高密度CO_2对虾优势腐败菌的杀菌效果及机理

Sterilizing effect of dense phase carbon dioxide on dominant spoilage bacteria from shrimp and its mechanism

为了探讨高密度CO2(dense phase carbon dioxide,DPCD)对水产品腐败菌的杀菌效果和机制,以一株凡纳滨对虾优势腐败菌(Chryseobacterium sp.LV1)为研究对象,研究了DPCD处理温度(30～55℃)、压力(5～25MPa)、时间(5～60min)对杀菌效果的影响,分析了DPCD处理前后该菌理化性质的变化。结果表明:DPCD对其具有较好的杀菌效果,温度升高、压力增大、延长时间都会增强杀菌效果,而且超临界CO2比亚临界CO2的杀菌效果好。当在45℃、15MPa和55℃、15MPa下处理菌悬液30min时,菌落总数均能下降5个对数;菌悬液的pH值从6.97分别下降至5.58和5.56;细胞外蛋白由最初的78.69μg/mL分别增至151.91和157.40μg/mL,200～800nm范围内的吸光度值增大,这说明DPCD处理改变了其细胞膜的通透性,造成胞内蛋白质和核酸泄漏;可溶性和不溶性蛋白的电泳图谱发生变化,说明DPCD处理能够诱导Chryseobacterium sp.LV1可溶性蛋白质变性,降低其溶解度;能够钝化与其新陈代谢相关的14种酶类;但不会造成其DNA的降解。因此,DPCD处理致使其理化性质的改变可能是杀菌的主要原因之一。研究结果将为DPCD技术在对虾加工中的应用提供参考。

Dense phase carbon dioxide （DPCD） is a non-thermal pasteurization method that affects microorganisms and enzymes through molecular effects of CO2 under pressures below 50MPa and temperature below 60℃. The DPCD sterilization technique could be one of the most promising techniques for sterilizing foods without exposing them to adverse effects of heat, thereby retaining their fresh physical, nutritional, and sensory qualities. In order to investigate the sterilization effect and mechanism of aquatic product spoilage bacteria induced by dense phase carbon dioxide （DPCD）, using a strain of Litopenaeus vannamei dominant spoilage bacteria （Chryseobacterium sp. LV1） as the research object, the effects of temperature （30-55 ℃）, pressure （5-25 MPa）, time （5-60 min） on sterilization were studied and the changes of Chryseobacterium sp. LV1 physicochemical properties were analyzed before and after DPCD treatment. The results showed that DPCD had a good bactericidal effect on Chryseobacterium sp. LV1. The sterilization effect is enhanced with increasing temperature, pressure and time, and the sterilization effect of supercritical CO2 was better than that of subcritical CO2. Under DPCD conditions of 45℃/15 MPa /30 min or 55℃/15 MPa /30 min, the total bacterial count decreased by 5 logs; the pH value of the bacterial suspension decreased from 6.97 to 5.58 and 5.56; the content of extracellular protein increased from the initial 78.69 to 151.91 and 157.40 μg/mL; and the absorbance value from 200 to 800 nm increased. These results indicated that DPCD could result in intracellular protein and nucleic acid leakage of Chryseobacterium sp. LV1 because of permeability changes in its cell membrane. The SDS-PAGE electrophoretogram of Chryseobacterium sp. LV1 proteins showed that DPCD could reduce the solubility of Chryseobacteriurn sp. LV1 soluble protein because of soluble protein denaturation. The results detected by the API ZYM system kit showed that DPCD could inactivate 14 enzymes related to the metabolism of Chryseobacterium sp. LV1. The agarose gel electrophoretogram of Chrygeobacterium sp. LV1 DNA showed that DPCD could not degrade the DNA of Chryseobacterium sp. LV1. Therefore, changes in the physicochemical properties of Chryseobacteriurn sp. LV1 induced by DPCD may be one of the main mechanisms of DPCD sterilization. The research results will provide a reference for the application of DPCD in the processing of shrimp.