Department of Nutrition and Food Science, University of Maryland, College Park, MD 20740, USA.
Department of Food Science and Technology, University of California, Davis, CA 95616, USA.
Ultrason Sonochem. 2020 Jun;64:104983. doi: 10.1016/j.ultsonch.2020.104983. Epub 2020 Jan 22.
Ultrasound has potential to be used for disinfection, and its antimicrobial effectiveness can be enhanced in presence of natural compounds. In this study, we compared the antimicrobial effects of ultrasound at 20 kHz (US 20 kHz) or 1 MHz (US 1 MHz) in combination with carvacrol, citral, cinnamic acid, geraniol, gallic acid, lactic acid, or limonene against E. coli K12 and Listeria innocua at a constant power density in water. Compared to the cumulative effect of the individual treatments, the combined treatment of US 1 MHz and 10 mM citral generated >1.5 log CFU/mL additional inactivation of E. coli K12. Similarly, combined treatments of US 1 MHz and 2 mM carvacrol (30 min), US 20 kHz and 2 mM carvacrol, 10 mM citral, or 5 mM geraniol (15 min) generated >0.5-2.0 log CFU/mL additional inactivation in L. innocua. The synergistic effect of citral, as a presentative compound, and US 20 kHz treatment was determined to be a result of enhanced dispersion of insoluble citral droplets in combination with physical impact on bacterial membrane structures, whereas the inactivation by US 1 MHz was likely due to generation of oxidative stress within the bacteria. Combined ultrasound and citral treatments improved the bacterial inactivation in simulated wash water in presence of organic matter or during washing of inoculated blueberries but only additive antimicrobial effects were observed. Findings in this study will be useful to enhance fresh produce safety and shelf-life and design other alternative ultrasound based sanitation processes.
超声技术具有消毒潜力，在天然化合物存在的情况下，其抗菌效果可以得到增强。在本研究中，我们比较了 20 kHz（US 20 kHz）或 1 MHz（US 1 MHz）超声与香芹酚、柠檬醛、肉桂酸、香叶醇、没食子酸、乳酸或柠檬烯联合使用时对水中大肠杆菌 K12 和无害李斯特菌的抗菌效果，在恒定功率密度下。与单独处理的累积效应相比，1 MHz 超声和 10 mM 柠檬醛的联合处理使大肠杆菌 K12 的失活数额外增加了>1.5 log CFU/mL。同样，1 MHz 超声和 2 mM 香芹酚（30 分钟）、US 20 kHz 和 2 mM 香芹酚、10 mM 柠檬醛或 5 mM 香叶醇（15 分钟）的联合处理使无害李斯特菌的失活数额外增加了>0.5-2.0 log CFU/mL。以代表性化合物柠檬醛为例，其与 US 20 kHz 处理的协同作用是由于不溶性柠檬醛液滴的分散增强与对细菌膜结构的物理冲击相结合所致，而 1 MHz 超声的失活作用可能是由于细菌内产生了氧化应激。联合超声和柠檬醛处理提高了存在有机物时模拟洗涤水中或接种蓝莓洗涤时的细菌失活率，但仅观察到相加抗菌效果。本研究的结果将有助于提高新鲜农产品的安全性和货架期，并设计其他替代超声基消毒工艺。
