A HV pulse generator for PEF applications

In this work, a high voltage (HV) pulse generator for pulsed electric fields (PEF) application in treatment of liquid food is presented. A complete overview of the target application is followed by a detailed analysis and design of a 10 stages Marx generator. The pulse generator uses semiconductor switches to generate up to 30kV pulses of 2μs and 2400Hz frequency. Simulation of the electrical characteristics of the pulse generator and of the electric field, and temperature variations inside the chamber are presented as well as measured results of a 3-stage prototype

ASPECTS REGARDING THE PRESERVATION OF FOOD PRODUCTS USING HIGH VOLTAGE PULSED ELECTRIC FIELD

Food preservation is an important link in ensuring their quality. The ways in which this desideratum is achieved include a wide range of conservation, thermal and athermal techniques. The paper presents aspects regarding the preservation of food products using the high voltage pulsed electric field, as well as the current stage of the realization of technical equipment that uses this technology

Non-Thermal Processing of a Protein Functional Beverage Using Pulsed Electric Fields: Escherichia coli Inactivation and Effect on Proteins

The application of pulsed electric fields (PEFs) for the inactivation of Escherichia coli, suspended in a protein shake beverage and diluted with sterilized distilled water was carried out. Square bipolar pulses in the range of 25–40 kV/cm electric field intensities were applied at different frequencies (400–900 Hz) to investigate the effect of different PEF conditions on the microbial population and proteins relevant to this functional beverage. The treatment temperature was kept below the lethal temperature of the microorganism under investigation. As power consumption plays an important role in the efficiency of the PEF application, the dissipated power was also estimated. Four log reductions in the E. coli population were obtained with 10 pulses at a 40 kV/cm field intensity and 25 pulses at a 25 kV/cm field intensity. PEF-treated whey-protein concentrates showed less denaturation in proteins than thermally treated concentrates, especially for lower electric field intensities (0% denaturation ± 0.007 at 25 kV/cm and 900 Hz, 4.41% denaturation ± 0.008 at 40 kV/cm and 400 Hz). Soy protein isolates manifested high sensitivity to PEF processing and resulted in denaturation and aggregation in the protein structure.info:eu-repo/semantics/publishedVersio

An innovative and non-invasive technology for PEF food processing

The use of pulsed electric fields (PEFs) is a mature technology used in the industrial processing of food, for example, fruit juice. It is however restricted to liquid (pumpable) food and involves metal electrodes in direct contact with the foodstuff – i.e. it is at present an inherently ‘invasive’ technology. Recently, Loughborough University has undertaken an experimental programme aimed at demonstrating a new and ‘non-invasive’ technology that uses an antenna coupled to a fast high-voltage pulse generator to produce an intense pulsed electric field. The machine that has been built and undergone preliminary testing uses a Teslatransformer- based pulse forming line generator coupled to a Valentine antenna to produce very intense electric fields in water. The technology developed offers considerable scope for use with any type of food, including solid foods such as meat. Apart from the much greater volume available for processing, and other more or less obvious advantages, the new technique is also highly energy efficient as, unlike the existing invasive approach, it does not drive a current through the food being processed. The paper presents the experimental equipment and explains the type of sensors that need to be developed for measurement of the electric field produced. Some of the major implications the technique may offer for the future of PEF food processing are introduced

Engineering Aspects of Pulsed Electroplasmolysis of Vegetable Tissues

Rosana G. Moreira, Editor-in-Chief; Texas A&M UniversityThis is an Invited Paper from International Commission of Agricultural Engineering (CIGR, Commission Internationale du Genie Rural) E-Journal Volume 5 (2003): M.O. Ngadi, M.I. Bazhal, and G.S.V. Raghavan. Engineering Aspects of Pulsed Electroplasmolysis of Vegetable Tissues. Vol. V. February 2003

TiO₂-coated electrodes for pulsed electric field treatment of microorganisms

Pulsed electric fields (PEF) can cause irreversible damage to bio-membranes and may result in inactivation of microorganisms. The aim of this paper is to investigate the PEF treatment of the yeast Saccharomyces cerevisiae, using a novel treatment cell with parallel-plane electrodes coated with a 2 µm thin TiO2 film. Two different PEF waveforms, square and exponential, with magnitudes of 67 kV/cm and 80 kV/cm, were used in this study. The efficacy of the PEF treatment was assessed by comparison of the surviving treated and untreated yeast populations, and it was shown that a treatment cell with TiO2-coated electrodes can be successfully used for the PEF treatment of microorganisms: 3-log10 reduction in the yeast population was achieved with 100 impulses. The energy efficacy of the PEF process in the proposed treatment cell has been compared with the energy losses in the PEF treatment cell with uncoated, conductive electrodes. It is shown that the electrodes coated with TiO2 provide better performance as compared with the traditional uncoated electrodes

Prednosti i nedostaci različitih pristupa generiranja impulsa za elektroporaciju

Electroporator is a generator of electric pulses that is used for permeabilization of cells. There are five major concepts of electroporation design. Capacitor discharge, square wave generator, and analog generator are used to generate classical electroporation pulses that are longer than microsecond and pulse forming network, and resonant charging generator that are used to generate nanosecond electroporation pulses. The choice of an electroporator design is always driven by the biotechnological or biomedical application. Electroporators can be used for introduction of small (electrochemotherapy) and large molecules (gene electrotransfer), cell fusion, insertion of proteins into cell membrane, electroporation of organelles, pasteurization, tissue ablation etc. Basic concepts and foreseeable future developments in electroporator design are presented in this article.Elektroporator je generator impulsa koji se koristi za permeabilizaciju stanica. Postoji pet glavnih izvedbi elektroporatora. Pražnjenje kondenzatora, generator pravokutnog valnog oblika i analogni generator se koriste za klasične elektroporacijske impulse koji su duži od mikrosekunde, a mreža za formiranje impulsa i generator s rezonantnim nabijanjem se primjenjuju za generiranje nanosekundnih elektroporacijskih impulsa. Izbor izvedebe elektroporatora vođen je uvijek biotehnološkom ili biomedicinskom primjenom. Elektroporatori se mogu koristiti za ubacivanje malih (elektrokemoterapija) i velikih molekula (elektro genski prijenos), fuziju stanica, umetanje proteina u staničnu membranu, elektroporaciju organela, pasterizaciju, ablaciju tkiva itd. U radu su prikazani temeljni pristupi u izvedbama elektroporatora i predvidivi budući razvoj

Pulsed Electric Fields for Moscatel Graúdo wine production: Investigation on wine sensory and physico-chemical characteristics

Mestrado em Engenharia de Viticultura e Enologia. Universidade de Lisboa, Instituto Superior de Agronomia. Universidade do Porto, Faculdade de CiênciasPulsed electric field (PEF) processing of white grape (cv. Moscatel de Setúbal) before pressing for juice extraction, and before bottling for finished wine stabilization, was studied at pilot scale, to investigate the effect of the treatment on sensorial aspects and physico-chemical composition of wine. The application of PEF treatment before extraction increased yield of grape juice and wine colour assessed analytically with a spectrophotometer, although this change in colour was not perceived by the sensory panel. The PEF assisted extraction treatment did not affect the overall smell and taste of the wine, and content of phenolics. . A slight increase in pH and turbidity, and a slight decrease in total acidity were observed. CIE L* colour coordinate was slightly lower (darker) in wine produced using PEF extraction. CIE a* and b* colour parameters increased in wine with pulsed electric fields applied in extraction. The second PEF treatment applied for microbial stabilization of the wine did not influence pH, total acidity, but decreased total phenol contents and affected CIE colour parameters. Based on a statistic analysis of sensory results, panellists were not able to detect any difference between treated and non-treated wines, thus confirming the possibility to use PEF to improve the extraction and for microbial inactivation.O tratamento do campo eléctrico pulsado (PEF) de uva branca (cv. Moscatel de Setúbal) antes da prensagem para extracção de sumo, e antes do engarrafamento para estabilização do vinho acabado, foi estudado à escala piloto, para investigar o efeito do tratamento nos aspectos sensoriais e na composição físico-química do vinho. A aplicação do tratamento PEF antes da extracção aumentou o rendimento do sumo de uva e a cor do vinho avaliada analiticamente com um espectrofotómetro, embora esta mudança de cor não tenha sido percebida pelo painel sensorial. O tratamento de extracção assistida por PEF não afectou o odor e sabor geral do vinho, nem o conteúdo de fenóis. . Foi observado um ligeiro aumento do pH e turbidez, e uma ligeira diminuição da acidez total. A coordenada de cor CIE L* foi ligeiramente mais baixa (mais escura) no vinho produzido utilizando a extracção de PEF. Os parâmetros de cor CIE a* e b* aumentaram no vinho com campos eléctricos pulsantes aplicados na extracção. O segundo tratamento de PEF aplicado para estabilização microbiana do vinho não influenciou o pH, acidez total, mas diminuiu o teor total de fenol e afectou os parâmetros de cor do CIE. Com base numa análise estatística dos resultados sensoriais, os entrevistados não foram capazes de detectar qualquer diferença entre vinhos tratados e não tratados, confirmando assim a possibilidade de utilizar PEF para melhorar a extracção e para inactivação microbiana.N/

Superposition of DC voltage and submicrosecond impulses for energization of electrostatic precipitators

This paper discusses the development of an impulsive microelectrostatic precipitation technology, which uses superposition of submicrosecond high-field pulses and dc electric field. Short impulses allow the application of higher voltages to the ionization electrodes of a precipitation system without the initiation of breakdown. These higher levels of electric field generate higher ionic concentrations, resulting in more efficient charging of the airborne particles, and can potentially improve precipitation efficiency. This work is focused on the analysis of the behavior of impulsive positive corona discharges in a coaxial reactor designed for precipitation studies. The efficiency of precipitation of coarse and fine particles has been investigated using different dc and impulse voltage levels in order to establish optimal energization modes