High Microwave Power Levels Research Articles

Effects of microwave drying on physicochemical characteristics, microstructure, and antioxidant properties of propolis extract.

The heat sensitivity of phenolics and flavonoids leads to considerable losses of these compounds during conventional drying. Microwave drying has the advantage of shorter drying time and rigorous process control, minimizing damage to heat-sensitive compounds. Microwave drying kinetics and the impacts of microwave drying on physicochemical characteristics, morphological structure, antioxidant properties, total phenolics, and flavonoid content of propolis extract were investigated. Increasing the microwave power output from 180 to 900 W resulted in a 67% reduction in drying time. Morphological changes were more noticeable at higher microwave power levels as shown in scanning electron microscopy images. Water activity values of microwave dried propolis extracts were below 0.4, which satisfied the requirement for shelf-stable dry products. The solubility of microwave dried propolis extract increased with increasing microwave power level, and the highest solubility was achieved for the propolis extract microwave dried at 900 W. Microwave dried propolis extracts exhibited lower total phenolic content levels than fresh propolis extract. The microwave power level did not affect the total flavonoid content but it affected 2,2-diphenyl-1-picrylhydrazyl (DPPH) free-radical scavenging activity of microwave dried propolis extracts. The DPPH free-radical scavenging activity closest to the fresh propolis extract was obtained for the microwave dried propolis extract at 900 W. This also showed the highest 6-hydroxy-2,5,7,8-tetramethyl-2-carboxylic acid (Trolox) equivalent antioxidant capacity. Microwave drying of propolis extract at 900 W was found to be the most efficient drying condition because it yielded the shortest drying time, the highest effective moisture diffusivity, and phenolic and flavonoid content levels that were very similar to those in fresh propolis extract. © 2023 Society of Chemical Industry.

Experimental and numerical analysis of thermodynamic performance of microwave dryer of onion

AbstractThe present study was designed for the experimental and modeling investigations on thermodynamic analysis of drying onion slices using four microwave power levels (100, 350, 500, and 750 W) and the four samples thicknesses (2.5, 5, 7.5, and 10 mm). A multilayer feedforward artificial neural network was employed in order to predict energy and exergy performance of the dryer and the prediction success were compared using three evaluation criteria. The average values for energy efficiency and specific energy loss ranged from 13.52% to 37.94% and from 1.35 to 7.43 MJ/kgwater, respectively. Findings showed that the exergy efficiency changed from 11.79% to 30.84%. In addition, the statistical analysis revealed that higher microwave power levels and the thinner samples significantly (p < .05) enhanced both the energy and exergy efficiencies. The obtained results for exergy improvement potential (accounted for 37.83%–69.41% from the total exergy inlet) indicated that the drying process has good potential for exergy performance improvement. Based on the modeling outcomes, the energy efficiency was well predicted by an artificial neural network with a topology of 3–18–18–1 and LM training algorithm and threshold function of Tan–Tan–Lin. However, the best topology for the exergy efficiency prediction had 3–20–16–1 structure, LM training algorithm and Log–Log–Lin transfer function (R2 of .94).Practical ApplicationsIn this study, onion slices were dried in a domestic microwave oven and the influence of the power level and thickness of the samples on energy and exergy parameters was investigated. In addition to experimental evaluation, the multi‐layer feed‐forward neural network can be used to model and predict changes in energy efficiency and exergy during the process.

Microwave assisted drying and extraction technique; kinetic modelling, energy consumption and influence on antioxidant compounds of fenugreek leaves

Fenugreek leaves contains bioactive compounds, which are helpful in maintaining human health. These compounds are adversely affected in conventional drying methods. Therefore, this study was carried out to retain maximum amount of these components through microwave-assisted drying and extraction technique. The technique was optimized for simultaneous drying and extraction process for fenugreek leaves. The drying rate and drying time were influenced by the level of microwave power; time was reduced from 21 to 5 minutes, when microwave power was changed from 30 to 100 W. Unlikely, the drying rate increased from 1.79 to 4.56 ± 0.05 g/(100 g.min) with the change in power (30 to 100 W). Moreover, moisture ratio analysis determined that two term model was the best to demonstrate the fitness with experimental values. The energy consumption was lowest for 100W compared to other powers. Furthermore, comparison between microwave-based extraction and methanol-extraction indicated that the antioxidant activity was better preserved compared to conventional ones even at higher microwave power levels.

Inactivation of Salmonella spp., Escherichia coli O157:H7 and Listeria monocytogenes in Tahini by Microwave Heating.

Tahini (sesame paste) is a traditional food. Numerous foodborne outbreaks have been associated with it. This study aimed to (i) explore the efficiency of 2450 MHz microwave heating at 220, 330, 440, 550, and 660 W on the inactivation of Salmonella spp, Escherichia coli O157:H7, and Listeria monocytogenes in tahini; (ii) determine the impact of desiccation and starvation stresses on pathogen survival; (iii) assess the impact of microwave heating on the physicochemical characteristics of tahini. The inoculated microorganisms in tahini were reduced with higher microwave power levels (p < 0.05) and longer exposure times. The D-values of unstressed Salmonella spp., Escherichia coli O157:H7, and L. monocytogenes ranged from 6.18 to 0.50 min, 6.08 to 0.50 min, and 4.69 to 0.48 min, respectively, at power levels of 220 to 660 W, with z-values of 410, 440, and 460 W, respectively. Generally, desiccation and starvation stress levels prior to heating increased microbial resistance to heat treatment. Microwave heating did not affect acid, peroxide, p-anisidine, or color values of tahini up to 90 °C. These findings reveal microwave heating as a potential method for lowering the risk of Salmonella spp., E. coli O157:H7 and L. monocytogenes in tahini with no compromise on quality.

Paramagnetic Centers of Mineral Component in Annealed Bone Tissue

The mineral components of powdered samples of cortical dense bone tissue of domestic animals (pig and cow) were studied by electron paramagnetic resonance (EPR). Bone tissue was heated in a temperature range 600-1000 ºС in an oven and then held for more than one year at room temperature. This was done to allow short-lived defects to decay and to let the mineral structures stabilize. In these heat-treated samples, within the limits of the sensitivity of the experiments, no EPR signals were detected, but after irradiation with X-rays, multicomponent EPR signals appeared. Spectra vary depending on the heating temperatures. Paramagnetic centers related to РО32–, NO42–, CO2–, CO33– and O– groups are observed. The g-factor of spectroscopic splitting and amplitude of ultrafine interaction of the indicated paramagnetic centers in the spectra were determined. Due to different relaxation behavior of the paramagnetic centers, and hence their saturation effects, the form of the total EPR signals significantly depends on the microwave power level at which the spectra are recorded. Therefore, EPR signals were recorded at high (5 mW) and low (0.13 mW) microwave power levels. The temperature dependency of EPR signal amplitude was determined for some paramagnetic centers in the range of 600-1000 ºС. The EPR signal properties of the heated bone samples and synthetic hydroxylapatites were compared. The spectra indicate that phosphates in bone tissue have a more complex structure than simple synthetic hydroxylapatite. The results of this work can be used to create synthetic analogs of bone tissue, to help in the manufacturing of implants that are used to treat bone tissue, and to study the processes related to the assimilation of mineralogic-based implants by living bone tissue.

Nonlinear Oscillations of Magnetization in a Tangentially Magnetized Ferromagnetic Film Resonator

Introduction. Resonators based on epitaxially grown single-crystal films of yttrium iron garnet are used in various applications of microwave electronics. It is known that with increasing of microwave power incident on a resonator, various nonlinear effects begin to manifest themselves. There are: bistability effect, nonlinear frequency shift, nonlinear damping, etc. By now, the listed nonlinear effects have been quite good studied experimentally. Previously, when describing oscillations of various dynamical systems, the nonlinear damping and the nonlinear frequency shift were usually considered separately. At the same time, it was known that, when studying nonlinear magnetization oscillations in ferromagnetic film resonators with an increase in oscillation amplitude, these effects could occur simultaneously. Aim. Development of a model of magnetization oscillations taking into account the nonlinear frequency shift and nonlinear damping, as well as its experimental justification for a ferromagnetic film resonator. Materials and methods. The development of the model was carried out by the method of slowly varying amplitudes. An experimental study was carried out with a ferromagnetic film resonator. For the measurements, we used Rohde & Schwarz ZVA 40 vector network analyzer. We measured the frequency dependence of the reflection coefficient of the microwave signal from the resonator. Results. A model of nonlinear magnetization oscillations was developed taking into account both a nonlinear frequency shift and a nonlinear attenuation. The resonance curves were experimentally measured at various levels of the microwave power incident on the resonator. It was shown that nonlinear damping limits the nonlinear frequency shift of the magnetization oscillations in a tangentially magnetized ferromagnetic film resonator. Conclusion. The developed model adequately describes behavior of the resonance curves of ferromagnetic film resonators at high microwave power levels. The nonlinear damping leads to broadening of the resonance curves, thereby increasing losses. This effect also increases the reflection coefficient of the microwave signal from the resonator.

A novel method for metals extraction from municipal solid waste using a microwave-assisted acid extraction

This paper investigated the development and evaluation of an extraction process for copper, chromium, cobalt, iron, manganese, zinc, lead, cadmium, barium, magnesium, and vanadium from municipal solid waste incineration ash (bottom and fly ashes) based on microwave-assisted acid extraction method. In this study, a novel conventional microwave-mediated technique was applied by using various acidic extracting agents, namely, hydrochloric acid, nitric acid, and phosphoric acid. Several experimental conditions and parameters were modified and optimized to determine the most effective conditions for maximizing metal extraction. The results were also compared with our preliminary research, which investigated the optimization of conventional heating for extracting the same metals. The current study concluded that the microwave-assisted acid extraction method was much more effective than conventional heating. The metals from the bottom ash were much easier to extract in contrast with the fly ash. For the bottom ash, 71 wt% of Co, 75.69 wt% of Cr, 56.19 wt% of Cd, 35.23 wt% of Ba, 30.2 wt% of Pb, and 5.41 wt% of Mn were effectively extracted using the protocol C (2 M HCl and 3 M H3PO4). 13.87 wt% of Al, 10.59 wt% of Cu, 7.2 wt% of Fe, 5.25 wt% of Mg were also extracted using the protocols D and E (3 M HNO3 and 3 M H2O2) from MSW-BA. On the other hand, for the fly ash, 2.27 wt% of Cu, 0.93 wt% of Fe, 2.32 wt% of Zn, 6.28 wt% of Cd, 1.98 wt% of Ba, 3.46 wt% of Mg and 4.7 wt% of V were extracted by using the protocol A (5 M HCl and 5 M HNO3). 1.48 wt% of Cr, 0.93 wt% of Fe, 1.19 wt% of Mn, and 1.18 wt% of Al were extracted using the protocol C (2 M HCl and 3 M H3PO4). It was also confirmed that higher microwave power levels had a positive effect on the metal extraction, and longer contact times had an adverse effect. When comparing the cost analyses for both methods, it was found that the microwave-assisted acid extraction was less expensive than the conventional heating. The present study offers a promising method, which is simple and cost-effective and presents a minimal environmental risk to extract metals from municipal solid waste incineration ash.

Shrinkage and rehydration characteristics of vacuum assisted microwave dried green bell pepper

AbstractGreen bell pepper was dried under vacuum assisted microwave (VAM) drying conditions. The effect of microwave power (100, 200, 300 W) and vacuum pressure (200, 400, 600 mmHg) were observed on shrinkage and rehydration characteristics of the sample. Shrinkage was modeled as a linear function of volume change of material and its moisture content. A model was proposed where apparent density could be evaluated as a function of product's moisture content. The sample volume in case of VAM drying shrunk by 59 to 78%, while in case of hot air drying, the shrinkage occurred up to 90%. At a given power level of 100 W, equilibrium rehydration values (Req) increased from 5.04 to 5.75 for samples dried at increasing vacuum pressure from 200 to 600 mmHg. Rehydration rate constant decreased correspondingly for samples dried at higher microwave power levels. Higher level of microwave power and vacuum pressure played significant (p &lt; 0.01) role in producing more porous (lesser shrunken) product leading to higher diffusion (and thus better rehydrated product) of water through it. Diffusion coefficient in rehydration was calculated using Fick's second law. The values of “k” and “R2” varied from 1 × 10−3 to 6.4 × 10−3 and 0.986 to 0.999, respectively.Practical applicationsShrinkage and rehydration characteristics of dried vegetables are of utmost importance when it comes to culinary preparations, premixes, convenient foods and retention of sensory qualities. The model proposed in the present study will be helpful in evaluating shrinkage as a function of apparent density and moisture content of dried green bell pepper. Several changes such as shape, size, structure, color, bulk density, porosity, and rehydration capacity are induced due to structural alteration in green bell pepper followed by drying. This information could help in safe commercial packaging of dried products. Further, dried green bell pepper must be rehydrated to be used in preparation of foods such as soups, pizzas, stews, casseroles, and many other recipes. Outcome of the current study can also be referred and implemented while accessing the rehydration characteristics of dried and shrunken vegetables.

Direct Thrust Measurements of an 8-GHz Microwave Electrothermal Thruster

Direct thrust measurements of an 8-GHz microwave electrothermal thruster were performed. Experimental work involved the redesign of the thruster cavity to minimize its weight and the construction of a vertical thrust stand. Thrust measurements were made using ammonia and simulated hydrazine (50% and 100% decomposed) as propellants. Testing was performed over a range of 100–250 W of microwave power input into the thruster. For all three propellants, the thrust increased with the increasing mass flow at higher microwave power levels able to sustain plasma at higher flow rates. Ammonia specific impulse increased with increasing cavity input power, reaching 264 s at 250 W. The 50% and 100% simulated decomposed hydrazine exhibited an initial increase in specific impulse with increasing power; however, further increases in power did not result in increased specific impulse. Higher levels of thrust and specific impulse at the same microwave input power were measured for the 100% decomposed simulated hydrazine compared to the 50% decomposed due to the absence of ammonia in the 100% decomposed hydrazine.

Effect of Microwave Frying on Acrylamide Formation in Potato Chips

The occurrence of acrylamide, a probable carcinogen and a neurotoxin, is currently a global issue. Therefore, the main objective of the present study was to determine the effects of microwave frying on acrylamide formation in potato chips. A simple method using high-performance liquid chromatography has been applied for determination of acrylamide in microwave-fried potato chips. The results showed that microwave frying could form more acrylamide at high microwave power level 800 W compared with low microwave power level 200 W. The highest level was 13230 ppb at 800 W for 120 s. Moreover, the acrylamide content was higher than the levels people might be exposed to in foods 1000 ppb. As a result of this study, it was concluded that microwave frying at high thermal process 180°C, 800 W, 120 s could form high level of acrylamide.

Analysis of dehydration kinetics, status of water and oil distribution of microwave-assisted vacuum frying potato chips combined with NMR and confocal laser scanning microscopy

In this study, the dehydration kinetics, status of water and oil distribution of microwave-assisted vacuum frying (MVF) potato chips were analyzed combining with NMR and confocal laser scanning microscopy (CLSM). Results showed that the MVF markedly increased the moisture evaporation kinetics and effective moisture diffusivity compared to vacuum frying (VF). The higher microwave power level (1000W) used achieved higher moisture evaporation rate and higher effective moisture diffusivity, The Logarithmic model exhibited the best fit for the obtained data of MR versus frying time in the MVF. The NMR analysis showed the free water in the samples firstly evaporate and the linkage between water and structure of materials becomes tighter with the frying time. The total oil content, surface and structural oil content were all significantly lower in MVF samples than that in VF samples. The CLSM analysis confirmed that less oil adhere to the surface and less oil trapped in the structure in MVF slices. The surface morphology showed that there were less ruptured and damaged cells in MVF samples and helped to explain the reduction of oil content.

Effect of microwave pre-treatment on physico-chemical properties of donut containing Persian gum and carrot pomace powder sources of dietary fiber

پژوهش حاضر با هدف بررسی اثر پیش فرآیند مایکروویو بر محتوی رطوبت و چربی، حجم مخصوص، ویژگی های بافتی (سفتی و ارتجاعیت) و خصوصیات ساختار مغز (تعداد سلول های گاز و تخلخل) دونات غنی شده با منابع مختلف فیبر خوراکی (حاوی صمغ فارسی و پودر تفاله هویج) انجام شد. همچنین شرایط فرآیند با استفاده از روش سطح پاسخ و یک طرح باکس-بنکن با 3 فاکتور بهینه‌سازی شد. فاکتورهای مورد استفاده در این پژوهش شامل توان مایکروویو (900-300 وات)، مدت زمان پیش فرآیند مایکروویو (90-30 ثانیه) و مدت زمان سرخ کردن (130-70 ثانیه) بود. نتایج نشان داد با افزایش سطح هر یک از فاکتورها، محتوی رطوبت کاهش ولی محتوی چربی، سفتی مغز و ارتجاعیت، تعداد سلول ها و تخلخل دونات حاوی فیبر خوراکی افزایش می یابد. شرایط بهینه فرآیند شامل پیش فرآیند در توان 400 وات به مدت 60 ثانیه و سپس سرخ کردن به مدت 108 ثانیه بود. در این شرایط، محتوی چربی دونات سرخ شده کمتر از دونات های سرخ شده در شرایط معمول بود.

Microwave torrefaction of sewage sludge and leucaena

Abstract This study attempted to investigate and compare sewage sludge and leucaena torrefaction using a single-mode microwave oven. To discuss reactivity, product characteristics, and energy recovery, microwave torrefaction of the two feedstocks was carried out at various microwave power levels. Besides, thermal properties of raw feedstocks and torrefied products were observed by the deconvolution of derivative thermogravimetric profiles. The volatile matter contents of the two biomass feedstocks were substantially reduced at relatively low microwave power levels. Because of high heating value and fuel ratio as well as low atomic H/C and O/C ratios, the biochar could replace coal. Compared with sewage sludge, microwave torrefaction of leucaena produced thermally stable biochar at lower microwave power levels, which means that the microwave heating performance of leucaena is better. Compared with conventional torrefaction, mass and energy yields of microwave torrefaction were lower, which could be attributable to the more severe reaction accomplished by microwave heating. The atomic H/C and O/C ratios of leucaena biochar were close to those of anthracite, so combustion or gasification of the biochar could form less smoke. After microwave torrefaction at relatively high microwave power levels, a high HHV (dry ash-free basis) of sewage sludge biochar was found.

Non-resonant Microwave Absorption in Nano Nickel Added YBCO Powders: Observation of Multiple Phase Reversals

We report on the non-resonant microwave absorption in the system of a nominal 2 wt % nano nickel particles added into YBCO powders (Ni–YBCO). With this dilute mixture of nano nickel particles, one is expected to have groups of normal Josephson junctions (JJs) and π JJs due to YBCO–nickel–YBCO interparticle weak links and as nickel is ferromagnetic. We experimentally show, for the first time multiple phase reversals in the non-resonant microwave absorption (NRMA) spectra from Ni–YBCO possibly due to the formation of π JJs. We also showed that these multiple phase reversals then depend on microwave power and temperature. We argue that microwave power induced coherence among some groups of JJs and breaking of some of the weaker JJs can then lead to the disappearance of multiple phase reversals at higher microwave power levels. Further, we also reported a role of pair breaking effects that shall give a linear field dependence of the derivative microwave absorption signal, essentially which is the NRMA signal. This pair breaking effect dominates at closer temperatures to T c which is expected thermodynamically.

Co-torrefaction of sewage sludge and leucaena by using microwave heating

Microwave co-torrefaction of sewage sludge and leucaena can be a workable technique, because it not only produces biofuels but also solves the problems in waste treatment. When the sewage sludge blending ratio was 25–50 wt% and the microwave power level was 100 W, a synergistic effect was found to influence the mass and energy yields as well as product properties. The relatively small amount of sewage sludge could play a role as a catalyst, since the synergistic effect was hard to be identified at higher sewage sludge blending ratios. Besides, it was difficult to find out the synergistic effect at higher microwave power levels. This could be attributable to the effect of microwave heating which increases with its power level. The elemental compositions of biochar were close to those of anthracite and bituminous coal. The energy return on investment (EROI) of microwave co-torrefaction of the 25/75 (w/w) sewage sludge/leucaena blend at a microwave power level of 100 W in a processing time of 30 min can be approximately 10.1 or 4.7, when the gaseous and liquid products are utilized or not. Therefore, the technique should be energetically and economically feasible.

Microwave drying characteristics of microalgae (Chlorella vulgaris) for biofuel production

Algal biofuels serve as a promising alternative energy source for liquid fuels. However, one of the bottlenecks in the conversion of microalgae to biofuels is the drying process. A moisture content of at most 10 % is desired for algal biomass prior to oil extraction to maximise biofuel yield. Conventional means of drying results to longer drying time and uneven drying of algal biomass. This study investigated the drying characteristics of microwave for microalgae (Chlorella vulgaris). Three microwave intensity levels (300, 600, and 900 W) were considered to dry 10, 20, and 30 of algal mass. Page model gave a better fit on the moisture ratio with time of microwave drying than the exponential model. Furthermore, the specific energy requirement was computed, and a relationship was found between moisture ratio with power and mass. Fourier transform infrared spectroscopy results showed significant reduction of infrared signal intensities of the functional groups present in the algae after drying at higher microwave power level. It was concluded that the 20 W/g microwave drying setting gave a lower specific energy requirement with good quality of remaining high lipid content qualitatively. Furthermore, it was recommended to use gas chromatography mass spectroscopy to further quantify the algal lipids and other functional groups.

Microwave pyrolysis of lignocellulosic biomass: Heating performance and reaction kinetics

Lignocellulosic biomass is an abundant renewable resource and can be efficiently converted into bioenergy and green materials by using microwave pyrolysis. In this study, microwave pyrolysis of seven biomass feedstocks (corn stover, rice straw, rice husk, sugarcane bagasse, sugarcane peel, coffee grounds, and bamboo) was studied. The maximum temperature of microwave pyrolysis was highly correlated with the combustible content of the feedstocks. The influence of microwave power level on both maximum temperature and heating rate was substantial. Either maximum temperature or heating rate had a linear relationship with microwave power level. However, there was a breakpoint at a power level of 250 W. Compared with conventional pyrolysis, microwave pyrolysis was faster and needed less input energy. Microwave pyrolysis provided higher weight losses than conventional pyrolysis, and this difference was more substantial at lower temperatures. Kinetic parameters of microwave pyrolysis at lower and higher microwave power levels were different. Reaction rates at higher microwave power levels can be higher than those at lower power levels by approximately one order of magnitude. Compared with conventional pyrolysis, the rate constant of microwave pyrolysis was much higher, and its activation energy and pre-exponential factor were much lower.

Microwave Thermolysis and Lipid Recovery from Dried Microalgae Powder for Biodiesel Production

AbstractThird‐generation microalgae‐derived biodiesel has become increasingly important in recent years because of the depletion of fossil fuels and to reduce global dependence on oil from crop sources that may use or displace agricultural land for food crops. This work investigates the microwave treatment of dried microalgae powder to improve the oil extraction efficacy. This study has revealed that the lipid yield from Nannochloropsis oculata dried powder with microwave thermal treatment at 50 % microwave power (443 W) was greater than that with 100 % power (943 W). However, the efficacy of the cell wall destruction after 5 min microwave thermal treatment at full power was higher (70.0±2.30 %) than that at 50 % power (46.0±2.05 %). The greatest lipid yield at 943 W was achieved with 1 min treatment, 0.093±0.001 g g−1 of dry algae weight, with 17.3±1.19 % cell lysis at 42.2 °C. Initially, the lipid content yield increased from 0.082±0.002 to 0.093±0.001 g g−1 dry algae weight compared to the control sample (with no treatment applied). With the increase in temperature, the lipid yield was reduced because of oxidation at elevated temperatures. With the reduced power setting (443 W), the highest lipid yield of 0.149±0.003 g g−1 of dry algae weight was achieved after 5 min of treatment, with 46.0±2.05 % cell lysis at 58.5 °C. Statistically, the treatment time and temperature are correlated strongly to the extracted lipid yield. The kinetic study showed that the rate constant for lipid extraction with microwave pre‐treatment was higher at 443 W compared to the control sample and the higher microwave power level. The extracted lipid was analysed and found to have physical and chemical properties that were comparable to those of vegetable seed oils and they were suitable for use as a feedstock to produce biodiesel.

Inhibitory effect of microwaved thinned nectarine extracts on polyphenol oxidase activity

By-products from agricultural practices or from the fruit processing industry are a source of bioactive compounds that could be used in the food industry. Such by-products include thinned fruits, which are expected to contain high quantities of interesting compounds. One possible application of this fruits is the prevention of the enzymatic browning suffered by fruits and vegetables after minimal processing. The aim of this study is to determine the in vitro and in vivo activity of microwaved extracts obtained from thinned nectarines. It has been observed that in vitro the extracts obtained after the application of high microwave power levels (500, 1000 and 1500W) are mixed type inhibitors of polyphenoloxidase enzyme, showing an irreversible inactivation. This inhibition could be attributed to the Maillard reaction products formed during the microwave treatment. In vivo, a solution of 2% of the extract obtained at 1500W inhibited the enzymatic browning in minimally processed peaches for 8days of storage.

Enhanced inverse spin Hall contribution at high microwave power levels in La0.67Sr0.33MnO3/SrRuO3 epitaxial bilayers

We have investigated microwave power dependence of dc voltage generated upon ferromagnetic resonance in a La0.67Sr0.33MnO3/SrRuO3 epitaxial bilayer film at room temperature. With increasing microwave power above ∼75 mW, the magnitude of the voltage signal decreases as the sample temperature approaches the Curie temperature of La0.67Sr0.33MnO3 due to heating effects. By analyzing the dependence of the voltage signal on the direction of the magnetic field, we show that with increasing microwave power the contribution from the inverse spin Hall effect becomes more dominant than that from the anisotropic magnetoresistance effect.