Chen Wenbo, Hu Honghai, Zhang Chunjiang, Huang Feng, Zhang Dequan, Zhang Hong
Institute of Food Science and Technology, Chinese Academy of Agricultural Sciences/Key Laboratory of Agro-Products Processing, Ministry of Agriculture, Beijing, 100193, People's Republic of China.
College of Staple Food Technology, Chinese Academy of Agricultural Sciences, Institute of Food Science and Technology, Harbin, 151900, People's Republic of China.
BMC Microbiol. 2017 Feb 10;17(1):32. doi: 10.1186/s12866-017-0945-2.
Moderate electric field (MEF) technology is a promising food preservation strategy since it relies on physical properties-rather than chemical additives-to preserve solid cellular foods during storage. However, the effectiveness of long-term MEF exposure on the psychrotrophic microorganisms responsible for the food spoilage at cool temperatures remains unclear.
The spoilage-associated psychrotroph Pseudomonas fragi MC16 was obtained from pork samples stored at 7 °C. Continuous MEF treatment attenuated growth and resulted in subsequent adaptation of M16 cultured on nutrient agar plates at 7 °C, compared to the control cultures, as determined by biomass analysis and plating procedures. Moreover, intracellular dehydrogenase activity and ATP levels also indicated an initial effect of MEF treatment followed by cellular recovery, and extracellular β-galactosidase activity assays indicated no obvious changes in cell membrane permeability. Furthermore, microscopic observations using scanning and transmission electron microscopy revealed that MEF induced sublethal cellular injury during early treatment stages, but no notable changes in morphology or cytology on subsequent days.
Our study provides direct evidence that psychrotrophic P. fragi MC16 cultured on nutrient agar plates at 7 °C are capable of adapting to MEF treatment.
中等电场（MEF）技术是一种很有前景的食品保鲜策略，因为它依靠物理特性而非化学添加剂在储存期间保存固态细胞性食品。然而，长期MEF暴露对在低温下导致食品腐败的嗜冷微生物的影响仍不清楚。
从储存在7°C的猪肉样品中获得了与腐败相关的嗜冷菌脆弱拟杆菌MC16。通过生物量分析和接种程序确定，与对照培养物相比，连续MEF处理减弱了生长，并导致在7°C营养琼脂平板上培养的M16随后出现适应性变化。此外，细胞内脱氢酶活性和ATP水平也表明MEF处理有初始效应，随后细胞恢复，而细胞外β-半乳糖苷酶活性测定表明细胞膜通透性无明显变化。此外，使用扫描电子显微镜和透射电子显微镜的微观观察显示，MEF在处理早期阶段诱导了亚致死性细胞损伤，但在随后几天形态学或细胞学上无明显变化。
我们的研究提供了直接证据，表明在7°C营养琼脂平板上培养的嗜冷脆弱拟杆菌MC16能够适应MEF处理。
