Oven Heating Research Articles

Non-Thermal Effects of Microwave Oven Heating on Ground Beef Meat Studied in the Mid-Infrared Region by Fourier Transform Infrared Spectroscopy

ABSTRACT The effects of cooking by microwave oven on the secondary structure of lipid and protein contents in bovine ground beef were investigated in the midinfrared region by Fourier transform infrared (FTIR) spectroscopy to highlight the nonthermal effects of microwave oven heating. Samples of bovine ground beef were cooked in a conventional electric oven at the temperature of 175°C for 15 min and in a microwave oven at 800 W for 1½ min. Spectra analyses of bovine meat after cooking in the conventional oven evidenced a relevant increase in intensity of the carbonyl band at 1742 cm−1 and of the methylene group at 2921 and 2853 cm−1 that can be attributed to the Maillard reaction. In contrast, the increase in intensity of these bands after microwave oven heating was less than that which occurred after conventional cooking, showing that the temperature in ground beef meat samples during microwave heating was less than that induced by conventional heating. Spectral analysis in the amide I, II, and III regions showed that a significant increase in intensity occurred in the region from 1660 to 1675 cm−1 and around 1695, 1635, 1575, and 988 cm−1 after cooking by means of a microwave oven. These features, which can be attributed to β-turns and β-sheet structures, are characteristic of disorder processes in meat protein contents and increasing transition dipole coupling due to higher contents in aggregated β-sheet structures. This result highlighted nonthermal effects of microwave oven heating in the protein's secondary structure.

Thermal analyses of LiCoO2 lithium-ion battery during oven tests

A three dimensional thermal abuse model for graphite/LiPF6/LiCoO2 batteries is established particularly for oven tests. To investigate the influence of heat release condition and oven temperature on battery thermal behaviors, we perform a series of simulations with respect to a unit cell during oven thermal abuses of various oven temperatures and under various heat release conditions. Simulation results enable detailed analyses to thermal behaviors of batteries. It is found that during oven thermal abuse processes that do not get into thermal runaway, the negative electrode is the maximum heat generation rate zone; during oven thermal abuse processes that do get into thermal runaway, the positive electrode is the maximum heat generation rate zone. The positive-solvent reaction is found to be the major heat generation source causing thermal runaway. It is also found that the heat release condition and the oven temperature are combined to dictate thermal behaviors of the battery. The critical oven temperature that causes thermal runaway rises if the heat release condition is better and the critical heat release coefficient that can effectively restrain the occurrence of thermal runaway increases with the increase of oven temperature.

Microwave-assisted crystallization into anatase of amorphous TiO2 nanotubes electrochemically grown on a Ti substrate

Hybrid thermal heating induced by a microwave oven was unprecedentedly used to successfully attain rapid and facile crystallization into the anatase phase of amorphous TiO2 nanotubes grown on a Ti substrate. Amorphous TiO2 nanotubes were obtained by anodic oxidation of a Ti foil either in aqueous or organic medium. Afterward, these TiO2 nanotubes were thermally treated by hybrid heating in a common commercial microwave oven. The as-grown amorphous nanotubes were characterized by SEM and XRD, whereas the evolution of the nanotubes crystallization with thermal treatment time was followed by XRD. The crystallization into the anatase phase of the amorphous TiO2 nanotubes occurred after only 2 or 3min of hybrid thermal treatment, which is very short and convenient as compared with several hours that are needed when conventional thermal treatment is used.

Physico-chemical of organo-functionalized magnesium phyllosilicate prepared by microwave heating

In this work, organo-functionalized magnesium phyllosilicates were prepared via hydrothermal synthesis with four sources of silicon: 3-aminopropyltriethoxysilane (AMPTS), N-[3-(trimethoxysilyl)propyl]-ethylenediamine (TMSPEDA), N-[3-(trimethoxysilyl)propyl]-diethylenetriamine (TMSPETA) and tetraethoxyorthosilane (TEOS). Microwave radiation (MW) was employed as heating source and the results were compared with the analogous materials synthesized by conventional heating in an oven (CE). The materials obtained were characterized using X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR), solid state 29Si and 13C nuclear magnetic resonance (NMR), thermogravimetry (TG) and elemental analysis of carbon, nitrogen and hydrogen (CHN). The 2:1 type of trioctahedral phyllosilicate was confirmed by the presence of the 060/330 reflection, at 59.5° 2θ. The presence of the organic modifier was proven by the bands at 2930, 2850, and 1490cm−1 and the typical features of the phyllosilicate were found at 3700cm−1 (Mg–OH) and 1014cm−1 (Si–O–Si). 13C-NMR showed that the organic chains were intact in the interlayer space (5–64ppm). Thermogravimetry indicated that these pending groups were stable in this support until 200°C when they begin to decompose. Silicon-29 NMR confirmed that the pending groups were bound directly to the silicon atoms by the resonance of Si–C bond at 48 and 55ppm. The results showed the success of the procedure for all the proportions of the silicon sources used, with a reduction of reaction time in the range from 91% to 96% using microwave radiation in relation to the conventional heating oven.

Estimating the activation energy of exothermic reactions in substances that undergo self heating processes with the Heat Release method: Use of sub critical data

Substance liable to self heat and spontaneously ignite under storage or transportation conditions can be a serious fire hazard in several industries. In order to estimate if, under specific storage conditions, a substance will dangerously self heat up to ignition, it is necessary to have knowledge of several thermochemical properties of the substance itself. Among this properties, one of the most relevant is the overall activation energy of the exothermic reactions that are responsible of the internal heat generation. In this short communication it will be discussed the possibility to retrieve the value of the overall activation energy from oven heating experiments conducted at temperature below the critical temperature of the sample, taking as an example a set of experimental data retrieved for commercially available charcoal briquettes.

Characterization of newfound natural luminescent properties of melamine, and development and validation of a method of high performance liquid chromatography with fluorescence detection for its determination in kitchen plastic ware.

Experimental studies of the natural photoluminescence of melamine in aqueous solutions showed that its fluorescence intensity (at 250/365 nm) was appropriated for analytical purposes. The exploitation of such melamine property provided the basis of development of a new, simple, precise and accurate method based on high performance liquid chromatography with fluorescence detection (HPLC-Fluo) to determine melamine in kitchen plastic ware following aqueous extraction using a microwave oven. Optimization of analytical parameters such as solvent composition, pH and extraction conditions led to limits of detection and quantification of melamine of 0.0081 and 0.027 μg mL(-1), respectively, with a linear range up to 10 μg mL(-1). Sample extracts fortified with melamine at three concentration levels produced an average recovery of 98±6%, which was in agreement with the results achieved with a reference HPLC-UV method. Different samples of kitchen plastic ware analyzed by the developed and optimized method showed melamine concentrations in the aqueous extract up to 17 µg mL(-1), which corresponded to 86.0 mg kg(-1) in these utensils. The results obtained indicate that the use of kitchen plastic ware made of melamine can contaminate food with this compound after heating in a microwave oven.

Freeze-Drying Changes the Structure and Digestibility of B-Polymorphic Starches

Starch granules both isolated from plants and used in foods or other products have typically been dried. Common food laboratory and industry practices include oven (heat), freeze, and ethanol (solvent-exchange) drying. Starch granules isolated from maize (A-type polymorph) and potato (B-type polymorph) were used to understand the effects of different dehydration methods on starch structure and in vitro digestion kinetics. Oven and ethanol drying do not significantly affect the digestion properties of starches compared with their counterparts that have never been dried. However, freeze-drying results in a significant increase in the digestion rate of potato starch but not maize starch. The structural and conformational changes of starch granules after drying were investigated at various length scales using scanning electron microscopy, confocal laser scanning microscopy, X-ray diffraction, FTIR spectroscopy, and NMR spectroscopy. Freeze-drying not only disrupts the surface morphology of potato starch granules (B-type polymorph), but also degrades both short- and long-range molecular order of the amylopectin, each of which can cause an increase in the digestion rate. In contrast to A-polymorphic starches, B-polymorphic starches are more disrupted by freeze-drying, with reductions of both short- and long-range molecular order. We propose that the low temperatures involved in freeze-drying compared with oven drying result in greater chain rigidity and lead to structural disorganization during water removal at both nanometer and micrometer length scales in B-type polymorphic starch granules, because of the different distribution of water within crystallites and the lack of pores and channels compared with A-type polymorphic starch granules.

Sputtering of metals at ion-electron irradiation

It has been found that, in contrast to the commonly accepted opinion, simultaneous irradiation by 15-keV Ar+ ions and 2.5-keV electrons at temperatures above 0.5T m (T m is the melting temperature) induces much larger sputtering of metallic copper, nickel, and steel than irradiation only by Ar+ ions. The effect increases with the temperature. At T = 0.7T m, the sputtering coefficients in the case of ion-electron irradiation are more than twice as large as the sputtering coefficients in the case of irradiation by Ar+ ions. The experiments on the sublimation of copper show that the sublimation rate in the case of the heating of a sample by an electron beam is higher than that in the case of heating in an electric vacuum oven. The revealed effects are explained by the electron-induced excitation of adatoms (atoms stuck over the surface, which appear owing to ion bombardment). Excited adatoms have a smaller binding energy with the surface and are sputtered more easily.

Determination of methylmercury in marine biota samples: Method validation

Regulatory authorities are expected to measure concentration of contaminants in foodstuffs, but the simple determination of total amount cannot be sufficient for fully judging its impact on the human health. In particular, the methylation of metals generally increases their toxicity; therefore validated analytical methods producing reliable results for the assessment of methylated species are highly needed. Nowadays, there is no legal limit for methylmercury (MeHg) in food matrices. Hence, no standardized method for the determination of MeHg exists within the international jurisdiction. Contemplating the possibility of a future legislative limit, a method for low level determination of MeHg in marine biota matrixes, based on aqueous-phase ethylation followed by purge and trap and gas chromatography (GC) coupled to pyrolysis-atomic fluorescence spectrometry (Py-AFS) detection, has been developed and validated. Five different extraction procedures, namely acid and alkaline leaching assisted by microwave and conventional oven heating, as well as enzymatic digestion, were evaluated in terms of their efficiency to extract MeHg from Scallop soft tissue IAEA-452 Certified Reference Material. Alkaline extraction with 25% (w/w) KOH in methanol, microwave-assisted extraction (MAE) with 5M HCl and enzymatic digestion with protease XIV yielded the highest extraction recoveries. Standard addition or the introduction of a dilution step were successfully applied to overcome the matrix effects observed when microwave-assisted extraction using 25% (w/w) KOH in methanol or 25% (w/v) aqueous TMAH were used. ISO 17025 and Eurachem guidelines were followed to perform the validation of the methodology. Accordingly, blanks, selectivity, calibration curve, linearity (0.9995), working range (1-800pg), recovery (97%), precision, traceability, limit of detection (0.45pg), limit of quantification (0.85pg) and expanded uncertainty (15.86%, k=2) were assessed with Fish protein Dorm-3 Certified Reference Material. The major contributions to the expanded uncertainty, i.e. 86.1%, arose from the uncertainty associated with recovery, followed by the contribution from fluorescence signal. Additional validation of the methodology developed was effectuated by the comparison with the values reported for MeHg in the IAEA-452 inter-laboratory comparison exercise.

Two appealing alternatives for MOFs synthesis: solvent-free oven heating vs. microwave heating

Four types of benchmark MOFs are prepared by using solvent-free reactions under oven heating or minute-scale fast microwave heating, obtaining competitive yields and high adsorption performance when compared to conventional synthesis methods.

Hipotermia Acidental: Implicações para os cuidados de enfermagem no transoperatório

Objective: to describe the nursing interventions in surgical anesthetic procedures in the intraoperative period for the prevention and/or treatment of accidental hypothermia. Method: a descriptive research with quantitative methodological approach carried out in a surgery center of a public hospital in Fortaleza, Ceara state. The study sample comprises 12 nursing interventions conducted by the nurses, auxiliaries, or technicians who assisted patients undergoing surgery in 120 surgical procedures, between January and March 2011. Results: it was possible to verify that the temperatures of the admission room, heating oven, storage container for heated fluids, and operating room were not in compliance with the recommended standards. Conclusion: results showed that there is a need to implement effective interventions to prevent hypothermia and that the nursing staff plays an important role in this context, because patient safety and decreased complications owing to surgical anesthetic procedures are nursing care goals.

Effects of Heat Treatments on the Milling, Physicochemical, and Cooking Properties of Two Long‐Grain Rice Cultivars During Storage

ABSTRACTDuring storage, the milling, physicochemical properties, and eating quality of rice change, which is generally termed “aging.” Aged rice is preferred by processors because of better processing characteristics, and therefore there are attempts to develop accelerated aging processes. In this study, the effects of various heat treatments and their influences on the milling, physicochemical, and cooking properties of two long‐grain rice cultivars during storage were investigated with a randomized complete block design with an 8 × 5 × 2 full‐factorial treatment design. Two long‐grain rice cultivars, Wells and XP723, were treated with eight different heat treatments, including two levels of UV irradiation, two levels of autoclaving, three levels of convection oven heating, and one control, and then stored for 180 days at room temperature. The heat treatments significantly influenced all properties, including head rice yield (HRY), surface lipid content, peak gelatinization temperature, pasting properties, and cooked rice texture. All properties except HRY exhibited a significant two‐way interaction of cultivar and heat treatment. The severe autoclaving treatment resulted in rice of significantly different protein compositions when compared with the control. Storage impacted all properties except HRY and peak gelatinization temperature. Autoclaving (particularly severe autoclaving) produced samples with more distinct characteristics for most properties. Cooked rice hardness and stickiness exhibited not only significant main effects but also significant two‐ and three‐factor interactions.

Advanced Modelling and Optimization of Infared Oven in Injection Stretch Blow-moulding for Energy Saving

In the production process of polyethylene terephthalate (PET) bottles, the initial temperature of preforms plays a central role on the final thickness, intensity and other structural properties of the bottles. Also, the difference between inside and outside temperature profiles could make a significant impact on the final product quality. The preforms are preheated by infrared heating oven system which is often an open loop system and relies heavily on trial and error approach to adjust the lamp power settings. In this paper, a radial basis function (RBF) neural network model, optimized by a two-stage selection (TSS) algorithm combined with particle swarm optimization (PSO), is developed to model the nonlinear relations between the lamp power settings and the output temperature profile of PET bottles. Then an improved PSO method for lamp setting adjustment using the above model is presented. Simulation results based on experimental data confirm the effectiveness of the modelling and optimization method.

Recent Developments in the Microwave Processing of Ceramics

Highly absorbing ceramics can be heated in a standard multimode microwave oven. However, most of the microwave energy is dissipated in their ceramic surfaces and heat is transported slowly throughout the sample volume by the usual thermal conduction mechanisms. As with conventional methods, this process leads to non-uniform heating. In contrast, ceramics that are fairly transparent to microwave energy are difficult to heat in standard microwave ovens. When they can be heated, reverse temperature gradients often develop. Reverse temperature gradients can be beneficial in some processes, e.g., combustion synthesis, chemical vapor infiltration (CVI) and binder burnout, but in most ceramic processes, temperature gradients are undesirable. These characteristics have presumably been partially responsible for the ceramic industry's failure to examine microwave processing more closely.The ability of dipoles to respond to the oscillating electric field and their subsequent inability to keep up with rapid reversals in the field result in dielectric losses that are manifested as heat. While some of the mechanisms by which electromagnetic radiation interacts with ceramics are well known, interaction mechanisms in the microwave frequency range are less well understood. Since several mechanisms, including electrical conductivity, can operate simultaneously, the total energy dissipation and heat generation depends on the effective loss factor. The effective loss factor (e″eff) is described bywhere e′ is the dielectric constant and is a measure of the extent of polarization, and tan δ indicates how responsive the dipoles are to the oscillating field.

Analysis and Observations of Current Density Sensitivity and Thermally Activated Mechanical Behavior in Electrically-Assisted Deformation

The flow of electric current through a metal during deformation has been observed to reduce its flow stress and increase its ductility. This observation has motivated the development of advanced “electrically-assisted” metal forming processes that utilize electric current to assist in the forming of high-strength and difficult-to-form materials, such as titanium and magnesium alloys. This method of heating provides attractive benefits such as rapid heating times, increased energy efficiency due to its localized nature, as well as the ability to heat the workpiece in the forming machine thus eliminating the transfer process between oven heating and forming. In this paper, a generalized method is proposed to relate applied electric current density to thermally activated mechanical behavior to better understand and improve the processing of metals during electrically-assisted deformation. A comparison is made of engineering metals studied experimentally as well as in the literature, and it is shown that the method provides insight into what some researchers have observed as the occurrence or absence of a “current density threshold” in certain materials. A new material parameter, “current density sensitivity,” is introduced in order to provide a metric for the relative influence of current density on a material's thermally activated plastic flow stress. As a result, the electric current necessary to induce thermal softening in a material can be estimated in order to effectively parameterize a wide range of advanced electrically-assisted forming processes. Thermally induced changes in material microstructure are observed and discussed with respect to the underlying deformation mechanisms present during electrically-assisted deformation. Finally, a strong correlation between thermally activated mechanical behavior and elastic springback elimination during sheet bending is demonstrated.

Curing of a Bisphenol E Based Cyanate Ester Using Magnetic Nanoparticles as an Internal Heat Source through Induction Heating

We report on the control of cyclotrimerization forming a polycyanurate polymer using magnetic iron oxide nanoparticles in an alternating-current (ac) field as an internal heat source, starting from a commercially available monomer. Magnetic nanoparticles were dispersed in the monomer and catalytic system using sonication, and the mixture was subjected to an alternating magnetic field, causing the magnetic nanoparticles to dissipate the energy of the magnetic field in the form of heat. Internal heating of the particle/monomer/catalyst system was sufficient to start and sustain the polymerization reaction, producing a cyanate ester network with conversion that compared favorably to polymerization through heating in a conventional laboratory oven. The two heating methods gave similar differential scanning calorimetry temperature profiles, conversion rates, and glass transition temperatures when using the same temperature profile. The ability of magnetic nanoparticles in an ac field to drive the curing reaction should allow for other reactions forming high-temperature thermosetting polymers and for innovative ways to process such polymers.

Surface reconstruction and hemocompatibility improvement of a phosphorylcholine end‐capped poly(butylene succinate) coating

Control over cell-material surface interactions is the key to many new and improved biomedical devices. In this study, we present a simple yet effective surface modification method that allows for the surface reconstruction and formation of cell outer membrane mimetic structure on coatings that have significantly increased hemocompatibility. To achieve this, a phosphorylcholine end-capped poly(butylene succinate) (PBS-PC) was synthesized and dip-coated on coverslips. The surface structure of the amphiphilic PBS-PC film was reconstructed by heating in a vacuum oven to obtain the less hydrophilic surface and by immersing in hot water to obtain the more hydrophilic surface. Significant changes in the surface element concentration were observed by X-ray photoelectron spectroscopy analysis and changes in surface wettability were measured by sensitive dynamic contact angle technique. Scanning electron microscope images showed different morphologies of the reconstructed surfaces. Interestingly, the reconstruction between the less hydrophilic and more hydrophilic surfaces is reversible. More importantly, both the reconstructed surfaces are stable in room condition for more than 6 months, and both the surfaces show significant improvement in hemocompatibility as revealed by protein adsorption and platelet adhesion measurements. This reversible surface reconstruction strategy and the interesting results may be significant for fabricating stable and hemocompatible surfaces on differently shaped biomedical devices.

Smoking Methods and Their Effects on Nutritional Value of African Catfish (Clarias gariepinus)

African catfish (Clarias gariepinus) is very popular with fish farmers and consumers, and commands a very high commercial value in Nigeria markets. The fresh fish sample collected from the fish farmer was smoked in a smoking kiln using sawdust, rice bran and melon husk while electric oven was used as the control. In the study proximate, mineral and amino acid compositions of the smoked fish samples were evaluated using standard analytical techniques. The crude protein content of the smoked fish samples ranged from 15.18% in sawdust heat treatment to 63.23% in electric oven heat source with CV% of 10.68 while crude fat range values were 9.47 - 16.44% (CV% = 18.80). The most highly concen- trated mineral was sodium (7.00 - 9.95 mg/100g sample) and strictly followed by magnesium (5.45 - 7.45 mg/100g sam- ple). Lead and cadmium were not at the detectable range of AAS. The total essential amino acid (TEAA) with histidine in the smoked fish samples ranged from 40.25 g/100g crude protein in rice bran to 70.09 g/100g protein in sawdust heat sources while lysine had the highest concentrations (7.02 - 7.78 g/100g protein). The calculated isoelectric point (pI) and predicted protein efficiency ratio (P-PER) were (4.99 - 6.91) and (2.30 - 2.52), respectively while first limiting amino acid (LAA) was isoleucine for electric oven and sawdust heat sources, and valine for melon husk and rice bran smoking. The number of essential amino acids where supplementation may be required in the smoked fish samples using four dif- ferent heat sources was three each. Generally, all the fish samples were found to be good sources of essential minerals and amino acids.

Composite Fuzzy Control Method for Temperature in Intelligent Moisture Analyzer

Temperature control system of infrared heating oven in moisture analyzer is characteristic of nonlinear, time-varying and time-lag. A composite fuzzy control (CFC) method is proposed, which combines improved Bang-Bang control with two-stage intelligent fuzzy control. The control algorithm is implemented by MSP430F5438. When the temperature error e between the desired temperature and actual temperature in heating oven is larger than threshold value, the improved Bang-Bang controller is employed in rapidly reducing the error; to decrease the system overshoot, the basic fuzzy controller is used; to reduce the steady-state error of basic fuzzy controller, the auxiliary fuzzy controller is applied. The steady-state error of improved fuzzy controller for oven temperature is less than 0.5°C, which is better than the Chinese National Standards for moisture content measurement.

Design of Microwave-Oven Hybrid Heat Treatment System Based on LabVIEW

The heat treatment technology is a weak link in engineering technology in china. For the traditional microwave heat treatment system, the microwave electric field inside the oven can not be well-distributed. In case of the traditional oven heat treatment system, however, the materials dried process is very long. In this paper, we introduce a microwave-oven hybrid heat treatment system related to industrial production line, the proposed with both advantages of high efficiency of microwave and good thermal distribution of the oven, which can be applied for the determination of degree in heat treatment process according to the concentration of the produced gases. Based on the computer and LabVIEW, the control system can control the whole process of heat treatment directly and accurately in real-time.