小龙虾产品加工具有一定的可行性。

Inactivation Kinetics and Mechanisms of Dominant Spoilage Bacteria in Cooked Crayfish(Procambarus clarkii) by Superheated Steam

【Objective】The aim of this work was to study the bactericidal effect of superheated steam treatment on dominant spoilage bacteria from cooked crayfish.【Method】The dominant spoilage bacteria were isolated from the rotten cooked crayfish samples and identified by the 16S rDNA gene sequences information.The effects of superheated steam treatment parameters such as temperature,flow rate and time on the dominant spoilage bacteria isolated were investigated.Inactivation kinetics of the dominant spoilage bacteria by superheated steam was fitted by using the Weibull model.The sterilization mechanism of superheated steam was explained by analyzing the values of conductivity and ultraviolet absorption,and observing the microbial morphology of the bacteria.【Result】The results showed that the dominant spoilage bacteria of the cooked crayfish were identified as Bacillus pumilus,Bacillus amyloliquefaciens,Bacillus cereus and Lysinibacillus macroides.In the initial stage of superheated steam sterilization,the survival rate of dominant spoilage bacteria decreased rapidly,and with the prolongation of sterilization time,the decline rate became slow,and finally tended to be stable.It indicated that superheated steam could completely inactivate the dominant putrefactive bacteria of crayfish.Inactivation kinetics curves of 4 colonies of the dominant spoilage bacteria by superheated steam were well fitted by the Weibull model,with R2≥0.935.The predicted value of the Weibull model is close to the measured value.According to the analysis of the model,increasing of superheated steam temperature and flow rate and shortening of the sterilization time could achieve better inactivation effect on spoilage bacteria from crayfish.After superheated steam treatment,the conductivity and UV absorbance of bacterial suspension increased rapidly,and the observation of the microbial morphology of the bacteria showed that the bacterial cell membrane was seriously damaged,resulting in the death of the bacteria,which may be one of the main reasons to reach inactivation.【Conclusion】Superheated steam technology was a promising sterilization technology during crayfish products processing.