Intensity Pulsed Electric Fields Research Articles

Low‐Temperature Pasteurization of Liquid Whole Egg using Intense Pulsed Electric Fields

SUMMARYThis paper describes the pasteurization of liquid whole egg (LWE) using intense pulsed electric fields (PEF) combined with mild heat. Four kinds of liquids as solvents including carboxymethyl cellulose (CMC) solution, CMC solution with adding lipoproteins extracted from LWE (CMC+), LWE, and centrifuged LWE for reducing lipoproteins (LWE−) were compared for the effectiveness of the PEF pasteurization. The liquids including Enterobacter aerogenes (107 /mL) were subjected to a number of PEF with an amplitude of 30 kV/cm or 50 kV/cm. Pre‐ and post‐PEF thermal treatments with a temperature below 55 °C were used to enhance the killing effect. Our experiments show that the bacteria logarithmic reduction ratio of the pasteurization using 30 kV/cm PEF for CMC, CMC+, LWE, and LWE− were 6.6, 2.4, 1.4, and 1.6, respectively, whereas the reduction ratios were all more than 6 when the increased field of 50 kV/cm. Only bacteria in CMC solution were effectively killed compared to other liquids, which include lipoproteins, more or less. Numerical analysis of the electric field indicates the presence of lipoproteins in the vicinity of bacteria lessens the bacterial membrane potential, which results in weakening the killing effect.

Red cherries (Prunus avium var. Stella) processed by pulsed electric field – Physical, chemical and microbiological analyses

This study examined, for the first time, the effect of mild or moderate intensity pulsed electric field (PEF) processing on cherries, in particular changes in physicochemical properties, release of anthocyanins and polyphenols, and the potential growth of lactic acid bacteria. Cherry samples were treated at a constant pulse frequency of 100Hz and a constant pulse width of 20μs with different electric field strengths between 0.3 and 2.5kV/cm. Titratable acidity and total soluble solids values of most PEF samples stored for 24h significantly decreased compared to other samples. Stored samples also had increased cyanidin glucoside content. However, concentration of rutin, 4-hydroxybenzoic acid and isorhamnetin rutinoside significantly decreased in samples stored for 24h. In conclusion, sweet cherries were only influenced by storage after PEF processing. PEF processing did not affect the growth of probiotic bacteria.

Effects of high intensity pulsed electric fields on yield and chemical composition of rose essential oil

Abstract: High intensity pulsed electric fields (PEF) combined with distillation was used to extract essential oil from rose. Three main parameters, namely electric field intensity, pulse number and distillation times, which can affect the efficiency of extraction, were optimized. Then, in order to demonstrate the feasibility of the method, oil obtained under optimal conditions was compared quantitatively and qualitatively with that obtained by conventional hydro distillation. Considering the extraction yield, the optimal parameters combination was obtained with electric field intensity of 20 kV/cm, pulse number of 8 and distillation time of 2 h. PEF treatment had no significant influence on the quality of essential oils. However, there was an increase in methyl eugenol percentage, which is a disadvantage from qualitative point of view. Keywords: rose, hydro distillation, pulsed electric fields, PEF, extraction, essential oil DOI: 10.3965/j.ijabe.20171003.3153 Citation: Zhou Y J, Xue C M, Zhang S S, Yao G M, Zhang L, Wang S J. Effects of high intensity pulsed electric fields on yield and chemical composition of rose essential oil. Int J Agric & Biol Eng, 2017; 10(3): 295–301.

Mineral and fatty acid profile of high intensity pulsed electric fields or thermally treated fruit juice-milk beverages stored under refrigeration

The influence of High Intensity Pulsed Electric Fields (HIPEF) or Thermal Treatment (TT) on minerals and fatty acids of fruit juice-whole (FJ-WM) or skimmed milk (FJ-SM) beverages was assessed after processing and during chilled storage. Mineral profile of both beverages was characterized by Ca, Zn, Fe, Mg, Cu, and Mn; being Ca the macroelement detected at the highest concentration (3.06–3.17mg/100 mL). Neither HIPEF nor TT significantly affected mineral concentration of the beverages, except Fe, which augmented after HIPEF (300%) or TT (43%). During storage (56 days), mineral content in both bevearges remained highly stable, regardless of the treatment applied. 11 fatty acids were identified in untreated and processed FJ-WM beverages. Palmitic acid was detected at highest concentration (21.83–24.37 mg/100 g of fat). Immediately after HIPEF or TT, most fatty acids remained with no significant changes, only linoleic acid increased (20%) in HIPEF treated beverage. Fatty acid content of HIPEF treated FJ-WM beverages was kept constant along storage; only palmitic, linoleic and linolenic acids showed lower concentrations (12–20%) at day 56. Conversely, the concentration of most fatty acids in the heated beverage underwent a significant reduction (7–19%) with time, except palmitic acid, which remained constant. HIPEF can be considered as a potential alternative to conventional pasteurization to obtain stable mixed beverages with significant concentrations of health-related compounds.

Miniaturized two-stack Blumlein pulser with a variable repetition-rate for non-thermal irreversible-electroporation experiments.

Non-thermal irreversible electroporation (NTIRE) to avoid thermal damage to cells during intense DC ns pulsed electric fields (nsPEFs) is a recent modality for medical applications. This mechanism, related to bioelectrical dynamics of the cell, is linked to the effect of a DC electric field and a threshold effect with an electrically stimulated membrane for the charge distribution in the cell. To create the NTIRE condition, the pulse width of the nsPEF should be shorter than the charging time constant of the membrane related to the cell radius, membrane capacitance, cytoplasm resistivity, and medium resistivity. It is necessary to design and fabricate a very intense nanosecond DC electric field pulser that is capable of producing voltages up to the level of 100 kV/cm with an artificial pulse width (∼ns) with controllable repetition rates. Many devices to generate intense DC nsPEF using various pulse-forming line technologies have been introduced thus far. However, the previous Blumlein pulse-generating devices are clearly inefficient due to the energy loss between the input voltage and the output voltage. An improved two-stage stacked Blumlein pulse-forming line can overcome this limitation and decrease the energy loss from a DC power supply. A metal oxide silicon field-effect transistor switch with a fast rise and fall time would enable a high repetition rate (max. 100 kHz) and good endurance against very high voltages (DC ∼ 30 kV). The load is designed to match the sample for exposure to cell suspensions consisting of a 200 Ω resistor matched with a Blumlein circuit and two electrodes without the characteristic RC time effect of the circuit (capacitance =0.174 pF).

Enhancing the lycopene in vitro bioaccessibility of tomato juice synergistically applying thermal and non-thermal processing technologies.

The influence of moderate intensity pulsed electric field pre-processing on increasing the lycopene bioaccessibility of tomato fruit, and the combined effect of blanching, ultrasonic and high intensity pulsed electric field processing on further enhancement of the lycopene bioaccessibility after juicing were investigated. Maximum total lycopene bioaccessibility (9.6%) of the tomato fruit was achieved by a 4μs pre-processed treatment after 24h holding period and further processing results revealed that all treatments were effective to increase the total lycopene. Most of juice processing treatments decreased the release of lycopene from the tomato matrix during digestion. Only the treatment of blanching followed by high intensity pulsed electric field showed a significant release of trans-(4.01±0.48) and cis-(5.04±0.26μg/g) lycopene, achieving 15.6% total lycopene bioaccessibility. Thus, processing of pre-blanched juice using high intensity pulsed electric field, derived from pre-processed tomato was the best overall process to achieve the highest nutritive value.

Effects of High Intensity Pulsed Electric Fields or Thermal Treatments and Refrigerated Storage on Antioxidant Compounds of Fruit Juice-Milk Beverages. Part II: Carotenoids

Effects of high intensity pulsed electric fields (HIPEF) or thermal treatments over carotenoids of mixed beverages were evaluated after processing and during refrigerated storage. Nine carotenoids were identified in all samples, being β-carotene the major compound. Just after processing, concentration of most individual carotenoids diminished around 6–30% in fruit juice-skim milk (FJ-SM) and fruit juice-whole milk (FJ-WM) beverages; except, 9-cis-violaxanthin-neoxanthin, antheraxanthin and phytoene-phytofluene which increased in the thermally treated FJ-SM (5–19%) and 9-cis-violaxanthin-neoxanthin which also augmented in HIPEF processed FJ-SM (24%). Total carotenoid (TC) content decreased (6–13%) in both beverages, irrespectively of the treatment applied. Through the storage, individual carotenoid concentration varied widely in all beverages, depending on the carotenoid structure; however, TC tended to decrease. Nonetheless, changes observed HIPEF-treated beverages were less than those in the conventionally pasteurized ones. Hence, HIPEF is as effective treatment, or even more, than heat processing to preserve bioactive compounds in mixed beverages. Practical Applications Nowadays, modern population is claiming for products with high antioxidant properties and attractive flavor. In this sense, mixed beverages formulated with fruit juices and milk are attracting the attention of consumers due to their exotic taste and their elevated concentration of bioactive substances, such as carotenoids. However, these compounds are very susceptible to heat and are easily degraded during processing and storage. Hence, finding preservation technologies for mixed beverages capable to maintain their carotenoid concentration as high as possible after treatment and during shelf-life is one of the greatest challenges for the food industry. In this sense, the relevance of this study is to demonstrate that high intensity pulsed electric fields processing is a potential alternative to thermal pasteurization in order to obtain not only safe but nutritious fruit juice-mixed beverages with elevated concentration of carotenoids, especially those with pro-vitamin A activity, such as β-carotene.

Effect of guard cells electroporation on drying kinetics and aroma compounds of Genovese basil ( Ocimum basilicum L.) leaves

Abstract In this study the effect of the application of pulsed electric fields as pre-treatment before air drying of basil leaves at 50 °C was investigated. The parameters of the electric treatment were designed in such a way that they either (i) electroporated the tissue reversibly (tissue remains viable) and without electroporating the guard cells in the stomata complex (65 pulses of 600 V/cm, 120 μs pulse width, 500 μs between pulses), (ii) electroporated the tissue reversibly causing the guard cells to irreversibly open the stomata (65 pulses of 600 V/cm, 150 μs pulse width, 760 μs between pulses), or (iii) irreversibly electroporated the tissue leading to cell death (65 pulses of 1500 V/cm, 150 μs pulse width, 760 μs between pulses). Results demonstrate that dehydration of basil leaves at 50 °C can be aided by the application of pulsed electric fields (PEF). If the applied PEF conditions are such that stomata are irreversibly opened while the rest of the tissue remains viable, the drying process is faster and the product keeps a better colour, is richer in aroma compounds and has better rehydration capacity than the untreated control. Irreversible tissue damage provoked by high intensity PEF drastically decreased the drying time but the measured quality characteristics of the dried leaves were inferior compared to those of the dried product when the stomatal function of the fresh leaf was selectively targeted. Industrial relevance This paper addresses the ever-increasing global demand from consumers for high-quality foods, reporting a novel methodology which improves the quality of dried aromatic herbs using pulsed electric fields.

Antioxidant activity of thermal or non-thermally treated strawberry and mango juices by Saccharomyces cerevisiae growth based assays

The antioxidant activity of strawberry or mango juice [untreated or treated by high intensity pulsed electric fields (HIPEF) or heat] has been studied on a Saccharomyces cerevisiae yeast strain exposed to different oxidants (tert-butyl hydroperoxide, diamide and diethyl maleate). Cellular biomass production was higher in the juices compared to the synthetic medium, which contained all required amino acids, nitrogen bases and vitamins needed for growth, indicating that growth-limiting nutrient concentrations in the natural juices were higher. In addition, the inhibitory effect of tert-butyl hydroperoxide or diamide in yeast growth was lower in the juices compared to synthetic medium, supporting an antioxidant effect of both juices. In contrast, juices did not confer significant protection against diethyl maleate. HIPEF or thermal treatments did not negatively influence the antioxidant activity of the juices. In fact, HIPEF-treated strawberry juices presented enhanced antioxidant effect on yeast cell growth in the presence of tert-butyl hydroperoxide compared to fresh juice in terms of adaptation period and the final cellular biomass.

Application of Novel Processing Methods for Greater Retention of Functional Compounds in Fruit-Based Beverages

Eating habits of western populations are changing due to modern lifestyles. As a result, people are becoming more susceptible to chronic and degenerative diseases. This fact has motivated the food industry to develop functional products that could decrease the incidence of those disorders. It is well known that fruit juices, milk and soymilk possess high concentrations of antioxidant and bioactive substances. Hence, the development of these functional beverages is a potential way to take advantage of their nutritional properties and exotic flavors that could attract the interest of consumers. At the same time, application of the right preservation treatment is of high relevance in order to obtain safe products with convenient shelf life and high concentration of health-related compounds. This fact represents a great challenge that scientists and technologists are currently facing. Today, novel preservation processes such as high hydrostatic pressure (HHP), high intensity pulsed electric fields (HIPEF) and ultrasound (US), among others, are being evaluated as an alternative to heat pasteurization, obtaining promising results. Hence, this review gathers the most relevant information about the development of mixed beverages containing fruit juices and milk or soymilk. Furthermore, the advantages and drawbacks of the application of non-thermal treatments for functional beverages’ preservation with high content of bioactive compounds are also mentioned.

Semi‐Bionic Extraction of Effective Ingredient from Fishbone by High Intensity Pulsed Electric Fields

AbstractSemi‐bionic extraction method and high intensity pulsed electric fields (PEF) were combined to rapidly extract effective ingredients (calcium, chondroitin sulfate and collagen) from fishbone. In order to simplify the analytical process, comprehensive index formula was determined by principal component analysis. Based on the principle of bionics, the optimal fluid pHs in human stomach, small intestine and large intestine are 2.0, 7.5 and 8.3. The simulated pHs were 2.0, 7.5 and 8.3, respectively, and variation of PEF parameters and the comprehensive evaluation index were determined by single factor experiments. Too low or too high liquid‐material ratio and electric field strength were not conducive to the comprehensive evaluation index Y. The value of Y increased with the increase of pulse number. The maximum contents of calcium, chondroitin sulfate and collagen in the extract were obtained simultaneously by response surface methodology (RSM), that is, 19.8, 39.268 and 3.875 mg/mL, respectively The optimum condition is as the following: liquid‐material ratio 11, electric field strength 22.79 kV/cm and pulse number 9.Practical ApplicationsSBE and PEF technique were combined to analyze the effective ingredients in fishbone. The prepared fishbone hydrolysate can be processed into multi‐active and high‐added‐value compound products suitable for absorption and utilization by the digestive tract. This paper provides a new technique for comprehensive utilization of fishbone and fishbone waste, serves as a new clue for processing and extraction of natural products and provides a basis for promotion of SBE and PEF.

Application of the pulsed electric field to release bound phenolics in sorghum flour and apple pomace

Abstract The mild intensity pulsed electric field (PEF) was studied to release bound phenolics in sorghum flour (SF) and apple pomace (AP). In this study, SF and AP, naturally fermented at optimized conditions, were treated at different flour to water ratios (FWRs) of 10, 27.5, 45% (w/v) and 5, 8.75, 12.5% (w/v), respectively. In addition, three levels of PEF electric field intensity (EFI) as 1, 2 and 3 kV/cm were used to treat SF and AP for the treatment time of 500, 875 and 1250 μs. Both the treated samples were analyzed for total phenolic content (TPC), antioxidant activity (AA) and phenolic characterization. For SF, optimized conditions were determined as 45% (w/v) FWR, 2 kV/cm EFI and 875 μs treatment time, while these values were 12.5% (w/v) FWR, 2 kV/cm EFI and 500 μs for AP. At these conditions, TPC and AA of SF were 24.8% and 33.9%, respectively higher than the control SF, while for AP, these numbers were observed as 37.4% and 86%, respectively. The study suggests that PEF treated SF and AP may be very useful for the preparation of processed foods with the increased levels of phenolic antioxidants. Industrial relevance Sorghum, millets and fruit or vegetable by-products contain high amounts of flavonoids and phenolic acids among other bioactive compounds. Results explicate that the application of a PEF treatment following the fermentation could improve the phenolic antioxidants in the sorghum flour and apple pomace. Consequently, this technology could be used in the food industry to enhance the healthy properties of millets and other by-products prior to further processing like mild extrusion or baking. Also the use of the mild intensity pulsed electric field has the benefit of minimizing any damage to the other nutrients of any product.

High intensity pulsed electric field as an innovative technique for extraction of bioactive compounds—A review

ABSTRACTHow to extract bioactive compounds safely and efficiently is one of the problems for the food and pharmaceutical industry. In recent years, several novel extraction techniques have been proposed. To pursue a more efficient method for industrial production, high intensity pulsed electric field (HIPEF) extraction technique has been developed. HIPEF extraction technique, which is based on the conventional pulsed electric field (PEF), provided higher electric field intensity and a special continuous extraction system, and it has confirmed less extraction time, higher extraction yield, and mild processing temperature. So this innovative technique is promising for application of industrial production. This review was devoted to introducing the recent achievement of HIPEF extraction technique, including novel HIPEF continuous extraction system, principles and mechanisms; the critical process factors influencing its performance applications; and comparison of HIPEF extraction with other extraction techniques. In the end, the defects and future trends of HIPEF extraction were also discussed.

Inactivation of enterobacter aerogenes in carboxymethyl cellulose solution using intense pulsed electric fields (iPEF) combined with moderate thermal treatment

This paper describes low-temperature sterilization of Enterobacter aerogenes in carboxymethyl cellulose solution using intense pulsed electric fields (iPEF) combined with moderate thermal energy. The bacterial suspension was exposed to moderate temperatures of up to 55°C for 2 minutes after tens of 530 ns-long, 50 kV/cm pulses in a single-pass continuous flow system. Suspension temperatures at the entrance and exit of the iPEF exposure chamber were maintained at 40°C by means of an electrode cooling system. The iPEF combined with subsequent thermal energy of 55 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sup> C reduced bacterial population by 6.6 Log10 cycles or more, compared with a reduction of only 2.1 Log10 cycles by iPEF without heat treatment. Sterilization effects increased with increasing thermal treatment temperature and pulse number. Results obtained after culturing the iPEF-exposed bacteria in NaCl rich agar, which hinders the reorganization of the damaged membrane, implies that even bacteria surviving the iPEF exposure are damaged to some extent though may later recover. Bacteria were made vulnerable to subsequent thermal treatment by iPEF-induced membrane damage. This indicates that moderate thermal stress after iPEF exposure increases sterilization effects.

Chilling prior to low intensity pulsed electric field processing improved vitamin C stability of carrot purée (Daucus carotacv. Nantes)

Summary Effects of chilling (5 °C) prior to low intensity pulsed electric fields (PEF) (0.1–1.1 kV cm−1) on vitamin C and activity of peroxidase (POD) and ascorbic acid oxidase (AAO) in carrot puree were studied. The effect of PEF on carotenoids extractability was evaluated and compared to that of puree pre-conditioned at 20 °C (control). PEF enhanced carotenoids extractability for puree with and without pre-chilling, up to 25% and 66%, respectively. Vitamin C content decreased after PEF but combined pre-chilling and PEF maintained vitamin C stability and reduced AAO and POD activities. AAO and the heat-stable POD fraction were found to be more thermolabile (i.e. higher kref value) after PEF, particularly at 0.6 kV cm−1, which implies elimination of their enzymatic action towards oxidation of bioactive compounds. It was suggested that chilling prior to low intensity PEF modified enzyme properties and secured the stability of vitamin C and carotenoids.

Effect of pulsed electric field treatment on hot-boned muscles of different potential tenderness

In this study, the effect of pulsed electric field (PEF) treatment and ageing on the quality of beef M. longissimus lumborum (LL) and M. semimembranosus (SM) muscles was evaluated, including the tenderness, water loss and post-mortem proteolysis. Muscles were obtained from 12 steers (6 steers for each muscle), removed from the carcasses 4hour postmortem and were treated with pulsed electric field within 2h. Six different pulsed electric field intensities (voltages of 5 and 10kV×frequencies of 20, 50 and 90Hz) plus a control were applied to each muscle to determine the optimum treatment conditions. Beef LL was found to get tougher with increasing treatment frequency whereas beef SM muscle was found to have up to 21.6% reduction in the shear force with pulsed electric field treatment. Post-mortem proteolysis showed an increase in both troponin and desmin degradation in beef LL treated with low intensity PEF treatment (20Hz) compared to non-treated control samples.

Compact Electro-Permeabilization System for Controlled Treatment of Biological Cells and Cell Medium Conductivity Change Measurement

Abstract Subjection of biological cells to high intensity pulsed electric field results in the permeabilization of the cell membrane. Measurement of the electrical conductivity change allows an analysis of the dynamics of the process, determination of the permeabilization thresholds, and ion efflux influence. In this work a compact electro-permeabilization system for controlled treatment of biological cells is presented. The system is capable of delivering 5 μs - 5 ms repetitive square wave electric field pulses with amplitude up to 1 kV. Evaluation of the cell medium conductivity change is implemented in the setup, allowing indirect measurement of the ion concentration changes occurring due to the cell membrane permeabilization. The simulation model using SPICE and the experimental data of the proposed system are presented in this work. Experimental data with biological cells is also overviewed

Optimisation extraction of chondroitin sulfate from fish bone by high intensity pulsed electric fields

High intensity pulsed electric fields (PEF) was used to extract chondroitin sulphate (CS) from fish bone. Results show that PEF extraction speed is much faster, and the content of CS is much higher compared with traditional methods. Variation of PEF parameters and the content of CS were determined by single factor experiments. The processing conditions were optimised by quadratic general rotary unitised design experiments. The maximum yield of 6.92g/L was achieved under the following conditions: material–liquid ratio of 1:15g/mL, electric field intensity of 16.88kV/cm, pulse number of 9, and NaOH concentration of 3.24%. The purity of CS was analysed by agarose gel electrophoresis. CS purity was high, and the extract did not contain any other glycosaminoglycans. PEF can be widely used to extract CS with non-thermal performance, high speed, and low pollution.

Integrated Optical $E$-Field Sensor for Intense Nanosecond Electromagnetic Pulse Measurement

A lithium niobate (LiNbO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> )-based integrated optical E-field sensor utilizing Mach-Zehnder optical waveguide interferometer and bow-tie antenna has been designed and fabricated for the detection of nanosecond intense pulsed electric field. Experimental data demonstrate that the average rise time, fall time, and pulsewidth of the input/output electromagnetic pulse (EMP) are 1.31/1.28, 3.63/3.61, and 34.19/34.25 ns, respectively. Correspondingly, the relative errors are 2.3%, 0.6%, and 0.2%, respectively. In addition, the input/output of the sensor system shows a linear relationship as the correlation coefficient between measured and fitting is 0.9991. The minimum and maximum measured EMP fields are approximately equal to 3 and 50 kV/m, respectively.

Demonstration of a Novel Pulsed Electric Field Technique Generating Neither Conduction Currents Nor Joule Effects

This paper is devoted to a detailed presentation of all aspects involved in a demonstration of a novel pulsed electric field (PEF) technique that does not generate neither conduction currents nor Joule effects. Details are given of both the experimental arrangement and the electro-optic Kerr-effect-based diagnostic used in the measurement of the intense PEFs in water. The results show unequivocally that the novel technique is effective in significantly reducing the initial concentration of Escherichia coli bacteria. Finally, a brief comment on the way ahead is provided.