Effect Of Pulsed Electric Fields Research Articles

Cooking does not impair the impact of pulsed electric field on the protein digestion of venison (Cervus elaphus) during in vitro gastrointestinal digestion

SummaryThe present study was conducted to elucidate whether cooking impairs the positive effect of pulsed electric field (PEF) on the digestibility of venison during in vitro gastrointestinal protein digestion. Previous studies have used fresh uncooked meat to demonstrate the effect of PEF on protein digestibility during gastrointestinal digestion neglecting the effect that cooking could induce during meat preparation process. PEF‐treated samples (T1, 10 kV, 90 Hz, 20 µs) were cooked (core temperature of 75 °C) and subjected to in vitro simulated gastrointestinal protein digestion along with non‐treated controls. A 3% increase of in vitro protein digestibility was found in cooked PEF‐treated venison (P < 0.05). A positive (P < 0.05) impact of PEF processing was observed on overall protein digestion as measured by soluble protein (%) and SDS‐PAGE. PEF did not change (P > 0.05) the release of minerals from cooked venison during digestion. Cooking had no negative influence on the mechanism through which PEF operates in improving the protein digestibility of venison.

Combined effect of pulsed electric fields and ultrasound on mass energy transfer and diffusion coefficient of plum

The aim of the study was to investigate the impact of combined application of pulsed electric fields (PEF) and ultrasound (US) pre-treatment on drying kinetics, mass transfer and convective water diffusion coefficient on plum fruit. The treatment was performed by using plum fruit in water for uniform distribution of electric conductivity and PEF treatment was applied at 1, 2 and 3 kV/cm, 50 pulses followed by US, 40 kHz with 99% frequency for 30 min and 27 ± 2 °C. Cell disintegration, drying kinetics, mass transfer and diffusion coefficient were calculated, and results showed that plums treated at 3 kV/cm intensity exhibited higher cell disintegration followed by 2 and 1 kV/cm. Furthermore, the investigation of PEF and US pre-treatment for drying kinetics and convective diffusion coefficient revealed that plums treated at 3 kV/cm contributed higher drying rate and convective water diffusion coefficient at uniform, pulse number, temperature and sonication time followed by 2 and 1 kV/cm. This study stated that combined treatment of PEF and US increased the cell disintegration, drying rate and also facilitate convective water diffusion as compared to untreated intact tissues.

SUPERCRITICAL EXTRACTION OF LYOPHILIZED STRAWBERRY ANTHOCYANINS WITH PULSED ELECTRIC FIELDS PRETREATMENT

The lyophilized strawberry anthocyanins were extracted using a supercritical extraction (SE) process. The effect of pulsed electric fields (PEF) as pretreatment and the influence of the addition of ethanol as a cosolvent on the percentage of extraction yield (EY) and the total anthocyanin concentration (TAC) were analyzed. The effect of PEF was evaluated at 0.5 and 1.0 kV/cm, while the effect of the cosolvent was studied in mixtures of supercritical carbon dioxide - ethanol (SCCO2 + ethanol) at 1.6 and 3.3% by weight. The best results (% EY = 0.506, TAC = 0.428 g /100 g of lyophilized strawberry) were obtained with a PEF pretreatment of 1.0 kV cm-1, 3.3%wt. ethanol at 200 bar and 333.15 K. The experimental results of solubility were suitably adjusted with the Kumar and Johnston model. The maximum solubility (0.114 g/100 g of solvent mixture) was obtained at 300 bar and 313.15 K.

Effect of pulsed electric fields on carotenoid and phenolic bioaccessibility and their relationship with carrot structure.

Phenolic compounds (PC) and carotenoids from carrots are bound to dietary fibre or stored in vacuoles and chromoplasts, respectively. To exert their antioxidant effects these compounds must be released during digestion, which is hindered by such barriers. Pulsed electric fields (PEF) modify cell membrane permeability, thus enhancing their bioaccessibility. The effect of PEF on the carrot carotenoid and PC content and bioaccessibility was investigated. With this purpose, PEF-treated carrots (5 pulses of 3.5 kV cm-1) were stored for 24 h at 4 °C and microstructure was evaluated before subjecting them to in vitro digestion. PEF did not affect carotenoid content, whereas their bioaccessibility improved (11.9%). Likewise, PEF increased the content of some PC, e.g. coumaric acid (163.2%), probably caused by their better extractability. Conversely, caffeic acid derivatives decreased, which may be associated to greater contact with oxidative enzymes. Total PC bioaccessibility (20.8%) and some derivatives increased, e.g. caffeoylshikimic (68.9%), whereas some decreased (e.g. ferulic acid). Structural changes caused by PEF may improve bioaccessibility of carotenoids and PC by favouring their release and easy access to digestive enzymes. However, other antioxidants may be further degraded or entrapped during digestion. Therefore, PEF is an effective technology for obtaining carrots with enhanced carotenoids and phenolic bioaccessibility.

Effects of Pulsed Electric Field and Thermal Treatments on Microbial Reduction, Volatile Composition, and Sensory Properties of Orange Juice, and Their Characterization by a Principal Component Analysis

The effects of pulsed electric field (PEF) treatments on microbial reduction, volatile composition, and sensory characteristics of orange juice were investigated. Mild (Thermal-1) and intensive (Thermal-2) thermal treatments were applied for comparison. A pilot-scale PEF system, with a flow rate of 30 L/h and maximum field strength of 20 kV/cm, was used. PEF treatment at a specific energy of 150 kJ/L resulted in 9.0 and 8.0 decimal reductions of Escherichia coli and Saccharomyces cerevisiae, respectively. The PEF treatments preserved the characteristic compounds associated with a fresh flavor (e.g., dl-limonene, β-myrcene, α-pinene, and valencene) more effectively than an intensive thermal treatment. This was verified by descriptive analysis of sensory evaluations. Based on the principal component analyses (PCAs) and partial least-squares (PLS) regression analyses, PEF-treated orange juice showed higher similarity to untreated orange juice. Our results indicate that PEF may be an alternative processing technique that can preserve the fresh flavor and taste of freshly squeezed orange juice.

Effects of pulsed electric fields on sour cherry juice properties and formations of furfural and hydroxymethylfurfural

Abstract Impacts of pulsed electric fields (PEF) on physicochemical properties, bioactive compounds, and furfural and hydroxymethylfurfural (HMF) formations were quantified for sour cherry juice (SCJ). pH, titratable acidity (TA), total soluble solids (TSS), a*, b*, chroma, and total monomeric anthocyanin content (TMAC) were not significantly affected by 0–0.0341 J/L. The initial total antioxidant capacity (TAC) significantly rose with all the PEF treatments but initial citric, malic, fumaric, oxalic, succinic (−)-epicatechin, ferrulic, gallic, luteolin, p-coumaric, and o-coumaric acids, Cy-3-sop, and Cy-3-glu did not significantly degrade with no formations of furfural and HMF. The best-fit regression models explained 60.1, 39.7, and 36.3% of variation in TAC, TMAC, and TSS, respectively. Frequency exerted a greater impact than did electric field strength (EFS) on TA, pH, TSS, total color difference (TCD), hue, chroma, TMAC, TAC, sinapic, oxalic, quinic and tartaric acids, Cy-3-glu-rut, and furfural formation. 350.9 µs, 6.78 kV/cm, and 98 Hz were pointed as optimal settings.

Pulsed electric fields (PEF) as hot air drying pre-treatment: Effect on quality and functional properties of saffron (Crocus sativus L.)

This study aimed to investigate the use of pulsed electric fields (PEF) (2 kV/ cm; 1.5 KJ kg−1) as pre-treatment to the hot air drying process for the improvement of quality and functional properties of saffron. Analysis of flavouring, aroma and colouring strength (E1%λmax), crocins pattern (UHPLC-MS/MS), total polyphenol content (TPC) and antioxidant activity (AOA) were performed after processing and during aging at room temperature. Microstructure of fresh and processed stigmas was also assessed.PEF decreased (≈ −41%) the flavour, aroma and colouring strength of stigmas and negatively influenced the safranal production during drying; nevertheless, stigmas pre-treated by PEF (PD) after 3 months of aging showed quality properties similar to those of not pre-treated sample (D). Analysis of crocins by UHPLC-MS/MS highlighted a negative effect of PEF on trans-cis crocins ratio and showed poor correlation with colour strength. PEF did not influence the TPC of fresh stigmas but after drying and aging PD showed the highest value among the samples. PEF negatively influenced (−24%) the AOA of fresh stigma while favored its increase during drying. Loss of AOA during aging (up to 86%) was processing independent. Microstructure analysis showed that PEF treatment strongly impaired the stigmas' cells, thus enhancing the extractability of intracellular compounds.

Effects of pulsed electric fields and preliminary vacuum drying on freezing assisted processes in potato tissue

The effects of pulsed electric field (PEF) treatment and preliminary vacuum drying (VD) on freezing assisted processes for the potato tissue were studied. The PEF treatment was done at 600 V/cm using the protocol to insure the high level of potato disintegration. The VD was done at sub-atmospheric pressure of p = 0.30 bar. Such conditions allowed relatively fast dehydration accelerated by PEF treatment at low or moderate temperatures inside sample (<50 °C). Impacts of PEF and VD on freeze-thawing (FT) and freeze-drying (FD) processes were tested. The duration of the freezing and thawing processes noticeably increased with increasing of the moisture ratio. The PEF treatment also accelerated the FD and affected the final level of dehydration after prolonged FD for 24 h. It was demonstrated that application of VD and VD combined with FT deteriorated the rehydration, whereas VD combined with FD facilitated the rehydration of deeply dried potato tissue. The obtained regularities can be useful in future practical implementations of freezing assisted processes with fine control of deterioration of product quality and reduced operating and maintenance costs.

Effects of combined pulsed electric field and blanching pretreatment on the physiochemical properties of French fries

The aim of this work was to explore the effect of combining pulsed electric field (PEF) with blanching pretreatment on the physiochemical properties of French fries. The effects of PEF plus blanching pretreatment on the color parameters, texture, content and spatial distribution of moisture and oil, microstructure, colony count and acrylamide content of French fries were investigated. Results showed that the pretreated French fries were brighter (L value was 60.44) and golden yellow, with lower hardness (312.27 g), higher springiness (0.81) and higher chewiness (119.71). In addition, moisture and oil contents of the fries were reduced, with more uniform distributions. The cross-section microstructure of these French fries also showed near-complete gelatinization of starch particles, and the internal structure of fries was fluffy. Finally, French fries obtained by the combined pretreatment had an improved food safety profile, with a lower colony count (13 CFU/g) and acrylamide content (1533.75 ng/g). Industrial relevanceBlanching is a traditional thermal processing technology widely used in the field of fried potatoes. However, blanching has some disadvantages such as slow heat conduction, long processing time, substantial loss of soluble nutrients, and huge water wastage. PEF is an emerging technology in the 21st century that can maintain the original flavor, color, taste, and nutritional value of foods treated by it. The French fries obtained by combining PEF and blanching pretreatment were brighter and golden yellow, and were also softer, and more springy and chewy – an overall net improvement in aesthetic appeal and organoleptic profile. The above findings may provide useful information to guide effective strategies for the practical application of PEF combined with blanching in the preparation of fried potato foods.

Understanding the impact of moderate-intensity pulsed electric fields (MIPEF) on structural and functional characteristics of pea, rice and gluten concentrates

AimThe effect of moderate-intensity pulsed electric fields (MIPEF) was evaluated on vegetable protein concentrates from pea, rice, and gluten.MethodsFive percent (w/w) suspensions of protein concentrates (pH 5 and 6) were exposed to up to 60,000 MIPEF pulses at 1.65 kV/cm. Both structural modifications (absorbance at 280 nm, free sulfhydryl groups, FT-IR-spectra) and functional properties (solubility, water and oil holding capacity, foamability) were analyzed.ResultsMIPEF was able to modify protein structure by inducing unfolding, intramolecular rearrangement, and formation of aggregates. However, these effects were strongly dependent on protein nature and pH. In the case of rice and pea samples, structural changes were associated with negligible modifications in functional properties. By contrast, noticeable changes in these properties were observed for gluten samples, especially after exposure to 20,000 pulses. In particular, at pH 6, an increase in water and oil holding capacity of gluten was detected, while at pH 5, its solubility almost doubled.ConclusionThese results suggest the potential of MIPEF to steer structure of proteins and enhance their technological functionality.

Influence of pulsed electric field (PEF) and ultrasound treatment on the frying behavior and quality of potato chips

The effect of pulsed electric field (PEF) and ultrasound (US) on the frying behavior of potato chips was investigated. For this purpose, a special fryer with a window was designed to enable the investigation of water evaporation by the characterization of bubble formation during frying. The number of water vapor bubbles and the bubble volume distribution were analyzed in order to gain an insight into heat and mass transfer affected by PEF and US treatment. Quality parameters of the potato chips such as moisture, fat and acrylamide content were measured. Overall, the results of this study show for the first time impacting effects on the frying process that can be achieved by combining PEF as a volumetric cell disintegration technology and ultrasound as a mean to affect interface phenomena. The obtained results can be used to further optimize frying processes used for the production of chips and other products.

Effects of pulsed electric field on fat globule structure, lipase activity, and fatty acid composition in raw milk and milk with different fat globule sizes

To modify the structure of milk fat globules (MFGs), raw milk (RM) with native MFGs, and milk with small (MS) and large (ML) MFGs, were subjected to moderate pulsed electric field (PEF) treatment at 9 and 16 kV·cm−1 for 30 μs. The changes caused by PEF on MFG structure leading to MFG-MFG and MFG-protein aggregation were found to depend on the size, composition and/or previous damage caused by the separation and mixing processes during production of MS and ML, in addition to the intensity of the PEF treatment. Although, PEF treatment had a more pronounced effect on MFGM proteins of MS, these MFG were less affected by PEF due to significant adsorption of milk proteins. The structural changes caused by PEF were accompanied by changes in lipase activity and fatty acid (FA) profiles, i.e. increase in the proportion of C6:0, C8:0, C10 and some long-chain FAs and a decrease in medium and other long chain FAs. Industrial relevancePEF is gaining attention in the dairy industry. However, information regarding the effect of PEF processing on milk components and functionality is still limited. The present investigation contributes to understand the potential of PEF at moderate field intensities to modify the MFGs and consequences for milk stability, lipolysis and composition of FAs. The new insight is relevant in development of new products and ingredients containing milk fat.

A Multilevel Pulse Generator Based on Series Capacitor Structure for Cell Electroporation

Research on the effect of pulsed electric field in cell electroporation attracts more attention, especially tumor ablation. This puts forward higher requirements for pulsed electric field parameters. The shape of the pulse waveform was also required in different electroporation applications. Based on this, a multilevel pulse generator with series capacitor structure was proposed in this article. Besides, it can also obtain the different shapes of the pulse waveforms by controlling the timing of semiconductor switches. The voltage amplitude, the number of pulses, and the pulsewidth are all adjustable. A ten-level test prototype with 11 switches was built. The structure was simple and was more compact. It can work stably under the simulated small resistance load. Finally, when the dc charging voltage was 1 kV, the system can achieve a maximum output voltage of ±500 V. The number of pulse in one pulse sequence was 1–500. The pulsewidth was adjustable from 1 to $10~\mu \text{s}$ . By controlling the switch’s timing, it can also obtain the multilevel voltage output, exponential waveform voltage output, and composite waveform output combined narrow pulse with wide pulse.

The impact of pulsed electric fields on quality parameters of freeze‐dried red beets and pineapples

AbstractThe effect of pulsed electric fields (PEF) on the cell disintegration index (Zp), the freeze‐drying process and the final product quality of red beet and pineapple tissue was studied. Red beets and pineapples were PEF‐treated at an electric field strength of 1.07 kV/cm and specific energy inputs of 1 kJ/kg and 4 kJ/kg (PEF1 and PEF2, respectively). Freeze‐drying was performed at a pressure of 1 mbar and heating plate temperature of 50 °C for red beet and 40 °C for pineapple. The quality of freeze‐dried tissue was evaluated by the analysis of residual moisture content, macrostructure, texture, colour and rehydration properties. For freeze‐dried red beets, the betalain content from extracts was studied. It could be stated that PEF pre‐treatment had no significant influence on drying time reduction, however significantly improved the final quality of freeze‐dried product. Moreover, the effect of PEF was strongly depending on type of plant material used.

Effects of pulsed electric fields on the conformation and gelation properties of myofibrillar proteins isolated from pale, soft, exudative (PSE)-like chicken breast meat: A molecular dynamics study

The potential of pulsed electric field (PEF) of different intensities (8, 18, and 28 kV/cm) on the conformation and gelation properties of myofibrillar proteins (MPs) extracted from pale, soft, and exudative-like (PSE-like) chicken meat was investigated. The results showed a positive correlation between gelation properties and PEF intensities in the range of 8–18 kV/cm; however, a further increase in intensity had a negative impact. Optimized PEF treatment (18 kV/cm) was capable of inducing MPs with a relatively small particle size, thus contributing to the production of a more homogeneous gel structure. The water distribution and mobility in the gel system significantly changed with increasing PEF intensities, the proportion of immobilized water (P21) increased, and that of free water (P22) decreased. Based on molecular dynamics simulations (MDS), an increasing trend in the number of hydrogen bonds and a reduction in the radius of gyration (Rg) after PEF treatment.

Pulsed Electric Fields (PEF) to Mitigate Emerging Mycotoxins in Juices and Smoothies

The development of innovative food processing technologies has increased to answer the growing demand to supply of fresh-like products. The aim of the present study is to investigate the effect of pulsed electric fields (PEF) technology on reducing the emerging mycotoxins (enniatins (ENs) and beauvericin (BEA)) contents in juice and smoothie samples. The products of degradation obtained after PEF treatment were identified and their toxicological endpoint toxicities predicted by Pro Tox-II web. Mycotoxin reduction ranged from 43 to 70% in juices and smoothies, but in water the expected effect was lower. The acidified pH increased BEA reduction in water. The degradation products that were produced were the result of the loss of aminoacidic fragments of the original molecules, such as HyLv, Val, Ile, or Phe. Pro Tox-II server assigned a toxicity class I for enniatin B (ENB) degradation products with a predicted LD50 of 3 mg/Kgbw. The other degradation products were classified in toxicity class III and IV.

Saving energy on meat air convection drying with pulsed electric field coupled to mechanical press water removal

The present study analyses the effects of low intensity pulsed electric fields (PEFs), coupled to mechanical press dewatering on meat drying with air convection. Process parameter optimization using Taguchi design showed that the number of pulses had most significant effect on meat dewatering. A maximum effective diffusivity of 2.31 × 10−9 m2 s−1 was observed for PEF assisted drying of chicken meat at 80 °C. An overall energy saving of 933.18 ± 22 J g−1 was observed for drying at 60 °C when the meat was treated with a voltage of 75 V with initial distance between electrodes of 6.917 ± 0.38 mm, pulse length 7 ms, 300 pulses with a frequency of 2 Hz under 125.44 kPa continuous mechanical load. Our study suggests that PEF coupled to mechanical dewatering saves energy in conventional meat drying with air convection. Such a strategy could provide a scalable model for PEF assisted drying of various food products with higher energy efficiency and improved diffusivity.

Changes in Quality Characteristics of Strawberry Juice After Equivalent High Pressure, Ultrasound, and Pulsed Electric Fields Processes

Understanding the efficacy of viable emerging technologies in preserving overall quality attributes and antioxidant characteristics of fruit juices is of great interest. This study aimed to evaluate the effect of high pressure (HP), ultrasound (US), and pulsed electric fields (PEF) processes on natural microbiota inactivation, as well as changes in physicochemical attributes and phytochemical content of strawberry juice (SJ). HP at 300 MPa (1 min), US at 55 °C (3 min) and 517.1 mW/mL acoustic energy density, and PEF at 35 kV/cm (27 μs) using monopolar square pulses with 2 μs pulse width were applied, and then compared with a conventional thermal pasteurization treatment (72 °C, 15 s). The nonthermal processes were equivalent in terms of Escherichia coli (E. coli) inactivation since the selected processing conditions led to almost identical inactivation level (at least 5-log) of inoculated E. coli. The current study analyzes why these equivalent processes had different effect on SJ quality. All treatments significantly reduced the initial natural microbiota (i.e., total mesophilic aerobic bacteria and yeast-molds) below 2 log CFU/mL. No significant changes were observed on the total soluble solid content (7.83–8.00 °Brix), titratable acidity (0.79–0.84 g/100 mL), and pH (3.45–3.50; except in sonication) between SJ processed samples and the untreated ones (p > 0.05). HPP and PEF significantly promoted higher retention of total phenolic content (TPC) and radical scavenging activity (RSA) than thermal pasteurization, and significantly enhanced total anthocyanin content (TAC) compared with unprocessed SJ. HPP and PEF increased the TPC (4–5%), RSA (18–19%), and TAC (15–17%) in comparison with unprocessed SJ. Multivariate data analysis tools, i.e., principal component analysis (PCA) and hierarchical cluster analysis (HCA), were successfully applied for discrimination and classification of SJ samples based on the similarities or differences among physicochemical and phytochemical characteristics. PCA and HCA indicated that HPP- and PEF-treated samples had similar enhanced properties in terms of phytochemical content and were superior to sonicated, thermally pasteurized, and unprocessed samples. The multivariate data analysis methods were very useful to compare and classify SJ quality characteristics as a function of the processing technology. This study demonstrated that the application of the equivalent processing approach may reveal new opportunities to produce equivalent or even enhanced quality fruit juices.

Effect of pulsed electric field pretreatment on oil content of potato chips

The purpose of this work was to reduce the oil content of potato chips by the pulsed electric field (PEF) pretreatment. The effects of PEF on oil content, color parameters, texture, microstructure, and acrylamide content of potato chips were investigated. The following appropriate pulse parameters were selected for pretreatment: the number of pulses was 2000, the pulse width was 5 μs, the frequency was 20 Hz, and pulse direction was unidirectional pulse. The results showed that the electric field strength had a significant effect on the oil content and texture of potato chips. When pretreating the potato slices under the electric field strength of 10 kV/cm, the oil content of potato chips was reduced by 21.2%, and the hardness and crispness were significantly improved. The surface of the potato chips became smoother, and the porosity in the cross-section increased, which might be the reason for the reduced oil content of the potato chips. Finally, the potato chips prepared in current experiment had a low acrylamide content, approximately 10 ng/g (fresh weight). The above findings may provide useful information to guide the effective strategies for the practical application of PEF in reducing the oil content of fried foods.

Impact of pulsed electric fields on vacuum drying kinetics and physicochemical properties of carrot

The effect of pulsed electric fields (PEF) on the kinetics of vacuum drying (VD) and rehydration of carrot tissue was studied. The intensity of PEF treatment was E = 0.6 kV/cm and the total PEF treatment duration was tPEF = 0.1 s. The VD was performed at sub-atmospheric pressure p = 3.03 × 104 Pa for different temperatures Td = 25 °C and 90 °C. During VD, the kinetics of moisture removal and temperature evolution inside of untreated and PEF pretreated samples were studied. The color and structure of the samples were also investigated. PEF pretreatment enhanced VD kinetics at different studied temperatures. However, its effect on VD was more evident at lower drying temperatures. With the PEF pretreatment, the drying time was reduced by 55% and 33% at 25 °C and 90 °C respectively. After the drying and rehydration process, the change in color of PEF pretreated samples was less significant compared to untreated ones. After rehydration, the untreated and PEF pretreated samples were nearly restored to their initial form and size.