Application Of Moderate Electric Fields Research Articles

Effect of moderate electric field voltage on the quality and heat transfer characteristics of potato strips during deep-frying process

The application of moderate electric field (MEF) on frying can influence the quality of fried products; however, the associated mechanism is unknown. This study investigated the effects of MEF voltage on the quality and surface heat transfer of potato strips fried with an MEF. With increasing MEF voltage, the moisture content, hardness, starch gelatinization rate, and shrinkage of the potato strips significantly increased (p < 0.05), while their oil content and brightness decreased (p < 0.05). The decrease in their oil content and brightness indicated improved crust formation, which reduced oil absorption. The potato strips fried under higher voltages exhibited lower oil contents and better microstructure than those fried under lower voltages. A possible mechanism comprised MEF increasing the heat transfer coefficient (h) between oil and potato strips, thereby accelerating crust formation; moreover, h values increased with MEF voltage. The results indicate the potential application of MEF in food frying.

Electric field tuning of the optical absorbance of topological insulator thin films

In view of electro-optic modulators and switches operating in the terahertz frequency range, we study the absorbance of a topological insulator (TI) thin film subjected to a static electric field. Adopting the Hamiltonian for the three-dimensional ${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$ class of TIs including terms to second order in the electron wave vector and to first order in the electric field, we present an effective model for a TI thin film. We demonstrate the distinct influences of in-plane and out-of-plane external electric fields, the in-plane electric field-induced dichroism, and the electric field and chemical potential tuning of the absorbance edge. Under the influence of an out-of-plane electric field, a TI film with a thickness of about 2 nm exhibits a considerable absorbance at the absorbance edge. Of prime practical importance, the absorbance edge can be shifted about $0.3\phantom{\rule{0.28em}{0ex}}\mathrm{eV}$ with the application of moderate electric fields about $0.4\phantom{\rule{0.28em}{0ex}}\mathrm{V}{\mathrm{nm}}^{\ensuremath{-}1}$ or with chemical potential variations about $0.3\phantom{\rule{0.28em}{0ex}}\mathrm{eV}$.

Effect of moderate electric field on the quality, microstructure and oil absorption behavior of potato strips during deep-fat frying

Effect of moderate electric field (MEF) on oil distribution and microstructure of fried potato strips was analyzed in this study. MEF with 400 V/m of electric fields strength and 40 KHZ of frequency significantly decreased the matrix oil content from 26.56% to 17.44% ( p = 0.001) and increased the moisture content of potato strips from 51.60% to 54.02% ( p = 0.015) compared with potato strips with intact cell structure, probably due to the electroporation. MEF significantly reduced the L* and b* values and significantly increased P -hardness from 129.76 g to 142.93 g ( p = 0.024). Low-field nuclear magnetic resonance (LF-NMR) found that more oil is distributed on the surface of samples, and scanning electron microscopy (SEM) showed the microstructure of samples was improved with MEF. A similar pattern was observed in potato strips without intact cell structure with MEF. All results suggest the application of MEF in frying industry is helpful. • MEF could significantly reduce the oil absorption of fried potato strips. • The texture and color of fried potato strips was significantly changed by MEF. • The microstructure of fried potato strips was significantly improved by MEF.

Improving the Extraction of Juice and Bioactive Compounds from Blueberry Fruits and Their By-products by Application of Moderate Electric Field (mef)

The influence of Moderate Electric Field (MEF) pre-treatment of blueberry fruits on the yield and quality of the expressed juice as well as the subsequent extraction yield of bioactive compounds from berry by-products (press cake left after MEF-assisted pressing), was investigated. Thermal MEF pre-treatments were performed under different combinations of electric field strengths (E=18-55 V.cm-1) and final heating temperature (Tf=25-80 °C) before applying a pressure of 1.32 bar for 5 min. For the sake of comparison, the effect of conventional heating (CH) (Tf=25-80 °C), was also investigated. Results showed that the Zp values increased with increasing the field strength and heating temperature. However, at the same final heating temperature, MEF treatment achieved higher Zp values (up to 0.66) than CH (up to 0.45). Coherently, thermal MEF pre-treatment (36.4 V.cm-1, 60 °C) significantly increased the juice yield, which also showed higher TPC, TAC, and AA, as compared with either untreated or CH-treated samples. Moreover, compared to the untreated and CH-treated samples, higher amounts of total phenolics, total anthocyanins and antioxidant activity were detected in the press cake extracts. These results were explained by the combined non-thermal and thermal effect of MEF on the cell disintegration and extraction efficiency.

Application of moderate electric fields and CO2-laser microperforations for the acceleration of the salting process of Atlantic salmon (Salmo salar)

The main limitation of salting is its extended processing time, mainly caused by the slow diffusion of salt into the muscle tissue. The diffusion process can be accelerated by different technologies such as moderate electric fields (MEF) and CO2-laser microperforations.The main objective of this research was to evaluate the implementation of a combined MEF-CO2-laser-microperforation treatment on the acceleration of the salting process in Atlantic salmon (Salmo salar) and its influence on the effective diffusion coefficient (Deff).Salmon fillets were cut in cylinders. Microperforations at 50 and 100% depth into salmon tissue were produced axially with a 100 W CO2 laser. For MEF treatment an electric field strength of 1 V/cm was used. Salt concentrations along time were analyzed through Fick’s second law and anomalous diffusion models, considering a finite cylindrical geometry.As a result, treatment with micropores-MEF achieved a salt concentration of 3.5% after 4 h, while the control required 12 h to reach the same salt concentration. When both technologies were simultaneously applied, both Deff and final equilibrium salt concentration were increased, thus resulting in a significant reduction in salting time. The mathematical analysis showed good fit through the anomalous, presenting a sub-diffusive (α < 1) behavior for all treatments.

Increase of mass transfer rates during osmotic dehydration of apples by application of moderate electric field

Abstract Osmotic dehydration (OD) is a drying process that consists in placing the food in contact with concentrated solutions of soluble solids to reduce its water activity. The use of moderate electric field (MEF) may promote increase of the mass transfer rates due to the non-thermal effects of electroporation and permeabilization of the cells. In this context, the objective of this study was to investigate the mass transfer process kinetics during apples OD assisted by MEF, evaluating the non-thermal effects of this emerging technology. The experiments were conducted with sucrose solutions (40, 50 and 60%, m/m) at 40 °C. Samples were submitted to electrical field strength (0, 5.5 and 11.0 Vcm−1), according to an experimental design. Results indicated that the application of MEF favoured water loss and solid gain. The effective mass diffusivities of water and solids increased as voltage applied increases. Moreover, MEF negatively influenced color and reducing capacity of the samples.

Electric Field Processing: Novel Perspectives on Allergenicity of Milk Proteins.

Milk proteins are being widely used in formulated foods as a result of their excellent technological, functional, and biological properties. However, the most representative proteins from casein and whey fractions are also recognized as major allergens and responsible for the prevalence of cow's milk protein allergy in childhood. Electroheating technologies based on thermal processing of food as a result of application of moderate electric fields, also known by ohmic heating (OH) or Joule effect, are establishing a solid foothold in the food industry. Currently, the influence of OH on allergenic aspects of milk proteins is under debate but still undisclosed. The occurrence of electrical effects on the protein structure and its function has already been reported; thus, the impact of OH over allergenicity should not be overlooked. On the basis of these recent findings, it is then relevant to speculate about the impact of this emergent technology on the potential allergenicity of milk proteins.

Effect of moderate electric fields in the properties of starch and chitosan films reinforced with microcrystalline cellulose

Microcrystalline cellulose (MCC) can provide improved properties when the aim is the development of biodegradable packaging materials. In this work the physicochemical properties of polysaccharide-based films (chitosan and starch) with the incorporation of MCC and the application of moderate electric field (MEF) and ultrasonic bath (UB) as treatments, were evaluated. For each treatment, the thickness, moisture content, solubility, water vapor permeability, contact angle, mechanical properties, along with its color and opacity were determined. The surface morphologies of the films were assessed by scanning electron microscopy (SEM). X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA) were also performed. It was observed that the addition of different concentrations of MCC as well as the application of MEF are responsible for changes in the properties of the films, being this effect dependent on the polysaccharide used. Chitosan-based films were slightly yellow, transparent and presented a more homogeneous structure. The use of MEF was efficient in decreasing the permeability to water vapor in chitosan based films without MCC, as well as in production of films with a more hydrophobic surface. The addition of MCC promoted more opaque, rigid, less flexible and less hydrophobic films. Starch-based films were whitish, with a more heterogeneous structure and the application of MEF generated more hydrophilic films with lower tensile strength and Young’s modulus. The films with MCC were more opaque, less flexible and less hydrophilic than the films without MCC. The composites presented good thermal properties, which increases their applicability as packaging materials. Therefore, the incorporation of MCC into polysaccharide-based films as well as the application of MEF can be an approach to change the properties of films.

Effects of ohmic heating on extraction of food-grade phytochemicals from colored potato

The influence of ohmic heating (OH) through the application of moderate electric fields on phytochemical compounds recovery from colored potato (Solanum tuberosum L. var. Vitelotte) was studied. A Box–Behnken design was used to simultaneously assess the effects of operational parameters such as electric field strength, temperature and process time on the yields of anthocyanins and total phenolic recovery on pretreatment of potato samples. From the analysis of the model, electric field, temperature and time were shown to have independent and interactive effects on the values of extraction yields. Aqueous extraction of phytochemical compounds after pretreatments can be described by using a two-step model involving simultaneous washing and diffusion of the solutes from the samples. Results shows that electrical fields of low energy levels and thermal effects can be combined and optimized into a single step treatment on extraction of anthocyanins and phenolic compounds from vegetable tissues providing high recovery yields with a reduced treatment time, less energy consumption and with no utilization of organic solvents (green extraction).

Carotenoid and lipid extraction from Heterochlorella luteoviridis using moderate electric field and ethanol

This study evaluated the effect of moderate electric field (MEF) and ethanol concentration on carotenoid and lipid extraction from the microalgae Heterochlorella luteoviridis. The extraction was performed using 0–180V and 25mL/100mL of ethanol/water solution during 10min of pretreatment, followed by a diffusive step using 25–75mL/100mL of ethanol/water solution during 50min. Carotenoid and lipid content analyses were performed on the supernatant after each extraction process. Results showed that MEF and ethanol concentration affected carotenoid extraction, while lipid extraction was only affected by ethanol concentration. The application of MEF combined with ethanol as solvent (180V, 75mL/100mL of ethanol solution) yielded up to 73% of carotenoid extraction, proving to be an attractive alternative method to extract these compounds from the microalgae Heterochlorella luteoviridis biomass. The highest lipid extraction yield (83%) was achieved when 75mL/100mL of ethanol solution was used.

Flame nanotube synthesis in moderate electric fields: From alignment and growth rate effects to structural variations and branching phenomena

The flame synthesis of carbon nanotubes (CNTs) coupled with application of moderate electric fields is studied experimentally as a means to control CNTs growth rates and morphology. The nanotubes are grown on a conductive metal-based catalytic probe positioned at the fuel side of the opposed flow oxy-flame. The probe was connected to an external voltage source to generate radial electric fields on its surface. At low applied voltages (from 0.3 to 2 V), the effect of the electric field on alignment and growth rate enhancement revealed the generation of vertically aligned carbon nanotube (VACNT) arrays with uniform distribution of CNT diameters. Further increases of the applied voltage resulted in structural modifications of the generated nanotubes. In particular, helically coiled CNTs were observed at applied voltages of ∼3 V. At higher voltages the arrays contained multi-walled CNTs with fascinating modified morphologies such as Y, T, and multi-junction patterns. Analysis of the samples generated at applied voltage of 5 V showed the presence of particle sprouting and early CNT junctions in the form of small bumps extruding from the outer surface of the CNTs. Analysis of material samples synthesized at 12 and 25 V showed the presence of fully branched CNT structures.

Dielectric breakdown and current switching effect in the incommensurate layered compound(LaS)1.196VS2

A current switching effect of several orders of magnitude was observed in the incommensurate misfit layered compound ${(\mathrm{La}\mathrm{S})}_{1.196}\mathrm{V}{\mathrm{S}}_{2}$. This effect involves correlated vanadium ${t}_{2g}$ states in a hexagonal $[\mathrm{V}{\mathrm{S}}_{2}]$ layer. Application of moderate electric fields $(\ensuremath{\sim}50\phantom{\rule{0.3em}{0ex}}\mathrm{V}∕\mathrm{cm})$ induces a dielectric breakdown and restores a metallic state. The large pretransitional nonlinearities are consistent with a Poole-Frenkel mechanism which highlights the role of Coulomb interactions. This behavior and the strong modulation of the vanadium atom positions, revealed by single crystal x-ray structure determination, are in favor of a heterogeneous charge distribution. With respect to recent theoretical works, we suggest that the current switching effect observed in ${(\mathrm{La}\mathrm{S})}_{1.196}\mathrm{V}{\mathrm{S}}_{2}$ is related to the breakdown of a remaining Mott insulator state.

Electric field induced shifts in exciton luminescence in ZnSe/(Zn,Mn)Se superlattices

Application of moderate electric fields to ZnSe/(Zn,Mn)Se quantum wells yields distinct spectral shifts of the recombining exciton luminescence. This shows that confinement effects in this heterostructure are sufficient to increase the exciton ionization threshold. At high applied fields and low temperatures, injection of hot electrons from the n+GaAs/ZnSe heterojunction at our substrate/buffer layer excites yellow luminescence from internal transitions of the Mn ion in (Zn,Mn)Se layers.

Computerized apparatus for thermally stimulated current (TSC) measurements

A computer-controlled apparatus for thermally stimulated polarization and depolarization current (TSPC/TSDC) measurements over the temperature range −196 to 250 °C is described. The instrument is designed to combine state-of-the-art current sensitivity with computerized data acquisition and reduction. The apparatus is capable of detecting small (as low as 0.1 ppm) dipole concentrations (charge carriers) in solid dielectrics with the application of moderate electric fields (2–5 kV/cm).

Electron mobilities in gaseous, critical, and liquid xenon: Density, electric field, and temperature effects: Quasilocalization

The mobility μ of electrons in xenon varies with the density n : μαnx. For thermal electrons in the gas, x=−1.0 when n&amp;lt;4×1020 molecule/cm3, independent of temperature. This corresponds to pressures ≲20 atm at 300 K and is characteristic of simple scattering by a polarization field. At higher gas densities x becomes more negative, then passes through a minimum, and μ has a positive temperature coefficient at constant n. At these densities thermal electrons form quasilocalized states in, or suffer enhanced scattering by, microscopic regions of relatively high density. The localization effect maximizes in the critical fluid, at n=5×1021 molecule/cm3 and T=290 K, and appears to be negligible again at n?6.8×1021. In the liquid phase x?+9 up to n=1.2×1022 molecule/cm3, then changes to x?−8 at higher densities. The positive value of x is due to the formation of a conduction band, and the negative value to scattering by the repulsive cores of the closely spaced atoms. In the gas and the low density liquid (n&amp;lt;1.2×1022), μ at low electric field strengths E is independent of E; at higher E, μ increases with E then passes through a maximum and decreases. The maximum in μ reflects the Ramsauer–Townsend minimum in the scattering cross section σε of the atoms as a function of electron energy ε. Quasilocalization is inhibited by the application of moderate electric fields, and this enhances the observed dependence of μ on E at 4×1020&amp;lt;n&amp;lt;7×1021. The electron drift velocity vd tends to become independent of E at high E in the gas, liquid, and solid phases. The ’’plateau’’ drift velocity was 1.0 km/s at n?2×1021, 1.2 at 5×1021, 3.0 in the normal liquid at 1.4×1022, and 5.5 km/s in the solid at 1.6×1022 molecule/cm3 (Miller, Howe, and Spear). The velocity plateau in all phases is attributed to the steep rise in σε on the high energy side of the Ramsauer–Townsend minimum. The maxima in μ vs E curves for heavy ions are discussed.