Pulsed Electric Field Processing Research Articles

Improvement in uniformity of co‐linear pulsed electric field treatment chamber by sub‐electrodes and its optimization

AbstractThe uniformity of performance parameters such as electric field and temperature for a co‐linear pulsed electric field (PEF) processing system is one of main factors affecting the processing effect and quality of liquid food. We have proposed a co‐linear PEF treatment chamber configuration with sub‐electrodes to improve the uniformity and processing efficiency. We have first examined how the position of the sub‐electrodes alone affects the uniformity of the performance parameters. Then, we have investigated the variation of the uniformity while changing simultaneously the electrode radius, inter‐electrode gap, and position of sub‐electrodes. As a result, we have found that the most uniform field could be obtained when the electrode radius is 5.5 mm, the inter‐electrode gap is 15 mm, and the sub‐electrodes situate at the middle of the chamber. In this chamber, the region between 95% and 105% of the average electric field covers 83%, which shows much improvement compared to the formers' results, 69.5% and 76%, respectively. Also, the optimal treatment chamber provides greater average electric field under the same voltages as the voltages reported by the formers.Practical applicationsA novel treatment chamber with sub‐electrodes is proposed for pulsed electric fields food processing. The improved treatment design was obtained by changing position of sub‐electrodes, inner radius of electrodes and distance between electrodes. The more uniform electric field was obtained in treatment region. The temperature distribution was more uniformed by increasing flow rates and uniformed electric field strength. The treatment throughput was increased by sub‐electrodes.

Protein enrichment of the red macroalga Palmaria palmata using pulsed electric field and enzymatic processing

Protein enrichment of the red macroalga Palmaria palmata using pulsed electric field and enzymatic processing

Improved lifetime of a pulsed electric field (PEF) system-using laser induced surface oxidation

In this research, we explore the possibility and effectiveness of using laser-induced surface oxidation methods to enhance the durability and effectiveness of PEF (Pulsed Electric Field) systems. Despite advantages over thermal pasteurisation, PEF faces challenges like electrode corrosion and biofouling, hindering its adoption. This research introduces laser-induced oxidation to mitigate metal ion release during PEF, directly targeting electrode alteration. Our examination adopts a comprehensive method, integrating Design of Experiments (DoE) parameter sets for PEF trials, morphological analysis, evaluation of metal ion release via Inductively Coupled Plasma Quadrupole Mass Spectrometry (ICP-QMS), waveform capture utilizing a Data Acquisition (DAQ) system, electrochemical assessment via impedance spectroscopy, and examination of oxide layer composition employing X-ray photoelectron spectroscopy. Pulse waveform characteristics shows the intricate relationship between PEF processing parameters with metal ion release, alongside XPS analysis providing insights into surface chemistry. Optimized results show a three-fold reduction in metal ion release post-PEF, with laser-treated samples outperforming untreated stainless steel due to selective surface chemistry alteration, notably an increased Cr/Fe ratio, reducing harmful elements. This study highlights laser-induced oxidation as a practical solution for enhancing PEF electrode performance and reducing metal ion release, addressing key challenges in PEF technology. It advances sustainable food processing, promising extended PEF system lifespan while maintaining efficiency and product quality.

Continuous pulsed electric field processing for intensification of aqueous extraction of protein from fresh green seaweed Ulva sp. biomass

The green marine macroalgae Ulva sp. can reach a high protein content and a high composition of essential amino acids. In this study, we have developed a novel device and investigated the parameters for a continuous Pulsed Electric Field (PEF) process, coupled with enzyme treatment followed by a spray drying, to facilitate the aqueous fractionation of Ulva protein. The process demonstrated 8.79 ± 0.58 (% w/w) protein extraction yield. Furthermore, the aqueous fractionation of protein exhibited a substantial 41.45% essential amino acid content and a branched amino acids composition of 17.58%. Additionally, it displayed an in vitro relative digestibility of 87.4 ± 1.36% compared to soy protein, along with a water holding capacity of 7.15 ± 0.17 g water/g sample and an oil holding capacity of 1.76 ± 0.11 g oil/g sample. These findings suggest that employing a continuous PEF process in conjunction with enzyme-induced cell wall degradation could position green marine macroalgae as an important potential source for food protein ingredients.

Trends, Recent Advances, and Application of Pulsed Electric Field in Food Processing: A Review

AbstractGenerally, thermal inputs dominate the food processing industry for food preservation. Pulsed electric field (PEF) is one of the most promising nonthermal microorganism‐killing techniques. The most important factors in PEF processing are electric field strength and treatment duration. At the laboratory level, encouraging results are reported; however, industrialization raises the cost of the command charging power supply and the high‐speed electrical switch. In this review, the results of previous experimental studies on PEFs and proposed future research directions in this field are discussed. There is currently no successful PEF processing system for industrial applications. Those who wish to promote the industrial application of the PEF processing system face a significant barrier in the form of the system's high initial cost of installation. Innovative developments in high‐voltage pulse technology will reduce the cost of pulse generation and make PEF processing competitive with thermal processing methods.

Membrane assisted Pulsed Electric Field (M-PEF) a novel technique for preservation of functional and biological properties of sugarcane juice.

Abstract According to market prospects there is a demand for the bottled fresh sugarcane juice than any other fruit based beverages because of its nutritional and therapeutic properties. Sugarcane juice short shelf life and deterioration are linked to the existence of active enzymes like peroxidase and polyphenol oxidase as well as its microbial composition. The membrane assisted pulsed electric field technology (M-PEF) was used for this experiment in which the hollow spiral wound ultra-filter membrane for 10 kDa pore size at 1 bar pressure employed as a pretreatment to pulsed electric field processing for the treatment of sugarcane juice. The process parameters are 20, 30, and 40 kV/cm field strength for the pulse width of 100, 150, and 200 μs. The reduction of 92% in polyphenol oxidase and 80% in peroxidase enzyme activity was achieved due to Pulsed electric field at a field strength and pulse width of 30 kV/cm for 150μs respectively retaining the overall quality of the sugarcane juice and there was 85-95% reduction was observed in the protein and polysaccharide content of the sugarcane juice due to the membrane filtration pore size exclusion effect. Ascorbic acid content was retained in the M-PEF samples while increasing its antioxidant capacity. The experiment results showed that due to Pulsed electric field treatment there was 3 log reductions are observed on total plate count. This technology showed that, it can be used as novel technique for the preservation of the fresh juices.

Processing of sugar kelp: Effects on mass balance, nutrient composition, and color

The European production of seaweed, including kelp species, is increasing, but efficient processing schemes for complete biomass valorization are still lacking. In this study, we investigated the effect of combining pulsed electric field (PEF) processing and soaking/blanching treatments (10, 45, and 60 °C) on the chemical composition of sugar kelp. Furthermore, we suggest applications for the various fractions resulting from the different pre-processing steps.More dry matter was extracted from the biomass with increasing degree of processing. Combining PEF and blanching gave the highest extraction yield (˜60 %) compared to only using one of the steps (˜40 %). The extracted compounds contained ash (including iodine), polyphenols, and mannitol. Proteins, heavy metals, other sugars, and (presumably) fiber were concentrated in the solid fractions. Based on the composition, applications within food, feed, agriculture, nutraceuticals, and cosmeceuticals are suggested for the fractions and extracts.These results can be relevant to researchers investigating novel technologies, processing of seaweed, and food safety, as well as to the seaweed industry, for the selection of processing technologies and product applications.

Low-intensity pulsed electric fields pre-treatment on yogurt starter culture: Effects on fermentation time and quality attributes

Low-intensity pulsed electric fields (PEF) were applied to a starter culture mix (Streptococcus thermophilus, Lactobacillus bulgaricus, and partially skimmed milk) before the fermentation stage of natural yogurt. The impact of PEF processing conditions on yogurt fermentation time and quality characteristics was evaluated. PEF parameters were set based on a factorial experimental design; independent variables: electric field strength, pulse-frequency, and pulse-width, were explored, having fermentation time as a response. Most PEF treatments reduced fermentation time by 0.31–0.52 h compared to conventional yogurt processing (CY) (4.70 ± 0.23 h). The shortest time (4.18 ± 0.04 h) resulted from PEF pre-treatment with 8-μs monopolar pulses at 1 kV/cm and 150 Hz during 400 μs. The physicochemical and sensory characteristics of PEF-treated yogurt were similar to those of the CY immediately after processing and during refrigeration storage. Low-intensity PEF could be a promising alternative pre-treatment of yogurt production, reducing fermentation time while maintaining quality attributes of natural yogurt. Industrial relevanceConventional yogurt processing lasts around 4.5–6 h, representing high energy consumption and production costs. The application of pulsed electric fields (PEF) processing to the starter culture before yogurt fermentation represents a potential alternative to diminish production time by stimulating lactic acid bacteria and accelerating fermentation stage. This study demonstrated that low-intensity PEF (1–3 kV/ cm) reduced fermentation time by 0.31–0.52 h without compromising yogurt's quality properties, including physicochemical characteristics and sensory attributes. Obtained results suggest that this technology allows more efficient and sustainable yogurt production methods, positively impacting industry and consumers.

Effect of pulsed electric field processing on microbial and enzyme inactivation in blended plant-based milk alternatives: A case study on a microbial challenge test for a non-presterilized oat-based beverage enriched with pea protein

Microbial and enzyme inactivation by pulsed electric field (PEF) treatment was assessed in a blended plant-based milk alternative (PBMA) containing oats and pea protein without the application of presterilization. This was conducted to investigate a novel approach that permits PEF process validation for PBMA containing heat-labile components (protein and starch). Continuous PEF processing at moderate field strengths (9–10 kV/cm) combined with mild preheating (30–45 °C) for 25 s was applied over a range of specific energy inputs (77–245 kJ/L). Selective plating permitted bacterial enumeration of inoculated surrogate organisms, despite the presence of natural microbial contaminants in the non-presterilized product. A minimum 5-log reduction of inoculated surrogates Escherichia coli and Listeria innocua alongside native microbiota was identified after preheating to 35–45 °C followed by PEF at 192–215 kJ/L. α-amylase activity was reduced by up to 89% during a similar PEF treatment (205 kJ/L, 40 °C preheating). Overall, continuous PEF combined with mild preheating temperature was shown to achieve microbial inactivation in the pea protein enriched PBMA in compliance with current food safety regulations. Industrial relevancePresterilization is typically applied prior to conducting microbial challenge testing on food products to validate novel pasteurization treatments according to current regulatory requirements that a minimum 5-log reduction of relevant inoculated food pathogens must be achievable. However, for a variety of blended PBMA containing heat-labile proteins, presterilization is not advisable as the occurrence of irreversible changes in the product quality linked to protein coagulation and phase separation will affect the inactivation efficacy during subsequent microbial challenge testing. Hence, an alternative approach is presented utilizing a non-presterilized PBMA and thorough microbiological analysis, combining non-selective and selective plating techniques. This allows an identification of PEF treatment parameter with a minimum 5-log reduction of inoculated surrogate organisms alongside naturally present microbial contaminants. This may serve as a valuable guideline for stakeholders in the food industry when addressing the efficacy of novel preservation treatments such as PEF in PBMA products with similar heat-induced product stability challenges.

Effect of pulsed electric field processing on the quality characteristics and enzyme activity of tender coconut water.

Tender coconut water (TCW) is a natural drink rich in natural electrolytes, minerals, salts and sugars; it has good health benefits. But, its shelf-life is very limited because of the active nature of enzymes present in it when exposed to air. Therefore, the processing of TCW is necessary to inactivate the enzymes. So, this study aims to observe the effect of various process parameters of pulsed electric field (PEF) on the quality parameters of TCW. For the treatment of TCW with PEF, a full-factorial design of experiments was followed with process parameters such as three levels of electric field intensity (8, 12, and 16 kV/cm), two levels of pulse width (PW) (50 and 70 μs), and six levels of the number of pulses (2000 to 12,000 pulses) were considered at a constant pulse OFF time of 75 ms. PEF treatment did not significantly change pH, total soluble solids, and viscosity. However, it significantly affected vitamin C, colour, and total and reducing sugars. PEF treatment significantly enhanced the total phenolic content and antioxidant activity by 23.17% and 42.49%, respectively. At the same time, significant inactivation of polyphenol oxidase (100%) and peroxidase (60.2%) was observed at PEF treatment conditions of 16 kV/cm, 70 μs PW, and 12,000 pulses. Moreover, no significant change in the sensory acceptability of PEF-treated TCW (16 kV/cm, 70 μs PW, 12,000 pulses) when compared to the untreated/fresh TCW, which is a promising sign.

Disentangling the effects of electroporation and heat during pulsed electric field (PEF) processing of oat-based milk alternative: A case study on Lactiplantibacillus plantarum inactivation

The study aimed to quantify the resistance of two L. plantarum strains and estimate the contribution of temperature during the pulsed electric field (PEF) processing of oat beverage. PEF and thermal inactivation kinetic experiments of L.plantarum strains were performed separately. Log10 reductions ≥5.7 of L. plantarum was achieved when 10–24 kV/cm, 110–115 kJ/L, 80–522 μs, and 35 °C inlet temperature were applied, while strain variability was evident in the performed assessments. Accurate monitoring of the temperature profiles for PEF allowed the estimation of the thermal microbial inactivation which was separated from electroporation effect. The electroporation impact was found to increase with increasing electric field strengths. Temperature measurements in the treatment zone confirmed the presence of hot spots. At higher specific energy inputs, there was significant contribution of temperature to the total observed inactivation. This contribution became smaller when the flow rate was increased, as shorter residence time reduced the exposure to high temperature peaks. Industrial relevanceThe findings demonstrated the potential of PEF as a promising technology for the microbial decontamination of oat-based milk alternative. Knowledge of strain variability in response to emerging food processing technologies is critical during process optimisation and quantitative microbial risk assessment. New developments in PEF equipment and process should ideally aim to maximize inactivation while minimizing the impact of high temperature on sensitive food constituents.

Pulsed electric field processing of fruit juices with inactivation of enzymes with new inactivation kinetic model and determination of changes in quality parameters

Pulsed electric fields (PEF) processing of fresh grape, orange and tomato juices by 17.2–24.1 kV/cm electric field strengths, 130.0–1040.5 μs treatment times and 1.43–29.13 J/kg energies with respect to determination of the changes in the physical and bioactive properties, color parameters in addition to inactivation of pectin methyl esterase (PME), polyphenol oxidase (PPO), and lipoxygenase (LOX) enzymes were studied. In general, decrease in pH, increase in conductivity (except for grape juice), total phenolic substance content, and total antioxidant capacity with no significant change (p > 0.05) in total soluble solids were observed by PEF treatment for all juices. Except for hue value for orange juice, no significant changes (p > 0.05) were observed in color values. Inactivation of the enzymes were increased with increased energy, and calculated electrical activation energies for PME, PPO, and LOX enzymes were 8.31, 7.06, and 4.31 kJ/mol, respectively. Industrial relevanceEnzymes in addition microorganisms causing quality degradation is of great concern in fruit juice industry as most of the enzymes are resistant to processing technologies. Increased PEF treatment time provided over 95% inactivation on PME, PPO, and LOX enzymes with no adverse effect on quality properties of grape, orange, and tomato juices revealing a viable alternative to juice processing industry.

Low-intensity pulsed electric field processing prior to germination improves in vitro digestibility of faba bean (Vicia faba L.) flour and its derived products: A case study on legume-enriched wheat bread

This study investigated the effect of low-intensity pulsed electric field (PEF) (0.3–0.7 kV/cm) and/or germination (0–72 h, 20 °C) on faba beans prior to flour- and breadmaking. PEF (0.5 and 0.7 kV/cm) had no significant effect on the germination performance of faba bean but had a positive effect on in vitro starch and protein hydrolysis of PEF-treated beans germinated for 72 h. The incorporation of flour from soaked, germinated, PEF-treated, and PEF-treated+germinated faba beans into wheat bread, at 30% mass level, improved the nutritional composition (total starch and protein contents) and protein digestibility but it reduced the specific volume and increased the density, brownness, and hardness of the bread. This finding shows for the first time that PEF-treatment (<0.7 kV/cm) of faba beans followed by germination (72 h) improved in vitro starch and protein hydrolysis of its flour and the protein digestibility at gastric phase of its enriched wheat bread.

Higher dose makes higher lethality? A dose–response model of pulsed electric fields inactivation from multiscale coarse-graining method

As an emerging technology in liquid inactivation, one of the main challenges of pulsed electric fields (PEFs) inactivation lies in quantitatively describing and predicting its lethality to microorganisms. However, due to its cross-scaled complexity and the consequent numerous regulatory factors, there is currently still no unified framework to understand the PEF dose–response relationship and the population dynamics theoretically. In this study, a simple yet powerful model from multiscale coarse-graining method is proposed to simulate the bacterial inactivation in suspensions during PEF processing. The complex dose–response effects at the macroscale are successfully reconstructed from simple evolution rules and several coarse-graining parameters, while considering the damage and death of a single bacterium at the microscale. Our model uncovers the seemingly chaotic and even controversial dose–response relationship of PEF in literatures and systematically explores the regulatory effect of experimental parameters in a unified framework. One of the interesting findings is that PEF with shorter pulsed width enhances lethality and reduces the minimal inhibitory time at a constant energy output per pulse, owing to the phase transitions in three bacterial population dynamics (Bistability mode, Avalanche mode, and Hybrid mode). Our study provides a new insight for numerically modeling PEF lethality in liquid inactivation and could serve as a guide for dosage management in practical applications.

Pulsed electric field (PEF) processing of microalga Chlorella vulgaris and its digestibility in broiler feed

Microalgae have potentially beneficial effects on animal health and nutritional value when added to feed. Crucial hereby is that intracellular bio-active molecules are released in the intestinal tract. Digestibility of Chlorella vulgaris and its impact on total digestibility of broiler feed is a first step in assessing its characteristics as feed supplement. Different methods could be used to increase the digestibility of the algae. Among other, pulsed electric field (PEF) and freezing to disrupt autotrophic (A) and heterotrophic (H) Chlorella vulgaris cells was assessed to increase their availability followed by in-vivo trials. In these trials effect of algae type (A and H) and effect of PEF-processing was evaluated on the apparent nutrient digestibility. Pulsed electric field showed to have a disruption efficiency of 83.90% and 79.20% for heterotrophic and autotrophic C. vulgaris respectively. Freezing C. vulgaris only showed efficiencies ranging from 3.86 to 11.58%. In the in-vivo trials, microscopic counting of intact C. vulgaris cells showed an increase in digested intact C. vulgaris cells of PEF-processed C. vulgaris compared to nonprocessed cells ranging from 12.16% to 15.20%. Autotrophic C. vulgaris had a higher digestibility compared to heterotrophic C. vulgaris, with an increase of 7.29, 9.44, and 17.29% in digestibility of C. vulgaris in the 1, 2, and 5% feed respectively. Feeds with PEF-processed C. vulgaris showed no significant increase in digestibility compared to nonprocessed C. vulgaris supplemented feeds. The 5% C. vulgaris feeds showed lower fat digestibility than the 1 and 2% and control feeds. Protein digestibility was lower for all C. vulgaris feeds compared to the control feed. There was a significant linear decreasing effect (P < 0.001) for all digestibility parameters. Except for crude ash digestibility, which first lowered for the 1 and 2% feeds, but then increased at 5% inclusion. Considering this study, including low dosages of 1 and 2% of C. vulgaris in broiler feed does not compromise its digestibility.

Evaluation of pulsed electric field and high-pressure processing on the overall quality of refrigerated Concord grape juice

Consumers' demands for minimally processed juices are prompting the expansion of refrigerated, cold-pressed juice market. To develop a nutritious, cold-pressed Concord grape juice, high pressure processing (HPP, 600 MPa, 3 min, 5 °C) and pulsed electric field (PEF, 0.85 kV/cm, 300 pulses) were utilized and the resultant juice was compared with the heat treated (HT, 63 °C, 3 min) juice. HPP was able to preserve the physicochemical properties, reduce microbial load and extend the shelf-life of juice under refrigeration. PEF treatment significantly increased the juice yield (p < 0.01), antioxidants contents and antioxidant activity (p < 0.05). Macroscopic observation indicated that the skin cell structure was altered after PEF. PEF + HPP treated juice had significantly higher purchase intent, appearance and aroma likings (p < 0.05). Combination of PEF and HPP can produce a superior cold-pressed Concord grape juice that meets consumers’ demands for fresh and nutritious fruit juices.

Impact of pulsed electric fields on membrane disintegration, drying, and osmotic dehydration of foods

AbstractDrying is one of the oldest and most conventional methods used to preserve foods. Unique traditional methods have been applied for the drying of plant‐based food products. However, the disadvantage of this approach is the low drying rate, high energy, and processing costs accompanied by the loss of nutritional quality in food products. As a substitute, pulsed electric field (PEF) is a modern and promising technique that has various advantages over thermal treatments. Nowadays, it has become an area of innovation to meet increasing industrial demands. Application of PEF during drying and osmotic dehydration has beneficial impacts on the extension of shelf‐life, increases in storage stability, and improvement of nutritional quality. Upscaling the use of PEF from laboratory to industrial scale while maintaining productivity is an area for further research and development. The aim of this commentary review is to give an overview of a newly proposed PEF process, which improves drying rate, mass‐energy transfer, retention of bioactive compounds, and osmotic dehydration in food. PEF processing led to achieving the innovative development of a wide range of foods and was extended to solve environmental issues. Drying food products is the most promising area in the food industry which needs improvement in terms of achieving energy efficiency and cost‐effectiveness to dry food products with the maintenance of nutritional properties to adequate levels. In this regard, PEF could be a suitable and novel drying method to overcome the limitations of conventional drying methods which might open new horizons for valuable research in manufacturing dried fruits and vegetables on an industrial scale.

Pulsed electric field processing in the dairy sector: A review of applications, quality impact and implementation challenges

SummaryCustomer priority for consuming dairy products with intact natural characteristics is leading the food processing trends towards the extensive exploration of non‐thermal technologies. Pulsed electric field (PEF) technique has arisen as a potential and sustainable processing solution. This review discusses the microbial and enzyme inactivation potential of PEF technique in milk and milk products. Alongside its effect on their natural characteristics. Its potential for better probiotic retention in spray‐dried powders, dairy waste treatment and nutrient enrichment application in dairy products has also been highlighted. PEF has demonstrated its effectiveness in ensuring the dairy product's safety with minimal effects on quality parameters. However, these findings are limited to lab and pilot scale level. Further, extensive research is needed at a commercial scale for the implementation of this technology in the dairy industry.

Emerging Food Processing and Preservation Approaches for Nutrition and Health

This comprehensive review critically evaluates contemporary and emergent food processing and preservation technologies with a primary focus on enhancing nutrition and promoting health. The discourse delves into a spectrum of innovative methodologies, encompassing high pressure processing, pulsed electric field processing, oscillating magnetic field processing, nonthermal plasma, ultrasound processing, and avant-garde thermal technologies. A detailed analysis is provided, shedding light on the manifold impacts of these technologies on diverse facets such as food quality, sensory attributes, nutrient preservation, shelf-life augmentation, and the effective inactivation of pathogens. Furthermore, the document accentuates recent applications that exemplify the successful enhancement of nutritional profiles across a gamut of food products. The review not only scrutinizes the advantages but also delineates the challenges associated with the implementation of these cutting-edge technologies. An insightful exploration of potential future opportunities is incorporated, offering a forward-looking perspective on the evolving landscape of food processing and preservation. By expanding the discourse on these pivotal technologies, this review serves as a valuable resource for researchers, practitioners, and stakeholders interested in advancing nutrition and health outcomes through state-of-the-art food processing and preservation approaches.

Investigation of Xinomavro Red Wine Aging with Various Wood Chips Using Pulsed Electric Field

This study explored the potential of pulsed electric field (PEF) as an alternative wine-aging method in four Xinomavro red wines with the implementation of several wood chips (apricot, peach, apple, cherry, acacia, and oak trees). The evolution of total polyphenol content (TPC) and sensory properties of the wines were investigated. Sensory evaluation revealed that PEF treatment increased volatile compound extraction from each wood chip, thereby enhancing the overall quality of the wines. The utilization of acacia tree wood chips in Goumenissa wine led to a notable increase of 10.84% in TPC from the control sample, reaching 2334.74 mg gallic acid equivalents/L. A notable outcome was that PEF decreased TPC, a trend that was also verified through correlation analyses. The highest positive impact of PEF was observed in peach tree wood chips in Goumenissa wine, with a significant increase of 11.05% in TPC. The results from the volatile compound analysis revealed an increase in alcohols and esters from 0.24% to 23.82%, with the highest proportion found in 2-phenylethanol (16.92 mg/L) when utilizing peach tree wood chips in the production of Amyndeo wine. This study could provide a benchmark for rapid, efficient, and cost-effective wine aging through the implementation of the PEF process.