本文主要探究热压结合处理(50 ℃,350 MPa保压10 min)对低温火腿中绿色魏斯菌和肠膜明串珠菌的抑制作用。通过薄层平板计数法对热压结合处理的杀菌效果进行判断,使用流式细胞技术判断细胞的生理状态,通过扫描电镜(scanning electron microscope,SEM)和透射电镜(transmission electron microscope,TEM)观察细胞形态结构的变化,利用紫外分光光度法测定热压结合处理对细菌细胞膜通透性的影响。结果表明:经热压结合处理后,绿色魏斯菌和肠膜明串珠菌的存活率分别为-4.74和-6.61lg(CFU/mL),其生长变得迟缓,对数期生长速率降低。扫描电镜结果显示热压结合处理对两种菌的形态造成明显的变形,透射电镜结果显示细胞内部出现团状聚集和透电子区。热压结合处理对细胞膜产生损伤,细胞膜通透性变大,导致细胞外紫外吸收物质也极显著增加(p<0.001),细胞处于亚致死状态。热压结合处理会对细胞膜产生一定的形变及损坏,使得细胞内核酸和蛋白质流出,同时细胞内部也会发生蛋白变性和细胞质皱缩,达到抑制耐压菌生长繁殖的目的。
The inhibition of high pressure thermal sterilization treatment (350 MPa and 50℃ for 10 min) on Weissella viridescens and Leuconostoc mesenteroides of low temperature cooked ham were investigated in the study. The germicidal efficacy of high pressure thermal sterilization was evaluated by thin layer plate counting method. The flow cytometry was used to determine the physiological state of the cell, SEM and TEM were used to observe cell morphological changes and ultrastructure of bacteria. The influence of cell membrane permeability was evaluated by UV spectrophotometry. The results showed that, after high pressure thermal sterilization, the survival rate of Weissella viridescens and Leuconostoc mesenteroides was-4.74 and-6.61lg (CFU/mL), respectively. These two baroduric bacteria appeared growth retardation and lower growth rate in exponential phase under high-pressure thermal sterilization. SEM and TEM results showed high pressure thermal sterilization induced obvious morphologic changes of cells and intracellular cytoplasm aggregate with large electron transmission area. The combination of heat and pressure treatment damaged the cell membrane, and made the cell membrane permeability larger, which caused a significant increase in extracellular ultraviolet absorption content (p<0.001), and the cells would be in a sublethal state. The combination of heat and pressure would cause certain deformation and damage to the cell membrane, which would lead to the flow out of nucleic acid and protein in cell, and the protein denaturation and cytoplasm shrinkage would occur inside the cell, thereby inhibiting the growth and reproduction of the pressure-resistant bacteria.