Pulsed Electric Field Conditions Research Articles

Pulsed electric field treatment applied to barley before malting reduces Fusarium pathogens without compromising the quality of the final malt

The growth of micromycetes and the associated production of mycotoxins during malting represents a potential safety issue and an economic challenge regarding the quality of beer as a product manufactured from malt. The treatment of malted cereals with a pulsed electric field (PEF) may be one method to overcome this issue. In this work were tested PEF conditions that would lead to a reduction in fungal growth without suppressing germination and thus causing deterioration in the technological parameters of the malt. Pre-soaking the grain for more than 3.5 h prior to PEF treatment was found to significantly reduce the germination energy and, compared to the untreated sample, enzymatic activity of the resulting malt. Therefore, a modification consisting of a short pre-soaking (10 min) and PEF treatment (field intensity 3.8 kV/cm, 100 pulses with peak width 20 μs) in a high conductivity environment (0.05 mol/L phosphate buffer) was implemented. This treatment led to a reduction (up to 80%) in growth of some Fusarium species (F. sporotrichoides and F. poae) and the production of corresponding mycotoxins, mainly trichothecenes A and ennianthins. Moreover, the treated malt did not differ significantly from the control malt in terms of enzymatic activity.

Effect of Pulsed Electric Field Pretreatment on the Concentration of Lipophilic and Hydrophilic Compounds in Cold-Pressed Grape Seed Oil Produced from Wine Waste.

Pretreatment of grape pomace seeds with a pulsed electric field (PEF) was applied to improve the extraction yield of cold-pressed grape seed oil. The effects of different PEF conditions, electric field intensities (12.5, 14.0 and 15.6 kV/cm), and durations (15 and 30 min) on the oil chemical composition were also studied. All PEF pretreatments significantly increased the oil yield, flow rate and concentration of total sterols (p < 0.05). In addition, similar trends were observed for total tocochromanols and phenolic compounds, except for PEF pretreatment under the mildest conditions (12.5 kV/cm, 15 min) (p < 0.05). Notably, the application of 15.6 kV/cm for 30 min resulted in the highest relative increase in oil yield and flow rate (29.6% and 56.5%, respectively) and in the concentrations of total tocochromanols, nonflavonoids, and flavonoids (22.1%, 60.2% and 81.5%, respectively). In addition, the highest relative increase in the concentration of total sterols (25.4%) was achieved by applying 12.5 kV/cm for 30 min. The fatty acid composition of the grape seed oil remained largely unaffected by the PEF pretreatments. These results show that PEF pretreatment effectively improves both the yield and the bioactive properties of cold-pressed grape seed oil.

Accelerated pork salting using needle electrode-derived pulsed electric fields

This study aimed to evaluate the effects of pulsed electric field (PEF) pretreatment on the NaCl content, protein composition, and microstructure of pork during the marination process. The results showed that needle PEF could promote salt penetration into the center of pork pieces. Under optimal PEF conditions (3.0 kV/cm, 200 Hz, and 2400 pulses), the marination time could be reduced by almost 12 h. Protein characterization also revealed that PEF pretreatment changes myofibrillar protein properties by promoting salt penetration toward the center of pork. Furthermore, microstructural analysis demonstrated that the enhanced marination effect could be attributed to the PEF treatment-induced expansion of gaps between muscle bundles. Industrial relevanceIn this study, a PEF-assisted curing technique significantly (P < 0.05) improved salt penetration into the center of pork. Reducing the differences between internal and external salt concentrations can produce a more homogeneous marinade and reduce the marination time. Our findings suggest that PEF pretreatment is a promising and effective pretreatment technique for curing meat products.

Comparative Study of Microwave, Pulsed Electric Fields, and High Pressure Processing on the Extraction of Antioxidants from Olive Pomace.

Olive oil production is characterized by large amounts of waste, and yet is considerably highly valued. Olive pomace can serve as a cheap source of bioactive compounds (BACs) with important antioxidant activity. Novel technologies like Pulsed Electric Fields (PEF) and High Pressure (HP) and microwave (MW) processing are considered green alternatives for the recovery of BACs. Different microwave (150-600 W), PEF (1-5 kV/cm field strength, 100-1500 pulses/15 µs width), and HP (250-650 MPa) conditions, in various product/solvent ratios, methanol concentrations, extraction temperatures, and processing times were investigated. Results indicated that the optimal MW extraction conditions were 300 W at 50 °C for 5 min using 60% v/v methanol with a product/solvent ratio of 1:10 g/mL. Similarly, the mix of 40% v/v methanol with olive pomace, treated at 650 MPa for the time needed for pressure build-up (1 min) were considered as optimal extraction conditions in the case of HP, while for PEF the optimal conditions were 60% v/v methanol with a product/solvent ratio of 1:10 g/mL, treated at 5000 pulses, followed by 1 h extraction under stirring conditions. Therefore, these alternative extraction technologies could assist the conventional practice in minimizing waste production and simultaneously align with the requirements of the circular bioeconomy concept.

Effect of Pulsed Electric Fields on the Shelf Stability and Sensory Acceptability of Osmotically Dehydrated Spinach: A Mathematical Modeling Approach.

This study focused on the osmotic dehydration (OD) of ready-to-eat spinach leaves combined with the pulsed electric field (PEF) pre-treatment. Untreated and PEF-treated (0.6 kV/cm, 0-200 pulses) spinach leaves were osmotically dehydrated at room temperature for up to 120 min. The application of PEF (0.6 kV/20 pulses) prior to OD (60% glycerol, 25 °C, 60 min) lowered water activity (aw = 0.891) while achieving satisfactory product acceptability (total sensory hedonic scoring of 8). During the storage of the product (at 4, 8, 12, and 20 °C for up to 30 d), a significant reduction in total microbial count evolution was observed (9.7 logCFU/g for the untreated samples vs. 5.1 logCFU/g for the PEF-OD-treated samples after 13 d of storage at 4 °C). The selection of these PEF and OD treatment conditions enabled the extension of the product shelf life by up to 33 d under chilled storage. Osmotically treated spinach could find application in ready-to-eat salad products with an extended shelf life, which is currently not possible due to the high perishability of the specific plant tissue.

Optimizing Extract Preparation from Laurel (Laurus nobilis L.) Leaves Using a Pulsed Electric Field

This study explores the bioactive compound extraction from laurel (Laurus nobilis L.) leaves using a pulsed electric field (PEF) as a standalone extraction technique. The primary parameters impacting the extraction process were optimized through response surface methodology. Specifically, solvent composition (ethanol and water mixtures) and liquid-to-solid ratio, along with other key PEF conditions (i.e., electric field intensity, pulse period, and pulse length) were examined. The antioxidant capacity was evaluated through DPPH and FRAP assays, whereas total polyphenol content was also measured. A comparison was also made between the extracts produced with and without PEF. The results showed that after 30 min of extraction, the best parameters were a pulse period of 355 μs, a pulse duration of 55 μs, and an electric field intensity of 0.6 kV/cm. A liquid-to-solid ratio of 10 mL/g was chosen, whereas the best solvent was determined to be 25% (v/v) ethanol/water mixture. The PEF-treated extract contained 77% more polyphenols compared to the untreated sample. In addition, PEF-treated samples had a rise of up to 288% for certain individual polyphenols. Correlation analyses also revealed interesting trends among bioactive compounds and the antioxidant capacity of the extracts. The effect of the investigated parameters on polyphenol recovery was demonstrated, indicating that comparable investigations should consider these parameters to optimize polyphenol extraction yield. Regarding green and non-thermal standalone techniques, PEF outshines other extraction techniques as it could also be used as a sustainable way to swiftly generate health-promoting extracts from medicinal plants.

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.

Accelerating Xinomavro Red Wine Flavor Aging Using a Pulsed Electric Field and Various Wood Chips

Pulsed electric field (PEF) treatment has gained significant attention within the food industry. This study examines the application of PEF combined with wood chips of diverse species to expedite the flavor aging process of Xinomavro red wine. Various wood chip species, including black locust, common juniper, apricot, sweet chestnut, cherry, apple, peach, and European oak, sourced from pruning residues were immersed in the wine prior to subjecting it to PEF treatment. The samples underwent a range of pulse durations and intervals during treatment. Comparative preparations encompassing wine without chips and wine infused with each wood type left at ambient temperature for 5 days were also examined. The sensory attributes and the volatile compounds (VC) were assessed through the utilization of headspace solid-phase microextraction and GC-MS. In the control sample, 12 VCs were identified, whereas in the samples, 22 distinct VCs were identified. Favorable sensory attributes across all PEF conditions were associated with the incorporation of cherry wood chips. These findings highlight the potential of PEF treatment to enhance the quality parameters of the aging process in Xinomavro red wine, capitalizing on the synergistic interaction between PEF and various wood chip species. This innovative approach holds promise for augmenting crucial oenological parameters of red wine, strengthening the use of PEF as an efficient technique to enhance the overall quality.

Extracting Water-Soluble Proteins from the Red Macroalgae Gracilaria sp. with Pulsed Electric Field in a Continuous Process

Marine macroalgae are an emerging sustainable source of protein; however, protein extraction from macroalgae is challenging. In this work we report a novel, screw-press-based device for continuous high-voltage pulsed-electric-field (PEF) processing of fresh biomass to extract water-soluble protein from the red seaweed Gracilaria sp. The water extracts from the PEF-treated biomass showed higher protein yield (37.82 ± 7.96 to 47.56 ± 10.54 mg/g initial dry weight (DW) of biomass, depending on PEF conditions) compared to extracts without PEF (33.82 ± 6.01 mg/g initial DW of biomass). PEF followed by aqueous extraction removed 69.11% of the ash from the Gracilaria sp. biomass. The in vitro digestibility of the proteins in the water-soluble extract from the PEF process was 70% compared to that of casein, but it was only 25% for the juice protein extracted with a screw press alone. The energy consumption for PEF was 2.94 ± 0.91 kJ/(kg fresh weight (FW)) – 4.06 ± 0.48 kJ/kgFW, depending on the applied voltage. This study is the first report of processing Gracilaria sp. biomass using a continuous PEF system and successfully demonstrates the protein extraction with relatively lower energy inputs.

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

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

Targeted regulation of pulsed electric field (PEF) treatment on responsive amino acids based on the molecular dynamic simulation

In this study, to analyze the structural changes of the peptide Val-Asn-Ala-Val-Lys-His (VNAVKH) under PEF treatment and determine their response to amino acids, the atomic charge distribution, root mean square deviations (RMSD), root mean square fluctuation (RMSF), and atomic distance were analyzed using molecular dynamics (MD) simulations. The RMSF value under 40 kV/cm was significantly (P < 0.05) lower than that under other PEF conditions. However, calculations of the distances of the oxygen atom indicated that O57 on Val and O97 on His oxygen atoms became closer under all conditions. At 30 kV/cm, the changes were unique, and the α-C atom distance of C44 on Val and C82 on His decreased under all conditions. The results indicated that histidine was more sensitive and responsive after PEF treatment, and the peptide backbone was bent and exposed to some active atoms, which might lead to changes in biological activity.

Effect of Pasteurization by Moderate Intensity Pulsed Electric Fields (PEF) Treatment Compared to Thermal Treatment on Quality Attributes of Fresh Orange Juice.

Novel pulsed electric field (PEF) process conditions at moderate electric field strength and long pulse duration have recently been established to obtain microbial inactivation. In this study, the effect of these PEF conditions (E = 0.9 and 2.7 kV/cm, with pulse duration 1000 µs) at variable maximum temperatures was evaluated on quality attributes of freshly squeezed orange juice. Results were compared to orange juice that received no treatment or a mild or severe thermal pasteurization treatment. No differences for pH and soluble solids were found after application of any treatment, and only small differences were observed for color and vitamin C content (ascorbic acid and dehydroascorbic acid) after processing, mainly for conditions applied at higher temperature. Variations in the maximum temperatures of the PEF and thermal processes led to differences in flavor compounds and the remaining activity of pectinmethylesterase (PME). At PEF conditions with a maximum temperature of 78 °C or higher, PME activity levels were below a critical value, meaning that the cloud is stable. At this temperature volatiles associated with fresh juice (such as octanal and nonanal) are statistically identical to untreated juice, while they are statistically distinguishable from thermal treated. This papers demonstrates the potential of using moderate intensity PEF as an adequate alternative to thermal pasteurization of orange juice with a better retention of the fresh flavor.

Impact of Pulsed Electric Fields and pH on Enzyme Inactivation and Bioactivities of Peptic Hydrolysates Produced from Bovine and Porcine Hemoglobin.

The production of bioactive peptides from hemoglobin via peptic hydrolysis is a promising alternative to valorizing slaughterhouse blood proteins. Nevertheless, it has some limitations such as low yield, high cost of enzymes, and the use of chemical reagents. The latter is aggravated by the pH increase to inactivate the enzyme, which can affect the bioactivity of the peptides. Thus, this study aimed to evaluate the effect of pulsed electric fields (PEF) on the pepsin inactivation and biological activities (antimicrobial and antioxidant) of hemoglobin hydrolysates. Bovine (Hb-B) and porcine (Hb-P) hemoglobin were hydrolyzed with pepsin for 3 h and treated with PEFs to inactivate the enzyme. The degree of hydrolysis (DH) did not show significant changes after PEF inactivation, whereas peptide population analysis showed some changes in PEF-treated hydrolysates over time, suggesting residual pepsin activity. PEF treatments showed no significant positive or negative impact on antimicrobial and antioxidant activities. Additionally, the impact of pH (3, 7, and 10) on bioactivity was studied. Higher pH fostered stronger anti-yeast activity and DPPH-scavenging capacity, whereas pH 7 fostered antifungal activity. Thus, the use of hemoglobin from the meat industry combined with PEF treatments could fit the circular economy concept since bioactive peptides can be produced more eco-efficiently and recycled to reduce the spoilage of meat products. Nevertheless, further studies on PEF conditions must be carried out to achieve complete inactivation of pepsin and the potential enhancement of peptides' bioactivity.

Combined effect of pulsed electric field and osmotic dehydration pretreatments on mass transfer and quality of air-dried pumpkin.

Pulsed electric field (PEF) and osmotic dehydration (OD) pretreatment can accelerate the time-consuming drying process and minimize its high energy demands. The effect of PEF and OD pre-processing conditions and osmotic solution composition on mass transfer kinetics (water loss, solid gain, water activity) and quality properties (color, texture, total sensory quality) during OD and subsequent air-drying (AD) of pumpkin was studied. Application of PEF (2.0kV/cm-1500 pulses) significantly enhanced mass transfer during subsequent air-drying (increased effective diffusivity coefficient Des and drying rate kdrying , respectively). PEF and OD treatments led to a significant reduction of the processing time by 12 and 10%, respectively (p<0.05). The maximum reduction of processing time by 27% (p<0.05) (compared to untreated sample) resulted in combined use of PEF and OD as pretreatments prior to AD. When PEF pretreatment was combined with OD prior to AD, the corresponding energy was by 50% less than the respective energy required for nonprocessed samples. PRACTICAL APPLICATION: Pulsed electric fields (PEF) and osmotic dehydration (OD) can be applied for the production of air-dried pumpkin cuts of superior quality (in terms of quality and sensory characteristics) and reduced energy requirements (as a result of total processing time decrease).

The Volatile Profile of Brussels Sprouts (Brassica oleracea Var. gemmifera) as Affected by Pulsed Electric Fields in Comparison to Other Pretreatments, Selected to Steer (Bio)Chemical Reactions

Pulsed electric fields (PEF) at low field strength is considered a non-thermal technique allowing membrane permeabilization in plant-based tissue, hence possibly impacting biochemical conversions and the concomitant volatile profile. Detailed studies on the impact of PEF at low field strength on biochemical conversions in plant-based matrices are scarce but urgently needed to provide the necessary scientific basis allowing to open a potential promising field of applications. As a first objective, the effect of PEF and other treatments that aim to steer biochemical conversions on the volatile profile of Brussels sprouts was compared in this study. As a second objective, the effect of varying PEF conditions on the volatile profile of Brussels sprouts was elucidated. Volatile fingerprinting was used to deduce whether and which (bio)chemical reactions had occurred. Surprisingly, PEF at 1.01 kV/cm and 2.7 kJ/kg prior to heating was assumed not to have caused significant membrane permeabilization since similar volatiles were observed in the case of only heating, as opposed to mixing. A PEF treatment with an electrical field strength of 3.00 kV/cm led to a significantly higher formation of certain enzymatic reaction products, being more pronounced when combined with an energy input of 27.7 kJ/kg, implying that these PEF conditions could induce substantial membrane permeabilization. The results of this study can be utilized to steer enzymatic conversions towards an intended volatile profile of Brussels sprouts by applying PEF.

Investigation of Pulsed Electric Field Conditions at Low Field Strength for the Tenderisation of Beef Topside.

Tenderness is the most critical eating quality trait of meat, and consequently, processing interventions for meat tenderisation have significant economic relevance. The objective of this study was to investigate pulsed electric field (PEF) conditions for the tenderisation of beef topside. The PEF settings included combinations of three field strengths (0.25, 0.50 and 1.00 kV/cm), two frequencies (20 and 100 Hz) and three treatment times (10, 30 and 50 ms). The effect of PEF on meat quality parameters (pH, drip loss, shear force, cook loss and colour) immediately after treatment and after storage (1 and 14 days at 4 °C) was evaluated. PEF did not affect meat tenderness after 1 day of chilled storage but resulted in a 5–10% reduction in the shear force in some cases (0.25–0.5 kV/cm) compared to the untreated control after 14 days of storage. Other quality traits (cook loss and colour) were not impaired. Thus, we concluded that PEF technology is a possible intervention to improve meat tenderness of beef topside after 2 weeks of storage.

Pulsed electric field technology for the manufacturing processes of wine: A review

To improve wine safety and quality, the pulsed electric field (PEF) offers a rapid, nonthermal, and highly effective technology for inactivating key wine spoilage yeasts while maintaining the organoleptic qualities. PEF can be readily integrated into existing industrial processes and offers relatively low energy consumption and high-throughput production that could benefit winemakers worldwide. In this review, studies of PEF treatment combined with other techniques for enhancing wine quality and safety, the processing principles of PEF, equipment parameters, and the sterilization mechanism are summarized. In addition, the main limitations and advantages of PEF technology and the prospects of PEF technology in combination with other technologies for sulfur dioxide (SO2) substitution in winemaking in the future are discussed. Practical applications In recent years, several physical and chemical methods have been applied in wine processing to reduce or substitute the use of SO2. Among them, PEF is emerging as one of the most promising and green technologies. The present review aims to provide new perspectives on the application of PEF technology for improving aspects of wine quality and wine storage and report on the development of the optimization conditions of PEF in winemaking for industrial purposes.

Effects of ionic liquids and pulsed electric fields on the extraction of antioxidants from green asparagus roots

SummaryAsparagus officinalis root (AR) contains valuable bioactive compounds that have beneficial health properties. The aim of this study was to optimize the extraction of polyphenols and flavonoids in green AR using two novel technologies; pulsed electric field (PEF) and ionic liquids (IL). Further, the antioxidant activity of the obtained extracts was determined. The total polyphenol content, total flavonoid content (TFC), and antioxidant activity (2,2‐diphenyl‐1‐picrylhydrazyl, oxygen radical absorbance capacity and Ferric reducing/antioxidant power assays) were determined. The PEF conditions (PEF strength of 1.6 kV/cm, frequency of 200 Hz and pulse width of 20 µs) resulted in a higher extraction yield as compared to conventional solvent extraction, but had lower antioxidant activities. The optimal conditions for IL extraction were by using 0.5% 1‐butyl‐3‐methylimidazolium chloride at a solid: liquid (S:L) ratio of 1:10 for four min. The IL extraction resulted in a total of 122 mg RE/ mL TFC which was 70 to 80 folds more than the TFC obtained by PEF. The IL extracts had higher TFC and antioxidant activity than PEF, but the safety of the ILs need further research.

Pulsed Electric Field-Assisted Extraction of Aroma and Bioactive Compounds From Aromatic Plants and Food By-Products.

In this work, the effect of pulsed electric field (PEF) pre-treatment on the extractability in green solvents (i. e., ethanol–water mixture and propylene glycol) of target aroma and bioactive compounds, such as vanillin from vanilla pods, theobromine and caffeine from cocoa bean shells, linalool from vermouth mixture, and limonene from orange peels, was investigated. The effectiveness of PEF as a cell disintegration technique in a wide range of field strength (1–5 kV/cm) and energy input (1–40 kJ/kg) was confirmed using impedance measurements, and results were used to define the optimal PEF conditions for the pre-treatment of each plant tissue before the subsequent solid–liquid extraction process. The extracted compounds from untreated and PEF-treated samples were analyzed via GC-MS and HPLC-PDA analysis. Results revealed that the maximum cell disintegration index was detected for cocoa bean shells and vanilla pods (Zp = 0.82), followed by vermouth mixture (Zp = 0.77), and orange peels (Zp = 0.55). As a result, PEF pre-treatment significantly enhanced the extraction yield of the target compounds in both solvents, but especially in ethanolic extracts of vanillin (+14%), theobromine (+25%), caffeine (+34%), linalool (+114%), and limonene (+33%), as compared with untreated samples. Moreover, GC-MS and HPLC-PDA analyses revealed no evidence of degradation of individual compounds due to PEF application. The results obtained in this work suggest that the application of PEF treatment before solid–liquid extraction with green solvents could represent a sustainable approach for the recovery of clean labels and natural compounds from aromatic plants and food by-products.

Evaluation of temperature and pulsed electric field conditions on sugar extraction from carrots

Evaluation of temperature and pulsed electric field conditions on sugar extraction from carrots