Pulsed Electric Field Parameters Research Articles

Enhancing catechins, antioxidant and sirtuin 1 enzyme stimulation activities in green tea extract through pulse electric field-assisted water extraction: Optimization by response surface methodology approach

Green tea is an economic resource in Thailand because it is derived from smallholder agriculture and has expanded into food production. The purpose of this study is to optimize the parameters of pulsed electric field (PEF) assisted green tea extraction to produce a natural health product. A central composite design was involved to determine the effect of independent variables, including the intensity of electric field (I; 3–5 kV/cm), number of pulses (Np; 1000 to 3000 pulses) and green tea-to-water ratio (GT/W; 0.05–0.15 g/mL) on catechin (C), epicatechin (EC), epicatechin gallate (ECG), epigallocatechin (EGC) and epigallocatechin gallate (EGCG), total phenolic compound, antioxidant and sirtuin 1 enzyme stimulating activities. The results indicated that the Np had the most significant impact (p < 0.05) on the content of catechin and its derivatives and sirtuin 1 enzyme stimulating activity. The observations revealed that the I had a greater impact on antioxidant activities compared to the Np. The optimal conditions for PEF using the response surface method were determined to be I of 5 kV/cm, Np of 3000 pulses, GT/W of 0.14 g/mL and specific energy of 27 kJ/kg. Under the optimized conditions, the content of C, EC, ECG, EGC and EGCG were 7.34 ± 0.33, 11.26 ± 0.25, 3.75 ± 0.13, 7.53 ± 0.77 and 37.78 ± 0.58 mg/g extract, respectively. Furthermore, it was observed that green tea extract exhibited the ability to modulate the deacetylation activity of the sirtuin 1 enzyme, with a value of 22.63 ± 0.17 FIR. The results emphasized that the PEF led to achieving better responses compared to without pre-treatment using the PEF. Therefore, innovative technologies as PEF can be utilized for green tea extraction to produce natural ingredients, which can contribute to improved accessibility to healthcare. Additionally, the implementation of innovation techniques, such as PEF, in the extraction industry can enhance productivity growth and economic development.

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 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.

Impact of pulsed electric field treatment on barley germination for malting

The malting process takes one week to steep, germinate, and kiln barley to make malt. Making quality malt is critically important to achieve the desired attributes of the finished beer, and the process is time-intensive and costly. Malt quality is assessed by indicators including β-glucan quantity, α-amylase activity, Free Amino Nitrogen (FAN) content, and overall extract concentration in the finished malt. Here, we report Pulsed Electric Field (PEF) treatment of barley to accelerate malt production. A small-scale trial of 250 g to 1.00 kg barley, was evaluated for germination at two PEF treatment conditions, generically referred to as “low” and “high”, that resulted in increased barley rootlet length during germination of 1.3 mm longer than was observed for the control. Large-scale trials of 1.00 kg–3.00 kg barley, resulted in an increase in germination rate and a decrease of β-glucan concentration in the PEF treated barley. Micromalted barley using PEF parameters of 1.0 kV/cm and 15.0 kJ/kg displayed a reduction in β-glucan concentration by 38%, and increase in malt extract by 1.5%, FAN by 6.2%, and α-amylase by 8.4%, supporting the hypothesis that PEF treated barley generates more and better malt, leading to greater efficiency in the beer making process.

Defining winery processing conditions for the decontamination of must and wine spoilage microbiota by Pulsed Electric Fields (PEF)

This study investigated the PEF-resistance of Saccharomyces bayanus, Brettanomyces bruxellensis, Lactobacillus plantarum, and Oenococus oeni in must or wine under continuous PEF processing. Results showed the capacity of PEF to achieve 3.0-log10-cycles (CFU/mL) of inactivation of all the microorganisms under moderate conditions (< 155 kJ/kg). Developed tertiary models accurately predicted the effect of PEF parameters on microbial inactivation, and Monte Carlo simulation considered the variability of factors and the maximum assumable microbial load in the final treated product. Results showed that PEF-treatments at 15 kV/cm and 129 or 153 kJ/kg would ensure the adequate decontamination (< 10 CFU/mL) of spoilage microorganism in must or wine, respectively. Industrial relevancePEF technology has been shown to achieve adequate levels of microbial inactivation (3-log10) in must and wine under industrial applicable processing parameters, making it a suitable alternative to SO2 or sterilizing filtration for microbial control in winemaking. Reductions of 3-log10 CFU/mL of must and wine microbiota were found by continuous flow PEF-processing at 15 to 25 kV/cm and 175 to 148 kJ/kg, parameters applicable at industrial scale at 1 ton/h.

Effect of pulsed electric field on spore germination rate and enzyme activity of Aspergillus niger

Pulsed electric field (PEF) treatment on Aspergillus niger, which is an important source of several enzymes, was conducted to investigate the effects of different PEF parameters on spore germination of A. niger and the production of lipase and glucoamylase. The results showed that the spore germination rate and the relative activities of lipase and glucoamylase could be promoted when the electric field strength was in the range of 5– 15 kV/cm and the treatment time was in the range of 1– 7.5 ms. During the processing, the concentration of spores was maintained within a range of approximately 3.5 × 106 CFU/mL. Maximum increase of spore germination rate, lipase and glucoamylase activities were 217%, 25.6% and 31.3% respectively, which were observed when the spore suspension was subjected to PEF treatment with 10 kV/cm field strength for 5 ms. Lipase activity was inhibited with the increase of field strength and treatment time. Further analysis of the input energy density during PEF showed that the spore germination rate and the relative activities of enzymes were also promoted and then inhibited with increasing input energy density, but the electric field strength was more decisive. Industrial relevancePEF is an emerging non-thermal microbial treatment technology with the characteristics of short treatment time and low energy consumption. Aspergillus niger is an important microbial species in the food industry, as the enzymes it produces play an important role in various fields. This study applied PEF technology to A. niger and significantly promoted the germination of its spores, and the activity of its lipase and glucoamylase, which suggests PEF technology has the potential to be used to shorten the industrial production cycle of A. niger and its enzyme products.

Behaviour and mechanisms of molecular vibrations induced by a pulsed voltage in a silicone elastomer used for device encapsulation

AbstractSilicone elastomers are widely used to encapsulate power electronic devices. However, such devices may be subjected to square‐wave pulsed voltages with a high rate of change, which can create significant challenges for encapsulation insulation. In this article, the molecular vibration of silicon elastomer at the edge of pulsed electric field is studied. Firstly, the relationship between the intensity of molecular vibration and the parameters of pulsed electric field is explored. The experimental results show that the amplitude of the vibrations decreases as the pulse‐edge time increases, and it increases linearly as the pulse‐edge slope increases. Furthermore, the amplitude of the vibrations is proportional to the square of the amplitude of the pulsed electric field, and it increases as the space charge density increases. Then, the force analysis of charged molecule at the pulse edges is calculated, and the theoretical change law of molecular vibration intensity with pulse edge slope is deduced. Comparing the theoretical results with the experimental results, it is found that they are highly consistent. Finally, electrically induced mechanical stress caused by molecular vibration was shown to be an important factor in insulation failure.

Pulsed Electric Field (PEF) and High-Power Ultrasound (HPU) in the Hurdle Concept for the Preservation of Antioxidant Bioactive Compounds of Strawberry Juice-A Chemometric Evaluation-Part I.

This work investigated the influence of pulsed electric field (PEF) and high-power ultrasound (HPU) combined with hurdle technology to preserve the bioactive compounds (BACs) content and antioxidant activity in stored strawberry juices. PEF was performed at 30 kV cm-1, 100 Hz during 1.5, 3, and 4.5 min, while HPU was performed at 25% amplitude and 50% pulse during 2.5, 5.0, and 7.5 min. Total phenols and hydroxycinnamic acids were the most stable BACs during the hurdle treatment without influence of the duration of both treatments, while flavonols and condensed tannins showed a significant stability dependence with respect to the duration of both treatments. Total phenols were also stable during storage, in contrast to the individual groups of BACs studied. A chemometric approach was used to optimize the parameters of the hurdle treatments with respect to the highest level of BACs and the antioxidant activity of the treated juices. In general, shorter treatment times in the hurdle approach resulted in better stability of BACs and antioxidant activity. The hurdle technology investigated in this study has the strong potential to be an excellent concept for optimizing the operating parameters of PEF and HPU technologies in the preservation of functional foods.

Pulsed electric field and pre-heating treatment effect on free fatty acid (FFA), pH, vitamin C, and organoleptic properties of milk

The pulsed electric field (PEF)has been extensively studied in milk processing. However, treatment conditions still need to be improved to meet safety for consumption. This study aimed to determine optimum conditions by varying PEF and preheating treatment time. Free fatty acids (FFA), pH, and vitamin C are used to assess the milk quality. Preheating temperature is fixed at 70°C and the treatment time: 10, 20, and 30 minutes. PEF parameters are electric field, 66 μs pulse width, and the applied time of 2, 4, and 6 minutes. The pH value and preheating treatment time show a negative linear relationship in the range of 6.75-7.15, while PEF treatment time did not significantly affect pH. The FFA linearly increases as preheating treatment time increases from 0.0053-0.0097%. Vitamin C decreases as preheating treatment time increase from 0.003-0.0049 mg/ml. PEF treatment significantly affects vitamin C, where vitamin C decreases as treatment time increases. Preheating and PEF treatment time show positive effects on the organoleptic properties of milk. The organoleptic properties values are flavor 3.93, aroma 4.00, and color 3.9 out of 5.

Absence of Arrhythmogenicity with Biphasic Pulsed Electric Fields Delivered to Porcine Airways.

Pulsed electric field (PEF) technologies treat many types of tissue. Many systems mandate synchronization to the cardiac cycle to avoid the induction of cardiac arrhythmias. Significant differences between PEF systems make the assessment of cardiac safety from one technology to another challenging. A growing body of evidence suggests that shorter duration biphasic pulses obviate the need for cardiac synchronization, even when delivered in a monopolar fashion. This study theoretically evaluates the risk profile of different PEF parameters. It then tests a monopolar, biphasic, microsecond-scale PEF technology for arrhythmogenic potential. PEF applications of increasing likelihood to induce an arrhythmia were delivered. The energy was delivered throughout the cardiac cycle, including both single and multiple packets, and then with concentrated delivery on the t-wave. There were no sustained changes to the electrocardiogram waveform or to the cardiac rhythm, despite delivering energy during the most vulnerable phase of the cardiac cycle, and delivery of multiple packets of PEF energy across the cardiac cycle. Only isolated premature-atrial contractions (PAC) were observed. This study provides evidence that certain varieties of biphasic, monopolar PEF delivery do not require synchronized energy delivery to prevent harmful arrhythmias.

Electrical impedance decreases in annulus fibrosus cartilage exposed to microsecond pulsed electric fields ex vivo

Electropermeabilization of biomembranes often is measured by microscopic imaging of a membrane-impermeable fluorophore that penetrates the cells following pulsed electric field (PEF) exposure. PEF exposure subsequently changes physiological properties of tissue. One way to probe these changes in tissue is measuring electrical properties by way of electrochemical impedance spectroscopy (EIS). In this study, we analyse impedance and conductivity of bovine annulus fibrosus (AF) cartilage before and after exposures to PEF of 100 μs duration. Two PEF parameters–electric field amplitude and number of pulses–are varied, and total specific dose of PEF is calculated. AF tissue conductivity increases with both amplitude and number of pulses, indicating electropermeabilization of the AF cells. A Live/Dead cell imaging assay validates the EIS measurements, indicating intratissue cell permeabilization by μsPEF exposure. These results support the extension of EIS to monitor extent of electropermeabilization of cells within cartilage tissue.

Pre-Treatment of Starter Cultures with Mild Pulsed Electric Fields Influences the Characteristics of Set Yogurt.

The aim of this study was to investigate the effect of pulsed electric field (PEF) pre-treatment of a dairy starter culture of Lactobacillus delbrueckii subsp. bulgaricus LB186 and Streptococcus thermophilus ST504 on the fermentation and final product characteristics of set-style yogurt. The effects of PEF treatment parameters, voltage (4-20 kV), pulse number (20-80 pulses), frequency (1-21 Hz), and pulse (5-8 µs) width on pH development, cell counts, and proteolytic activity, as well as on texture and degree of syneresis in yogurt were investigated by use of a two-level full factorial design. Pulse frequency and pulse width had a significant effect on the yogurt stiffness (p < 0.05) and the interaction of voltage and frequency had a significant effect on both stiffness and proteolytic activity (p < 0.05). Further experiments confirmed that pre-treatment of the dairy culture with specific PEF parameters immediately before addition to milk could accelerate fermentation of, increase stiffness of, and reduce syneresis in the final yogurt. This effect of the PEF-pre-treated culture was partially retained even after flash-freezing and 14 days of storage of the culture at -20 °C. The effects were attributed to responses to oxidative stress induced by the PEF pre-treatment.

Human in vitro assay for irreversible electroporation cardiac ablation.

Introduction: Pulsed electric field (PEF) cardiac ablation has been recently proposed as a technique to treat drug resistant atrial fibrillation by inducing cell death through irreversible electroporation (IRE). Improper PEF dosing can result in thermal damage or reversible electroporation. The lack of comprehensive and systematic studies to select PEF parameters for safe and effective IRE cardiac treatments hinders device development and regulatory decision-making. Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) have been proposed as an alternative to animal models in the evaluation of cardiac electrophysiology safety. Methods: We developed a novel high-throughput in vitro assay to quantify the electric field threshold (EFT) for electroporation (acute effect) and cell death (long-term effect) in hiPSC-CMs. Monolayers of hiPSC-CMs were cultured in high-throughput format and exposed to clinically relevant biphasic PEF treatments. Electroporation and cell death areas were identified using fluorescent probes and confocal microscopy; electroporation and cell death EFTs were quantified by comparison of fluorescent images with electric field numerical simulations. Results: Study results confirmed that PEF induces electroporation and cell death in hiPSC-CMs, dependent on the number of pulses and the amplitude, duration, and repetition frequency. In addition, PEF-induced temperature increase, absorbed dose, and total treatment time for each PEF parameter combination are reported. Discussion: Upon verification of the translatability of the in vitro results presented here to in vivo models, this novel hiPSC-CM-based assay could be used as an alternative to animal or human studies and can assist in early nonclinical device development, as well as inform regulatory decision-making for cardiac ablation medical devices.

Influence of pulsed electric field on mortality of yeasts of the genus Candida

Pulsed electric field (PEF) is a technology that uses short duration high intensity electrical pulses. Application of such a field causes electroporation of the cell membrane and consequently increases its permeability [1]. The genus Candida includes about 200 species, some of which are pathogenic to humans. These microorganisms are potentially used as a source of proteins, polysaccharides and biocomplexes in nutrition [7]. The mechanism of microbial inactivation by PEF is related to the formation of pores in the membrane, as indicated by many authors. The aim of this study is to determine the parameters of pulsed electric field affecting the lethality of selected Candida yeast strains, as well as to determine the percentage of dead cells, after PEF exposure. Depending on the voltage applied and the number of pulses, variation in yeast cell mortality is noted. In comparison with the control samples, with the increase in the number of pulses at each voltage variant, an increase in mortality among the tested yeast strains is observed.

Effect of pulsed electric field parameters on the alkaline extraction of valuable compounds from perilla seed meal and optimization by central composite design approach

Perilla seed meal (PSM) is the by-product of the oil extraction industry and a potential source of bioactive compounds. Pulsed electric field, a non-thermal technology, can be used to recover heat labile bioactive compounds from plant materials such as perilla seed meal. This study found that pulsed electric field (PEF) assisted alkaline extraction influenced the protein content and antioxidant activity of perilla seed meal (PSM). Among all PEF parameters, electric field strength (EFS) and pulse width (PW) were found to be the most significant as judged by F-value. Consequently, a central composite rotatable experimental design was applied to investigate the effect of electric field strength (EFS) and pulse width against protein content, antioxidant activity, and total phenolic content (TPC) of PEF treated PSM extract. Compared to conventional alkaline extraction, an increase in the yield of protein content by 10.58%, antioxidant activity by 7.48%, and total phenolic content by 21.59% was recorded at the optimal values of electric field strength (4 kV/cm) and pulse width (120 µs). Moreover, Karl pearson correlational analysis revealed a strong relationship (linear, R2=0.963) between antioxidant activity and total phenolic content. The validation was done at 95% confidence level for which the predicted values were compared with the actual experimental values, and the means were found to be insignificantly different from each other (p > 0.05). Industrial relevanceNon-thermal extraction techniques such as pulsed electric field used in this study can be used for the recovery of valuable compounds from the food materials especially heat sensitive compounds. PEF treatment increased the extractability of the water-soluble compounds from the perilla seed meal (PSM) samples and increased the recovery of valuable compounds from PSM while maintaining the nutritional and functional viability. Hence, this technology is having the potential to be used as assistant technology for the extraction of heat sensitive components from the plant cells which may find its applications in neutraceutical and pharmaceutical industries.

Abstract 13129: Human in vitro Study on Pulsed Electric Field Cardiac Ablation Cell Sensitivity

Introduction: Catheter cardiac ablation is a standard treatment for atrial fibrillation for patients that do not respond to drugs. Pulsed electric field (PEF) cardiac ablation has been proposed as a nonthermal technology to cause cell death by irreversible electroporation (IRE). IRE has shown to minimize off target damage. The lack of systematic studies to inform optimal PEF ablation parameters has significantly slowed down device development and regulatory process. Hypothesis: As part of a larger effort to develop a standard laboratory assay for PEF parameter optimization, in this study we investigate tissue specificity of IRE cardiac ablation treatments. Methods: Human induced pluripotent stem cell cardiomyocytes derived (hiPSC-CMs, Fujifilm Cellular Dynamic, Inc.), human esophageal muscle cells (HESMC, ScienCell Research Laboratories), and human bronchial epithelial cells (HBEC3-KT, ATCC) were cultured in monolayer formats on 96-well NanoFiber plates. PEF were delivered by an FID pulse generator connected to two needle electrodes (1.7 mm center-to-center distance). PEF parameters investigated in this study are: phase duration tp=1, 5, 10 μs; phase intensity Vp=284, 372, 568V; pulse repetition frequency PRF=10, 100, 1000 Hz, pulse number p#=100. We quantified IRE areas 4 hours post-treatment by propidium iodide (PI). Results: Preliminary results show that increasing the tp, Vp and decreasing the PRF resulted in a larger IRE area in all the cell types studied. For the range of PEF parameters investigated, a treatment with same tp, p# and PRF required higher Vp to induce IRE in HESMC and HBEC3-KT than hiPSC-CMs, i.e., 100 pulses with tp=5 μs and PRF=1000 Hz, to achieve the same IRE area, hiPSC-CMs needed half Vp than HESMC and HBEC3-KT. Conclusions: Our data suggests that same PEF treatments induced larger IRE areas in hiPSC-CM than in HESMC and HBEC3-KT. Future work will focus on validating these results in tissues to assess safety of IRE cardiac ablation devices.

Effect of Pulsed Electric Field on the Electrodialysis Performance of Phosphate-Containing Solutions.

A comparative analysis of mass transfer characteristics and energy consumption was carried out for the electrodialysis recovery of PV from of NaH2PO4 solutions and multicomponent (0.045 M NaxH(3-x)PO4, 0.02 M KCl, 0.045 M KOH, 0.028 M CaCl2, and 0.012 M MgCl2, pH 6.0 ± 0.1) solution in conventional continuous current (CC) and pulsed electric field (PEF) modes. The advantages of using PEF in comparison with CC mode are shown to increase the current efficiency and reduce energy consumption, as well as reduce scaling on heterogeneous anion-exchange membranes. It has been shown that PEF contributes to the suppression of the "acid dissociation" phenomenon, which is specific for anion-exchange membranes in phosphate-containing solutions. Pulse and pause lapse 0.1 s-0.1 s and duty cycle 1/2 were found to be optimal among the studied PEF parameters.

Effect of Pulsed Electric Fields (PEF) Pre-Treatment on the Quality of Sous Vide (SV) Processed Beef Short Ribs and Optimisation of PEF and SV Process Parameters Using Multiple Polynomial Regression Model

To maximise tenderness, minimise cooking loss, and decrease the adverse effects on the colour of beef short ribs, third-order multiple regression models were used to optimise the processing parameters during the pulsed electric fields (PEF) followed by sous vide (SV) processing. Electric field strength (EFS) and specific energy (SE) of PEF ranged from 0 to 0.85 kV/cm and 0 to 110.96 kJ/kg, respectively, and SV processing for 12, 24, or 36 h at 60 °C was applied. The optimum PEF-SV processing conditions for short ribs were found at EFS of 0.85 kV/cm and SE of 110.96 kJ/kg with SV processing at 60 °C for 23.96 h. In the absence of PEF pre-treatment, the optimum SV time at 60 °C was 36 h. PEF pre-treatments (SE, 99–110.96 kJ/kg) followed by SV (24 h) at 60 °C resulted in a significantly lower cooking loss (%) and texture profile analysis hardness compared to PEF at all treatment intensities, followed by SV at 60 °C for 36 h. Furthermore, significant differences were not observed in the redness, hue angle, and chroma at different PEF-SV processing parameters. Therefore, for industrial applications, PEF-SV processing with EFS (0.85 kV/cm), pulse width (20 µS), pulse frequency (50 Hz) and SE (110.96 kJ/kg), and SV temperature–time combination of 60 °C and 23.96 h is highly recommended.

Accumulation of Vitamin C in Yeast under Pulsed Electric Field (PEF) Conditions

Enriching food with vitamin C is a process that challenges food engineers. To prevent the degradation of this vitamin, a microencapsulation can be used in Saccharomyces cerevisiae cells. Previous works have shown that applying a pulsed electric field can increase the efficiency of the accumulation of minerals in yeast. The aim of this study was to optimize PEF parameters in order to increase the accumulation of vitamin C in yeast cells, to evaluate the effect of electroporation on biomass and yeast viability, and to assess the effect of storage conditions on the vitamin C content and its antioxidant activity. The most effective accumulation of vitamin C in cells (approx. 1.3 mg/g dry mass) was achieved when a 20-h yeast culture was treated with PEF at a concentration of 5 mg/mL vitamin C in the medium. The optimal PEF parameters were: voltage of 1000 V, pulse width of 10 µs, treatment time of 20 min, and number of pulses, 1200. The process conditions did not affect significantly biomass production nor cell viability. Yeast cells with vitamin C were stored for 7, 14, and 28 days at 20 °C (after prior freeze-drying), 4 °C, and −22 °C. The lowest decrease in vitamin C content was observed for the freeze-dried yeast stored at 20 °C.

The Pulsed Electric Field Assisted-Extraction Enhanced the Yield and the Physicochemical Properties of Soluble Dietary Fiber From Orange Peel.

The study aimed to investigate the effects of pulsed electric field (PEF)-assisted extraction on the yield, physicochemical properties, and structure of soluble dietary fiber (SDF) from orange peel. The results showed that the optinal parameters of PEF assisted extraction SDF was temperature of 45oC with the electric field intensity of 6.0 kV/cm, pulses number of 30, and time of 20min and SDF treated with PEF showed the higher water solubility, water-holding and oil-holding capacity, swelling capacity, emulsifying activity, emulsion stability, foam stability and higher binding capacity for Pb2+, As3+, Cu2+, and higher which resulted from the higher viscosity due to PEF treatment. Compared with the untreated orange peel, the SDF obtained with PEF exhibited stronger antioxidant activities, which was due to its smaller molecular weight (189 vs. 512 kDa). In addition, scanning electron micrograph images demonstrated that the surface of PEF-SDF was rough and collapsed. Overall, it was suggested that PEF treatment could improve the physicochemical properties of SDF from the orange peel and would be the potential extraction technology with high efficiency.