Mechanisms of enhanced bacterial endospore inactivation during sterilization by ohmic heating

Schottroff, Felix; Pyatkovskyy, Taras; Reineke, Kai; Setlow, Peter; Sastry, Sudhir K.; Jaeger, Henry

doi:10.1016/j.bioelechem.2019.107338

Cited by 27 publications

(14 citation statements)

References 56 publications

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“…After prions [28] and along with certain protozoans, endospores demonstrate the highest resistance to harsh environmental conditions, enabling them to survive in dormant state for up to thousands of years and to germinate when conditions become favorable. Endospores, such as G. stearothermophilus exhibit a remarkably high degree of resistance to inactivation by most physical treatments and oxidizing agents [29,30]. Bacterial endospores can serve as excellent reference tools in inactivation studies, due to the remarkable stability of their suspensions [31].…”

Section: Introductionmentioning

confidence: 99%

Visible Light Driven Photocatalytic Decolorization and Disinfection of Water Employing Reduced TiO2 Nanopowders

et al. 2021

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Defect-engineering of TiO2 can have a major impact on its photocatalytic properties for the degradation of persisting and non-biodegradable pollutants. Herein, a series of intrinsic and extrinsic defects are induced by post annealing of crystalline TiO2 under different reducing atmospheres. A detailed optoelectronic characterization sheds light on the key characteristics of the defect-engineered TiO2 nanopowders that are linked to the photocatalytic performance of the prepared photocatalysts. The photodegradation of a model dye, malachite green, as well as the inactivation of bacterial endospores of the Geobacillus stearothermophilus species were studied in the presence of the developed catalysts under visible light illumination. Our results indicate that a combination of certain defects is necessary for the improvement of the photocatalytic process for water purification and disinfection under visible light.

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Section: Introductionmentioning

confidence: 99%

Visible Light Driven Photocatalytic Decolorization and Disinfection of Water Employing Reduced TiO2 Nanopowders

et al. 2021

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“…Kim, Choi, et al (2017) and Kim, Ryang, et al (2017) evaluated Lack of data for fungi; comprehension of the extension of the nonthermal effects depending on the different process variables, such as the microorganism and foodstuff. (Cho et al, 1999;Schottroff et al, 2019;Uemura & Isobe, 2002) Electric field Increase of the nonthermal effects in some situations; increase in the heat rate.…”

Section: Aspects Concerning Vegetative Speciesmentioning

confidence: 99%

“…To clarify the mechanism of nonthermal spore inactivation, Schottroff et al (2019) studied the inactivation of Bacillus subtilis endospores, focusing on determining which components of the spore cell were more affected by the electric field. The authors prepared three mutant species lacking different components known to contribute to spore heat resistance: (i) small-acid soluble proteins that protect the DNA; (ii) the coat covering the spore; (iii) the spore germination enzyme SleB.…”

Section: Frequencymentioning

confidence: 99%

Microbial inactivation by ohmic heating: Literature review and influence of different process variables

Müller

Marczak

Sarkis

2020

Trends in Food Science & Technology

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Background: The elimination of microbial cells is one of the most critical steps in food processing. Conventional heating is the application of diffusive and convective heat mechanisms and is traditionally applied to assure food safety. However, such process is also harmful to others thermosensitive compounds, compromising desirable sensorial characteristics. The large temperature gradients caused by conventional heating result in lower thermal efficiency, overheated zones and high processing times. To overcome these limitations, emergent technologies have been studied in the past years, such as ohmic heating. Scope and approach: The aim of this review was to analyse the state of the art of microbial inactivation by ohmic heating. This study emphasizes comparisons of ohmic and conventional heating, as well as comparisons of ohmic heating in several distinct scenarios (such as variations in the frequency and electric field). Key findings and conclusions:The literature analysis shows that the most analysed microbial species was Escherichia coli and studies dealing with fungi were less numerous comparing with studies dealing with bacteria. Concerning the lethality of conventional and ohmic heating, authors have shown that ohmic treated foods had smaller D values in various temperatures. The effect of frequency lacks of experimental data to explain the real impact of this parameter in the inactivation rate, once different authors have found divergent results. Moreover, increases in the electric field and salt content and decreases in the pH, fat and solid content have demonstrated higher heating rates and, therefore, higher inactivation rates.

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“…Kim et al, 2017;S.S. Kim et al, 2017;Rodrigues et al, 2018;Schottroff et al, 2019;Tian et al, 2018). The high potential of OH for microbial death is related to two aspects: (i) compared to CH, in general the heating ramp is faster and the temperature profile is more homogeneous, reducing processing time, energy costs and losses of desirable compounds; (ii) the presence of nonthermal effects may provide additional inactivation rates.…”

Section: Introductionmentioning

confidence: 99%

“…However, these studies failed to specify if the temperature profiles were matched for CH and OH technologies. According to several authors (Cho et al, 1999;Rodrigues et al, 2018;Schottroff et al, 2019;Somavat et al, 2012Somavat et al, , 2013, similar profiles are necessary to properly evaluate the occurrence of nonthermal effects.…”

Section: Introductionmentioning

confidence: 99%

Effect of pasteurization on Aspergillus fumigatus in apple juice: Analysis of the thermal and electric effects

Müller

Pasin

Sarkis

et al. 2021

International Journal of Food Microbiology

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Fungal spoilage in fruit juices is a currently relevant issue considering that recent reports have found unacceptable fungal levels even after traditional pasteurization processes. Ohmic heating demonstrated to be a good alternative process to conventional pasteurization, as it can promote higher heating rates and additional cell damage in some scenarios (nonthermal effects). However, the application of ohmic processing for fungi inactivation has not been properly investigated. The objective of this study was to analyze the inactivation of Aspergillus fumigatus, a highly distributed fungi species, in apple juice by ohmic and conventional heating at 75, 80, 85, 90 and 94 • C. Predictive primary and secondary models were fitted and the Weibull-Mafart models were the most accurate to describe the experimental behavior considering the statistical indices applied. Statistical differences between both thermal processes were found in the three lower analyzed temperatures (75, 80 and 85 • C), which is possibly related to nonthermal effects. When ohmic heating was applied, processing time was up to 23% shorter. The resulted model was successfully validated in two distinct temperatures (83 and 92 • C) and could be applied to obtain adequate processing times for apple juice pasteurization. This study contributes to deepen the knowledge concerning the use of ohmic heating for fungi inactivation.

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Mechanisms of enhanced bacterial endospore inactivation during sterilization by ohmic heating

Cited by 27 publications

References 56 publications

Visible Light Driven Photocatalytic Decolorization and Disinfection of Water Employing Reduced TiO2 Nanopowders

Visible Light Driven Photocatalytic Decolorization and Disinfection of Water Employing Reduced TiO2 Nanopowders

Microbial inactivation by ohmic heating: Literature review and influence of different process variables

Effect of pasteurization on Aspergillus fumigatus in apple juice: Analysis of the thermal and electric effects

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