The present study highlighted the importance of equipment design for the experimental differentiation of thermal and electric field effects during ohmic heating. Based on these findings, a specifically designed setup was capable of reducing temperature inhomogeneities of conventional and ohmic heating, thus allowing for a maximum comparability of the processes. The effects of the treatments were evaluated by determination of inactivation kinetics, using different microorganisms, i.e. Microbacterium lacticum, Escherichia coli, Listeria innocua, Staphylococcus carnosus, Saccharomyces cerevisiae, and Rhodotorula glutinis in neutral as well as acidic (pH 3.8) solutions. Selected kinetics were further analyzed by flow cytometry, using SYBR green and propidium iodide staining. Based on comparable T, t-profiles and plate counts, conventional and ohmic heating were shown to be capable of effectively inactivating all tested microorganisms (max. 2.5–6.5 log), depending on treatment intensity (2.5 kW, up to 140 s) and pH level. No additional, non-thermal inactivation effects were determined for ohmic heating treatments, independent of the used matrix, pulse repetition rate/frequency, or waveform.

Industrial relevance

Ohmic heating is an alternative thermal preservation treatment increasingly used in the food and biotechnological industries for sensitive matrices, which are otherwise difficult to thermally process. It is able to overcome heat transfer limitations usually present in conventional thermal treatments, by application of an electric current flow through the product. The present paper contributes to better understand preservation by electrotechnologies and to the elucidation of inactivation mechanisms by ohmic heating. Thus, the understanding of the effects of ohmic heating on microorganisms is increased, which is crucial for industrial implementation of the technology and the corresponding process design.

中文翻译：

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通过千赫兹范围内的欧姆加热灭活营养微生物–实验装置和非热效应的评估

本研究强调了设备设计对于欧姆加热过程中热和电场效应的实验区分的重要性。基于这些发现，经过特殊设计的设置能够减少常规加热和欧姆加热的温度不均匀性，从而实现工艺的最大可比性。的处理的效果被确定灭活动力学的评价，使用不同的微生物，即微杆菌lacticum，大肠杆菌，无害利斯特氏菌，肉葡萄球菌，啤酒糖酵母，和粘红酵母在中性和酸性（pH 3.8）溶液中均可使用。使用SYBR green和碘化丙啶染色，通过流式细胞仪进一步分析选定的动力学。根据可比的T，t曲线和板数，常规和欧姆加热能够有效地灭活所有测试微生物（最大2.5–6.5 log），具体取决于处理强度（2.5 kW，长达140 s）和pH值。对于欧姆加热处理，未确定额外的非热灭活效果，与所使用的基质，脉冲重复频率/频率或波形无关。

行业相关性

欧姆加热是食品和生物技术行业中越来越多地用于敏感基质的替代性保温方法，否则很难进行热处理。通过施加流过产品的电流，它能够克服常规热处理中通常存在的传热限制。本论文有助于更好地理解电子技术的保存，并有助于阐明欧姆加热的失活机理。因此，增加了欧姆加热对微生物影响的理解，这对于该技术的工业实施和相应的工艺设计至关重要。