Time-temperature Profiles Research Articles

Novel rapid cooling system design and modeling for continuous flow food processing systems

The commercial sterility in thermal processing is achieved by implementation of high temperatures that often has a negative impact on the heat sensitive health promoting nutrients like vitamins, antioxidants, flavors, and phytochemicals. Although tremendous progress has been made in rapid heating with the advancements in volumetric heating technologies like ohmic and microwave heating, the advancement in rapid cooling remains unexplored to further minimize the product quality degradation. A novel rapid cooling heat exchanger design modification was made to the traditional cooling system to improve the rate of cooling by direct injection of cooling gas media. Pilot-scale tests were conducted on a model food with an Ultra High Temperature (UHT) processing unit and an add-on novel cooling design. The cooling rate achieved by the rapid cooling design was found to be 7.5 ± 0.01 °C/s, which was 15 times the cooling rate provided by the traditional UHT cooling system. Mathematical models were developed to predict the time-temperature profile and the nutrient retention based on the new design. The model simulations for the new cooling design showed additional retention of 14.81% antioxidant content, 4.13% anthocyanins, 14.43% total flavonoid content as compared to the traditional cooling system.

A Quantitative Analysis of the Fire Hazard Generated from Hydrogen Fuel Cell Electric Vehicles

There is a lack of information on (i) the potential fire load of new green-technology vehicles, (ii) flame spread behavior, (iii) thermal impacts on high-pressure hydrogen storage vessels (HSVs) and lithium-ion batteries (LIBs) during fuel cell electric vehicles fires (FCEVs), and (iv) thermal damage to adjacent vehicles and upper structural members during FCEV fires occurring in civil structures, such as underground spaces, multi-story parks, and tunnels. In view of this, a full-scale fire test was conducted in this study to quantitatively assess the fire risk of hydrogen FCEVs. Large-scale cone calorimetry was used to quantify the thermal intensity released from the FCEV fire. The flame spreading behavior through an FCEV with HSVs and LIBs was observed using the thermocouples installed. Changes in the temperature and irradiance around the FCEV fire were also measured using an instrumented test rig. The peak heat release rate, total heat released, and fire growth rate were observed to be 5.99 MW, 11.8 GJ, and 0.0055 kW/s², respectively. The temporal point of hydrogen gas release from the HSVs' thermal pressure relief device (TPRD) was estimated to be 16.2-26.2 min. The initiation of thermal runaway of LIBs was deduced from the temperature-time profiles of the LIB modules and their metal housing approximately 22.2 min after HCEV ignition. Moreover, FCEV fires could thermally impair adjacent upper structural members by 800 ℃ combustion gas for at least 13 min and emit a median heat flux of 27.2 kW/m² (peak heat flux of 76.5 kW/m²) to adjacent vehicles. The measurements and findings obtained from this study can contribute to the evaluation of and further studies on newly emerging fire hazards.

Synthesis and performance of Ti subchlorides (TiClx, x = 2, 3) as a Ti-ion transport agent in NaCl-CaCl2 molten electrolyte

To manufacture titanium subchlorides (TiClx, x = 2, 3), a combustion synthesis technique based on a displacement reaction between PbCl2 and Ti is devised. During the combustion reaction at 670–940°C, a molten product including TiCl2 (and/or TiCl3) and Pb is formed. The reaction mechanism and high-temperature kinetics are described in addition to temperature-time profiles measured by thermocouples. XRD examination confirms the formation of TiCl2 and TiCl3 phases depending on the PbCl2/Ti ratio. SEM and XPS analysis techniques are also used to characterize Ti subchlorides. The selective dissolution of titanium via the generated titanium subchlorides and subsequent deposition on the cathode at 650°C is achieved by electrorefining Ti-Cu alloy (anode) in NaCl-CaCl2-TiCl2 molten chlorides.

Impact of the electric field intensity and treatment time on whey protein aggregate formation

Whey proteins are being integrated as high-value food product ingredients due to their versatile and tunable techno-functionality. To meet high food quality and clean label expectations by consumers, electric field (EF) technologies have been proposed to open new frontiers in this field. Despite a variety of studies, it remains ambiguous which EF parameters are crucial to achieving targeted whey protein modifications. Reconstituted liquid whey protein concentrate (WPCL) and filtered, non-heat-treated liquid whey (WPL_filt) at low protein dry weight concentrations (0.4% wt/wt) were exposed to microsecond pulsed electric field (μsPEF) treatments at EF intensities between 1.25 and 12.5 kV/cm, pulse repetition frequencies between 0.38 and 85 Hz, and pulse lengths set to 10 or 100 μs. Protein aggregations were quantified spectroscopically. We report here that aggregates formed at lower temperatures for μsPEF compared with purely thermal treatments in identical treatment geometries at similar time-temperature profiles. We suggest that the observed increase in absorbance is linked to protein migration, the isoelectric point, local deprotonation phenomena of thiol groups, and cation precipitation. The μsPEF treatment time, which is dependent on the pulse repetition frequency, pulse length, and time of process, is the main driver of the increase in absorbance. High EF intensities balanced with shorter pulse repetition frequencies to ensure similar energy inputs resulted in no aggregate formation. For WPL_filt, 12.5 kV/cm, 10 μs, 0.38 Hz (620 ± 96 kJ/kg; ± standard deviation) did not result in an increase in absorbance, whereas 1.25 kV/cm, 10 μs, 50 Hz (634 ± 57 kJ/kg) with similar time-temperature profiles increased the absorbance at a wavelength of 380 nm by a factor of 8.2 ± 1.7 compared with untreated WPL_filt. In conclusion, the treatment time seems to dominate over high EF intensities at similar energy inputs for aggregate formation and increase in absorbance.

Time-Temperature Profiles Effect on Thermoluminescence Glow Curve Formation of Germanium Doped Optical Fibres

The development of optical fibres technology grows in response to seeking a radiation detector with better thermoluminescence (TL) performance. Concerning the dosimetric characterization study by previous researchers, this research work has widened the exploration to optimize the time-temperature profile (TTP) in connection with the glow curve formation of the optical fibres. Two forms of germanium (Ge) doped optical fibres, namely cylindrical optical fibre (CF) and flat optical fibre (FF) were fabricated, and the TTP were investigated prior to commissioning the optical fibres for fieldwork. CF and FF were irradiated to the dose of 2 Gy using a 6 MV linear accelerator. Various TTP profiles, including preheat temperature, preheat time, acquisition temperature rate, and acquisition time were varied to determine the best thermal profile for the CF and FF based on the glow curve formations. Out of 4 parameters, an increase in preheat temperatures ranging from 40 to 120 °C caused a significant variation in the glow curve formation, thus possibly giving rise to different TL signals of the optical fibres. The maximum glow peak temperature of CF and FF was unvarying when different preheat temperatures employed. These findings support the conceptual idea that manipulating the optical fibres’ readout system can alter the glow curve formation. Thus, an optimized TTP will provide the correct glow curve configuration for kinetic parameter analysis.

Determination of size and porosity of chars during combustion of biomass particles

This research focused on the size and overall porosity (pore volume) of carbonaceous chars, originating from high-heating rates and high-temperature pyrolysis and/or combustion of biomass. Emphasis was given to torrefied biomass chars. First, the porosity of char residues of single biomass particles of known mass was determined, based on an assumed value of skeletal density and by comparing experimentally observed temperature-time histories with numerical predictions of their burnout times. The average char porosities (effective porosities) of several raw and torrefied biomass particles were calculated to be in the range of 92–95%. Thereafter, these deduced porosity values were input again to the model to calculate the size of chars of other biomass particle precursors, whose initial size and mass were not known. Such biomass particles were sieve-classified to different nominal size ranges. This time, besides the porosity, representative time-temperature profiles of biomass particles in the aforementioned size ranges were also input to the model. Biomass particles are highly irregular with large aspect ratios and, in many cases, they melt and spherodize under high heating rates and elevated temperatures. Knowledge of the initial size of the chars, upon extinction of the volatile flames, is needed for modeling their heterogeneous combustion phase. For this purpose, numerical predictions were in general agreement with measurements of char size obtained from both scanning electron microscopy of captured chars and real-time high-speed, high-magnification cinematographic observations of their combustion. Results showed that the generated chars of the examined biomass types were highly porous with large cavities. The average initial dimension of the chars, upon rapid pyrolysis, was in the range of 50–60% the mid-value of the mesh size of the sieves used to size-classify their highly irregular parent biomass particles.

Brushite bone cement containing polyethylene glycol for bone regeneration.

Bone cements aid in bone regeneration; however, if the handling time is not well established for the material to harden, complications may arise. This work investigates the effect of using polyethylene glycol (PEG) and characterize it in brushite bone cement in order to obtain desirable handling times as well as its regeneration invivo to analyse if addition of this polymer may significantly modify its properties. PEG 4000 was synthesised with wollastonite by phosphorization reaction in order to form brushite which was further cured by oven drying. They were further characterised and tested invivo as tibial bone defect model using rabbits. Addition of PEG exhibited handling times of 60min with a low increase in temperature when curing. Brushite phase of ∼71% was obtained after cement hardening with good compressive strength (25MPa) and decent values of porosity (33%). Invivo presented that, at 40 days postoperatively, accelerated bone neoformation with partial consolidation at 30 days and total after 60 days when using bone cement. Addition of PEG does not disrupt the beneficial properties of the bone cement and can be a potential alternative to control the time-temperature profile of hardening these materials.

Correlating strength and durability to time-temperature profiles of high-performance mass concrete

The temperature rise in mass concrete usually leads to premature distresses and early-age cracking. This paper correlates the time-temperature profiles to the mechanical properties and durability of high-performance mass concrete (HPMC). Five types of cement having different specific surface areas (SSA) and granulated blast furnace slag (GBFS) replacement rates are tested. Thirteen thermocouples were inserted at various locations inside a 1-m3 formwork to record the rate of concrete temperature rise, maximum temperature (Tmax), and time needed to attain Tmax. The mechanical properties were characterized by the compressive and flexural strengths, while the durability was evaluated using the drying shrinkage, water permeability, and chloride migration. Experimental results showed that concrete containing fine cement exhibited better strength and durability, yet increased tendency to thermal cracks and drying shrinkage. The partial cement replacement by GBFS reduced the concrete rate of temperature rise and Tmax, which led to reduced shrinkage. Analytical correlations and multivariable linear regression models were developed to predict the effect of SSA, GBFS replacement rate, and 28-day heat of cement hydration on the time-temperature characteristics and durability of HPMC.

Solution combustion synthesis of MnFeCoNiCu and (MnFeCoNiCu)3O4 high entropy materials and sintering thereof

Single-phase, fine-grained high entropy MnFeCoNiCu alloy and (MnFeCoNiCu)3O4 oxide powders have been pioneered by an in-situ solution combustion synthesis without post-treatment, utilizing alanine and glycine as organic reducers and ammonium nitrate as an auxiliary oxidizing agent. In order to regulate the porosity, homogeneity, phase composition and morphology of the obtained powders, multivariate studies on the influence of the following parameters were performed: type and quantity of reducers, pH of solution, ignition temperature, presence of oxidizing agent, etc.. It has been shown that the amount of the reducer holds the key for governing combustion temperature and speculation of lower and upper combustion limits in the systems under study. In turn, according to the temperature-time profiles of combustion, product microstructure, as well as phase composition of the product, the combustion area turned out to be divided into two sub-domains: volume combustion (with vigorous flaming) and self-propagation combustion. After thorough characterization, high entropy MnFeCoNiCu alloy and high entropy (MnFeCoNiCu)3O4 oxide powders were subjected to consolidation by spark plasma sintering and mechanical properties were evaluated. The influence of sintering temperature on the phase transformation of the products was revealed.

A kinetic study on the thermal inactivation of barley malt α-amylase and β-amylase during the mashing process

To obtain an efficient conversion of starch into fermentable sugars and dextrins during the brewing process, mashing time-temperature profiles need to promote starch gelatinisation and enzyme activity while avoiding thermal inactivation of the amylases. This study focused on the second part of this balance by investigating the thermal stability of α-amylase and β-amylase of Planet barley malt throughout mashing. Thermal inactivation in wort was modelled for both enzymes resulting in the estimation of thermal inactivation kinetic parameters such as rate constant of thermal inactivation kT (the rate of thermal inactivation of an enzyme at a constant temperature), activation energy for thermal inactivation Ea, decimal reduction time DT (the time needed to inactivate 90% of the enzyme activity at a given temperature) and the z-value. First-order inactivation was observed for α-amylase. For β-amylase, fractional conversion inactivation occurred with a residual fraction of 13% of the β-amylase activity that remained after prolonged heating at 72.5 °C. The β-amylase protein population hence seems to consist of thermolabile and thermostable isoforms. The kinetic parameters for thermal inactivation of the enzymes were used to predict their residual activities throughout a laboratory-scale mashing process. The predicted residual activities met the experimentally determined residual enzyme activities closely, except for β-amylase at temperatures higher than 72.5 °C. The results obtained in this work allow designing new mashing processes or tailoring existing processes towards variability in the input material, barley malt, without the need for trial-and-error experiments.

A study on effect of heat input on mode of welding, microstructure and mechanical strength in pulsed laser welding of Zr-2.5 wt.%Nb alloy

In the present study, Zr-2.5 wt.%Nb alloy plates of thickness 4 mm have been welded using pulsed Nd:YAG laser system at different process parameters and characterized in terms of microstructural evolution, hardness, residual stress, and mechanical properties. It has been observed that heat input plays an important role on mode of welding. The full penetration up to a thickness of 4 mm of the alloy has been achieved at a minimum laser heat input of 800 J mm−1 without any crack and porosity formation. For avoiding the porosity formation in the weld zones, a transition mode between conduction and keyhole has been used by optimizing laser process parameters. The microstructural analysis revealed that the fusion (FZ) is consists of predominant lath type α′ martensitic phase with small amount of randomly distributed acicular type of α′ martensite phase. However, the heat affected zone (HAZ) have lath type α′ martensitic phase together with αZr phase. Further, in the FZ and HAZ regions, the presence of retained βZr phase is higher as compared to the base metal (BM). The change in microstructure and phase field of different weld zones has been explained by evaluating the time-temperature profiles and cooling rates using COMSOL multi-physics simulation. In addition, the FZ and HAZ zones have been found to have tensile residual stress of the order of 280 MPa and 145 MPa as compared to the BM (-70 MPa). The microhardness in the FZ region has been observed to be higher (240–260 HV0.1) as compared to the BM (∼185 HV0.1) due to the formation of martensitic phase. The tensile room temperature testing showed that the mechanical strength of as welded sample is significantly higher than the base metal with lower ductility. The fractography of the fractured surfaces confirmed ductile nature of failure in the as welded samples.

Optimizing the In-Vessel Composting Process of Sugarbeet Dry-Cleaning Residue

Rapid urbanization and industrialization around the world have created massive amounts of organic residues, which have been prioritized for conversion into valuable resources through the composting process to keep their harmful effect at a minimum. This research aimed to assess the influence of active and passive aeration on composting mass of sugar beet residues in the case of using additives (e.g., charcoal only or manure only or combination). Some physicochemical properties of composting mass were analyzed on certain days of composting. Some parameters including temperature–time profile, carbon to nitrogen ratio (C/N ratio), moisture content, electrical conductivity, pH, germination and microbial population enumeration of compost were measured. Cress germination test was conducted for each medium of germination which contains a mixture of soil and compost (at a ratio of 3:1) taken from each treatment. The results showed that temperature–time profile data of composting mass showed an irregularity. Forcedly aerated composting mass did not demonstrate a thermophilic phase while passively aerated ones did not show a mesophilic phase. Carbon to nitrogen (C/N) ratio reduction was greater in most forcedly aerated composting mass than passively aerated on days from 1 to 33 of composting period. The results further showed that electrical conductivity decreased at the end of the composting period where it ranged from 2.55 to 3.1 dS/m. Germination medium containing forcedly aerated compost treated with a combination of charcoal and manure achieved the highest germination index which was higher than the control sample by 58.63% followed by forcedly aerated composting mass treated by charcoal only which exceeded the control sample by 5.35%. Strong correlation coefficient (r > 0.80) for the relationship between germination index and number of bacteria was obtained on day 17th of composting period.

Influence of polymers on flow and heat transfer due to peristaltic waves: a molecular approach

This work aims to have an insight into the effects of polymers on flow and heat transfer due to peristaltic waves. Oldroyd-B model, based on kinetic theory, is considered to study the relation between the molecular structure of the polymers and the rheological properties. The main advantage of using this model is the inclusion of information based on molecular structure. Such inclusion in stress tensor incorporates the effects of stretching and orientation of the molecules. Some significant applications polymer-peristalsis can be found in tissue engineering, intake of food, and medicines. Approximations of long-wavelength and low Reynolds number are used to investigate the main features of the problem. Pressure gradient, velocity, temperature, trapped bolus, drag coefficient, and heat flux at the wall are studied numerically. The analysis is based on the change in important parameters like polymer concentration, relaxation time, Weissenberg number, and Brinkman number. Results show that by increasing polymer concentration parameter, Weissenberg number, and relaxation time parameter, the negative pressure gradient in the flow geometry increases. By increasing the polymer concentration parameter and time relaxation parameter, the velocity and temperature profiles increase. An increase in polymer concentration increases the size of the trapped bolus. Drag parameter at the wall decreases while heat flux increases when polymer concentration and Weissenberg number are increased.

Refolding of Lysozyme in Glycerol as Studied by Fast Scanning Calorimetry.

The folding of lysozyme in glycerol was monitored by the fast scanning calorimetry technique. Application of a temperature–time profile with an isothermal segment for refolding allowed assessment of the state of the non-equilibrium protein ensemble and gave information on the kinetics of folding. We found that the non-equilibrium protein ensemble mainly contains a mixture of unfolded and folded protein forms and partially folded intermediates, and enthalpic barriers control the kinetics of the process. Lysozyme folding in glycerol follows the same or similar triangular mechanism described in the literature for folding in water. The unfolding enthalpy of the intermediate must be no lower than 70% of the folded form, while the activation barrier for the unfolding of the intermediate (ca. 140 kJ/mol) is about 100 kJ/mol lower than that of the folded form (ca. 240–260 kJ/mol).

Temperature control in a horticultural produce supply chain in Thailand and its influence on product quality

The present study was conducted in order to investigate the temperature conditions in the horticultural produce cold chain in Thailand, and fresh-cut baby corn was chosen for a case study. The field investigation together with in-person interviews were performed at 4 growers' premises and one packing house. The information collected provided details on current postharvest conditions at individual stages from the growers’ premises to an export distribution center. Temperature measurements were carried out to explore the time-temperature profiles throughout these stages. The results showed that the total duration of these stages was almost 32 h, and the temperature variations were between 6 and 33 °C. Precooling was delayed for at least 9 h, since baby corn cobs were primarily processed by dehusking and bulk packing. The baby corn was maintained at a temperature below 6.0 °C in a cold room for almost half of the total duration. The effect of the postharvest temperature conditions on the product quality evaluation was assessed by measuring various physiological quality attributes during storage. It was found that the marketability of the baby corn subjected to such postharvest temperature conditions remained possible with a salable period of up to two weeks. The result made it possible to identify the stages during which temperature control was inadequate, and recommendations were proposed to the stakeholder partner in order to modify the postharvest conditions in order to extend the product shelf life.

Metallic Additive Manufacturing

Abstract: As metallic additive manufacturing grew in many areas, many users have requested greater control over the systems, namely the ability to change the process parameters. The goal of this paper is to review the effects of major process parameters on the quality such as porosity, residual stress, and composition changes and materials properties like microstructure and microsegregation. In this article, we give an overview over the different kinds of metals specially steels in additive manufacturing processes and present their microstructures, their mechanical and corrosion properties, and their heat treatments and their application. Our aim is to detect the microstructures as well as the mechanical and electrochemical properties of metals specially the steels. Steels are subjected during additive manufacturing processing to time-temperature profiles which are very different from the conventional process. We do not describe in detail the additive manufacturing process parameters required to achieve dense parts. We discuss the impact of process parameters on the microstructure, where necessary.

Technical aspects of peanut butter production processes: Roasting and grinding processes review

A concise understanding of technical aspects underpinning successful peanut butter production is critical for the peanut butter industry. This paper reviews the critical technical drivers of quality peanut butter production. The synergetic relationship between roasting, grinding and stabilization processes and corresponding physiochemical changes and their influence on peanut butter color, flavor, texture, storage stability, shelf life, and overall consumer product acceptance is discussed. Potential of promising novel technologies like infrared, microwave roasting, and some novel peanut butter stabilization methods is evaluated. Quality of peanut butter is by far determined by temperature–time profile used in roasting, fineness of grind, type(s) and amount of added ingredients. The synergistic relationships between production technical aspects and resultant quality of peanut butter are more complex than what is usually assumed. Further research on the novel technologies like infrared and microwave roasting is still required for them to be fully adopted in the peanut butter industry. Practical applications Far from the general erroneous assumptions that peanut butter production is a simple process that does not require much technical and scientific rigor, successful and high-quality peanut butter production is informed by a solid technical and scientific knowledge base. The problems of poor peanut butter quality can be easily addressed by tapping from this scientific base. This study provides a single point, comprehensive reference source material on the technical drivers of peanut butter quality attributes from a processing perspective. Researchers, process, and production engineers can use this base knowledge in designing and optimization of peanut butter production processes. A clear understanding of the link between processes and physiochemical changes that are influential on peanut butter quality can be a key technical enabler to the peanut butter industry.

Combustion of C1 and C2 PFAS: Kinetic modeling and experiments

ABSTRACT A combustion model, originally developed to simulate the destruction of chemical warfare agents, was modified to include C1-C3 fluorinated organic reactions and kinetics compiled by the National Institute of Standards and Technology (NIST). A simplified plug flow reactor version of this model was used to predict the destruction efficiency (DE) and formation of products of incomplete combustion (PICs) for three C1 and C2 per- and poly-fluorinated alkyl substances (PFAS) (CF4, CHF3, and C2F6) and compare predicted values to Fourier Transform Infrared spectroscopy (FTIR)-based measurements made from a pilot-scale EPA research combustor (40–64 kW, natural gas-fired, 20% excess air). PFAS were introduced through the flame, and at post-flame locations along a time-temperature profile allowing for simulation of direct flame and non-flame injection, and examination of the sensitivity of PFAS destruction on temperature and free radical flame chemistry. Results indicate that CF4 is particularly difficult to destroy with DEs ranging from ~60 to 95% when introduced through the flame at increasing furnace loads. Due to the presence of lower energy C-H and C-C bonds to initiate molecular dissociation reactions, CHF3 and C2F6 were easier to destroy, exhibiting DEs >99% even when introduced post-flame. However, these lower bond energies may also lead to the formation of CF2 and CF3 radicals at thermal conditions unable to fully de-fluorinate these species and formation of fluorinated PICs. DEs determined by the model agreed well with the measurements for CHF3 and C2F6 but overpredicted DEs at high temperatures and underpredicted DEs at low temperatures for CF4. However, high DEs do not necessarily mean absence of PICs, with both model predictions and limited FTIR measurements indicating the presence of similar fluorinated PICs in the combustion emissions. The FTIR was able to provide real-time emission measurements and additional model development may improve prediction of PFAS destruction and PIC formation. Implications: The widespread use of PFAS for over 70 years has led to their presence in multiple environmental matrixes including human tissues. While the chemical and thermal stability of PFAS are related to their desirable properties, this stability means that PFAS are very slow to degrade naturally and potentially difficult to destroy completely through thermal treatment processes often used for organic waste destruction. In this applied combustion study, model PFAS compounds were introduced to a pilot-scale EPA research furnace. Real-time FTIR measurements were performed of the injected compound and trace products of incomplete combustion (PICs) at operationally relevant conditions, and the results were successfully compared to kinetic model predictions of those same PFAS destruction efficiencies and trace gas-phase PIC constituents. This study represents a significant potential enhancement in available tools to support effective management of PFAS-containing wastes.

Property Prediction of Ag-Filled Isotropic Conductive Adhesive through the Analysis of Its Curing and Decomposition Kinetics

In this study, various thermal analyses were carried out on a self-developed and commerce-oriented Ag-filled isotropic conductive adhesive (ICA) and its unfilled matrix resin through which glass transition temperature (Tg) and thermal endurance could be quantitatively predicted. An autocatalyzed kinetic model was used to describe the curing reaction, which was proven to be in good consistency with the experimental data. The activation energies for the curing reaction of the ICA and the matrix resin were determined to be 68.1 kJ/mol and 72.9 kJ/mol, respectively, which means that the reaction of the ICA was easier to occur than its unfilled matrix resin. As a result, the time–temperature profile could be calculated for any Tg requested based on the kinetic model of curing and the DiBenedetto equation. Further, the thermal decomposition stability of the ICA and its unfilled matrix resin were also studied. The activation energies for the thermal decomposition of the ICA and the matrix resin were calculated to be 134.1 kJ/mol and 152.7 kJ/mol, respectively, using the Ozawa–Flynn–Wall method, which means that the decomposition of ICA was easier to occur. The service life of the resin system at a specific temperature could therefore be calculated with their activation energy. The addition of micro-scale Ag flakes did not change the curing and decomposition mechanisms by much.

Ohmic tempering using a high frequency ohmic heating and model food of minced tuna based on Allaska pollock surimi – Evaluation of electrical conductivities

Inexpensive and practical model foods are necessary for developing ohmic tempering (OT) of tuna to reduce experimental costs. In this study, the effects of salt addition (0, 0.25, 0.5, 1.0, and 2.0%) in pollock surimi within the temperature range of −40 to 10 °C and frequency range of 50 Hz to 20 kHz, and adjusting voltage were evaluated to develop a model food for the OT of minced tuna by comparing their electrical conductivity (EC) values and temperature distribution. The EC values of the model food increased with the salt content, temperature, and frequency. The adjustment of voltage during OT in three steps (400 V, −35 to −20 °C; 200 V, −20 to −10 °C; 100 V, −10 to −4 °C), helped improve the uniformity of the temperature distribution of the samples. The EC values, time-temperature profiles, and temperature distribution results of the model food after the addition of 0.5% salt were the closest to the minced tuna during the 20 kHz OT process. The results laid a foundation for the development of inexpensive and effective frozen model foods for OT applications especially at high frequencies.