Ohmic Heating Research Articles

APPLICATION OF OHMIC HEATING IN THE FOOD INDUSTRY, IMPACT ON FOOD COMPONENTS AND "HURDLE APPROACH"

The application of thermal processes in the food industry causes a decrease in the quality of the final product, such as nutritional value and organoleptic characteristics. Many alternative methods offer uniform and rapid heating and provide the desired microbial lethality without reducing overall product quality. Ohmic heating is an emerging technique for food processing that has been used in recent decades as an alternative to conventional heating. It is a rapid heating method with big potential in the food industry. More particularly, ohmic heating of food is used for microbial inactivation, blanching, fermentation, gelatinization, peeling, evaporation, drying, extraction, pasteurization, and sterilization. This review summarizes the application of ohmic heating to different types of food products, the impact on food components, as well as the synergistic effect of ohmic heating with other non-thermal preservation techniques as well as the case of its combination with packed food items. The optimization of the ohmic heating approach reduces the duration of the process, achieves microbial and enzyme stability, increases the yield, and preserves the organoleptic and bioactive components in food commodities. Applying ohmic heating in combination with other non-thermal food preservation techniques such as UV-C radiation, pulsed electric field, high pressure, ultrasound, vacuum and the addition of preservatives contributes to reducing the intensity of the applied electric field, the temperature, and the treatment. In addition, it contributes to the extension of the shelf life as well as preserving the nutritional and organoleptic quality of food.

Entropy formation in second grade nanofluid flow across a curved surface with the impact of activation energy and chemical reaction

The heat and mass transfer through the second-grade nanofluid across a curved surface is investigated in the present article with the consequences of chemical reaction, activation energy and Ohmic heating. The Buongiorno model is employed to simulate the thermophoretic and Brownian diffusions effect. The flow phenomena for second-grade fluid (SGF) have been modelled in the form of system of partial differential equations (PDEs) which are converted into a system of ordinary differential equations (ODEs) by substituting the similarity variables. The model equations are converted into a system of ODEs by inserting a suitable variable. The set of dimensionless equations along with boundary conditions are evaluated computationally through the numerical differential equation solver (ND Solve) technique. The entropy optimization, energy curve, Nusselt number, mass transfer, Sherwood number, velocity and skin friction are computed and examined versus distinct physical parameters. The finding reveals that the concentration and velocity profile exhibits enhancement as the curvature parameter increases, whereas an opposite trend has been found in relation to the energy outline. Furthermore, the concentration profile raises as the activation energy increased, while diminishes with the augmentation of chemical reaction.

Enrichment of soybean oil with β-carotene and lycopene from Gac (Momordica cochinchinensis Spreng) powder using ohmic heating and ultrasound extraction

Enrichment of soybean oil with β-carotene and lycopene from Gac (Momordica cochinchinensis Spreng) powder using ohmic heating and ultrasound extraction

Characterization and Encapsulation Methods for Pomegranate Seed (P. Granatum) Oils, Review

The use of bioactive components in herbal products across different industries is growing.As a result, ecologically friendly techniques such simple mixing, pressure-assisted extraction, enzymatic extraction, ultrasound-assisted extraction, pulsed electric fields, high hydrostatic pressure, ohmic heating, and microwave-assisted extraction are being investigated. These methods enhance the equipment design, extraction efficiency and extraction method of bioactive constituents with organic solvents. Consequently, encapsulation techniques preserve oil quality and other pomegranate seed components. Encapsulation enables the safe delivery, preservation and regulation of the targeted release of bioactive constituents in food systems. This study provides information on encapsulation techniques that protect sensitive compounds and their benefits. Increasing problems related to food quality, safety and reliability cause undesirable effects on product quality. Capsulation and ecological methods are expected to achieve food safety and reliability goals in the future effectively.

Effect of Thermal Processing on Food Allergenicity: Mechanisms, Application, Influence Factor, and Future Perspective.

Thermally processed foods are essential in the human diet, and their induced allergic reactions are also very common, seriously affecting human health. This review covers the effects of thermal processing on food allergenicity, involving boiling, water/oil bath heating, roasting, autoclaving, steaming, frying, microwave heating, ohmic heating, infrared heating, and radio frequency heating. It was found that thermal processing decreased the protein electrophoretic band intensity (except for infrared heating and radio frequency heating) responsible for destruction of linear epitopes and changed the protein structure responsible for the masking of linear/conformational epitopes or the destruction of conformational epitopes, thus decreasing food allergenicity. The outcome was related to thermal processing (e.g., temperature, time) and food (e.g., types, pH) condition. Of note, as for conventional thermal processing, it is necessary to control the generation of the advanced glycation end products in roasting/baking and frying, and the increase of structural flexibility in boiling and water/oil bath heating, autoclaving, and steaming must be controlled; otherwise, it might increase food allergenicity. As for novel thermal processing, the temperature nonuniformity of microwave and radio frequency heating, low penetration of infrared heating, and unwanted metal ion production of ohmic heating must be considered; otherwise, it might be the nonuniformity and low effect of allergenicity reduction and safety problems.

Timelike Kasner singularities and Floquet states in 2+1d AdS/CFT

We consider a model of a holographic 2+1d CFT interacting with an oscillating background gauge field. It is solved by an AdS-Vaidya metric describing Ohmic heating of the boundary field theory. However, we also show that if timelike singularities of Kasner type are permitted then a time independent solution that may be interpreted as a Floquet state of the system can be constructed. In this state the system exhibits either Hall conductivity or kinetic induction, and we numerically evaluate the Kasner exponents for a range of boundary conditions. This model may contribute to the ongoing discussion on the validity and meaning of the Kasner metric in the AdS/CFT correspondence and its application in cosmology.

System Design, Modelling, Energy Analysis, and Industrial Applications of Ohmic Heating Technology

AbstractThe food and drink industry is gradually gaining sustainability pressure due to the high carbon emissions rate and limited availability of traditional energy supplies. Thus, it is essential to consider energy efficiency and decarbonisation of the ever-expanding food and drink industry. Ohmic heating technology is a highly energy-efficient and quick method of electrically heating food products. It uses the resistance of the food material to convert electrical energy into heat. However, the heating rate of ohmic heating depends on several process variables, such as electrical conductivity, voltage gradient, and voltage frequency. Therefore, it is important to study and understand the effects of these process variables to optimise the modelling and control of ohmic heating systems to obtain desirable output from food products. Hence, this study presents a review of the effects of process parameters on nutritional and organoleptic qualities, product yields, and energy efficiency of ohmic heating, along with its various industrial applications. The technology shows promising advancements in colour and nutritional quality, increasing energy efficiency, shorter processing times, and higher product yields compared to conventional heating processes.

Inactivation of Listeria monocytogenes in ready-to-consume liquid infant milk treated with Ohmic Heating

Ohmic heating is a promising alternative method to conventional heating for microbial inactivation. This study aimed to inactivate Listeria monocytogenes and assess some quality parameters in ready-to-consume liquid infant milk treated with different voltage gradients of ohmic heating. Different ohmic heating voltage gradients (5, 10, and 20V cm-1) were applied to the samples inoculated with Listeria monocytogenes (ATCC 13932) for 5 minutes. The application of 20 V cm-1 ohmic heating induced inactivation of Listeria monocytogenes at 4 minutes and resulted in approximately 5.34 log reduction; however, there was no significant reduction for the 5 and 10V cm-1 groups. Moreover, 20V cm-1 ohmic heating application did not cause any changes in pH, L*, and b* values. A significant decrease in a* value and an increase in hydroxymethylfurfural value was noted in this group. In conclusion, the effectiveness of ohmic heating in pathogen inactivation depends on the applied electric field intensity and the application time. As a result, the ohmic heating conditions must be carefully determined for the infant milk to inactivate pathogens and ensure public health protection. The results of this study contain significant and beneficial data that can be disposed of the listeriosis risk associated with the consumption of infant milk in infants.

Entropy generated nonlinear mixed convective beyond constant characteristics nanomaterial wedge flow

Background and objectiveNanomaterial flows at present have received much attention of the researchers. Such motivation stems for their utilization in pharmaceutical, industrial, petroleum, manufacturing and engineering applications including regenerative medicine, treatment of cancer, electronic device cooling, solar collector, mineral oil, antimicrobial agents, thermal storage system, transformer cooling and X-imaging etc. Higher thermal energy requirement in several electrical and mechanical systems is desired in recent time due to high advancement of science and technology. For important application here the stagnation point flow due to wedge with nonlinear convection is explored. For porous media, the Darcy-Forchheimer relation is considered. Characteristics of nanofluid is added by utilizing Buongiorno's model. Variable fluid characteristics are under consideration. Applied magnetic field is accounted. Energy expression comprises thermal radiation, Brownian motion, Ohmic heating, thermophoresis and heat generation. First order reaction and entropy rate are considered. MethodologyNonlinear differential expressions are changed into dimensionless ordinary systems through adequate transformations. The resultant nonlinear ordinary systems are solved through optimal homotopy analysis technique (OHAM). ResultsOutcomes for influential variables about temperature, velocity, concentration and entropy rate have been arranged. Here results show that for magnetic field the liquid flow and entropy rate have opposite scenarios. Thermal distribution and concentration have reverse effects for random motion variable while similar effect holds for thermophoresis parameter. Magnetic field and diffusion parameters contribute to augment entropy generation. Higher values of temperature dependent electrical conductivity variable lead to increase entropy rate. Thermal distribution for radiation and Eckert number is similar.

Comparing the impact of conventional and non-conventional processing technologies on water-soluble vitamins and color in strawberry nectar – a pilot scale study

A comprehensive comparison was conducted on the effect of conventional thermal processing (TT), high-pressure processing (HP), pulse electric field (PF), and ohmic heating (OH) on water-soluble vitamins and color retention in strawberry nectar. The ascorbic acid (AA) content increased by 15- and 9-fold after TT and OH treatment, respectively, due to rupturing of cells under heat stress and release of intracellular AA. Dehydroascorbic acid (DHA) content did not change considerably after TT and PF treatment but significantly decreased after HP and OH treatment. TT treatment offered the highest total vitamin C retention. The B vitamins remained largely unchanged after processing, with the highest loss of 34 % for riboflavin in OH-treated samples. All the technologies resulted in similar color retention after processing. The study concludes with a standardized comparison of mainstream preservation technologies using pilot-scale equipment. Such an approach significantly increases the applicability of the results presented in the study.

Magnetized dissipative Soret-Dufour effects on Walter’s-B fluid flow over a stretching sheet with nonuniform heat source/sink and thermal radiation under chemical reaction

The main motivation behind this numerical analysis is to disclose the salient magneto-thermo characteristic features of two-dimensional viscous incompressible magnetized Soret and Dufour effects on the boundary layer flow of Walter’s-B fluid over a stretching sheet under the influence of viscous dissipation. The novel physical effects such as nonuniform heat source/sink and magnetic Ohmic heating are included in the governing equations. Further, prescribed surface temperature condition is introduced in the boundary conditions to describe the thermal transport features. However, the deployed non-Newtonian Walter’s-B fluid rheology model finds its innumerable applications in numerous areas of science and engineering including electronic cooling, polymer processing, nuclear reactor cooling, extraction of polymer sheet, plastic sheet drawing, chemical engineering, metallurgy, injection molding and many more. Therefore, authors have motivated with these applications and advantageous of considered fluid model. Hence, an effort is made to describe the dynamic characteristic features of non-Newtonian Walter’s-B rheology model about a stretching sheet. However, present physical flow model produces highly nonlinear coupled two-dimensional partial differential equations and which are not acquiescent to available analytical methods. Owing to this, a robust MATLAB-based BVP4C technique is deployed to produce the appropriate numerical solutions through suitable similarity transformations. The graphical representations of velocity, temperature and concentration profiles along with skin-friction coefficient, Nusselt and Sherwood numbers are presented. Magnifying magnetic number decays the velocity profile and enhances the thermal and concentration fields. Rising viscoelastic parameter diminishes the thermal and concentration fields and magnifies the velocity field. Rising the radiation parameter diminish the thermal field. Magnifying Soret number raises the concentration field. Rising the space and temperature dependent heat source/sink coefficient amplifies the thermal diffusion field. Magnifying Dufour and Eckert numbers amplifies the thermal field. Finally, the guarantee and accuracy of the investigated problem is presented through a comparison with previous studies.

Ultralow degradation cold start of proton exchange membrane fuel cell with alternating hydrogen pump method

Cold start impedes widespread diffusion of fuel cell vehicles (FCVs) in regions with temperatures below zero. Alternating hydrogen pump (AHP) method, distinguished by its unlimited ohmic heating capability without generating water, has been shown to be a quick and efficient method of cold starts in both single cell and short stacks. In this paper, we continue to examine possible degradation with this novel method. For this purpose, we carefully designed three experiments with different levels of stress, aimed to separate the contribution to any degradation from major factors. It was found there was no significant difference among the three cases. AHP method incurred minimal degradation after 3600 times of equivalent −30 °C cold starts. This study concludes that AHP method is not only quick and efficient, but also highly durable, hence AHP is a promising alternative cold start strategy with great potential to facilitate the diffusion of FCVs.

Intelligent neuro-computational modelling for MHD nanofluid flow through a curved stretching sheet with entropy optimization: Koo–Kleinstreuer–Li approach

Abstract The present study explores the dynamics of a two-dimensional, incompressible nanofluid flow through a stretching curved sheet within a highly porous medium. The mathematical model is formulated by including external forces such as viscous dissipation, thermal radiation, Ohmic heating, chemical reactions, and activation energy by utilizing a curvilinear coordinate system. The viscosity and thermal conductivity of the nanofluids are examined using the Koo–Kleinstreuer–Li model. The choice of $Al_{2}O_{3}$ and $CuO$ nanoparticles in this model stems from their distinct thermal properties and widespread industrial applicability. By non-dimensionalizing the governing partial differential equations, the physical model is simplified into ordinary differential equations. BVP-5C solver in MATLAB is utilized to numerically solve the obtained coupled non-linear ordinary differential equation. Graphical results are presented to investigate the velocity, temperature, and concentration profiles with entropy generation optimization under the influence of several flow parameters. The artificial neural network backpropagated with Levenberg–Marquardt method (ANN-BLMM) used to study the model. The performance is validated using regression analysis, mean square error and error histogram plots. The outcome illustrates that the velocity and temperature profiles increase with increasing the Forchhiemer parameter. Also, the velocity profile increases with increasing curvature parameter, while, reverse effect is observed for temperature profile. This research augments our comprehension of nanofluid dynamics over curved surfaces, which has implications for engineering applications. The insights gained have the potential to significantly contribute to the advancement of energy-efficient and environmentally sustainable cooling systems in industrial processes.

Improving the accessibility of phytonutrients in Chlorella vulgaris through ohmic heating

The application of electric fields, coupled with its attendant ohmic heating effect, might represent a novel approach to process microalgae biomass. When exposed to temperatures above 70 °C, depending on the duration of exposure, significant effects were observed in the release of intracellular compounds from Chlorella vulgaris cells. The most significant effects were observed when they were treated at 90 °C with a constant electric field of 225 V.cm−1, resulting in a protein concentration of 108.52 ± 9.18 mg.L−1. This technology offers the advantage of achieving an extremely rapid heating rate, minimizing the risk of compound degradation due to thermal effects. Additionally, some effects on the cellular structure of microalgae were identified, which can enhance the extraction of biomolecules and metabolites, thereby promoting their digestibility as a food product.

Finite difference analysis for entropy optimized nanomaterial Darcy-Forchheimer flow with homogeneous and heterogeneous reactions

Hybrid nanoliquids are not underestimated for their involvement in microelectronics, transportation, coolant processes, ships, biological processes and power generation. Hence motivation for current work is to examine homogeneous-heterogeneous reactions in entropy optimized flow by curved sheet stretched with nonlinear velocity. Trihybrid nanoliquid is synthesized through 2 % of ferrous oxides(Fe3O4), 2 % of silver(Ag) and 2 % of copper(Cu). Kerosene oil is employed as the base fluid. These specific kinds of nanoparticles are taken into consideration because of their numerous applications in heat dissipation, air filters, dynamic sealing, biosensors and catalysts process. Kerosene oil may have applications in many different domains such as energy storage, cleaning agent, portable heaters, fuel additive and industrial lubricants. Darcy-Forchheimer model is employed. Analysis in presence of radiation, dissipation, Ohmic heating, entropy generation and heat generation/absorption are organized. Unlike the previous considerations, the thermal expression here consists of impacts through Darcy-Forchheimer relation. Adequate transformations are implemented. Computations have been arranged by applying finite difference technique (FDM) using MATLAB. Quantities for physical interest are addressed. The presented analysis may have relevance for solar systems, chemical reacting processes, cooling towers and polymer data processes. The conclusions are also organized for important key findings. It is noticed that trihybrid nanomaterial has more entropy rate when compared with hybrid and classical nanoliquids when volume fraction is chosen as 2 % for trihybrid fluid. It is proposed that the ability to transfer heat is enhanced when nanoparticles are added to conventional fluids. Decay in concentration is noticed for both homogeneous and heterogeneous parameters. Reduction for Bejan number is noticed through homogeneous diffusion factor. Comparison with previous study is also presented and found great consensus between them.

Numerical investigation of magnetized bioconvection and heat transfer in a cross-ternary hybrid nanofluid over a stretching cylinder

PurposeIn this study, we investigate the effects of an extended ternary hybrid Tiwari and Das nanofluid model on ethylene glycol flow, with a focus on heat transfer. Using the Cross non-Newtonian fluid model, we explore the heat transfer characteristics of this unique fluid in various applications such as pharmaceutical solvents, vaccine preservatives, and medical imaging techniques.Design/methodology/approachOur investigation reveals that the flow of this ternary hybrid nanofluid follows a laminar Cross model flow pattern, influenced by heat radiation and occurring around a stretched cylinder in a porous medium. We apply a non-similarity transformation to the nonlinear partial differential equations, converting them into non-dimensional PDEs. These equations are subsequently solved as ordinary differential equations (ODEs) using MATLAB’s bvp4c tools. In addition, the magnetic number in this study spans from 0 to 5, volume fraction of nanoparticles varies from 5% to 10%, and Prandtl number for EG as 204. This approach allows us to examine the impact of temperature on heat transfer and distribution within the fluid.FindingsGraphical depictions illustrate the effects of parameters such as the Weissenberg number, porous parameter, Schmidt number, thermal conductivity parameter, Soret number, magnetic parameter, Eckert number, Lewis number, and Peclet number on velocity, temperature, concentration, and microorganism profiles. Our results highlight the significant influence of thermal radiation and ohmic heating on heat transmission, particularly in relation to magnetic and Darcy parameters. A higher Lewis number corresponds to faster heat diffusion compared to mass diffusion, while increases in the Soret number are associated with higher concentration profiles. Additionally, rapid temperature dissipation inhibits microbial development, reducing the microbial profile.Originality/valueThe numerical analysis of skin friction coefficients and Nusselt numbers in tabular form further validates our approach. Overall, our findings demonstrate the effectiveness of our numerical technique in providing a comprehensive understanding of flow and heat transfer processes in ternary hybrid nanofluids, offering valuable insights for various practical applications.

Entropy optimization in ternary hybrid nanofluid flow over a convectively heated bidirectional stretching sheet with Lorentz forces and viscous dissipation: A Cattaneo–Christov heat flux model

Bidirectional stretching sheet models can represent surfaces in heat exchangers where fluids flow under continuous deformation. Ternary hybrid nanofluids could be employed in these systems to increase heat transfer rates between fluids in heat exchangers and improve the efficiency of energy conversion processes. In this work, we explore the novel application of a ternary hybrid nanofluid (water with titanium dioxide, cobalt ferrite, and magnesium oxide nanoparticles) for enhanced heat transfer in heat exchangers modeled by a bidirectional stretching sheet. This approach offers a potential advancement over traditional nanofluids (with one or two nanoparticles). Furthermore, we present a comprehensive analysis that incorporates ohmic heating, Cattaneo–Christov heat flux, thermal radiation, viscous dissipation, and irreversibility. The governing equations are transformed into a system of nonlinear ordinary differential equations using appropriate similarity transformations and then solved using the bvp4c solver, a MATLAB built-in function. This study's findings reveal that the Eckert number and radiation parameter increase fluid temperature, while the thermal relaxation parameter leads to a reduction in the temperature of the fluid. It is detected that an increase in magnetic field parameter and volume fraction of [Formula: see text] results in a decline of the skin friction factors in both directions. It is revealed that there is a reduction in the Nusselt number with the rise in Eckert number ([Formula: see text]), and the same number declines at a rate of 0.8252 when [Formula: see text]. It is noticed that the skin friction coefficient declines at a rate of 0.62179204 (in case of x-direction) and 0.621791816 (in case of y-direction), respectively, when the values of magnetic field parameter lie between 0 and 3.5. Furthermore, it is noticed that an upsurge in thermal relaxation parameter results in a fall in the temperature of the fluid.

Ohmic Heating in Food Processing: An Overview of Plant-Based Protein Modification

This review provides an analysis of ohmic heating in food processing and its effect on plant proteins. This study explores the effect of this technology on protein denaturation and aggregation, affecting both non-covalent and covalent bonds. These structural and chemical changes have significant implications for the techno-functional properties of proteins, contributing to their use in food processing. This article emphasizes the need to adjust processing conditions to maximize the benefits of ohmic heating, distinguishing it from other traditional thermal techniques due to its direct and controllable impact. By highlighting these contributions, this review serves as a resource for researchers and professionals interested in innovation and efficiency in food processing through the use of emerging technologies.

Effect of ohmic heating on the extraction of biocompounds from aqueous and ethanolic suspensions of Pavlova gyrans

Electric field technology has been highlighted as a promising strategy in the permeabilization of cell membranes and the corresponding bioactive release. In this work, aqueous and ethanolic suspensions of Pavlova gyrans were subjected to moderate electric fields (MEF) to promote rapid heating due to Ohmic Heating (OH) effect. Two approaches were tested: i) OH assisted extraction in a temperature range between 25 ºC and 85 ºC, and ii) OH pretreatment at 25 ºC and 55 ºC followed by solvent extraction. OH treatment at 55 ºC (performed in less than 10 s) in aqueous suspensions promoted a marked increase in the release of organic matter (2.1-fold), chlorophyll a (41.1-fold) and total carotenoids (56.6-fold) when compared to the freeze-thaw cycles (FTC ≈ 3 hours). OH-pretreated biomass subjected to a two-step passive extraction improved the release of proteins and chlorophylls over incubation (p < 0.05) when compared to untreated biomass. This procedure increased 2.2-, 3.9- and 31.9-fold the content of organic matter, protein and chlorophyll a, respectively, in comparison to the FTC procedure. This work presented the OH effect as a promising strategy for enhanced disruption and release of intracellular microalgae compounds.

Electric Resistance and Curing Temperature Development of Carbon Fiber-Reinforced Conductive Concrete: A Comparative Study.

The development of electric resistance is a key factor affecting the performance of conductive concrete, especially the electrical-thermal performance. In this work, the effects of different influencing factors (including the water-to-binder ratio, coarse aggregate content and carbon fiber (CF) content) on the electric resistance of conductive concrete were systematically investigated. At the same time, ohmic heating (OH) curing was applied to fabricate CF-reinforced conductive concrete (CFRCC) under a negative temperature environment at -20 °C. The effects of different factors on the electrothermal properties (curing temperature and conductive stability) of the samples were studied. The mechanical strengths of the CFRCC cured by different curing conditions were also tested, and the feasibility of OH curing for preparing CFRCC in a negative-temperature environment was verified at various electric powers. This work aims to give new insights into the effects of multiple factors on the performance of CFRCC for improved concrete construction in winter.