Impact of ohmic heating on mass transfer in electroporated plant tissue-insights from numerical modelling

Electroporation, electropermeabilization or pulsed electric field treatment is the application of electric pulses of sufficient amplitude to target tissue, which entails not only permeabilization of cell membranes, but also heat generation and dissipation, i.e. ohmic heating. Noticeable rise in temperature has been observed in a number of electroporation applications. The temperature rise is a potential source of alteration of thermodynamic properties of tissue wherein mass transport is occurring. In example, transport parameters such as liquid viscosity and solute diffusivity are temperature-dependent, as they relate to thermodynamic processes. There is a need to evaluate whether the rate of mass transport is altered significantly by the elevated temperature in plant tissue electroporation. The goal is to advance the basic knowledge of the phenomenon, as well as to optimize further treatment protocols for industrial purposes. This work presents a theoretical study of thermal relations in tissue immediately following electroporation and begins with a hypothetical spatio-temporal distribution of temperature in a sample of plant tissue as calculated during the course of a simulated electroporation experiment. This step is followed by a mass transfer analysis, where two mathematical models of mass transport in electroporated tissue are used to study the impact of transiently elevated temperature to i) kinetics of diffusion of a test solute, and ii) kinetics of liquid redistribution in tissue and its flow to sample exterior caused by an externally applied pressure. The main result of the study is a detailed theoretical analysis on the potential influence of heat generated due to the application of electroporation on kinetics of mass transport in tissue. Preliminary theoretical findings of this mass transport study coupled to the heat transfer model indicate that, provided the initial temperature increase in tissue is within reasonable bounds and heat is rapidly conducted away from tissue (i.e. tissue is not thermally insulated), influence of the temperature rise to mass transport in treated tissue is negligible.Papers presented at the 13th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Portoroz, Slovenia on 17-19 July 2017 .International centre for heat and mass transfer.American society of thermal and fluids engineers

Energy-efficient biomass processing with pulsed electric fields for bioeconomy and sustainable development

Fossil resources-free sustainable development can be achieved through a transition to bioeconomy, an economy based on sustainable biomass-derived food, feed, chemicals, materials, and fuels. However, the transition to bioeconomy requires development of new energy-efficient technologies and processes to manipulate biomass feed stocks and their conversion into useful products, a collective term for which is biorefinery. One of the technological platforms that will enable various pathways of biomass conversion is based on pulsed electric fields applications (PEF). Energy efficiency of PEF treatment is achieved by specific increase of cell membrane permeability, a phenomenon known as membrane electroporation. Here, we review the opportunities that PEF and electroporation provide for the development of sustainable biorefineries. We describe the use of PEF treatment in biomass engineering, drying, deconstruction, extraction of phytochemicals, improvement of fermentations, and biogas production. These applications show the potential of PEF and consequent membrane electroporation to enable the bioeconomy and sustainable development

COMBINING MODERATE PULSED ELECTRIC FIELDS WITH TEMPERATURE AND WITH ORGANIC ACIDS TO INACTIVATE ESCHERICHIA COLI SUSPENSIONS

The aim of this work was to study the efficiency of inactivation of Escherichia coli cells in aqueous suspensions using combined moderate pulsed electric field (PEF) and thermal treatments. The inactivation kinetics of E. coli cells in aqueous suspensions (1 wt%) was monitored using conductometric technique. The electric field strength E was within 5-7.5 kV/cm, the effective PEF treatment time was within 0-0.75 s, the pulse duration ti was within 0.3-1 ms, the medium temperature was 30-50°C, and the time of thermal treatment tT was within 0-7000 s. The organic acid concentration was within 0-0.5 g/L.The damage of E. coli was accompanied by release of intracellular components. The synergy between the PEF and thermal treatments in E. coli inactivation was clearly demonstrated. The damage efficiency was noticeably improved by addition of organic acids, especially lactic acid

Improvement of sludge electrodewatering by anode flushing

An improvement of the sludge electrodewatering process is proposed: the anode flushing by filtrate recirculation. According to this technique, the mixture of filtrates obtained at cathode and anode sides, is used for continuous flushing of anode chamber of the filter press during electrodewatering. The anode flushing is aimed to eliminate essential problems of electrodewatering: ohmic heating, rise of electric energy consumption, electrodes corrosion, and filtrate contamination. This is attained by better control of the filtrate pH, the filter cake temperature and the dryness at anode side, where the physicochemical conditions are most aggressive. The efficiency of the proposed technique is evaluated at lab scale on drilling sludge electrodewatering with and without anode flushing. In experiments without anode flushing, increasing of electric current density caused strong increase of anodetemperature, desiccation of the filter cake at anode side, rise of voltage and significant alkaline contamination of filtrate. The application of anode flushing allowed controlling the electric field strength and the temperature. Thus, the dewatering of the sludge has been extended at high electric field without damaging the filter equipment by drastic heating. Furthermore, it reduced the filtrate contamination by neutralization of theelectrolysis products

Model of electrofiltration in a filter press with anode flushing

The model of electrofiltration in two-sided filter press with anode flushing by filtrate recirculation ispresented. The model describes the impact of anode flushing, electrical current density, andapplied pressure on the electrofiltration rate. Main feature of this model is the possibility ofelectroosmotic backflow of filtrate at anode side of the filter press. The model can be used for theoptimization of electrofiltration parameters for sludges with different properties (zeta potential andspecific cake resistance). The model was applied for description of the drilling sludgeelectrofiltration at different values of applied pressure and electrical current density

Seed oil polyphenols: Rapid and sensitive extraction method and high resolution–mass spectrometry identification

International audiencePhenolic content is a primary parameter for vegetables oil quality evaluation, and directly involved in the prevention of oxidation and oil preservation. Several methods have been reported in the literature for polyphenols extraction from seed oil but the approaches commonly used remain manually handled. In this work, we propose a rapid and sensitive method for seed oil polyphenols extraction and identification. For this purpose, polyphenols were extracted from Opuntia stricta Haw seed oil, using high frequency agitation, separated, and then identified using a liquid chromatography–high resolution mass spectrometry method. Our results showed good sensitivity and reproducibility of the developed methods

Enhancement of pressing of sugar beet cuts by combined ohmic heating and pulsed electric field treatment

This article describes the influence of combined ohmic heating (OH) and pulsed electric field (PEF) treatment on the juice extraction from sugar beet cuts of different sizes. The experiments were carried out on a laboratory filter-press cell connected to OH and PEF-treatment systems. OH (60 V/cm, 50 Hz) was used to attain different temperatures (30-70C), which were maintained during a fixed time (10-30 min). It was followed by a PEF treatment (600 V/cm, 0.04 s). OH noticeably enhances the extraction kinetics even at a moderate temperature of 50C. With the increase of OH temperature to 60C, the juice yield obtained by pressing is comparable to the one obtained after PEF treatment. The results show that combining OH and PEF treatment leads to some synergetic effect, promoting 85-87% of juice extraction even from middle and coarse cuts. This affect might result from both the electropermeabilization of cell membranes and the thermal softening of tissues