Effect Of Pulsed Electric Fields Research Articles

Insight into the effects of pulsed electric field on the structure, aggregation characteristics and functional properties of whey proteins

The effects of pulsed electric field (PEF) under different electric field intensities (EFIs, 5–20 kV/cm) and treatment times (2–8 ms) on the structural properties, aggregation/dissociation, and rheological characteristics of whey proteins (WPs) were investigated. An increase of visual turbidity and particle size measurements in 5 and 10 kV/cm PEF treatment groups indicated the formation of larger, insoluble aggregates dominated by disulfide bonds cross-linking and enhanced surface hydrophobicity. However, with the augmentation of EFI reaching a pivotal level (15 and 20 kV/cm), the decrease of hydrophobic interaction coupled with the increased electrostatic repulsion due to increased helix structure can dissociate the aggregates in response to blue-shifted particle size and thin irregular cavern-like structure, causing the solubility increased by 5.24% (20 kV/cm treatment for 8 ms). Furthermore, WPs oxidation played an important role in aggregates disintegration and liberation of peptides due to protein polarization and attack of reactive radicals produced by electrochemical reaction. Rheological analysis showed that higher solubility and diminished particle size after 15 and 20 kV/cm treatments improved the emulsifying capacity and decreased viscosity and interfacial tension of WPs dispersion. Conclusively, structural modification and preeminent functional properties were prompted by the extension of EFI and treatment time. Therefore, an effective theoretical basis may be proposed for PEF used as a promising technology to modify the functional characteristics of WPs.

Pulsed Electric Field Treatment of Oat and Barley Flour: Influence on Enzymes, Non-starch Polysaccharides, Dough Rheological Properties, and Application in Flat Bread

AbstractThis study examined the effects of pulsed electric field (PEF) treatment on enzymes, non-starch polysaccharides, and bread-making potential of oat and barley flour. Enzyme activity, microstructure, β-glucan extractability, molecular weight (Mw) and structure of non-starch polysaccharides, dough rheology, and flat bread properties were determined. An exponential decay model explained better the residual activity of oat β-glucanase across electric field intensity than barley β-glucanase. PEF treatment of flour at 12 kV/cm for 162 ms significantly reduced β-glucanase activity (40.2–76.5%) while increasing the concentration of total β-glucans (33.5%) and water-extractable arabinoxylans (36–41%). Mw of linear β-d-glucans decreased (9%) while Mw of branched arabinoxylans increased (6–33%). Scanning electron microscopy showed changes in microstructure of barley proteins. Blending wheat flour (70%) with oat or barley flour (30% weight) after PEF treatment enhanced gluten aggregation energy (29–19%) and breakdown viscosity (18–43%) of dough, as well as increased β-glucan content (21–32%) but reduced specific volume (11–24%). The findings of this study provide a comprehensive insight into the PEF’s potential for retarding enzymatic reactions and preserving integrity of cereal non-starch polysaccharides.

Enhancing Nutritional Quality and Color Stability of Tomato Juice through Low-Intensity Pulsed Electric Field Treatment

Aims: This study aimed to evaluate the effect of low-intensity pulsed electric field (LIPEF) treatment on the lycopene content, ascorbic acid retention, and color enhancement of juice prepared by using Roma variety tomatoes.
 Methodology: The tomato slices were kept in the PEF treatment chamber with varying electric field strength ranging from 2-8 kV/cm and pulse numbers between 10-70 with a monopolar pulse of 1 Hz frequency having a pulse on/off time respectively of 10 µs. After the PEF treatment, the slices were processed to extract the juice for further analysis.
 Results: The study revealed significant findings regarding the effect of LIPEF treatment on Roma variety tomatoes. Treatment with 4 kV/cm and 50 pulses resulted in a remarkable 69.11% increase in lycopene content compared to untreated tomato juice. Additionally, there was a remarkable retention rate of 99.84% for ascorbic acid in the treated samples compared to the control. Furthermore, LIPEF treatment led to a substantial increase of 40.78% in the a* value, indicating enhanced red coloration of the extracted juice compared to the control. However, higher electric field strength affects the retention of ascorbic acid content. 
 Conclusion: The findings of this study demonstrate the effectiveness of low-intensity pulsed electric field (LIPEF) treatment in enhancing the lycopene content, retaining ascorbic acid, and improving the red coloration of Roma variety tomatoes. LIPEF treatment has the potential to be utilized in food processing industries to improve the quality and nutritional value of tomato-based products.

Effects of PEF pretreatment, combined with different drying methods, on the physicochemical properties, bioactive components, antioxidant potential as well as structural and thermal properties of dried yams

This work investigated the effects of pulsed electric field (PEF) pretreatment, combined with different drying methods, on the quality of dried yams. The results showed that the pretreatment resulted in the formation of large pores in the yam tissues, thereby affecting the rehydration capability and hardness of the dried yam slices. The type of drying method after treatment did not alter the free radical stretching bands of yam. Additionally, the pretreated samples had a higher peak viscosity, through viscosity, final viscosity and break down, alongside lower pasting temperatures, To, Tp, Tc, and △H. Rheological measurements further indicated that all doughs exhibited solid-like behavior to different extents. The pretreatment also decreased the amount of allantoin and polysaccharides in dried yam slices, while negatively influencing their antioxidant activity. Finally, the choice of drying methods significantly affected the quality of the dried yams. In highlighting the effects of PEF pretreatment, combined with different drying methods, on dried yam, the results can help to expand their application within the food industry.

Pulsed electric field treatment improves the oil yield, quality, and antioxidant activity of virgin olive oil

Pulsed electric field (PEF) is an innovative technique used to assist in the extraction of vegetable oils. There has been no research on the effects of PEF on virgin olive oil (VOO) quality and antioxidant activity to date. The present study aimed to analyze the effects of PEF on oil yield, quality, and in vitro antioxidant activity of “Koroneiki” extra virgin olive oil. The results show that the PEF treatment increased the oil yield by 5.6%, but had no significant effect on the saponification value, K232, K270, and ∆K value of the VOO. PEF treatment reduced the oleic acid content by 3.12%, but had no significant effect on the content of palmitic acid, linoleic acid, linolenic acid, arachidonic acid, stearic acid, oleic acid, and palmitic acid. After PEF treatment, the levels of total phenolics, total flavonoids, and oleuropein increased by 7.6%, 18.3% and 76%, respectively. There was no significant effect on the levels of 4 phenolic acids (vanillic acid, p-coumaric acid, ferulic acid and cinnamic acid), 2 lignans (lignans and apigenin), hydroxytyrosol, and 3 pigments (lutein, demagnetized chlorophyll, and carotenoids). In addition, PEF treatment significantly increased the content of tocopherols, with α, β, γ, and δ tocopherols increasing by 9.8%, 10.7%, 13.6% and 38.4%, respectively. The free radical scavenging ability of DPPH and ABTS was also improved. In conclusion, the use of PEF significantly increased the yield of VOO oil as well as the levels of total phenolics, total flavonoids, oleuropein, tocopherol, and in vitro antioxidant activity.

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.

Effects of high voltage pulsed electric field on structural properties and immune reactivity of arginine kinase in Fenneropenaeus chinensis

To evaluate the effect of high voltage pulsed electric field (PEF) treatment (10–20 kV/cm, 5–15 min) on the structural characteristics and sensitization of crude extracts of arginine kinase from Fenneropenaeus chinensis. By simulated in vitro gastric juice digestion (SGF), intestinal juice digestion (SIF) and enzyme-linked immunosorbent assay (ELISA), AK sensitization was reduced by 42.5% when treated for 10 min at an electric field intensity of 15 kV/cm. After PEF treatment, the α-helix content decreased, and the α-helix content gradually changed to β-sheet and β-turn. Compared to the untreated group, the surface hydrophobicity increased and the sulfhydryl content decreased. SEM and AFM analyses showed that the treated sample surface formed a dense porous structure and increased roughness. The protein content, dielectric properties, and amino acid content of sample also changed significantly with the changes in the treatment conditions. Non-thermal PEF has potential applications in the development of hypoallergenic foods.

Combined effect of prior pulsed electric field, dechlorophyllized soursop leaf extract and vacuum impregnation on melanosis inhibition and shelf-life extension of refrigerated Pacific white shrimp

Pacific white shrimp without and with prior pulsed electric field (PEF) followed by soaking in 0.5 and 1 % soursop leaf extract (SLE) without and with vacuum impregnation (VI) for 2 cycles were prepared. After soaking, PEF-treated shrimp in 1% SLE in combination with VI (PEF-SLE1-VI), 13 phenolic compounds in shrimp meat were found. When the changes in quality of shrimp with varying treatments were monitored, PEF-SLE1-VI showed the lowest alterations during 15 days of storage. It was the only sample having the microbial load below the maximum limit after 15 days and showed the lowest melanosis with likeness score defined as “like slightly”. Such treatment retarded microbial growth, particularly psychrotrophic bacteria and Pseudomonas. Overall, prior PEF treatment of whole shrimp before soaking in 1% SLE with the aid of VI maintained quality and lengthened shelf life via inhibiting melanosis and deterring microbial proliferation in refrigerated shrimp.

Improving the Composition and Bioactivity of Cocoa (Theobroma cacao L.) Bean Shell Extract by Choline Chloride-Lactic Acid Natural Deep Eutectic Solvent Extraction Assisted by Pulsed Electric Field Pre-Treatment.

An environmentally friendly method for the release of cocoa bean shell (CBS) extracts is proposed in this paper. This work aims to investigate the effect of pulsed electric field (PEF) pre-treatment on subsequent solid-liquid extraction (SLE) of metabolites with choline chloride-lactic acid natural deep eutectic solvent (NaDES) and bioactivity of cocoa bean shell (CBS) extract. Two different media for PEF application were evaluated: water and chlorine chloride-lactic acid. Total polyphenols (TPC), total flavonoids (TFC), individual major compounds, and antioxidant and antibacterial activity of CBS extracts were assessed. The performance of PEF-assisted extraction was compared with SLE and ultrasound-assisted extraction (UAE). The proposed method improved the release of TPC up to 45% and TFC up to 48% compared with the conventional extraction. The CBS extract showed medium growth inhibition of Escherichia coli and high growth inhibition of Salmonella sp, Listeria monocytogenes, and Staphylococcus aureus. Thus, an extract with enhanced antioxidant and antibacterial properties was obtained.

Combined effect of pulse electric field and probe ultrasound technologies for obtaining phenolic compounds from orange by-product

Orange peel by-product is a known source of bioactive compounds with several health benefits. This study focuses on optimizing the conditions for pulsed electric field (PEF) technology as a pretreatment to obtain extracts rich in phenolic compounds from the orange peel. A Box-Behnken design of 15 experiments with 3 independent factors (field energy, number of pulses and pulse width) was performed. The phenolic content was extracted by ultrasound technology and analyzed by HPLC-ESI-TOF-MS. Optimum conditions were 1.4 kV/cm and 30 pulses of 110 μs achieving a recovery of 40.8 mg/g dry weight of phenolic compounds, 27.5% higher than obtained without PEF. Besides, hesperidin and narirutin content increased by 29.4 and 38.9%, respectively. For the antioxidant assays also significative increments (≥ 53%) were achieved. The combination of optimized PEF pre-treatment with ultrasound extraction has let to obtain orange peel enriched extracts in polyphenols with higher antioxidant activity.

The Effects of Jet-Milling and Pulsed Electric Fields on the Preservation of Spinach Juice Lutein Contents during Storage.

This study aimed to investigate the effects of jet-milling on the lutein extraction contents of spinach powder (SP), as well as the effects of pulsed electric field (PEF), as a non-thermal pasteurization technology, on the preservation of spinach juice (SJ) lutein contents. SP particles were divided into SP-coarse (Dv50 = 315.2 μm), SP-fine (Dv50 = 125.20 μm), and SP-superfine (Dv50 = 5.59 μm) fractions, and SP-superfine was added to SJ due to its having the highest contents of lutein extract. PEFs and thermal treatment were applied to evaluate the effects of preserving the lutein content of PEF during storage (25 days). The juice was then designated as untreated (no pasteurization), PEF-1,2 (SJ treated with PEF 20 kV/cm 110 kJ/L, 150 kJ/L), or Thermal-1,2 (SJ treated with 90 °C, 10 min and 121 °C, 15 min). The sizes and surface shapes of the superfine SP particles were more homogeneous and smoother than those of the other samples. SJ made with SP-superfine and treated with PEF had the highest lutein content and antioxidant activities among the group during storage. A complex of jet-milling and PEF could have great potential as a method to improve the lutein contents of lutein-enriched juice in the food industry.

Tailoring the Techno-Functional Properties of Fava Bean Protein Isolates: A Comparative Evaluation of Ultrasonication and Pulsed Electric Field Treatments

The fava bean protein isolate (FBPI) holds promise as a sustainable plant-based protein ingredient. However, native FBPIs exhibit limited functionality, including unsuitable emulsifying activities and a low solubility at a neutral pH, restricting their applications. This study is focused on the effect of ultrasonication (US) and pulsed electric fields (PEF) on modulating the techno-functional properties of FBPIs. Native FBPIs were treated with US at amplitudes of 60–90% for 30 min in 0.5 s on-and-off cycles and with PEF at an electric field intensity of 1.5 kV/cm with 1000–4000 pulses of 20 μs pulse widths. US caused a reduction in the size and charge of the FBPIs more prominently than the PEF. Protein characterization by means of SDS-PAGE illustrated that US and PEF caused severe-to-moderate changes in the molecular weight of the FBPIs. In addition, a spectroscopic analysis using Fourier-transform infrared (FTIR) and circular dichroism (CD) revealed that US and the PEF induced conformational changes through partial unfolding and secondary structure remodeling from an α-helix to a β-sheet. Crystallographic and calorimetric determinations indicated decreased crystallinity and lowered thermal transition temperatures of the US- and PEF-modified FBPIs. Overall, non-thermal processing provided an effective strategy for upgrading FBPIs’ functionality, with implications for developing competitive plant-based protein alternatives.

Synergistic ultrasound pulsed electric field extraction of litchi peel polyphenols and determination of their properties

The effects of pulsed electric field combined with ultrasound (PEF-US) on the recovery of polyphenols from litchi peels were investigated. In addition, the optimal purification parameters for polyphenol extracts and their biological activities were also explored in this study. Single-factor and orthogonal experiments were used to optimize the extraction conditions of polyphenols. After optimization, the total phenol content (TPC) of the sample extracted by PEF-US was 2.30 times higher than that of the sample extracted by traditional hot-water extraction. The mechanism of PEF-US enhancing polyphenol recovery was also revealed by morphological analysis of the powder surface. LX-7 was the best resin by comparing the purification effect of nine macroporous resins. The optimum conditions for purification of litchi peel polyphenols by LX-7 resin were also optimized through adsorption and desorption experiments. UHPLC-MS and HPLC results revealed that gentisic acid, catechin, procyanidin A2 and procyanidin B1 are four main substances in purified samples. The results of bioactivity experiments showed that the purified polyphenol samples had strong antioxidant and antibacterial activity. Overall, PEF-US is an efficient method for recovering polyphenols from litchi peels. Our study also provides a strategy for the comprehensive utilization of fruit processing waste.

Effects of Voltage and Treatment Time of Pulsed Electric Field on Electroporation in Rhizoctonia solani.

The pulsed electric field (PEF) of μs duration can induce electroporation by causing permanent damage to the membrane, leading to cell death. The microbe was treated by a homemade PEF generator instrument. The sterilization effect of PEF on the Rhizoctonia solani was observed by scanning electron microscope (SEM) and transmission electron microscope (TEM), and the leakage of the intracellular contents was measured with a conductometer and an ultraviolet spectrophotometer. The increases in the electrical conductivity and the optical density (OD) value indicated that the cell membrane was damaged, and the intracellular contents overflowed. As a result, according to our experimental conditions, the optimum condition was the high-pulsed electric voltage of 26kV, and the treatment time was 4min. It could be concluded that the PEF could damage the cell membrane, and the ratio of electroporation reached 100%, which provides a new method of killing R. solani efficiently.

Synergistic effects of nanosecond pulsed plasma and electric field on inactivation of pancreatic cancer cells in vitro

Nanosecond pulsed atmospheric pressure plasma jets (ns-APPJs) produce reactive plasma species, including charged particles and reactive oxygen and nitrogen species (RONS), which can induce oxidative stress in biological cells. Nanosecond pulsed electric field (nsPEF) has also been found to cause permeabilization of cell membranes and induce apoptosis or cell death. Combining the treatment of ns-APPJ and nsPEF may enhance the effectiveness of cancer cell inactivation with only moderate doses of both treatments. Employing ns-APPJ powered by 9 kV, 200 ns pulses at 2 kHz and 60-nsPEF of 50 kV/cm at 1 Hz, the synergistic effects on pancreatic cancer cells (Pan02) in vitro were evaluated on the metabolic activities of cells and transcellular electrical resistance (TER). It was observed that treatment with ns-APPJ for > 2 min disrupts Pan02 cell stability and resulted in over 30% cell death. Similarly, applying nsPEF alone, > 20 pulses resulted in over 15% cell death. While the inactivation activity from the individual treatment is moderate, combined treatments resulted in 80% cell death, approximately 3-to-fivefold increase compared to the individual treatment. In addition, reactive oxygen species such as OH and O were identified at the plasma-liquid interface. The gas temperature of the plasma and the temperature of the cell solution during treatments were determined to be near room temperature.

Influence of mechanical comminution of raw materials and PEF treatment on the aqueous extraction of phenolic compounds from artichoke wastes

In this study the combined effect of mechanical comminution and pulsed electric fields (PEF) treatments on both cell disintegration and extractability of phenolic compounds during aqueous extraction from artichoke external bracts, was investigated. Different-sized bract discs were treated with varying PEF conditions, namely 0.5–5 kV/cm of electric field strength (E), and 1–20 kJ/kg of total specific energy input (WT). The cell disintegration index (Zp) of bract tissues, as well as the total phenolic content (TPC) and antioxidant activity (FRAP) of the extracts, were assessed.The results showed that increasing the comminution process intensity led to greater cell disintegration, resulting in a peak extraction yield of phenolic compounds (17.61 ± 1.24 mgGAE/100 g FW) achieved with the smallest sample size. Moreover, the application of PEF treatment further increased the Zp value of the bract tissues in a size-dependent manner. The greater the sample size, the stronger the PEF efficiency. Coherently, under optimized PEF conditions (E = 3 kV/cm, WT = 5 kJ/kg), the extracts exhibited higher TPC (+112–361%) and FRAP values (+83–836 %) as compared to the control samples after 120 min of diffusion. The extraction rate of phenolic compounds increased when the comminution degree was increased for both untreated and PEF-treated samples, and this was successfully predicted using Peleg's model.These findings suggest that PEF can be a viable alternative to energy-intensive comminution pretreatment, thus enhancing the extraction of phenolic compounds without requiring finely ground raw material handling.

Quality evaluation of house cricket flour processed by electrohydrodynamic drying and pulsed electric fields treatment

House crickets are expected to play a significant role in the future food sector. Electrohydrodynamic (EHD) drying offers an environmentally friendly alternative to conventional drying methods. Pulsed electric fields (PEF) is a non-thermal process that facilitates conventional processes. EHD was applied to house crickets with and without PEF pretreatment, and the effect of PEF and EHD on the quality of the insects was evaluated. PEF pretreatment positively affected the oven drying at 60 °C by reducing its duration and thus decreasing the energy consumption by 14.22%. Moisture removal of EHD was not sufficient to replace oven drying, but when combined with oven drying, the overall energy consumption was reduced by >50%. PEF processing also increased the protein solubility (53.07% higher than the respective control) and antioxidant activity (24.05% higher than the respective control) of the oven-dried samples and reduced the histamine content of the EHD-dried samples (25.87% lower than the respective control).

Effects of pulsed electric fields on controlling fermentation rate of brined Raphanus sativus

This study investigated the effects of pulsed electric fields (PEF) on the fermentation quality characteristics, morphology, and antioxidant activities of brined and fermented radish with different PEF strengths (1.5 kV/cm. 2.0 kV/cm). Electrical conductivity and Z-index showed that as the strength of PEF increased, the permeability of the cell membrane and the degree of disruption of the cell increased. The pretreatment with PEF accelerated the brining rate, thereby reducing the time required for brining by approximately PEF1.5 kV/cm (56.6%) and PEF2.0 kV/cm (70%) compared to Control. The growth rate of lactic acid bacteria viability was inhibited in the PEF group thus approximately 1–2 log CFU/ml lower than Control. The cellular structure maintenance of radish was improved in the PEF group than in the control group. Altogether, these findings suggest that PEF could effectively increase the storage period (2–5 days) for controlling the excessive growth of lactic acid bacteria which induce overripening during the fermentation of vegetables. Industrial relevanceA fermented food produced by lactic acid bacteria (LAB) is kimchi, a traditional Korean food that is consumed worldwide; however, excessive growth of LAB can reduce the quality of kimchi. PEF technology can be used to control LAB in kimchi to produce a superior product without the addition of antimicrobial agents.

Improving durum wheat germination: exploring the effects of ultrasound and pulsed electric field

Improving durum wheat germination: exploring the effects of ultrasound and pulsed electric field

The forgotten method? Pulsed electric field thresholds from the perspective of texture analysis

Pulsed electric field (PEF) technology has found applications in various industrial food sectors, including the potato industry, winemaking, biorefinery, and juice extraction, among others. The practical implementation of PEF technology in the food industry is however still hindered by several challenges. The detection and quantification of PEF effects are complex due to the variable characteristics and properties of raw materials, including cellular composition, structural organization, textural properties, and tissue porosity. Moreover, the PEF treatment parameters (e.g., pulse amplitude, duration, shape, rate), and process parameters (e.g., temperature, pH, medium conductivity) further complicate the optimization of PEF protocols, requiring a case-by-case approach. Knowledge of treated material properties and their functional dependence on PEF is a crucial prerequisite to informed, intelligent design of treatment protocols. We present an experimental study designed to gain insights into the mechanism behind the changes in textural properties induced by PEF in both plant and animal tissues. These changes in texture are then compared with findings from our previous study on electrical impedance, to highlight how different methods of detection of PEF-induced changes in tissue can yield vastly different results based on the method of analysis used depending on tissue properties. Furthermore, texture analysis unveiled the less-explored effects of PEF treatment on electroosmosis phenomena in both plant and animal tissues. We provide a comparative analysis between plant and animal tissues to elucidate the differences in deformation resulting from PEF treatment. We thus demonstrate how important it is, be it in the development phase or for process control during industrial operation, to choose an appropriate method of characterising PEF-induced changes in tissue to avoid under- or overtreatment.