Effect Of High Electric Field Research Articles

Effects of different pretreatment on the drying characteristics and pectin properties of jujube by microwave coupled with pulsed vacuum drying

AbstractThe effects of ultrasound (US), ultrahigh pressure (UP), cold plasma (CP), and high pressure and pulsed electric fields (PEF) pretreatments were evaluated for drying characteristics, bioactive components, and pectin properties of jujube slices during microwave coupled with pulsed vacuum drying (MPVD). US, CP, and PEF reduced drying time by 18.75%, while UP reduced it by 6.25%. Samples treated with US and PEF showed improved color and rehydration (345.11%, 319.24%), with SEM revealing larger pores post‐pretreatment. PEF‐treated jujube had highest phenol (16.95 mg GAE/g DW) and water‐soluble pectin(WSP) (43.71 mg/g AIR), correlating positively with rehydration (r = 0.67). CP had highest flavonoid content (17.01 mg RE/g DW) and US showed highest antioxidant activity (DPPH 80.57%, ABTS 89.65%). Chelate‐soluble pectin (CSP) Sodium carbonate‐soluble pectin (NSP) was positively correlated with hardness (r = 0.71, 0.69). These findings suggest pretreatments improve drying efficiency, nutrient retention, and pectin functionality in jujube products. Practical ApplicationsDrying for jujube (Ziziphus jujuba Mill.) is the most common method of processing and ensure the sale. Three kinds of non‐thermal processing pretreatment method (ultrasound, ultrahigh pressure, and cold plasma) combined with novel drying method, microwave coupled pulsed vacuum drying (MPVD) was studied in the application on the dehydration of jujube slice in this paper. The drying characteristics and pectin properties of winter jujube were analyzed and treated by MPVD compared with freeze drying and hot air drying, for both technological research and processing practice. The drying kinetics, bioactive compounds, antioxidant capacity, sensory attributes, and pectin properties were also used as descriptors in order to promising dehydration method for obtaining high value‐added jujube products. Moreover, the relationship between the cell wall pectin and the phenols, hardness and crispness were analyzed, which give a new insight to study the changing scheme in the nutrients and the texture during the dehydration for fruits and vegetables.

Effects of high voltage pulsed electric field on structural properties and immune reactivity of arginine kinase in Fenneropenaeus chinensis

To evaluate the effect of high voltage pulsed electric field (PEF) treatment (10–20 kV/cm, 5–15 min) on the structural characteristics and sensitization of crude extracts of arginine kinase from Fenneropenaeus chinensis. By simulated in vitro gastric juice digestion (SGF), intestinal juice digestion (SIF) and enzyme-linked immunosorbent assay (ELISA), AK sensitization was reduced by 42.5% when treated for 10 min at an electric field intensity of 15 kV/cm. After PEF treatment, the α-helix content decreased, and the α-helix content gradually changed to β-sheet and β-turn. Compared to the untreated group, the surface hydrophobicity increased and the sulfhydryl content decreased. SEM and AFM analyses showed that the treated sample surface formed a dense porous structure and increased roughness. The protein content, dielectric properties, and amino acid content of sample also changed significantly with the changes in the treatment conditions. Non-thermal PEF has potential applications in the development of hypoallergenic foods.

Analysis of Operational Characteristics of AlGaN/GaN MIS-HEMT with Different Slant-Recessed-Gate Structures

Purpose of WorkRecessed-gate metal-insulator-semiconductor high electron mobility transistors (MIS-HEMTs) have emerged as a promising technology for normally-off operation because of their ability to withstand high gate voltage sweeps while maintaining low levels of leakage current [1, 2]. Despite their excellent performance, the etch to leave nanometer-thin layers of AlGaN has proven to be a significant challenge due to difficulties in precisely controlling the etching process. Achieving a positive threshold voltage (Vth) while maintaining the high electron mobility characteristic of the two-dimensional electron gas (2DEG) requires atom-level etch control. Additionally, conventional dry etching techniques can potentially cause damage, presenting a second challenge [3]. However, atomic layer etching (ALE) offers a promising solution with its potential for low damage, uniformity, and high-resolution depth control [4]. In this work, we not only focus on the ALE process to leave nanometer-thin layers of AlGaN/GaN as recessed-gate structures but also analyze the breakdown voltage characteristics of the slant-recessed gate structure.ApproachNormally-off AlGaN/GaN MIS-HEMT with a recessed gate structure was fabricated on a 6-inch commercial Si substrate by MOCVD. The process involved mesa isolation by ICP-RIE, followed by the formation of the ohmic contact (Ti/Al/Ni/Au) at 825 °C annealing for source and drain metals, and the AlGaN/GaN recessed gate structure using ALE technology by O2/BCl3 multiple cycles of oxidation and etching [5]. After the recessed-gate process, the native oxide and carbon residue were removed by a wet cleaning process and O2 plasma treatment, and then the atom layer deposition (ALD) of about 12 nm thickness Al2O3 high-dielectric layer was also deposited. The backend process included gate field plate, SiNx passivation, and contact opening. Finally, the Ni/Au metal stack was deposited as pad electrodes, as shown in Fig. 1. The specific characteristics of the fabricated recessed MIS-HEMT were Lg of 3 μm, Lgs of 5 μm, Lgd of 10 μm, and Wg of 100 μm.Results and SignificanceIn Figure 2(a) and (b), TEM profiles of the recessed gate structure were presented. Following the ALE process for the recessed gate structure, the remaining thickness of AlGaN was approximately 5.1 nm and 5.6 nm for Slant A and Slant B, respectively. Although the thickness of AlGaN remaining was similar in both cases, the slant angle of the recessed gate structure differed, significantly. Specifically, Slant A had a 65-degree recessed gate structure, while Slant B had a 45-degree recessed gate structure. In order to analyze of operational characteristics of AlGaN/GaN MIS-HEMT with different slant-recessed gate structures (Slant A and Slant B), the three-terminal OFF-state breakdown voltage (BV) was measured, as shown in Fig. 3. Recessed gate MIS-HEMT feature design of Lg/Lgd/Lgd/Wg of 3/5/10/100 μm, and VG of -10 V was used as this BV measured condition. The Slant B structure demonstrated higher breakdown voltage (BV) performance compared to the Slant A structure. Specifically, the Slant B structure exhibited a BV of 470 V at 1 μA/mm and 750 V at 1 mA/mm, while the Slant A structure had a BV of only 70 V at 1 μA/mm and 140 V at 1 mA/mm. The reason for the superior BV performance of the Slant B structure (45-degree recessed gate structure) was attributed to the gradient of the AlGaN profile, which facilitates the thin film deposition process of materials such as Al2O3 and gate metal (Ni/Au). Additionally, the Slant B structure helps to reduce the high electric field effect between the gate and drain, further contributing to its improved BV performance.[1] Y. S. Lin, Y. W. Lain, and S. S. H. Hsu, "AlGaN/GaN HEMTs With Low Leakage Current and High On/Off Current Ratio," IEEE Electron Device Letters, vol. 31, no. 2, pp. 102-104, 2010.[2] Z. Tang et al., "600-V Normally Off SiNx/AlGaN/GaN MIS-HEMT With Large Gate Swing and Low Current Collapse," IEEE Electron Device Letters, vol. 34, no. 11, pp. 1373-1375, 2013.[3] T. H. Hung, P. S. Park, S. Krishnamoorthy, D. N. Nath, and S. Rajan, "Interface Charge Engineering for Enhancement-Mode GaN MISHEMTs," IEEE Electron Device Letters, vol. 35, no. 3, pp. 312-314, 2014.[4] T. Y. Yang et al., "A Normally-Off GaN MIS-HEMT Fabricated Using Atomic Layer Etching to Improve Device Performance Uniformity for High Power Applications," IEEE Electron Device Letters, vol. 43, no. 10, pp. 1629-1632, 2022.[5] I.-H. Hwang, H.-Y. Cha, and K.-S. Seo, "Low-Damage and Self-Limiting (Al)GaN Etching Process through Atomic Layer Etching Using O2 and BCl3 Plasma," Coatings, vol. 11, no. 3, p. 268, 2021. Figure 1

Investigation of dynamic ron stability and hot electrons reliability in normally-off AlGaN/GaN power HEMTs

The current collapse and hot electron effect of 100 V normally-off GaN power HEMTs are investigated. The 100 V GaN-on-Si power HEMTs are fabricated on an industrial 200 mm Si CMOS compatible technology platform. The double pulse test (DPT) and the dynamic high temperature operating life (DHTOL) test are implemented to verify the dynamic on-resistance (dynamic Ron) stability. Wafer level hot electron reliability test is performed to investigate the effect of high electric field and high current on GaN power HEMT. It is proved that the dynamic Ron stability of 100 V GaN power HEMT is qualified (Ron/Rini, static < 1.2) when the drain-source off-state voltage (Vdsoff) is less than 80 V. It is shown that the dynamic Ron degradation of GaN device is recoverable by means of annealing. Hot electrons reliability is dominated by the high electric field at drain edge and the high current which is source injected electrons flowing to the drain. It is demonstrated that the Vth drift and Ron degradation are extraordinary serious under semi on-state stress condition with Vdsoff = 60 V.

A Thorough Evaluation of GaN HEMT Degradation under Realistic Power Amplifier Operation

In this paper, we experimentally investigate the effects of degradation observed on 0.15-µm GaN HEMT devices when operating under realistic power amplifier conditions. The latter will be applied to the devices under test (DUT) by exploiting a low-frequency load-pull characterization technique that provides information consistent with RF operation, with the advantage of revealing electrical quantities not directly detectable at high frequency. Quantities such as the resistive gate current, play a fundamental role in the analysis of technology reliability. The experiments will be carried out on DUTs of the same periphery considering two different power amplifier operations: a saturated class-AB condition, that emphasizes the degradation effects produced by high temperatures due to power dissipation, and a class-E condition, that enhances the effects of high electric fields. The experiments will be carried out at 30 °C and 100 °C, and the results will be compared to evaluate how a specific RF condition can impact on the device degradation. Such a kind of comparison, to the authors’ knowledge, has never been carried out and represents the main novelty of the present study.

InGaAs-based Gunn light emitting diode

We report an n-type In0.53Ga0.47As based Gunn light emitting diode operated at around 1.6 μm. The device structure comprises of an n-type In0.53Ga0.47As epilayer with a thickness of 5 μm grown by Metal Organic Vapour Phase Epitaxy (MOVPE) on a semi-insulating InP substrate and fabricated in a planar architecture with a stepped structure at anode side to suppress the destructive effect of high built-in electric field in propagating Gunn domain. Gunn diode is operated under pulsed voltage with a pulse width of 60 ns and pulse duration of 4.5 ns to keep the duty cycle as low as 0.0013%. The Gunn oscillations with an 1 ns period are observed at around 4.1 kV/cm, which corresponds to the electric field threshold of Negative Differential Resistance (NDR). The light emission at around 1.6 μm also starts at the threshold electric field of the NDR region (E = 4.2 kV/cm) of the current-voltage curve, and the emission intensity increases drastically with increasing applied electric field. The observed light emission at NDR threshold electric field where Gunn oscillations appear on the voltage pulse is attributed to the impact ionisation process occurring in the current domains along the sample, which generates excess carriers to initiate the band-to-band recombination in In0.53Ga0.47As.

Influence of High Hydrostatic Pressure and Pulsed Electric Field Treatment on Moisture Absorption of Wheat Grains

AbstractThe effect of high pressure (0.1–600 MPa) and pulsed electric field (E = 3 and 6 kV cm−1) pretreatments on the moisture absorption properties of non‐hulled wheat grains were investigated. Microwave sensor was used as a non‐invasive technique for determination of the moisture content. The results demonstrated that high pressure soaking (&gt;100 MPa) of wheat grains significantly increased the water uptake. High pressure soaking (600 MPa) decreased the water uptake due to the starch gelatinization and as a result appearance of structural changes. Compared to control samples, PEF‐pretreated samples showed a sharp increase of water absorption at the initial process with a further reduction of equilibrium water content. Peleg's water absorption model was adapted to the measured data of non‐hulled wheat grains. Results showed a good prediction of Peleg's equation in all experiments, which gave the possibility for estimation of initial water absorption rate and equilibrium moisture content.

Magnetic and Electric Field Dependent Charge Transfer in Perovskite/Graphene Field Effect Transistors

AbstractStable all‐inorganic CsPbX3 perovskite nanocrystals (PNCs) with high optical yield can be used in combination with graphene as photon sensors with high responsivity (up to 106 A W−1) in the VIS‐UV range. The performance of these perovskite/graphene field effect transistors (FET) is mediated by charge transfer processes at the perovskite – graphene interface. Here, the effects of high electric (up to 3000 kV cm−1) and magnetic (up to 60 T) fields applied perpendicular to the graphene plane on the charge transfer are reported. The authors demonstrate electric‐ and magnetic‐field dependent charge transfer and a slow (&gt;100 s) charge dynamics. Magneto‐transport experiments in constant (≈0.005 T s−1) and pulsed (≈1000 T s−1) magnetic fields reveal pronounced hysteresis effects in the transfer characteristics of the FET. A magnetic time is used to explain and model differences in device behavior under fast (pulsed) and slowly (continuous) changing magnetic fields. The understanding of the dynamics of the charge transfer in perovskite/graphene heterostructures developed here is relevant for exploitation of these hybrid systems in electronics and optoelectronics, including ultrasensitive photon detectors and FETs for metrology.

Research on CH4-CO2 reforming over Ni-Fe catalyst enhanced by electric field

CH4-CO2 reforming is an important way to prepare syngas, but it is often difficult to achieve both high conversion rate and low energy consumption at the same time. High-voltage electric fields can provide high-density energy, and it helps to improve the catalytic effect as well as effectively reduce the reaction temperature. Based on the Ni-Fe catalytic supported on active carbon(AC), a high-voltage electric field was added to the reforming system in this paper. The effects of temperature, electric field strength, and catalytic performance of the catalyst were investigated, then the promotion effect of high voltage electric field on the reforming reaction was revealed. The results show that the Ni-Fe/AC catalyst has better catalytic performance than the single-metal component catalyst, and the comparatively best catalytic effect can be achieved with 10% component loading. After adding a 9 mA electric field at 400 °C, the conversion of CH4 increased from almost 0–19.6%, which was 9 times higher than that of 1 mA, and the conversion of CO2 also increased to 29.3%. This indicated that the enhancement of electric field strength could effectively promote the reforming reaction. Finally, according to the catalyst characterization analysis, it is speculated that the electric field can stimulate the AC support to generate a large amount of active substance, which facilitates the entire catalytic process.

Effect of High Hydrostatic Pressure and Pulsed Electric Fields Processes on Microbial Safety and Quality of Black/Red Raspberry Juice.

Black and red raspberries are fruits with a high phenolic and vitamin C content but are highly susceptible to deterioration. The effect of high hydrostatic pressure (HHP 400–600 MPa/CUT-10 min) and pulsed electric fields (PEF, frequency 100–500 Hz, pulse number 100, electric field strength from 11.3 to 23.3 kV/cm, and specific energy from 19.7 to 168.4 kJ/L) processes on black/red raspberry juice was studied. The effect on the inactivation of microorganisms and pectin methylesterase (PME) activity, physicochemical parameters (pH, acidity, total soluble solids (°Brix), and water activity (aw)), vitamin C and phenolic compounds content were also determined. Results reveal that all HHP-treatments produced the highest (p < 0.05) log-reduction of molds (log 1.85 to 3.72), and yeast (log 3.19), in comparison with PEF-treatments. Increments in pH, acidity, and TSS values attributed to compounds’ decompartmentalization were found. PME activity was partially inactivated by HHP-treatment at 600 MPa/10 min (22% of inactivation) and PEF-treatment at 200 Hz/168.4 kJ/L (19% of inactivation). Increment in vitamin C and TPC was also observed. The highest increment in TPC (79% of increment) and vitamin C (77% of increment) was observed with PEF at 200 Hz/168.4 kJ/L. The putative effect of HHP and PEF on microbial safety, enzyme inactivation, and phytochemical retention is also discussed in detail. In conclusion, HHP and PEF improve phytochemical compounds’ content, microbial safety, and quality of black/red raspberry juice.

An ultrasensitive bacteria biosensor using “multilayer cake” silver microelectrode based on local high electric field effect

A signal response mechanism of local high electric field effects was designed to detect bacteria using a chemically modified “multilayer cake” micro-nanostructured pillar electrode. Since the silver electrode has a strong specific electrochemical signal response to chloride ions, we choose silver as the electrode material. The microelectrode was prepared by a one-step localized electrochemical deposition method without the use of mold. Then the electrode was successively functionalized with chitosan, catechol, and aptamer. Many nano- and micro-scale protrusion tips on the electrode surface generated a local high electric field and drove the leakage of intracellular chloride ions when bacteria were captured by APT; thus, a reduced signal of the silver electrode related to chloride ions was recorded. A pseudocapacitor structure composed of chitosan, catechol, Ru3+, and Fc was constructed on an electrode surface to further amplify the signal. The electrochemical sensor based on this electrode showed excellent performance for template bacteria Staphylococcus aureus detection in terms of the detection limit (1 CFU mL−1), linear response range (1–105 CFU mL−1), and specificity. This work provides another way to design an electrochemical biosensor using the nanoeffect of the electrode rather than the conventional current response based on the electrical properties of the bacterial surface.

The Root Cause Behind a Peculiar Dual-Mode ON-State Breakdown in High Voltage LDMOS

This work investigates the often-observed current discontinuity much before avalanche breakdown (dual-mode ON-state breakdown) in the output characteristics of a laterally diffused metal–oxide–semiconductor (LDMOS) device. The physical origin of the dual-mode ON-state breakdown, often reasoned to be due to parasitic n-p-n, is shown to be independent of parasitic n-p-n. A laterally diffused tunnel FET (LDTFET) with a drift region profile same as LDMOS was experimented to rule out the effect of parasitic n-p-n. LDTFET device, which intrinsically cannot have parasitic n-p-n, also shows similar output characteristics with dual-mode ON-state breakdown. This proved that the parasitic bipolar turn-on is not the root cause behind the observed behavior. On the contrary, it was found to be dependent on the onset of space charge modulation (SCM) in the drift region, resulting in localized high electric field and quasi-saturation effects at low drain voltages. The effect of mobility degradation due to the high electric field in the drift region post-SCM is also presented, emphasizing that the observed behavior results from the high field mobility degradation of majority charge carriers.

Effects of high voltage electric field on storage life and antioxidant capacity of whole pomegranate fruit

The objective of this study was to investigate the effects of high voltage electric field (HVEF) on the antioxidant system in stored pomegranate fruit. The experiments were conducted at cold storage for two months under three selected electric field levels (0, 1.5 and 3 kV/cm). Results showed that non-enzymatic antioxidant contents including phenols and ascorbic acid were better preserved by 1.5 kV/cm treatment than control after 60 days of storage. While the activities of superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) in pomegranate fruit were significantly enhanced with 1.5 kV/cm treatment compared to control, Guaiacol peroxidase (G-POX) levels in the control group increased steadily and were highest at the end of the storage. Although the results obtained from 3 kV/cm treatment were acceptable till the end of the first month, due to oxidative damage of reactive oxygen species (ROS) produced in response to HVEF stress, their results come close to the control group at the end of the second month. These data suggest that the optimum electric field intensity for enhancing antioxidant contents in stored pomegranate fruits was 1.5 kV/cm.

Analysis of the post-stress recovery of reverse leakage current in GaN HEMTs

The recovery of high reverse gate leakage current in AlGaN/GaN HEMTs has been analyzed in this study. To demonstrate the recovery after a thermal stress for large time periods (8–12 h), two mechanisms: phonon assisted tunnelling (PAT) and trap assisted tunnelling (TAT) have been utilized. Charge-based analytical models from literature have been used to match experimental leakage currents in reverse bias conditions. The degradation in the devices has been activated through thermal stress and the effect of high electric field induced inverse piezo electric effect has been eliminated. PAT component shows dominance in higher temperature regime (T > 500 K) and the slow recovery at 300 K with characteristic τ values around 5–13 h has been attributed to the TAT component through a deep trap level within the AlGaN barrier.

Retention of polyphenols and vitamin C in cranberrybush purée (Viburnum opulus) by means of non-thermal treatments

The effects of high pressure processing (HPP; 200–600 MPa for 5 or 15 min) and pulsed electric field (PEF; 3 kV/cm, 5–15 kJ/kg) treatment on physicochemical properties (conductivity, pH and total soluble solids content), bioactive compounds (vitamin C, total phenolic (TPC), total flavonoid (TFC), total anthocyanin (TAC) and chlorogenic acid contents), antioxidant capacities (DPPH and CUPRAC assays) and polyphenol oxidase (PPO) activity of cranberrybush purée were evaluated immediately after processing. The results were compared to an untreated purée. According to the results, conductivity increased significantly after PEF (15 kJ/kg) treatment. PEF and HPP treatments resulted in a better retention of bioactive compounds (increase in TPC in the range of ~4–11% and ~10–14% and TFC in the range of ~1–5% and ~6–8% after HPP and PEF, respectively) and antioxidant activity (as measured with CUPRAC method) compared to untreated sample. HPP reduced residual enzyme activity of PPO comparatively better than PEF.

Effect of high hydrostatic pressure (HPP) and pulsed electric field (PEF) technologies on reduction of aflatoxins in fruit juices

The high demand of fresh-like products to meet the fruits and vegetables serving encouraged the implementation of non-thermal food processing techniques, such as high pressure processing (HPP) and pulsed electric fields (PEF), with low impact on nutritional components. The aim of the present work is to evaluate the application of HPP and PEF techniques as useful decontamination tool for aflatoxins (AFs) reduction in grape juice. Spiked grape juice samples with AFs treated by PEF or HPP were extracted using dispersive liquid-liquid microextraction (DLLME) and determined by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS-IT). Reduction percentages of 14–29% have been obtained with both HPP and PEF treatments even higher reductions were obtained for AFB2 and AFG1 under PEF treatment, reaching reduction of 72 and 84% respectively. Results obtained in grape juice samples differed slightly from those obtained in water controls highlighting the matrix effect. Both HPP and PEF techniques showed measurable impact on AFs levels. Furthermore, an AFB2 degradation product obtained after PEF has been identified by quadrupole time of flight mass spectrometry detector (qTOF-MS) and its toxicological endpoints predicted by Pro Tox-II web server.

Advantages of ohmic cooking in the kilohertz-range - part I: Impact of conductivity and frequency on the heating uniformity of potatoes

The heating uniformity of potato cubes and whole potato tubers was investigated during cooking by ohmic heating (OH) in the low (12 kHz) and high (300 kHz) kHz range. Potatoes were heated in aqueous NaCl solutions with various conductivities (1–5 mS/cm). Conductivities and cell disintegration index of the tissue were determined in dependency of the temperature and the frequency at different points in the tubers. Heating uniformity was characterized by analyzing the temperature profiles with up to four thermocouples and by thermal imaging. Heating behavior of peeled and unpeeled tubers were compared to evaluate the impact of the skin on the OH treatment. For the higher frequency applied, increased electrical conductivities in the potato tissue were observed. At 300 kHz a better heating uniformity, with lower temperature differences within the potato samples compared to OH at 12 kHz was observed. The results provide a better understanding of the effect of high frequency electric fields on the heating uniformity and the conductivity of intact potato tissue. Industrial relevanceOhmic heating (OH) is an alternative heating technology with the potential to reduce processing times and energy consumption. It can overcome limitations in the heat transfer particularly given for large-volume solid foods and provide a uniform heating. However, limited attention has been given to the effects of the product and process parameters on the heating uniformity during OH treatments of solid foods. The present paper highlights the importance of the electrical conductivity and the frequency of the applied electric field on the heating uniformity. The obtained results contribute to the understanding of the interaction of the electric field and the food matrix, which is the basis for the implementation of tailored and targeted processing concepts in the industry.

Enhanced electrocaloric effect of relaxor potassium sodium niobate lead-free ceramic via multilayer structure

Herein, 0.9(K0.49Na0.49Li0.02)(Nb0.8Ta0.2)O3–0.1CaZrO3 (KNLNT–0.1CZ) relaxor system in multilayer ceramic capacitor (MLCC) are designed to attain elevated electrocaloric effect (ECE). Based on direct measurement, a large ∆T of 2.45 K is achieved in KNLNT–0.1CZ MLCC, which is nearly 10 times higher than that of ceramic counterpart. The temperature span (Tspan) on a benchmark of ∆T above 1.5 K come up to 65 °C. Such excellent ECE benefits by synergistic effect of relaxor phase transition and high electric field. This study shed light a strategy on designing new ECE materials with large ∆T and wide Tspan for solid-state cooling.

Structural and functional changes of the protein β-lactoglobulin under thermal and electrical processing conditions

In the present study we have tried to explore the effect of static external electric field of strength 3.0 V/nm on the conformational changes adopted by the protein β-lactoglobulin. We have chosen different temperatures viz. 300 K, 400 K and 450 K to evaluate the temperature dependent effect of electric field. We have observed that combined effect of high temperature and static external electric field show significant changes on the structural conformation of the protein which in turn may affect the functional properties of the protein. Calculations of root mean square deviations reveal that both helical and β-sheet regions of the protein are noticeably affected at high temperature. We have used solvent accessible surface area (SASA) and dipole moment values to explain that there is changes in hydrophobicity of the protein surface due to presence of external electric field. The study reveals that electric field in combination with high temperature can be used to alter the conformation of the protein and the effect of external electric field is more pronounced at high temperature than that of low temperature. The study provides a better understanding of the conformational changes adopted by the protein under the stress of external electric field and high temperature and provide guidance to choose optimum conditions for processing without loss of nutritional properties.

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.