In this work a Pulsed Electric Field (PEF) prototype is developed. A 10 stage Marx generator for HV pulses was designed and implemented. A batch chamber suitable for small quantities was built and a ...3000V, 5μs pulse was measured. The system was tested with dried grape marc and works as expected.
The purpose of this article is to review matters dealing with application of electrical pulsed energy (pulsed electric field, pulsed ohmic heating and high voltage electrical discharges) for ...enhancing the solid–liquid extraction in the food industry. The quality of products (e.g., purity, color, texture, flavor and nutritients) extracted from solid foods (sugar beets, apples, grapes, etc.) and quality of proteins and polysaccharides extracted from biosuspensions (aqueous suspensions of yeast, e.coli cells, etc.) may be degraded by conventional mechanical, thermal or chemical pretreatment. The traditional treatments are restricted by temperature elevation and require high energy consumptions; moreover, chemical methods are based on application of unsafe organic solvents, enzymes and detergents. Physical treatments assisted by electrical pulsed energy are shown to be very remarkable for enhancing the solvent and pressure extraction and dehydration processes and of high interest for the food industry. This article provides an overview of the pulsed energy extraction technologies showing promise for commercial food processing.
Abstract The renin–angiotensin system (RAS) plays a key pathogenic role in heart failure. The adverse effects of angiotensin II (Ang II), a major player of the RAS, contributes to the development of ...heart failure. Heart failure is accompanied by significant perturbations in cardiac energy metabolism that can both decrease cardiac energy supply and decrease cardiac efficiency. Recent evidence suggests that Ang II might be involved in these perturbations in cardiac energy metabolism. Furthermore, new components of the RAS, such as angiotensin converting enzyme 2 and Ang1-7, have been reported to exert beneficial effects on cardiac energy metabolism. As a result, a further understanding of the relationship between the RAS and cardiac energy metabolism has the potential to improve the control of heart failure, and may lead to the development of new therapies to treat heart failure. This review summarizes what effects the RAS has on cardiac energy metabolism, highlighting how Ang II can induce cardiac insulin resistance and mitochondrial damage, and what role reactive oxygen species and sirtuins have on these processes.
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.
In this study, a cascaded cell disintegration process, based on pulsed electric fields (PEF - 20 kV/cm, 100 kJ/kg
) and high-pressure homogenization (HPH - 150 MPa, 5 passes) was designed for the ...efficient and selective release of intracellular compounds (water-soluble proteins, carbohydrates, and lipids) from
suspensions during extraction in water (25 °C, 1 h) and ethyl acetate (25 °C, 3 h). Recovery yields of target compounds from cascaded treatments (PEF + HPH) were compared with those observed when applying PEF and HPH treatments individually. Particle size distribution and scanning electron microscopy analyses showed that PEF treatment alone did not induce any measurable effect on cell shape/structure, whereas HPH caused complete cell fragmentation and debris formation, with an undifferentiated release of intracellular matter. Spectra measurements demonstrated that, in comparison with HPH alone, cascaded treatments increased the selectivity of extraction and improved the yields of carbohydrates and lipids, while higher yields of water-soluble proteins were measured for HPH alone. This work, therefore, demonstrates the feasibility of sequentially applying PEF and HPH treatments in the biorefinery of microalgae, projecting a beneficial impact in terms of process economics due to the potential reduction of the energy requirements for separation/purification stages.
Two brain signal acquisition (BSA) front-ends incorporating two CMOS ultralow power, low-noise amplifier arrays and serializers operating in MOSFET weak inversion region are presented. To boost the ...amplifier's gain for a given current budget, cross-coupled-pair active load topology is used in the first stages of these two amplifiers. These two BSA front-ends are fabricated in 130 and 180 nm CMOS processes, occupying 5.45 mm 2 and 0.352 mm 2 of die areas, respectively (excluding pad rings). The CMOS 130-nm amplifier array is comprised of 64 elements, where each amplifier element consumes 0.216 μW from 0.4 V supply, has input-referred noise voltage (IRNoise) of 2.19 μV RMS corresponding to a power efficiency factor (PEF) of 11.7, and occupies 0.044 mm 2 of die area. The CMOS 180 nm amplifier array employs 4 elements, where each element consumes 0.69 μW from 0.6 V supply with IRNoise of 2.3 μV RMS (corresponding to a PEF of 31.3) and 0.051 mm 2 of die area. Noninvasive electroencephalographic and invasive electrocorticographic signals were recorded real time directly on able-bodied human subjects, showing feasibility of using these analog front-ends for future fully implantable BSA and brain- computer interface systems.
Meat contains several amino acids related to taste, which have a significant impact on the overall acceptability of consumers. A number of volatile compounds have been studied in relation to meat ...flavor, but amino acids have not been fully explored in relation to the taste of raw or cooked meat. It would be interesting to find any changes in physicochemical characteristics, especially the level of taste-active compounds and flavor content during non-thermal processing such as pulsed electric fields (PEF), for commercial reasons. The effect of PEF at low intensity (LPEF; 1 kV/cm) and comparatively high intensity (HPEF; 3 kV/cm) with different pulse numbers (25, 50, and 100) was investigated on the physicochemical characteristics of chicken breast, including the free amino acid content (related to umami, sweet, bitter, or fresh pleasant taste). PEF is regarded as a "nonthermal" technology; however, HPEF induces moderate temperature rises as it increases with the treatment intensity (i.e., electric field strength and pulse number). The pH, shear force, and cook loss (%) of the LPEF and untreated samples were not affected by the treatments, but the shear force of the LPEF and untreated samples was lower than that of HPEF groups that showed PEF-induced slight structural modifications resulting in a more porous cell. In the case of color parameters, the lightness of meat (
*) was significantly higher with treatment intensity, whereas both
* and
* were unaffected by the PEF treatments. Moreover, PEF treatment significantly (
< 0.05) affected umami-related free amino acids (FAAs; glutamic acid and aspartic acid) and leucine and valine, which are precursors of flavor compounds. However, PEF decreases the level of bitter taste contributing FAAs such as lysine and tyrosine, which may prevent the formation of fermented flavors. In conclusion, both PEF treatments (LPEF and HPEF) did not adversely impact the physicochemical quality of chicken breast.
Microalgae cell membrane permeabilization has been studied, for Chlorella sp., in a continuous 6-L prototype for different field strengths in order to minimize the specific energy supplied and the ...treatment time. Regarding lower electrical field strength values, the optimal results were achieved at 10 kV/cm, 200 Hz, and 5-μs per pulse, corresponding to an energy delivered of 9 kJ/kg of culture, with 97% of cells affected after 300 ms of treatment time. Regarding energy delivered per kilogram of Biomass, the best result was 2.7 MJ/kg of biomass with 95% of cells affected after 300 ms of treatment time and was achieved at 15 kV/cm, 200 Hz, and 5-μs per pulse. Pulsed electric field effect was quantified by flow cytometry using propidium iodide as a viability stain. The influence of conductivity and cell concentration was also analyzed. The final goal was to evaluate the use of this technology in terms of increasing bioaccessibility of bioactive compounds present in microalgae for food and feed purposes. These results, obtained only for chlorophyll a and b, did not show any beneficial effect of this technology against nontreated biomass.
The application of pulsed electric fields (PEF) can be used to inactivate bacterial endospores if combined with thermal energy. A model was developed in the second part of the study aiming to ...separate thermal and PEF induced spore inactivation. Therefore thermal inactivation data of B. subtilis spores was obtained by glass capillary method and combined with temperature time profile of the PEF process. The PEF process can be separated in pre heating, PEF treatment and cooling phase. The temperature development in pre heating and cooling phase was simulated based on a theoretical numerical approach, the temperatures in the PEF unit were measured by fiber optic sensors. To evaluate the effect of pH on the inactivation the PEF treatment was performed in Ringer solution (4 mS/cm) at pH 4 and 7. The results of the developed model indicate a thermal and a PEF induced inactivation, where the temperature induced inactivation is slightly higher in acid Ringer solution. The impact of specific energy inputs up to 195 kJ/kg was evaluated, showing an increasing total inactivation of the spores, but also shift towards PEF induced inactivation. Applying an energy input of 195 kJ/kg an inactivation of 4.4 log was obtained in Ringer solution at pH 7, which could be separated in 1.15 log of thermal and 3.25 log of PEF related inactivation. The F-value, typically used to describe thermal spore inactivation processes was calculated for the combined PEF process based on the temperature time profile. The highest F-value determined for the maximum applied energy was 2.43 s, which confirms the low product heat load.
•Spore inactivation by the developed process can be divided in thermal and PEF induced inactivation.•Bacillus subtilis spores are more heat sensitive in acid environments.•No germination of B. subtilis is induced by PEF or pre heating temperature of 80 °C.•Small F-values indicate that PEF process is a temperature assisted process.
Summary
The effect of culture temperature on the conformation of membrane lipid of Salmonella Typhimurium as well as their pulsed electric field (PEF) resistance was investigated. Results revealed ...that S. Typhimurium cells cultured at relatively lower temperature (10 and 25 °C) were more easily inactivated by PEF treatment than those cultured at relatively higher temperature (37 and 45 °C). Using a Weibull model, it was determined that the PEF treatment time to inactivate 90% S. Typhimurium cells cultured at 45 °C was almost fourfold compared to those cultured at 10 °C. Results of micro‐Raman spectroscopy indicated that as the culture temperature increased, the order degree of C–C and lateral packing order of membrane lipid chain also increased, resulting in a drop in the membrane fluidity. These results are important in considering the use of heat and PEF to inactivate microbe contaminants in food.
Effect of culture temperature on the PEF treatment resistance of S. Typhimurium ATCC 14028.
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