Shi C, Jia Z, Chen Y, Yang M, Liu X, Sun Y, Zheng Z, Zhang X, Song K, Cui L, Baloch A B, Xia X
College of Food Science and Engineering, Northwest A&F University, Yangling, Shaanxi, China.
J Appl Microbiol. 2015 Dec;119(6):1700-6. doi: 10.1111/jam.12964.
The objective of this study was to determine the combined effect of thymoquinone (TQ) and mild heat on Cronobacter sakazakii in reconstituted infant formula.
Reconstituted infant formula samples inoculated with a mixture of four C. sakazakii strains (approx. 6·5 log CFU ml(-1) ) were prepared with various concentrations of TQ (0, 5, 10, 20 and 30 mmol l(-1) ) and were heated to 45, 50 and 55°C for 0, 10, 20, 30, 60 and 120 min, and the surviving populations of C. sakazakii at each sampling time were enumerated. To elucidate the mode of action of TQ, membrane integrity and changes in cell morphology were examined by LIVE/DEAD(®) BacLight(™) bacterial viability kit and field emission scanning electron microscope respectively. TQ at 30 mmol l(-1) reduced the pathogen to undetectable level in between 60 and 120 min at 45°C, 60 min at 50°C and 10 min at 55°C respectively.
Our results demonstrated that the combined treatments significantly reduced (P < 0·05) the population of C. sakazakii, compared to the control. Cronobacter sakazakii numbers were reduced much more rapidly with higher temperatures and increased concentrations of TQ. And combined treatment inactivated pathogen partly by causing cell membrane disruption.
These findings suggested that TQ, together with mild heat, may have potential application in infant formula to control C. sakazakii before consumption and therefore is a possible way to prevent infections associated with C. sakazakii in infant formula.
本研究的目的是确定百里醌（TQ）和温和加热对复原婴儿配方奶粉中阪崎肠杆菌的联合作用。
制备接种了四种阪崎肠杆菌菌株混合物（约6.5 log CFU ml⁻¹）的复原婴儿配方奶粉样品，添加不同浓度的TQ（0、5、10、20和30 mmol l⁻¹），并在45、50和55°C下加热0、10、20、30、60和120分钟，对每个采样时间的阪崎肠杆菌存活菌数进行计数。为阐明TQ的作用方式，分别使用LIVE/DEAD® BacLight™细菌活力试剂盒和场发射扫描电子显微镜检测膜完整性和细胞形态变化。30 mmol l⁻¹的TQ分别在45°C下60至120分钟、50°C下60分钟和55°C下10分钟将病原体减少到无法检测的水平。
我们的结果表明，与对照组相比，联合处理显著降低了（P < 0.05）阪崎肠杆菌的数量。阪崎肠杆菌数量随着温度升高和TQ浓度增加而更快地减少。联合处理部分通过引起细胞膜破坏使病原体失活。
这些发现表明，TQ与温和加热一起，可能在婴儿配方奶粉中有潜在应用，以在食用前控制阪崎肠杆菌，因此是预防婴儿配方奶粉中与阪崎肠杆菌相关感染的一种可能方法。
