Sterilization of liquid foods by pulsed electric fields – an innovative ultra-high temperature process
The intention of this study was to investigate the inactivation of endospores by a combined thermal and pulsed electric field (PEF) treatment. Therefore, self-cultivated spores of Bacillus subtilis and commercial Geobacillus stearothermophilus spores with certified heat resistance were utilized. Spo...
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doaj-1bacef6bf54e4061b8add4b989c8704a2020-11-24T20:57:43ZengFrontiers Media S.A.Frontiers in Microbiology1664-302X2015-05-01610.3389/fmicb.2015.00400122883Sterilization of liquid foods by pulsed electric fields – an innovative ultra-high temperature processKai eReineke0Kai eReineke1Felix eSchottroff2Nicolas eMeneses3Nicolas eMeneses4Dietrich eKnorr5Leibniz Institute for Agricultural Engineering (ATB)Technische Universitaet BerlinTechnische Universitaet BerlinTechnische Universitaet BerlinBuehler AGTechnische Universitaet BerlinThe intention of this study was to investigate the inactivation of endospores by a combined thermal and pulsed electric field (PEF) treatment. Therefore, self-cultivated spores of Bacillus subtilis and commercial Geobacillus stearothermophilus spores with certified heat resistance were utilized. Spores of both strains were suspended in saline water (5.3 mS cm-1), skim milk (0.3% fat; 5.3 mS cm-1) and fresh prepared carrot juice (7.73 mS cm-1). The combination of moderate preheating (70-90 °C) and an insulated PEF-chamber, combined with a holding tube (65 cm) and a heat exchanger for cooling, enabled a rapid heat up to 105-140 °C (measured above the PEF chamber) within 92.2-368.9 µs. To compare the PEF process with a pure thermal inactivation, each spore suspension was heat treated in thin glass capillaries and D-values from 90 to 130°C and its corresponding z-values were calculated. For a comparison of the inactivation data, F-values for the temperature fields of both processes were calculated by using Comsol Multiphysics combined with a Matlab routine.A preheating of saline water to 70 °C with a flow rate of 5 l h-1, a frequency of 150 Hz and an energy input of 226.5 kJ kg-1, resulted in a measured outlet temperature of 117 °C and a 4.67 log10 inactivation of Bacillus subtilis. The thermal process with identical F-value caused only a 3.71 log10 inactivation. This synergism of moderate preheating and PEF was even more pronounced for Geobacillus stearothermophilus spores in saline water. A preheating to 95 °C and an energy input of 144 kJ kg-1 resulted in an outlet temperature of 126 °C and a 3.28 log10 inactivation, whereas nearly no inactivation (0.2 log10) was achieved during the thermal treatment.Hence, the PEF technology was evaluated as an alternative ultra-high temperature process. However, for an industrial scale application of this process for sterilization, optimization of the treatment chamber design is needed to reduce the occurring inhomogeneous temperhttp://journal.frontiersin.org/Journal/10.3389/fmicb.2015.00400/fullEndospore-Forming BacteriaMilkSterilizationpulsed electric fieldsinactivation mechanisms |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Kai eReineke Kai eReineke Felix eSchottroff Nicolas eMeneses Nicolas eMeneses Dietrich eKnorr |
spellingShingle |
Kai eReineke Kai eReineke Felix eSchottroff Nicolas eMeneses Nicolas eMeneses Dietrich eKnorr Sterilization of liquid foods by pulsed electric fields – an innovative ultra-high temperature process Frontiers in Microbiology Endospore-Forming Bacteria Milk Sterilization pulsed electric fields inactivation mechanisms |
author_facet |
Kai eReineke Kai eReineke Felix eSchottroff Nicolas eMeneses Nicolas eMeneses Dietrich eKnorr |
author_sort |
Kai eReineke |
title |
Sterilization of liquid foods by pulsed electric fields – an innovative ultra-high temperature process |
title_short |
Sterilization of liquid foods by pulsed electric fields – an innovative ultra-high temperature process |
title_full |
Sterilization of liquid foods by pulsed electric fields – an innovative ultra-high temperature process |
title_fullStr |
Sterilization of liquid foods by pulsed electric fields – an innovative ultra-high temperature process |
title_full_unstemmed |
Sterilization of liquid foods by pulsed electric fields – an innovative ultra-high temperature process |
title_sort |
sterilization of liquid foods by pulsed electric fields – an innovative ultra-high temperature process |
publisher |
Frontiers Media S.A. |
series |
Frontiers in Microbiology |
issn |
1664-302X |
publishDate |
2015-05-01 |
description |
The intention of this study was to investigate the inactivation of endospores by a combined thermal and pulsed electric field (PEF) treatment. Therefore, self-cultivated spores of Bacillus subtilis and commercial Geobacillus stearothermophilus spores with certified heat resistance were utilized. Spores of both strains were suspended in saline water (5.3 mS cm-1), skim milk (0.3% fat; 5.3 mS cm-1) and fresh prepared carrot juice (7.73 mS cm-1). The combination of moderate preheating (70-90 °C) and an insulated PEF-chamber, combined with a holding tube (65 cm) and a heat exchanger for cooling, enabled a rapid heat up to 105-140 °C (measured above the PEF chamber) within 92.2-368.9 µs. To compare the PEF process with a pure thermal inactivation, each spore suspension was heat treated in thin glass capillaries and D-values from 90 to 130°C and its corresponding z-values were calculated. For a comparison of the inactivation data, F-values for the temperature fields of both processes were calculated by using Comsol Multiphysics combined with a Matlab routine.A preheating of saline water to 70 °C with a flow rate of 5 l h-1, a frequency of 150 Hz and an energy input of 226.5 kJ kg-1, resulted in a measured outlet temperature of 117 °C and a 4.67 log10 inactivation of Bacillus subtilis. The thermal process with identical F-value caused only a 3.71 log10 inactivation. This synergism of moderate preheating and PEF was even more pronounced for Geobacillus stearothermophilus spores in saline water. A preheating to 95 °C and an energy input of 144 kJ kg-1 resulted in an outlet temperature of 126 °C and a 3.28 log10 inactivation, whereas nearly no inactivation (0.2 log10) was achieved during the thermal treatment.Hence, the PEF technology was evaluated as an alternative ultra-high temperature process. However, for an industrial scale application of this process for sterilization, optimization of the treatment chamber design is needed to reduce the occurring inhomogeneous temper |
topic |
Endospore-Forming Bacteria Milk Sterilization pulsed electric fields inactivation mechanisms |
url |
http://journal.frontiersin.org/Journal/10.3389/fmicb.2015.00400/full |
work_keys_str_mv |
AT kaiereineke sterilizationofliquidfoodsbypulsedelectricfieldsaninnovativeultrahightemperatureprocess AT kaiereineke sterilizationofliquidfoodsbypulsedelectricfieldsaninnovativeultrahightemperatureprocess AT felixeschottroff sterilizationofliquidfoodsbypulsedelectricfieldsaninnovativeultrahightemperatureprocess AT nicolasemeneses sterilizationofliquidfoodsbypulsedelectricfieldsaninnovativeultrahightemperatureprocess AT nicolasemeneses sterilizationofliquidfoodsbypulsedelectricfieldsaninnovativeultrahightemperatureprocess AT dietricheknorr sterilizationofliquidfoodsbypulsedelectricfieldsaninnovativeultrahightemperatureprocess |
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