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Mathys A, Heinz V, Knorr D. Hochdruckunterstützte Sterilisationsprozesse – Grundlagen, Mechanismen und Herausforderungen. CHEM-ING-TECH 2007. [DOI: 10.1002/cite.200750314] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Heinz V, Sitzmann W, Töpfl S. Selektive Abtötung von zellulären Krankheitserregern und Verderbsorganismen: Das ELSTERIL®-Verfahren. CHEM-ING-TECH 2007. [DOI: 10.1002/cite.200600130] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Toepfl S, Mathys A, Heinz V, Knorr D. Review: Potential of High Hydrostatic Pressure and Pulsed Electric Fields for Energy Efficient and Environmentally Friendly Food Processing. FOOD REVIEWS INTERNATIONAL 2006. [DOI: 10.1080/87559120600865164] [Citation(s) in RCA: 198] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Koners U, Schmidt W, Löffler M, Heinz V, Knorr D. The effect of implemented pulsed electric field (PEF) treatment on the dehydrogenase activity of activated sludge. ACTA ACUST UNITED AC 2006. [DOI: 10.2495/wp060381] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Buckow R, Heinz V, Knorr D. Two Fractional Model for Evaluating the Activity of Glucoamylase from Aspergillus Niger Under Combined Pressure and Temperature Conditions. FOOD AND BIOPRODUCTS PROCESSING 2005. [DOI: 10.1205/fbp.04250] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Ananta E, Voigt D, Zenker M, Heinz V, Knorr D. Cellular injuries upon exposure of Escherichia coli and Lactobacillus rhamnosus to high-intensity ultrasound. J Appl Microbiol 2005; 99:271-8. [PMID: 16033457 DOI: 10.1111/j.1365-2672.2005.02619.x] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
AIMS To examine cellular injuries occurring in cells of Escherichia coli (Gram-negative bacteria) and Lactobacillus rhamnosus (Gram-positive bacteria) in response to a high-intensity ultrasound treatment using classical plate count technique and flow cytometry. METHOD AND RESULTS According to plate count results, E. coli (D-value 8.3 min) was far more sensitive than L. rhamnosus (D-value 18.1 min) in their response to the ultrasound intensity applied (20 kHz, 17.6 W). The dye precursor carboxyfluorescein diacetate (cFDA) could freely diffuse across the cytoplasmic membrane of intact cells of Gram-positive bacteria L. rhamnosus, resulting in its intracellular enzymatic conversion and emission of green fluorescence. In contrast, the presence of an outer membrane on E. coli, which represents the class of Gram-negative bacteria, apparently disabled the penetration of viability marker cFDA. Ultrasound application on E. coli yielded in an increasing population with disintegrated outer membrane, which allowed penetration of cFDA and its intracellular enzymatic conversion as well as accumulation. In both organisms evaluated only a small population was labelled by propidium iodide upon exposure to ultrasound for up to 20 min. Within the experimental conditions investigated ultrasound did not considerably affect the cytoplasmic membrane, although according to plate count results viability loss occurred. CONCLUSIONS The results compiled suggest, that ultrasound induced cell death, which may not be related to membrane damage. SIGNIFICANCE AND IMPACT OF THE STUDY Limitation on the use of bacteriocins, which are aimed on destabilization of cytoplasmic membrane but inhibited by the outer membrane, could be overcome by ultrasound-assisted physical disruption of the outer membrane.
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Pardey K, Schuchmann H, Schubert H, Heinz V, Knorr D. Wie gut sind unsere heutigen Entkeimungsverfahren? Abtöten von Mikroorganismen als stochastischer Vorgang. CHEM-ING-TECH 2005. [DOI: 10.1002/cite.200590098] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Ananta E, Heinz V, Knorr D. Assessment of high pressure induced damage on Lactobacillus rhamnosus GG by flow cytometry. Food Microbiol 2004. [DOI: 10.1016/j.fm.2003.11.008] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Heinz V, Zenker M. Experimentelle Untersuchung und Modellierung des Betriebsverhaltens eines Ultraschallreaktors zur akustisch-thermischen Behandlung von Flüssigkeiten. CHEM-ING-TECH 2004. [DOI: 10.1002/cite.200400082] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Schlüter O, Benet GU, Heinz V, Knorr D. Metastable States of Water and Ice during Pressure-Supported Freezing of Potato Tissue. Biotechnol Prog 2004; 20:799-810. [PMID: 15176885 DOI: 10.1021/bp0340279] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Different ice modifications were obtained during freezing processes at several pressure levels from atmospheric pressure up to 300 MPa. In the pressure range between 210 and 240 MPa, a metastable ice I modification area was observed, as the nucleation of ice I crystals in the thermodynamically stable region of ice III was reached. A significant degree of supercooling was obtained before freezing the tissue water to ice III, which has to be considered when designing pressure-supported freezing processes. The effect of supercooling phenomenon on the phase transition time is discussed using a mathematical model based on the solution of the heat transfer governing differential equations. Phase transition and freezing times for the different freezing paths experimented are compared for the processes: freezing at atmospheric pressure, pressure-assisted freezing, and pressure-shift freezing. Different metastable states of liquid water are defined according to their process-dependent stability.
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Kopplow O, Barjenbruch M, Heinz V. Vorbehandlung vonÜberschussschlamm durch Elektroporation. CHEM-ING-TECH 2004. [DOI: 10.1002/cite.200403341] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Ardia A, Knorr D, Heinz V. Adiabatic Heat Modelling for Pressure Build-up During High-pressure Treatment in Liquid-food Processing. FOOD AND BIOPRODUCTS PROCESSING 2004. [DOI: 10.1205/096030804322985362] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Kopplow O, Barjenbruch M, Heinz V. Sludge pre-treatment with pulsed electric fields. WATER SCIENCE AND TECHNOLOGY : A JOURNAL OF THE INTERNATIONAL ASSOCIATION ON WATER POLLUTION RESEARCH 2004; 49:123-129. [PMID: 15259946] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The anaerobic stabilization process depends - among other things - on the bio-availability of organic carbon. Through pre-treatment of the sludge which leads to the destruction of micro-organisms and to the setting-free of cell content substances (disintegration), the carbon can be microbially converted better and faster. Moreover, effects on the digestion are likely. However, only little experience is available in sludge treatment with pulsed electric fields. Laboratory-scale digestion tests have been run to analyse the influence of pulsed electric fields on the properties of sludge, anaerobic degradation, sludge water reload and foaming of digesters. The results will be compared with those of other disintegration methods (high pressure homogeniser, thermal treatment). The effect of pre-treatment on the sludge is shown by the COD release. Degrees of disintegration have been achieved up to 20%. The specific energy input was high. The energy consumption has been decreased by initial improvements (pre-heating to 55 degrees C). The filament bacteria were partially destroyed. The foam reduction in the digesters was marginal. The anaerobic degradation performance has been improved in every case. The degradation rate of organic matter increased about 9%. Due to the increase of degradation, there is a higher reload of the sludge-water with COD and nitrogen compounds.
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Dziurla MA, Leroy P, Strünkmann GW, Salhi M, Lee DU, Camacho P, Heinz V, Müller JA, Paul E, Ginestet P, Audic JM, Block JC. Measurement of glutathione in activated sludges. WATER RESEARCH 2004; 38:236-244. [PMID: 14630122 DOI: 10.1016/j.watres.2003.08.028] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Thermal, electric, mechanical or oxidative stress seem a promising way to reduce the production of excess activated sludge during biological wastewater treatment. However, the adaptation and the resistance of the sludge microbial ecosystem to stress conditions is a major question as it may definitively limit the effect of some treatments. Defence mechanisms developed by aerobic organisms, in particular, in response to oxidative stress involve various antioxidant activities and compounds such as glutathione. An HPLC method was developed for measuring reduced and total glutathione (GSH and GSHt) in perchloric acid sludge extracts. The method was sensitive, highly specific and validated for linearity, precision and recovery. Considering the extraction yield and the oxidation of GSH during extract storage, the measured GSH concentration was estimated to represent 60% of the GSH content from activated sludges. GSHt ranged from 0.32 to 3.34micromolg(-1) volatile solids and the GSH/GSHt ratio ranged from 32% to 91%. Measurements performed on sludges stressed in precise conditions selected to reach a reduction of sludge production showed a decrease of GSH and GSHt concentrations with thermal, mechanical, electric and ozone stress.
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Zenker M, Heinz V, Knorr D. Application of ultrasound-assisted thermal processing for preservation and quality retention of liquid foods. J Food Prot 2003; 66:1642-9. [PMID: 14503719 DOI: 10.4315/0362-028x-66.9.1642] [Citation(s) in RCA: 141] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
A continuously working pilot plant-scale prototype was used to evaluate the effects of continuous-flow ultrasound-temperature treatment for bacterial decontamination of model suspensions and various liquid food systems such as milk, fruit, and vegetable juices. Escherichia coli K12 DH 5 alpha and Lactobacillus acidophilus were used as test microorganisms. In addition, treated juices were investigated for damage caused by heat or ultrasound-induced degradation of sensory and nutritional properties after treatment and storage. Changes in color and destruction of heat-labile and slightly oxidizable L-ascorbic acid content were monitored as an index to measure processing effects. Results were assessed with respect to the total energy requirement and compared with those using a conventional, indirect heating method having similar processing conditions. For the bacteriological process evaluation, the temperature- and time-dependent process lethality was used as the basis; for the quality- and energy-related investigations, the degree of bacterial inactivation was used. At identical degrees of bacterial inactivation, the ultrasound-assisted thermal treatments required a lower processing temperature than treatment with conventional thermal processing. However, according to energy balances, the total energy consumption was not reduced compared to conventional heating. Indications for a positive influence on shelf life, with improvements in surface color stability (lightness) and L-ascorbic acid retention, were found among quality parameters of treated orange juice.
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Heinz V, Knorr D. Hochdruckbehandlung von Lebensmitteln– Neue anlagentechnische Ansätze. CHEM-ING-TECH 2003. [DOI: 10.1002/cite.200390243] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Heinz V, Toepfl S, Knorr D. Impact of temperature on lethality and energy efficiency of apple juice pasteurization by pulsed electric fields treatment. INNOV FOOD SCI EMERG 2003. [DOI: 10.1016/s1466-8564(03)00017-1] [Citation(s) in RCA: 132] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Heinz V, Knorr D. Non-thermal food preservation and its potential in meat processing. FORUM OF NUTRITION 2003; 56:369-70. [PMID: 15806941] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
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Ulmer HM, Heinz V, Gänzle MG, Knorr D, Vogel RF. Effects of pulsed electric fields on inactivation and metabolic activity of Lactobacillus plantarum in model beer. J Appl Microbiol 2002; 93:326-35. [PMID: 12147082 DOI: 10.1046/j.1365-2672.2002.01699.x] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
AIMS Inactivation and sublethal injury of Lactobacillus plantarum at different pulsed electric field (PEF) strengths and total energy inputs were investigated to differentiate reversible and irreversible impacts on cell functionality. METHODS AND RESULTS Lactobacillus plantarum was treated with PEF in model beer (MB) to determine critical values of field strength and energy input for cell inactivation. Below critical values, metabolic activity and membrane integrity were initially reduced without loss of viability. Above critical values, however, irreversible cell damage occurred. Presence of nisin or hop extract, during PEF treatment, resulted in an additional reduction of cell viability by 1;5 log cycles. Also, addition of the hop extract resulted in an additional two log cycles of sublethal injury. Partial reversibility of membrane damage was observed using propidium iodide (PI) uptake and staining. Inoculated MB containing hops was stored after PEF to evaluate the efficacy of such treatment for beer preservation. CONCLUSION Cells were inactivated only above critical values of 13 kV x cm(-1) and 64 kJ x kg(-1); below these values cell damage was reversible. Storage experiments revealed that surviving cells were killed after 15 h storage in MB containing hops. SIGNIFICANCE AND IMPACT OF THE STUDY Both reversible and irreversible cell damage due to PEF treatment was detected, depending on specific treatment conditions. The combination of PEF and hop addition is a promising nonthermal method of preservation for beer.
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Knorr D, Ade-Omowaye BIO, Heinz V. Nutritional improvement of plant foods by non-thermal processing. Proc Nutr Soc 2002; 61:311-8. [PMID: 12133214 DOI: 10.1079/pns2002162] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
As a result of the increasing consumer demand for minimally-processed fresh-like food products with high sensory and nutritional qualities, there is a growing interest in non-thermal processes for food processing and preservation. Key advanced technologies such as high-pressure processing, pulsed electric fields, dense gases and ultrasound are being applied to develop gentle but targeted processes to further improve the quality and safety of processed foods. These technologies also offer the potential for improving existing processes as well as for developing new process options. Furthermore, by adding new process dimensions (such as hydrostatic pressure, electric fields, ultrasonics, supercritical CO2) to the conventional process variables of temperature and time, they facilitate enlargement of the availability of unit operations. These operations might be applied effectively in unique combination processes, or as subsequent processing tools in more-targeted and subsequently less-intensive processes for food preservation and modification than the currently-applied processes.
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Lee DU, Heinz V, Knorr D. Biphasic inactivation kinetics of Escherichia coli in liquid whole egg by high hydrostatic pressure treatments. Biotechnol Prog 2001; 17:1020-5. [PMID: 11735435 DOI: 10.1021/bp010095o] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Kinetic studies on the isothermal high hydrostatic pressure (HHP) inactivation of Escherichia coli in liquid whole egg (LWE) were performed at 5 and 25 degrees C in the pressure range of 250-400 MPa. The characteristic tailing inactivation curves were described by a first-order biphasic model. As compared to a previous rheological study, it is suggested that the phase change of LWE during pressure treatment affects the inactivation rate of E. coli. Within the processing criteria where the rheological properties of LWE were still comparable to those of fresh LWE, HHP treatments at 5 degrees C induced more E. coli inactivations than those at 25 degrees C. From the results of approximately 3 log reductions of E. coli and over 5 log reductions of Pseudomonas and Paenibacillus, HHP treatment of LWE at 5 degrees C is regarded to be as effective as conventional thermal pasteurization. However, no post-process contamination and the consistency of temperature during preparation, HHP treatment, and storage provide clear processing advantages.
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Zenker M, Heinz V, Knorr D. Combined Application of Ultrasound and Temperature for Eenergy-Saving and Mild Preservation of Liquid Foods. CHEM-ING-TECH 2001. [DOI: 10.1002/1522-2640(200106)73:6<696::aid-cite6961111>3.0.co;2-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Heinz V, Ananta E, Knorr D. Spore Control in Food by Pressure Assisted Heating. CHEM-ING-TECH 2001. [DOI: 10.1002/1522-2640(200106)73:6<698::aid-cite6982222>3.0.co;2-l] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Ade-Omowaye B, Angersbach A, Heinz V, Knorr D. Effects of Pulsed Electric Fields on Cell Membrane Permeabilisation and Mass Transfer in Food Processing. CHEM-ING-TECH 2001. [DOI: 10.1002/1522-2640(200106)73:6<756::aid-cite7564444>3.0.co;2-p] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Angersbach A, Heinz V, Knorr D. Verfahrenstechnische Aspekte der Hochspannungsimpulsmethode (HELP) zum Zellaufschluss in der Lebensmittel- und Biotechnologie. CHEM-ING-TECH 2000. [DOI: 10.1002/1522-2640(200009)72:9<935::aid-cite9351>3.0.co;2-i] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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