Department of Food Science and Technology, University of Georgia, Athens, GA, United States of America.
Center for Food Safety, University of Georgia, Griffin, GA, United States of America.
Int J Food Microbiol. 2022 Dec 2;382:109913. doi: 10.1016/j.ijfoodmicro.2022.109913. Epub 2022 Sep 5.
Atmospheric cold plasma (ACP) is a promising non-thermal technology that has the potential to inactivate microorganisms in foods. In this work, the inactivation of E. coli K12, acid-adapted E. coli K12, and E. coli O157:H7 in apple cider by ACP was investigated using feed gases as simulated air (SA) (80 % N + 20 % O) and a mixture of 90 % N + 10 % O with various processing times (0 to 180 s). We obtained the reduced the populations of both acid-adapted and non-adapted E. coli K12 by 5 log CFU/mL within 120 s, and E. coli O157:H7 within 90 s. Additionally, no significant changes in the °Brix, pH, temperature, or titratable acidity (TA) of apple cider were observed after exposure to ACP. However, processing times longer than 120 s resulted in significant changes in the pH values. The highest concentration of ozone and hydrogen peroxide reached to 0.22 ± 0.1 mg/L for CG in 180 s and 0.07 ± 0.01 mg/L for SA in 150 s, respectively. Both acid-adapted and non-acid adapted E. coli K12 was found to be more resistant to ACP processing than E. coli O157:H7 after the 90 s, so it could serve as a surrogate for E. coli O157:H7. When we compared the effect of the gas type on inactivation, non-selective media, the results showed no significant differences between the gas types, while selective media demonstrated significant differences. In optical absorption spectroscopy measurements of plasma species, primarily ozone peaks were observed. Furthermore, the optical absorption spectroscopy also revealed that the inactivation of the bacteria could be attributed to some plasma species with wavelengths between 190 and 308 nm. The findings provided a perspective on the use of ACP as a method for decontaminating fruit juices as a non-thermal processing.
大气冷等离子体（ACP）是一种很有前途的非热技术，有可能使食品中的微生物失活。在这项工作中，使用模拟空气（SA）（80%N+20%O）和 90%N+10%O 的混合物作为进料气体，研究了 ACP 对苹果 cider 中大肠杆菌 K12、耐酸大肠杆菌 K12 和大肠杆菌 O157:H7 的灭活作用，并在不同的处理时间（0 至 180 秒）下进行了处理。我们在 120 秒内使耐酸和非耐酸大肠杆菌 K12 的菌数减少了 5 个对数 CFU/mL，使大肠杆菌 O157:H7 的菌数减少了 3 个对数 CFU/mL。此外，暴露于 ACP 后，苹果 cider 的 °Brix、pH 值、温度或滴定酸度（TA）均无明显变化。然而，处理时间超过 120 秒会导致 pH 值发生显著变化。在 180 秒时，CG 中臭氧和过氧化氢的最高浓度分别达到 0.22±0.1mg/L，在 150 秒时，SA 中达到 0.07±0.01mg/L。在 90 秒后，发现耐酸和非耐酸大肠杆菌 K12 比大肠杆菌 O157:H7 更能抵抗 ACP 处理，因此可以作为大肠杆菌 O157:H7 的替代品。当我们比较气体类型对灭活的影响时，在非选择性培养基上，结果显示两种气体类型之间没有显著差异，而在选择性培养基上则有显著差异。在等离子体物种的光吸收光谱测量中，主要观察到臭氧峰。此外，光吸收光谱还表明，细菌的灭活可能归因于一些波长在 190 至 308nm 之间的等离子体物种。这些发现为将 ACP 作为一种非热处理方法用于果汁消毒提供了一个视角。
