Emanuel Efrat, Dubrovin Irina, Hanya Ester, Pinhasi Gad A, Pogreb Roman, Cahan Rivka
Department of Chemical Engineering and Biotechnology, Ariel University, Ariel 40700, Israel.
Department of Physics, Ariel University, Ariel 40700, Israel.
Microorganisms. 2020 Oct 29;8(11):1684. doi: 10.3390/microorganisms8111684.
One of the promising technologies that can inactivate microorganisms without heat is pulsed electric field (PEF) treatment. The aim of this study was to examine the influence of PEF treatment (2.9 kV cm, 100 Hz, 5000 pulses in trains mode of 500 pulses with a pulse duration of 10 µs) on eradication and resealing in different conditions, such as current density (which is influenced by the medium conductivity), the sort of medium (phosphate buffered saline (PBS) vs. yeast malt broth (YMB) and a combined treatment of PEF with the addition of preservatives. When the were suspended in PBS, increasing the current density from 0.02 to 3.3 A cm (corresponding to a total specific energy of 22.04 to 614.59 kJ kg) led to an increase of eradication. At 3.3 A cm, a total eradication was observed. However, when the in PBS was treated with the highest current density of 3.3 A cm, followed by dilution in a rich YMB medium, a phenomenon of cell membrane resealing was observed by flow cytometry (FCM) and CFU analysis. The viability of was also examined when the culture was exposed to repeating PEF treatments (up to four cycles) with and without the addition of preservatives. This experiment was performed when the were suspended in YMB containing tartaric acid (pH 3.4) and ethanol to a final concentration of 10% (), which mimics wine. It was shown that one PEF treatment cycle led to a reduction of 1.35 log10, compared to 2.24 log10 when four cycles were applied. However, no synergic effect was observed when the preservatives, free SO, and sorbic acid were added. This study shows the important and necessary knowledge about yeast eradication and membrane recovery processes after PEF treatment, in particular for application in the liquid food industry.
能够在不加热的情况下使微生物失活的一项很有前景的技术是脉冲电场（PEF）处理。本研究的目的是考察PEF处理（2.9 kV/cm、100 Hz、5000个脉冲，以500个脉冲的串模式，脉冲持续时间为10 μs）在不同条件下对根除和重新封闭的影响，这些条件包括电流密度（受介质电导率影响）、介质种类（磷酸盐缓冲盐水（PBS）与酵母麦芽汁（YMB））以及PEF与添加防腐剂的联合处理。当将[具体微生物]悬浮于PBS中时，将电流密度从0.02 A/cm增加到3.3 A/cm（对应总比能从22.04 kJ/kg增加到614.59 kJ/kg）会导致[具体微生物]根除率增加。在3.3 A/cm时，观察到[具体微生物]被完全根除。然而，当PBS中的[具体微生物]用3.3 A/cm的最高电流密度处理，随后在富含YMB的培养基中稀释时，通过流式细胞术（FCM）和CFU分析观察到细胞膜重新封闭现象。当培养物在添加和不添加防腐剂的情况下接受重复的PEF处理（最多四个循环）时，也对[具体微生物]的活力进行了检测。该实验是在将[具体微生物]悬浮于含有酒石酸（pH 3.4）和乙醇至终浓度为10%（体积分数）的YMB中进行的，这模拟了葡萄酒的环境。结果表明，与应用四个循环时降低2.24 log10相比，一个PEF处理循环导致[具体微生物]减少1.35 log10。然而，添加防腐剂游离SO₂和山梨酸时未观察到协同效应。本研究揭示了关于PEF处理后酵母根除和膜恢复过程的重要且必要的知识，特别是在液体食品工业中的应用。
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