Electrochemical reactions and electrode corrosion in pulsed electric field (PEF) treatment chambers

Tuning the Locally Enhanced Electric Field Treatment (LEEFT) between Electrophysical and Electrochemical Mechanisms for Bacteria Inactivation

Efficient drinking water disinfection methods are critical for public health. Locally enhanced electric field treatment (LEEFT) is an antimicrobial method that uses sharp structures, like metallic nanowires, to enhance the electric field at tips and cause bacteria inactivation. Electroporation is the originally designed mechanism of LEEFT. Although oxidation is typically undesired due to byproduct generation and electrode corrosion, it can enhance the overall disinfection efficiency. In this work, we conduct an operando investigation of LEEFT, in which we change the electrical parameters to tune the mechanisms between electrophysical electroporation and electrochemical oxidation. Pure electroporation (i.e., without detectable oxidation) could be achieved under a duty cycle of ≤0.1% and a pulse width of ≤2 μs. Applying 2 μs pulses at 7-8 kV/cm and 0.1% duty cycle results in 80-100% bacteria inactivation with pure electroporation. A higher chance of oxidation is found with a higher duty cycle and a longer pulse width, where the antimicrobial efficiency could also be enhanced. For water with a higher conductivity, a higher antimicrobial efficiency can be achieved under the same treatment conditions, and electrochemical reactions could be induced more easily. The findings shown in this work improve the fundamental understanding of LEEFT and help optimize the performance of LEEFT in real applications.

Non-thermal techniques as an approach to modify the structure of milk proteins and improve their functionalities: a review of novel preparation

BACKGROUND

Milk proteins (MPs) have been widely used in the food industry due to their excellent functionalities. However, MPs are thermal-unstable substances and their functional properties are easily affected by heat treatment. Emerging non-thermal approaches (i.e., high-pressure homogenization (HPH), ultrasound (US), pulsed electric field (PEF)) have been increasingly popular. A detailed understanding of these approaches' impacts on the structure and functionalities of MPs can provide theoretical guidance for further development to accelerate their industrialization.

SCOPE AND APPROACH

This review assesses the mechanisms of HPH, US and PEF technologies on the structure and functionalities of MPs from molecular, mesoscopic and macroscopic levels, elucidates the modifications of MPs by these theologies combined with other methods, and further discusses their existing issues and the development in the food filed.

KEY FINDINGS AND CONCLUSIONS

The structure of MPs changed after HPH, US and PEF treatment, affecting their functionalities. The changes in these properties of MPs are related to treated-parameters of used-technologies, the concentration of MPs, as well as molecular properties. Additionally, these technologies combined with other methods could obtain some outstanding functional properties for MPs. If properly managed, these theologies can be tailored for manufacturing superior functional MPs for various processing fields.

Comprehensive review on pulsed electric field in food preservation: gaps in current studies for potential future research

In pulsed electric field (PEF) method sources of high voltage pulses are placed amid two electrodes in to fluid or paste type foods. Electricity is passed between two electrodes to sterilize the food. Almost all PEF technology entails the use of this technology in milk and milk product processing, eggs, poultry, juices and other liquid foods to prevent microorganisms. PEF technology, one of the promising methods of non-thermal preservation of food, can address the biological hazards efficiently. Recently available research papers explored PEF technology not only to facilitate the inactivation of microorganisms but also to alleviate the pressing competence for juice extraction purpose from plants for food application and also to intensify the drying and dehydration process of food. Most of the literatures are available on killing of microorganisms using PEF technology but the reports on influence of PEF technology on quality parameters of food after treatment and about their acceptability are limited. Now the technology is becoming popular and many recent papers reported about better yield and excellent quality of nutrient extracted by using PEF technology.

Application of electric field treatment (EFT) for microbial control in water and liquid food

Water disinfection and food pasteurization are critical to reducing waterborne and foodborne diseases, which have been a pressing public health issue globally. Electrified treatment processes are emerging and have become promising alternatives due to the low cost of electricity, independence of chemicals, and low potential to form by-products. Electric field treatment (EFT) is a physical pathogen inactivation approach, which damages cell membrane by irreversible electroporation. EFT has been studied for both water disinfection and food pasteurization. However, no study has systematically connected the two fields with an up-to-date review. In this article, we first provide a comprehensive background of microbial control in water and food, followed by the introduction of EFT. Subsequently, we summarize the recent EFT studies for pathogen inactivation from three aspects, the processing parameters, its efficacy against different pathogens, and the impact of liquid properties on the inactivation performance. We also review the development of novel configurations and materials for EFT devices to address the current challenges of EFT. This review introduces EFT from an engineering perspective and may serve as a bridge to connect the field of environmental engineering and food science.

Pulsed electric field processing as an alternative to sulfites (SO2) for controlling saccharomyces cerevisiae involved in the fermentation of Chardonnay white wine

The use of sulfites (SO₂) for microbial control in the winemaking process is currently being questioned due to its potential toxicity. Pulsed Electric Fields (PEF) are capable of inactivating microorganisms at low temperatures, thus avoiding the negative effects of heat on food properties. In this study, the capacity of PEF technology for the decontamination of yeasts involved in the fermentation process of Chardonnay wine from a winery was evaluated. PEF treatments at 15 kV/cm of low (65 µs, 35 kJ/kg) and higher intensity (177 µs 97 kJ/kg) were selected for evaluating the microbial stability, physicochemical and volatile composition of wine. Even with the least intense PEF-treatment, Chardonnay wine remained yeast-free during 4 months of storage without sulfites. PEF-treatments did not affect the wine's oenological parameters or its aroma during storage. This study, therefore, reveals the potential of PEF technology as an alternative to sulfites for the microbiological stabilization of wine.

Advances in pulsed electric stimuli as a physical method for treating liquid foods

There is a need for alternative technologies that can deliver safe and nutritious foods at lower costs as compared to conventional processes. Pulsed electric field (PEF) technology has been utilised for a plethora of different applications in the life and physical sciences, such as gene/drug delivery in medicine and extraction of bioactive compounds in food science and technology. PEF technology for treating liquid foods involves engineering principles to develop the equipment, and quantitative biochemistry and microbiology techniques to validate the process. There are numerous challenges to address for its application in liquid foods such as the 5-log pathogen reduction target in food safety, maintaining the food quality, and scale up of this physical approach for industrial integration. Here, we present the engineering principles associated with pulsed electric fields, related inactivation models of microorganisms, electroporation and electropermeabilization theory, to increase the quality and safety of liquid foods; including water, milk, beer, wine, fruit juices, cider, and liquid eggs. Ultimately, we discuss the outlook of the field and emphasise research gaps.

Pulsed Electric Field Processing of Red Wine: Effect on Wine Quality and Microbial Inactivation

Pulsed electric field (PEF) treatment of red wine samples with energies changing from 2.4 to 13.2 kJ to inactivate Saccharomyces cerevisiae, Hansenula anomala, Candida lipolytica, Lactobacillus delbrueckii ssp. bulgaricus, and Escherichia coli O157:H7 with the determination of the changes in the quality and sensory properties in addition to metal ion concentration (Na, Mg, K, and Mn) were explored. Increased applied energy resulted in a significant increase in pH, conductivity, lightness (L*), yellowness (b*), and total phenolic substance content with significant inactivation of all microorganisms with no significant change in metal ion concentration. Sensory properties of particle status, sour taste, and aftertaste were significantly decreased, whereas the other measured properties were significantly increased by 13.2 kJ PEF treatment (p < 0.05). Joint optimization studies for the most optimal processing parameters for the measured properties were 488 s, 0.13 kJ, and 0.22 kV; 488 s, 13.2 kJ, and 31 kV; 348 s, 9.39 kJ, and 31 kV/cm; and 488 s, 13.2 kJ, and 0 kV EFS, with 0.79, 0.69, 1.00, and 0.72 composite desirability, respectively.

Applications of Innovative Non-Thermal Pulsed Electric Field Technology in Developing Safer and Healthier Fruit Juices

The deactivation of degrading and pectinolytic enzymes is crucial in the fruit juice industry. In commercial fruit juice production, a variety of approaches are applied to inactivate degradative enzymes. One of the most extensively utilized traditional procedures for improving the general acceptability of juice is thermal heat treatment. The utilization of a non-thermal pulsed electric field (PEF) as a promising technology for retaining the fresh-like qualities of juice by efficiently inactivating enzymes and bacteria will be discussed in this review. Induced structural alteration provides for energy savings, reduced raw material waste, and the development of new products. PEF alters the α-helix conformation and changes the active site of enzymes. Furthermore, PEF-treated juices restore enzymatic activity during storage due to either partial enzyme inactivation or the presence of PEF-resistant isozymes. The increase in activity sites caused by structural changes causes the enzymes to be hyperactivated. PEF pretreatments or their combination with other nonthermal techniques improve enzyme activation. For endogenous enzyme inactivation, a clean-label hurdle technology based on PEF and mild temperature could be utilized instead of harsh heat treatments. Furthermore, by substituting or combining conventional pasteurization with PEF technology for improved preservation of both fruit and vegetable juices, PEF technology has enormous economic potential. PEF treatment has advantages not only in terms of product quality but also in terms of manufacturing. Extending the shelf life simplifies production planning and broadens the product range significantly. Supermarkets can be served from the warehouse by increasing storage stability. As storage stability improves, set-up and cleaning durations decrease, and flexibility increases, with only minor product adjustments required throughout the manufacturing process.

Effects of connection mode on acid hydrolysis of corn starch during induced electric field treatment

This study aimed to explore the effect of induced electric field (IEF) treatment on acid hydrolysis of corn starch by altering the connection modes of sample coils of a 4-reactor IEF system. Results suggested that IEF treatment could enhance the hydrolysis of corn starch and series connection (1. RRRR, η=16ESi2Pin4ZSi+Zload) exhibited higher energy efficiency than parallel (9. (RRRR), η=4ESi2PinZSi+4Zload), thus contributing to more extensive hydrolysis. Although no new functional group was formed, the starch granules were partially cracked into pieces and the crystallinity was slightly increased after IEF-assisted hydrolysis. Differential scanning calorimetry results indicated that IEF-assisted hydrolysis increased the gelatinization temperatures but decreased the enthalpy of starch, with a greatest variation was observed by series connection. Rapid visco-analysis showed that IEF-assisted hydrolysis greatly decreased the pasting viscosity of corn starch and also series connection showed the strongest reduction. The obtained results could provide a theoretical guide for the applications of IEF technology in biomaterial processing.

Cytotoxicity of a Cell Culture Medium Treated with a High-Voltage Pulse Using Stainless Steel Electrodes and the Role of Iron Ions

High-voltage pulses applied to a cell suspension cause not only cell membrane permeabilization, but a variety of electrolysis reactions to also occur at the electrode–solution interfaces. Here, the cytotoxicity of a culture medium treated by a single electric pulse and the role of the iron ions in this cytotoxicity were studied in vitro. The experiments were carried out on mouse hepatoma MH-22A, rat glioma C6, and Chinese hamster ovary cells. The cell culture medium treated with a high-voltage pulse was highly cytotoxic. All cells died in the medium treated by a single electric pulse with a duration of 2 ms and an amplitude of just 0.2 kV/cm. The medium treated with a shorter pulse was less cytotoxic. The cell viability was inversely proportional to the amount of electric charge that flowed through the solution. The amount of iron ions released from the stainless steel anode (>0.5 mM) was enough to reduce cell viability. However, iron ions were not the sole reason of cell death. To kill all MH-22A and CHO cells, the concentration of Fe³⁺ ions in a medium of more than 2 mM was required.

Effect of Pulsed Electric Field (PEF) on Bacterial Viability and Whey Protein in the Processing of Raw Milk

There is growing concern regarding the nutritional value of processed food products. Although thermal pasteurization, used in food processing, is a safe method and is widely applied in the food industry, food products lack quality and nutritional value because of the high temperatures used during pasteurization. In this study, the effect of pulsed electric field (PEF) processing on whey protein content and bacterial viability in raw milk was evaluated by changing the PEF strength and number of pulses. For comparison, traditional pasteurization techniques, such as low-temperature long-time (LTLT), ultra-high temperature (UHT), and microfiltration (MF), were also tested for total whey protein content, bacterial activity, and coliforms. We found that, after treatment with PEF, a significant decrease in total bacterial viability of 2.43 log and coliforms of 0.9 log was achieved, although undenatured whey protein content was not affected at 4.98 mg/mL. While traditional pasteurization techniques showed total bacterial inactivation, they were detrimental for whey protein content: β-lactoglobulin was not detected using HPLC in samples treated with UHT. LTLT treatment led to a significant decrease of 75% in β-lactoglobulin concentration; β-lactoglobulin content in milk samples treated with MF was the lowest compared to LTLT and UHT pasteurization, and ~10% and 27% reduction was observed.

Nanosecond pulse used to enhance the electrocoagulation of municipal wastewater treatment with low specific energy consumption

This study compares the performance of nanosecond pulse (NSP) and direct current (DC) power supplies for use in a municipal wastewater treatment by electrocoagulation (EC). Four Al plates connected in monopolar-parallel configuration (MP-P) were used as electrodes during the EC process. The maximum chemical oxygen demand (COD) removal efficiency reached 68% and 80% using DC and NSP, respectively. Moreover, NSP treatment reduced approximately 15% of the specific energy consumption (SEC) compared with that by DC at a similar COD removal efficiency of ≈ 68%, which was used as a benchmark value. In addition, when using NSP, the SEC required to increase the COD removal efficiency from 60% to 68% was two to three times less than that when DC was applied. The results suggest that an NSP operating at 10 kHz frequency (f) and 1 µs pulse width (pw) are preferred for obtaining higher COD removal efficiencies at a low SEC. The use of an NSP for EC can enhance the COD removal efficiency and reduce the wastewater treatment SEC. The results presented herein promote the use of EC systems combined with renewable energy sources for reducing the net carbon footprint of wastewater processing.

Electroporation with nanosecond pulses and bleomycin or cisplatin results in efficient cell kill and low metal release from electrodes

Nanosecond electric pulses have several potential advantages in electroporation-based procedures over the conventional micro- and millisecond pulses including low level of heating, reduced electrochemical reactions and reduced muscle contractions making them alluring for use in biomedicine and food industry. The aim of this study was to evaluate if nanosecond pulses can enhance the cytotoxicity of chemotherapeutics bleomycin and cisplatin in vitro and to quantify metal release from electrodes in comparison to 100 μs pulses commonly used in electrochemotherapy. The effects of nanosecond pulse parameters (voltage, pulse duration, number of pulses) on cell membrane permeabilization, resealing and on cell survival after electroporation only and after electrochemotherapy with bleomycin and cisplatin were evaluated on Chinese hamster ovary cells. Application of permeabilizing nanosecond pulses in combination with chemotherapeutics resulted in successful cell kill. Higher extracellular concentrations of bleomycin - but not cisplatin - were needed to achieve the same decrease in cell survival with nanosecond pulses as with eight 100 μs pulses, however, the tested bleomycin concentrations were still considerably lower compared to doses used in clinical practice. Decreasing the pulse duration from microseconds to nanoseconds and concomitantly increasing the amplitude to achieve the same biological effect resulted in reduced release of aluminum ions from electroporation cuvettes.

Incorporation of Reversible Electroporation Into Electrolysis Accelerates Apoptosis for Rat Liver Tissue

Tissue electrolysis is an alternative modality that uses a low intensity direct electric current passing through at least 2 electrodes within the tissue and resulting electrochemical products including chlorine and hydrogen. These products induce changes in pH around electrodes and cause dehydration resulting from electroosmotic pressure, leading to changes in microenvironment and thus metabolism of the tissues, yielding apoptosis. The procedure requires adequate time for electrochemical reactions to yield products sufficient to induce apoptosis of the tissues. Incorporation of electroporation into electrolysis can decrease the treatment time and enhance the efficiency of electrolytic ablation. Electroporation causes permeabilization in the cell membrane allowing the efflux of potassium ions and extension of the electrochemical area, facilitating the electrolysis process. However, little is known about the combined effects on apoptosis in liver ablation. In this study, we performed an immunohistochemical evaluation of apoptosis for the incorporation of electroporation into electrolysis in liver tissues. To do so, the study was performed with microelectrodes for fixed treatment time while the applied voltage varied to increase the applied total energy for electrolysis. The apoptotic rate for electrolytic ablation increased with enhanced applied energy. The apoptotic rate was 4.31 ± 1.73 times that of control in the synergistic combination compared to 1.49 ± 0.33 times that of the control in electrolytic ablation alone. Additionally, tissue structure was better preserved in synergistic combination ablation compared to electrolysis with an increment of 3.8 mA. Thus, synergistic ablation may accelerate apoptosis and be a promising modality for the treatment of liver tumors.

Innovative induction heating of grapefruit juice via induced electric field and its application in Escherichia coli O157:H7 inactivation

The proposed induction heating method was applied in the pasteurization of grapefruit juice. In this processing, an alternating magnetic field acted as the stimulus instead of conventional electrodes to create an induced electric field (IEF) for heat treatment of the continuous-flow juice sample, which excluded the possibility of electrochemical reaction and electrode corrosion that might occur in conventional electric field treatments. As a typical food pathogen, Escherichia coli O157:H7 was selected as a representative to investigate its inactivation by the heating process under different voltages and frequencies, initial temperatures, and flow rates (or retention time). The grapefruit juice was successfully heated up by IEF and the temperature curve was achieved when the juice exposed to IEF. The heating rate and terminal temperature increased with the increasing induced voltage, decreasing frequency and at higher initial temperature. A highest terminal temperature of 93.7 °C for grapefruit juice with an initial temperature of 20 °C was achieved under induced voltage of 2700 V, frequency of 300 Hz and residence time of 400 s. At the same time, E. coli O157:H7 in the grapefruit juice was thoroughly inactivated. There was a trend that the pathogen survival rate was reduced at higher induced voltage, lower frequency and higher initial temperature during the heating treatment. No significant changes in pH and °Brix was observed after this innovative induction heating, but the color of grapefruit juice was brightened. The proposed induction heating can be regarded as a sister technology of ohmic heating, and it provide a reference for the application of this heating method in liquid food pasteurization.

Innovative induction heating method is applied in the pasteurization of grapefruit juice.

Recent advances in continuous extraction of bioactive ingredients from food-processing wastes by pulsed electric fields

The food processing produces a great amount of wastes that are rich in nutrients. Extraction is the first and most important step in recovery and purification of active ingredients from these wastes. The traditional extraction technologies are known to be laborious and time-consuming, require large volumes of organic solvent, have high temperature and energy costs, and obtain relatively low extraction efficiency. In recent 10 years, a novel, efficient and green extraction method, pulsed electric fields (PEFs) continuous extraction, which is emerging non-thermal food-processing technology, has shown great promise in extracting these food wastes. This work gives an overview of development in the use of PEF continuous extraction for obtaining bioactive ingredients from food-processing wastes. The technology is described in detail with respect to the mechanism, equipment, critical parameters. The protocols and applications of the technology in the extraction of food-processing wastes are comprehensively summarized. Finally, the degradation of bioactive ingredients, industrial applications, problem of novel food, consumer acceptance, and future trends of the technology are discussed. The PEF continuous extraction is considered as the ideal technology of high efficiency and low temperature for natural ingredients extraction. The technology possesses many remarkable potential applications in the food-processing industries compared to the conventional extraction methods.

Pulsed Electric Field Processing of Red Grapes (cv. Rondinella): Modifications of Phenolic Fraction and Effects on Wine Evolution

Pulsed electric field (PEF) is a non-thermal technology able to promote color and polyphenols extraction from grape skins. Most of the publications about PEF in winemaking report data concerning international varieties, poorly considering minor cultivars and the medium/long-term effects of the treatment on wine composition during storage. PEF was applied at different specific energies (2, 10, and 20 kJ kg-1) on grapes of the low-color red cv. Rondinella, after crushing-destemming. Pressing yield, the evolution of color, and total phenolic index (TPI) were measured during skin maceration. Moreover, the wines were characterized for basic compositional parameters, color, anthocyanin profile, phenolic composition (glories indices), metal content (Fe, Cr, and Ni), and sensory characters, two and twelve months after the processing, in comparison with untreated samples and pectolytic enzymes (PE). PEF did not affect fermentation evolution, nor did it modify wine basic composition or metal content. Treatments at 10 and 20 kJ kg-1 led to higher color and TPI in wines, in comparison to PE, because of increased content of anthocyanins and tannins. The sensory evaluation confirmed these findings. Modifications remained stable in wines after twelve months. Glories indices and vitisin A content highlighted greater potential stability of wine color in PEF-treated wines.

Application of pulsed electric fields in meat and fish processing industries: An overview

The market demand for new meat and fish products with enhanced physicochemical and nutritional properties attracted the interest of the food industry and academia to investigate innovative processing approaches such as pulsed electric fields (PEF). PEF is an emerging technology based on the application of electrical currents between two electrodes thus inducing electroporation phenomena and enabling a non-invasive modification of the tissues' structure. This review provides an overview of the current knowledge on the use of PEF processing in meat and fish to enhance the physicochemical and nutritional changes, as a preservation method, as well as for improving the extraction of high added-value compounds. PEF treatment had the ability to improve several processes such as preservation, tenderization, and aging. Besides, PEF treatment could be used as a useful strategy to increase water holding properties of fish products as well as for fish drying. Finally, PEF could be also used in both meat and fish foods for by-products valorization, due to its potential to enhance the extraction of high added-value compounds. However, more studies are warranted to completely define specific treatments that can be consistently applied in the industry. This review provides the directions for this purpose in the near future.

Electrofluid enhanced hydrolysis of maize starch and its impacts on physical properties

To achieve high-output, successional, and efficient hydrolysis of carbohydrate polymers is an increasing concern in the food and chemical industries.

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.

Research advances in deriving renewable energy from biomass in wastewater treatment plants

Anaerobic digestion (AD) can be used to derive renewable energy from biomass in wastewater treatment plants, and the produced biogas represents a valuable end-product that can greatly offset operation costs.

Inactivation of Bacillus cereus spores in a tsuyu sauce using continuous ohmic heating with five sequential elbow-type electrodes

AIMS

The effect of ohmic heating (OH) in a pilot plant system which had a zig-zag shaped (elbow-type) ohmic heater with five sequential voltage electrodes was investigated on Bacillus cereus spores in a commercial tsuyu sauce.

METHODS AND RESULTS

The electrical field was fixed at 26·7 V cm(-1) with an alternating current frequency of 25 kHz. Raw tsuyu sauce (50 l) inoculated with B. cereus spores was submitted in a 4 × 3 factorial design to the OH system and heated at 95, 105, 115, and 125°C each for 30, 60, and 90 s. Survival of B. cereus spores and colour change in the commercial tsuyu sauce were both measured before and after treatment. As the treatment temperature and time increased, the number of surviving B. cereus spores decreased. The OH treatment in a bath-type process at 105°C for more than 30 s resulted in the total inactivation of the inoculated B. cereus spores (average 5·4 log reductions to undetectable levels after treatment). The OH protocol of heating at 105°C for 60 s which ensure complete eradication of the inoculated spores without compromising product quality was chosen and investigated for its suitability for commercial application on bulk quantities of samples (500 l). Reliable and reproducible reductions in B. cereus spore counts of 4·7-5·5 log CFU ml(-1) (mean ± standard deviation = 5·1 ± 0·3 CFU ml(-1) ) were achieved by the selected protocol of the continuous OH treatment (105°C for 60 s).

CONCLUSION

This study suggests that OH treatment with five sequential elbow-type electrodes has great potential as an industrial sterilizing method for liquid food contaminated with B. cereus spores.

SIGNIFICANCE AND IMPACT OF THE STUDY

This procedure will enhance the microbiological quality of liquid foods while minimizing quality deterioration.

Tumor growth delay by adjuvant alternating electric fields which appears non-thermally mediated

Delivery of the so-called Tumor Treatment Fields (TTFields) has been proposed as a cancer therapy. These are low magnitude alternating electric fields at frequencies from 100 to 300 kHz which are applied continuously in a non-invasive manner. Electric field delivery may produce an increase in temperature which cannot be neglected. We hypothesized that the reported results obtained by applying TTFields in vivo could be due to heat rather than to electrical forces as previously suggested. Here, an in vivo study is presented in which pancreatic tumors subcutaneously implanted in nude mice were treated for a week either with mild hyperthermia (41 °C) or with TTFields (6 V/cm, 150 kHz) and tumor growth was assessed. Although the TTFields applied singly did not produce any significant effect, the combination with chemotherapy did show a delay in tumor growth in comparison to animals treated only with chemotherapy (median relative reduction=47%). We conclude that concomitant chemotherapy and TTFields delivery show a beneficial impact on pancreatic tumor growth. Contrary to our hypothesis, this impact is non-related with the induced temperature increase.

Electroporation in food processing and biorefinery

Electroporation is a method of treatment of plant tissue that due to its nonthermal nature enables preservation of the natural quality, colour and vitamin composition of food products. The range of processes where electroporation was shown to preserve quality, increase extract yield or optimize energy input into the process is overwhelming, though not exhausted; e.g. extraction of valuable compounds and juices, dehydration, cryopreservation, etc. Electroporation is--due to its antimicrobial action--a subject of research as one stage of the pasteurization or sterilization process, as well as a method of plant metabolism stimulation. This paper provides an overview of electroporation as applied to plant materials and electroporation applications in food processing, a quick summary of the basic technical aspects on the topic, and a brief discussion on perspectives for future research and development in the field. The paper is a review in the very broadest sense of the word, written with the purpose of orienting the interested newcomer to the field of electroporation applications in food technology towards the pertinent, highly relevant and more in-depth literature from the respective subdomains of electroporation research.