Butscher Denis, Van Loon Hanne, Waskow Alexandra, Rudolf von Rohr Philipp, Schuppler Markus
ETH Zurich, Institute of Process Engineering, Sonneggstrasse 3, 8092 Zurich, Switzerland.
ETH Zurich, Institute of Process Engineering, Sonneggstrasse 3, 8092 Zurich, Switzerland; ETH Zurich, Institute of Food Science and Nutrition, Schmelzbergstrasse 7, 8092 Zurich, Switzerland.
Int J Food Microbiol. 2016 Dec 5;238:222-232. doi: 10.1016/j.ijfoodmicro.2016.09.006. Epub 2016 Sep 13.
Fresh produce is frequently contaminated by microorganisms, which may lead to spoilage or even pose a threat to human health. In particular sprouts are considered to be among the most risky foods sold at retail since they are grown in an environment practically ideal for growth of bacteria and usually consumed raw. Because heat treatment has a detrimental effect on the germination abilities of sprout seeds, alternative treatment technologies need to be developed for microbial inactivation purposes. In this study, non-thermal plasma decontamination of sprout seeds is evaluated as a promising option to enhance food safety while maintaining the seed germination capabilities. In detail, investigations focus on understanding the efficiency of non-thermal plasma inactivation of microorganisms as influenced by the type of microbial contamination, substrate surface properties and moisture content, as well as variations in the power input to the plasma device. To evaluate the impact of these parameters, we studied the reduction of native microbiota or artificially applied E. coli on alfalfa, onion, radish and cress seeds exposed to non-thermal plasma in an atmospheric pressure pulsed dielectric barrier discharge streamed with argon. Plasma treatment resulted in a maximum reduction of 3.4 logarithmic units for E. coli on cress seeds. A major challenge in plasma decontamination of granular food products turned out to be the complex surface topology, where the rough surface with cracks and crevices can shield microorganisms from plasma-generated reactive species, thus reducing the treatment efficiency. However, improvement of the inactivation efficiency was possible by optimizing substrate characteristics such as the moisture level and by tuning the power supply settings (voltage, frequency) to increase the production of reactive species. While the germination ability of alfalfa seeds was considerably decreased by harsh plasma treatment, enhanced germination was observed under mild conditions. In conclusion, the results from this study indicate that cold plasma treatment represents a promising technology for inactivation of bacteria on seeds used for sprout production while preserving their germination properties.
新鲜农产品经常被微生物污染，这可能导致变质，甚至对人类健康构成威胁。特别是豆芽被认为是零售市场上风险最高的食品之一，因为它们生长在几乎理想的细菌生长环境中，并且通常生食。由于热处理会对豆芽种子的发芽能力产生不利影响，因此需要开发替代处理技术来实现微生物灭活。在本研究中，对豆芽种子进行非热等离子体去污处理被评估为一种在保持种子发芽能力的同时提高食品安全的有前景的选择。具体而言，研究重点在于了解非热等离子体对微生物的灭活效率，其受微生物污染类型、底物表面性质和水分含量以及等离子体装置输入功率变化的影响。为了评估这些参数的影响，我们研究了在以氩气为气流的大气压脉冲介质阻挡放电中，非热等离子体对苜蓿、洋葱、萝卜和水芹种子上天然微生物群或人工接种的大肠杆菌的减少情况。等离子体处理使水芹种子上的大肠杆菌最多减少了3.4个对数单位。粒状食品等离子体去污的一个主要挑战是复杂的表面拓扑结构，其中带有裂缝和缝隙的粗糙表面可以保护微生物免受等离子体产生的活性物种的影响，从而降低处理效率。然而，通过优化底物特性（如水分水平）和调整电源设置（电压、频率）以增加活性物种的产生，可以提高灭活效率。虽然苛刻的等离子体处理会使苜蓿种子的发芽能力显著降低，但在温和条件下观察到发芽增强。总之，本研究结果表明，冷等离子体处理是一种有前景的技术，可用于灭活用于豆芽生产的种子上的细菌，同时保留其发芽特性。
