Electrode (potential applied electrode and ground electrodes) configuration and their orientations affect the electromagnetic field distribution within the radio frequency (RF) systems and temperature evolution inside the processed samples. Parallel flat plate and staggered through field or rod electrode systems are common electrode designs. Therefore, the objective of this study was to compare the effect of electrode configuration and orientation on electromagnetic field distribution in various RF systems and resulting temperature evolution. For this purpose, a mathematical model was first developed and validated with the experimental data obtained from three different RF systems (two staggered through field electrode configuration systems and a parallel plate electrode configuration system). Potential values of 2300 to 14,000 V through the charged electrode were obtained at the electrode gaps of 6 to 14 cm depending upon the electrode types (rod and parallel plate) and their configurations where the potential applied electrode was placed at top or bottom of the cavity. Temperature uniformity improved with increased electrode gap, and the parallel plate electrode design provided the higher heating rates at lower electrode gaps. The heating rate was lower at higher electrode gaps while contradicted results were obtained in the staggered through field electrode designs with respect to the electrode gap. The electromagnetic field distribution also differed significantly in these systems. The results of this study are considered to have the potential to be applied in industrial scale RF processing studies specially with more than one RF cavity systems.

Dry ice is one of the world's most in-demand commodities for cold-chain distribution of temperature-sensitive products. It offers an effective cooling solution without requiring mechanical refrigeration or specialized equipment. Dry ice is commonly produced as pellets and blocks. A widely used "rule of thumb" suggests that dry ice sublimates about 3%-8% per day. Mass of dry ice is typically the only packaging specification and/or regulatory limitation, even though sublimation rate is highly dependent on geometry. Therefore, the purpose of this study was to develop and validate a computational model for the sublimation process and to elucidate effects of geometry and orientation on dry ice sublimation. Experiments on sublimation of dry ice blocks were carried out and used to validate a multi-physics model involving radiation and convection heat transfer, computational fluid dynamics, and changes in the geometrical features. Following model validation, effects of dry ice geometry on sublimation rates were evaluated. Volume-to-surface area ratio was found to be a significant sublimation cooling performance parameter. Results showed that for the same mass, the rate of sublimation in the form of a sphere (high volume-to-surface area ratio) was almost half that of dry ice in the form of a block (lower volume-to-surface area ratio). This finding enhances our understanding of dry ice sublimation and cooling, which promises to help to improve practical cold-chain maintenance.

Toroidal cans have been presented recently to improve the canning process efficiency, and previous studies focused on static and axial rotational processes. End-over-End (EoE) rotation is a significant agitation approach to increase the temperature uniformity of liquid canned products, and it would be important to observe the effect of this process combined with the toroidal cans. Therefore, in this study, this combined effect was considered to improve the process in the view of temperature uniformity. For this purpose, a computational numerical model was developed using - Star CCM+, and this model was validated with experimental data. Then, the rotational rate and headspace amount effects in a toroidal can geometry, including a liquid, were determined using this validated model. The numerical results indicated that these parameters influenced the heat transfer process with a resulting uniform temperature distribution through the EoE processing.

Caning has been the effective thermal processing of food products to increase shelf life of food products. Following the retort applications, the agitation mechanism systems were introduced to increase the heat transfer rate in convection heated samples and to improve the quality with energy efficience, and the traditional cylindrical geometry cans have been used. However, it was demonstrated that the physical properties of the liquid samples, especially the viscosity showed a significant effect on the evolved heat transfer with respect to the increased agitation rates while high viscous samples might show a negative effect. Therefore, the objective of this study to determine the effect of liquid viscosity on the temperature evolution during axial rotation of toroidal cans with a computational approach and detailed force (Coriolis, centrifugal and gravitational) analysis. A previously developed and experimentally validated mathematical was used for this purpose, and the results of this study demonstrated a significant combined effect of the evolved Coriolis, centrifugal and gravitational forces on the temperature evolution and its uniformity during an axial rotation process of the toroidal cans.

Beer pasteurization is carried out in conventional systems where low temperature and long time process (56 min process with 13 min pre-heating, 14 min heating, 6 min holding time and 23 min cooling time) is applied for bottled or canned products. Longer process times lead to losses in the sensory properties. Another approach is flash pasteurization where the beer is first pasteurized and then filled into bottles or cans. For flash pasteurization, microwave (MW) process with rapid heating feature might be an innovative alternative. Therefore, the objective of this study was to explore the MW processing for beer pasteurization. For this purpose, a computational mathematical model was developed to determine the temperature change of beer during MW process and experimentally validated in a 2450 MHz lab-scale system. Following the validation, process design studies for a continuous flow system were carried out. These studies demonstrated the MW application as a rapid process (e.g. 60 s of total MW heating time at 5000 W with a short holding time of 27 s) to achieve the required pasteurization unit at a flow rate of 50.4 kg/h. This confirmed the MW process as a possible industrial application. Using these results, continuous flow process optimization studies for industrial process considerations might be planned.

The non-thermal effect of electromagnetic field (NEF) on the structural and thermal properties of heat-resistant globular sunflower protein isolate was investigated by exposing samples to varying power levels (70 W, defrost (DF), and 350 W). Only the lowest consecutive power modes of the electromagnetic unit were conducted to complete at least two exposure cycles (for certainty) without exceeding 45 °C (non-thermal processing condition). The total polar amino acid content of the treated samples decreased by 14% with NEF applications since polar amino acids were the main targets of the electromagnetic field due to absorbing that energy as kinetic energy and inducing structural changes. The DF and 350 W treatments dissipated large particles/aggregates over 5000 nm completely. The treatment with the lowest power (70 W) produced the lowest average particle size (14% decrease) while it increased after the DF and 350 W applications (34 and 16%, respectively), which indicated partial unfolding and/or reaggregation. Less ordered structures had increased α-helix (max with 350 W by 22%) and decreased β-sheet contents (max with 70 W by 30%) after the NEF treatments. The tertiary structures of the samples changed significantly following the NEF treatments with a blue shift on emission maxima with different fluorescence intensities. The thermal stability of the samples was analyzed with DSC and TGA; lower peak temperature (decreased by 28%) and denaturation enthalpy (decreased by 82%) besides higher gravimetric loss (by 1.3%) were obtained for DF and 350 W, compared to the control. The NEF could be considered a promising approach for structural alteration of globular sunflower protein.

Radio frequency (RF) processing, with its volumetric heating ability and a longer wavelength, is applied in industrial thawing and tempering processes for larger-sized frozen food products. However, overheating problems are observed at corners and edges of (specifically the sharp-edged foods) with a significant temperature non-uniformity, and tempering is preferred with its limited temperature increase right below the freezing point in most cases. The distance between the electrodes, charged electrode potential, and sample-electrode moving conditions in industrial-scale systems were investigated for temperature uniformity in the literature, but there has not been a confirmed solution presented for thawing yet. Therefore, air impingement coupled with RF heating was presented in this computational study using a previously (experimentally) validated model. Computational studies were carried out using Comsol Multiphysics for process design purposes, and RF system geometries included single and double cavity configurations with an air impingement speed of 0.5 and 2.5 m/s in a slot jet application. Significant temperature distribution uniformity was obtained within the samples even at higher electrode potentials, and air impingement coupled RF systems were presented for industrial-scale process conditions. 2750 V potential and 2.5 m/s air impingement speed were the optimal process condition for both single and double cavity RF systems. The results of this study are expected to be further used for system design and process optimization for industrial-scale RF thawing applications.(c) 2022 Institution of Chemical Engineers. Published by Elsevier Ltd. All rights reserved.

Radio frequency (RF) processing have been used for tempering and thawing. There have been significant experimental and mathematical model based studies for this process especially in the last two decades. The modeling studies applied the convective boundary condition with effective heat transfer coefficient and constant medium temperature in through field flat plate RF systems. The objective of this study was first to develop a mathematical model for conjugate heat transfer (natural convection) in a staggered through field electrode RF system and to use this model for natural convection effects in industrial scale processes. For this purpose, the developed comprehensive mathematical model was experimentally validated using the data from frozen tuna samples. The air temperature variation was also used for validation. Then, the developed model was used in industrial scale process simulations with the presence of natural convection. The industrially preferred flat plate systems were used in this part to determine the temperature and electric field evolutions. The results demonstrated the significant effect of the natural convection on sample surface temperature distribution and temperature change of air within the cavity. The evolved natural convection resulted in the variation of the heat transfer coefficient along the sample surfaces with significant changes in temperature. Based on these results, it might be concluded that the effect of air temperature change within the cavity during an RF processes should also be controlled and considered for industrial system design and process optimization.

The influence of food product viscosity on the temperature evolution inside distilled water and a high-viscosity liquid food model system during agitated retort processing (i.e., Shaka process) was investigated by simulations via a previously developed mathematical model. On the one hand, the volume average temperature increased at a faster rate in the high-viscosity liquid than in the water due to its lower specific heat. On the other hand, temperature distribution was rather uniform in the water, while a significant heterogeneity was observed in the high-viscosity liquid. Since significant thermal inactivation of bacteria occurs in local high- temperature zones, it would be beneficial to take simulated temperature profiles into account for bacterial inactivation predictions in future studies.

ABS T R A C T Microwave (MW) applications in food processing are used to reduce process time and increase process efficiency. While 915 MHz frequency is dominant for industrial processes, 2450 MHz systems are also observed. Attained temperature uniformity is specific concern with significant effect of the non-uniform electromagnetic field dis-tribution due to the cavity geometry and design. Therefore, the objective of this study was to determine the cavity geometry effect with applied frequency and to present industrial scale continuous process system with a computational approach. A computational model was developed for heating and thawing processes, and experimental validation was completed in a cylindrical MW cavity. Sample rotational movement and cavity geometry effects (conventional rectangular versus cylindrical, ellipsoidal and triangular) were determined, and industrial scale system designs were presented with frequency effect. Temperature change and electromagnetic field distribution were also introduced for improved design. The results demonstrated improved designs for industrial processes.

Axial rotation mechanism has been widely used during thermal processing of liquid containing cans. Besides this can geometry modification might be an innovative approach to increase heat transfer rates. Therefore, the objective of this study was to determine temperature distribution and effect of rotation rate in axially rotating toroidal cans. For this purpose, experimental and numerical modeling studies were carried out. In the experimental studies, toroidal cans including distilled water were processed in hot water, and temperature data were used for computational model validation and mesh independency. Then, the second set of simulations were conducted to determine the rotational effects on temperature evolution. Effects of gravitational buoyancy, centrifugal and Coriolis forces were determined, and Coriolis forces increased up to 4 times with increased rotation rates (20-160 rpm). With this aspect, process time for 70 degrees C increase was reduced by approximate to 40 and 33.3% at 80 and 160 rpm compared to conventinal cylindrical cans. This study is an introduction to modify can geometry and process parameters to reduce quality losses and decrease energy use. However, industrial practice has still significant challenge for manufacturing and using in the process line. (C) 2021 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

Heat transfer is mainly influenced by can geometry and product type. Agitating retorts have been widely used for heat transfer for liquid foods. Since convective heat transfer coefficient is high, this leaves the container geometry the only option to increase heat transfer rate and decrease process time for quality improvement. This is even valid for agitation processes due to applied limitation in the rotation rates. A recent innovation for this purpose was the introduction of toroidal cans. Therefore, the objective of this study was to investigate the potential of novel toroidal can geometries in processing of liquid and solid-liquid mixtures during an end-over-end (EoE) rotation canning process to decrease process time and improve product quality. For this purpose, canning was carried out using custom built toroidal cans processed in a horizontal multi-process EoE retort system. The products processed were distilled water, black salsify-water mix and tomato - based mushroom sauce. Temperature changes of the products were recorded during the EoE canning, and the results were analysed for the heating rate. Combination of toroidal cans and EoE agitation process resulted in a significant reduction in the process time depending upon the viscosity of the product. The results demonstrated the effect of product viscosity and toroidal can geometry on reducing process time. These results were shared with industrial partners and stakeholders to evaluate the potential implementation at industrial scale for expected increased energy efficiency with improved product quality.

This chapter brings a perspective to issues related to heating uniformity and modeling approaches of novel electrothermal technologies such as radio-frequency (RF) and microwave (MW) heating. Both RF (3 kHz–300 MHz) and MW (300 MHz–300 GHz) waves within the electromagnetic spectrum cause heat generation within foods as a result of molecular polarization and dipole rotation of existing water molecules (polar). RF and MW heating shows a great potential to achieve volumetric and rapid heat generation within food products, maintaining food quality and satisfying safety regulations in food industry compared with conventional heating systems. RF with larger penetration depth and better heating uniformity compared with MW could be applied in bulky sample sizes. Both RF and MW have been applied after baking, drying, thawing, and tempering, and for pasteurization/sterilization across the food industry. However, there are some limitations, including equipment design, microbial inactivation kinetics, temperature and process monitoring, and nonuniform heat distribution. Nonuniform heat distribution not only affects food quality but results in microbial safety problems because microorganisms or insects may not be controlled in cold spots across the packaged foods. Various modeling approaches or experimental studies have been extensively studied in a wide variety of food products to improve heating uniformity and optimize the processing parameters. This chapter presents knowledge about the principles of dielectric heating and heating uniformity experienced during RF and MW processing, discusses possible mechanisms to achieve possible temperature uniformity during the process, gives insight into modeling approaches to determine the efficiency of RF and MW heating patterns in food products, and discusses the advantages and disadvantages of both systems, as well as their similarities.

The effect of food matrix rheology and fat content on thermal inactivation of Listeria monocytogenes in the Shaka agitated retort (final retort temperatures of 59, 64, and 69 degrees C) was investigated using four fish-based artificial food model systems: low-viscosity liquid (liquid), high-viscosity liquid (xanthan), and emulsions containing 10% and 20% fat (emulsion 10% and emulsion 20%). Model system rheology, quantified by the consistency index K and the flow behaviour index n, influenced the thermal load to which the systems were exposed during treatments. Thermal loads followed the order liquid >= emulsion 10% >= emulsion 20% >= xanthan, a trend which was also valid for the sublethal injury induced to the cells. Log reductions followed the order liquid >= emulsion 10% >= xanthan >= emulsion 20%, indicating a protective effect of an increased fat content, not related to heat transfer differences. Between approximately 59 and 62 degrees C, the temperature range over which the largest portion of the inactivation was achieved, the maximum specific inactivation rate k(max )followed the same trend as the log reductions. Overall, the effect of food matrix rheology on inactivation efficacy could be linked to heat transfer dynamics, while the effect of fat content was more complex. (C) 2020 Published by Elsevier B.V. on behalf of Institution of Chemical Engineers.

Freezing and thawing are two significant food processing operations following each other in a process line. While freezing is one key unit operation for preservation, thawing is required for immediate consumption or further processing. Based on the final temperature of the product, tempering to final temperature of ≈−5°C to −2°C or thawing to ≈0°C or initial thawing temperature at the thermal centre are preferred approaches for a general defrosting. Thawing in still air and air blast thawing methods are considered to be the cheapest and oldest conventional methods with certain disadvantages involved, while microwave and radio frequency applications, with similar mechanism, are the innovative industrially applied approaches to increase the speed of thawing rate. The objective of this chapter is to demonstrate background on the use of conventional and innovative dielectric methods for thawing of frozen food products (seafood) and demonstrate the advantages and disadvantages of these methods with a computational approach.

Radio frequency (RF) processing has been widely used for thawing - tempering purposes, and electric field distribution due to electrode design of the RF systems has significant effects on temperature increase and temperature uniformity. Therefore, the objective of this study was to investigate the electric field distribution in a staggered through-field electrode RF system and thawing temperature uniformity with changes in quality parameters during RF thawing of frozen food products. For this purpose, frozen chicken breast samples were used. Electric field distribution in the staggered through-field electrode system (10 kW - 27.12 MHz) was determined as a function of electrode gap and applied power level. Higher electric field intensity was observed at center and middle edges of the bottom electrode of the system. Hence, thawing studies were carried out placing the frozen products at the center. Upon completion of thawing, texture changes and drip losses were determined and compared with conventional thawing at 4 degrees C refrigeration conditions. Complete RF thawing to - 0.73 +/- 0.79 degrees C using 65 mm electrode gap took 40 min compared to 18 h of conventional thawing with significantly reduced drip losses (0.32 compared to 4.84%).

Konduksiyon ve konveksiyona bagli olarak gerceklesen geleneksel cozdurme proseslerinde urun icerisinde olusan sicaklik farki onemli kalite kayiplarina neden olmaktadir. Cozdurme suresinin azaltilmasi ve urun ici sicaklik dagiliminin tekduze omasi icin cesitli yenilikci prosesler gelistirilmekte olup mikrodalga uygulamasi gida sanayinde uygulanma potansiyeli olan bir prosestir. Ancak, hacimsel isinma saglama ve proses suresini azaltma gibi avantajlarinin yaninda sistem icinde homojen olmayan elektromanyetik alan ve urun icinde duzensiz sicaklik dagilimina neden olmaktadir. Bundan dolayi urun icerisinde fazla isinmis bolgeler olusmaktadir. Bu durum, cozdurme prosesinde, donmus ve cozunmus bolgelerin dielektrik ozelliklerindeki farka bagli olarak gozlenmektedir. Uygulanan guc duzeyi, urune verilen donme hareketi ve urun geometrisi proses tasarimi amaciyla kullanilabilen parametreler olup literaturde genel olarak deneysel calismalara bagli deneme – yanilma yaklasimlari kullanilmaktadir. Bu nedenle, bu calismanin amaci mikrodalga isitma – cozdurme prosesini sistem ici elektik alan ve urun ici sicaklik dagilimi kapsaminda tanimlamak icin bir matematiksel model gelistirmektir. Bu calisma ozel tasarlanmis bir sistemde (Gigatherm (Flawil, Switzerland) firmasi tarafindan yapilan) gerceklestirilmis ve deneysel dogrulama calismalari icin %77 su oraninda Tylose jeli kullanilmistir. Cozdurme prosesine basincin etkisi dusunulerek 2 bar basinc altinda isitma ve cozdurme deneyleri ayrica gerceklestirilmis ve mikrodalga uygulama sirasinda sicaklik degisimine basincin etkisi belirlenmistir. Ayrica, gelistirilen matematiksel modeller kullanilarak dogrulanan proses kosullarinda, dondurulmus morina baliklarinin cozdurulmesi icin bir yontem gelistirilmis ve dur – kalk uygulamali guc etkisi ile donme prosesinin birlikte kullanilmasi ile en uygun cozdurme sartlari belirlenmistir. Bu calismanin universite – sanayi ortak calismalarina katki saglayacagi ve sonuclarinin endustriyel proses kosullarinin belirlenmesinde kullanilabilecegi dusunulmektedir. AbstractIn conventional thawing processes, heat transfer generally occurs by conduction and convection with a significant difference between surface and center temperatures leading to quality loses. Innovative approaches were developed to reduce thawing time and uniform the temperature distribution. Microwave heating is such a process to apply in food industry. It is accepted to provide volumetric heating and reduce process time. Compared to these advantages, non-homogeneous electromagnetic field in the cavity results in a non-uniform temperature distribution within product with overheated sections. This is especially valid during thawing due to the significant difference in dielectric properties of frozen and unfrozen parts. Various parameters such as rotation, power level and sample geometry affect microwave thawing, and design - optimization of this process generally relies on experimental trial-error approaches. Therefore, the objective of this study was to develop a mathematical model to evaluate heating - thawing process using a specially designed microwave system (built by Gigatherm, Flawil, Switzerland). Tylose gel (77 % moisture content - wb) heating - thawing experiments were carried out to validate the developed models. In addition, considering the pressure, mild pressure effects up to 2 bar were evaluated on heating rate. After demonstrating the pressure effects and effective use of the models for design purposes, thawing conditions were experimentally determined for cod fish where the best performance was obtained with a stop-go applied power and rotation. The results of this study are expected to be used for industrial process conditions and to contribute to industry – university collaborated studies.