Combination Of Microwave Heating Research Articles

TECHNOLOGICAL ASPECTS OF MICROWAVE HEATING EQUIPMENT IN THE FOOD INDUSTRY

The article describes the features of the interaction of microwave energy with food raw materials and food products and conducts an analytical review of the application of microwave processing for various technological processes in the food industry and hotel and restaurant business. The paper examines the peculiarities of the interaction of microwave energy with food raw materials and food products and gives an overview of the application of microwave processing for various technological processes in the food industry and the hotel and restaurant business. Despite the number of scientific works devoted to the topic of technological equipment, in particular, microwave heating, in Ukraine this is an insufficiently illuminated topic that requires research, taking into account the current conditions in the national economy. To create more rational technological processes, a combination of microwave heating with other energy carriers is used: steam, hot air, infrared heating, heated fat, vacuum, ultrasound. Heat treatment of food products in the cooking mode is divided into two stages: heating to a set temperature and maintaining this temperature until complete culinary readiness. The stepwise microwave heating method is also used, which ensures a high heating rate and avoids uneven heating of individual areas of the processed products. In this way, the possibility of temperature redistribution is ensured through the thermal conductivity of the material during its thermostating. One of the features of microwave processing is the possibility of rapid and relatively uniform heating of the product throughout the entire volume, which by its nature depends not so much on the thermophysical characteristics of the heated object, but on the presence of moisture in it and the nature of its distribution by volume. The ability of dielectric heating is effectively used in the food industry when defrosting products. Defrosting in the microwave field allows you to speed up the process tenfold and to a large extent preserve the quality of food products. Good results are given by combined methods of defrosting microwave heating with ultrasound, as well as with the method of blowing the product with cold air. The use of microwave heating with other physical methods and energy carriers makes it possible to intensify technological processes, reduce the cost of finished products, as well as increase the nutritional and biological value of raw materials, semi-finished products and finished products

Reduction of red blood spots in cooked marinated chicken breast meat by combined microwave heating and steaming

One of the defects commonly found in cooked marinated chicken breast products is a red blood spot (RBS), which is caused by undercooked blood in vessels. This problem was alleviated by microwave (MW) pre-heating for 6 to 7 min, followed by steaming. RBS formation decreased when samples were heated to a core temperature of 80°C and were completely eliminated at a core temperature of 82°C and 85°C when a MW pre-heating step was applied for 7 min. Based on synchrotron-based Fourier transform infrared spectroscopy (SR-FTIR), blood remaining in the blood vessel had a lower α-helical content when samples were cooked by the combination of MW heating and steaming as compared with those prepared by steaming alone (P < 0.05). MW pre-heating decreased cooking time by 28 to 48% as compared with steaming alone. Heating regimes had no effect on cooking loss, pH, water-holding capacity, and shear force. MW pre-heating for 7 min followed by steaming to a core temperature of 82°C appeared to be an effective heating regime to reduce the occurrence of RBS, with acceptable cooking loss.

Cooking and pasteurizing evaluation of barramundi (Lates calcarifer) meats subjected to an emerging microwave-assisted induction heating (MAIH) technology

Microwave-assisted induction heating (MAIH) is a complex heating process characterized by rapid and uniform heating based on a combination of microwave heating (power: 1000 W; frequency: 2450 MHz) applied from above and electromagnetic induction heating (power: 1500 W) applied from below. In this study, we assessed the utility of MAIH in processing the flesh of barramundi (Lates calcarifer), an important aquaculture species in Asian countries. To determine the effects of different heating conditions on the microbial contamination and physicochemical qualities of barramundi meat, fresh barramundi meats (100 g) were sealed in heat-resistant crystallized polyethylene terephthalate containers containing 150 mL of saline solution, and were subsequently heated in MAIH to 90 °C or 70 °C and held to different time. The results revealed that in response to an increase in the duration of heating, there were reductions in the aerobic plate count, psychrotrophic bacteria count, hydrogen sulphide-producing bacteria count, and coliform count, along with lower contents of total volatile basic nitrogen, in treated samples. Conversely, with a prolongation of the time exposed to heat, we detected increases in the L* (lightness),W (whiteness), ΔE(colour difference), and texture (hardness and chewiness) of fish meat, whereas there was a reduction of a* (redness). When the samples were heated for at least 110 s to 90 °C or for at least 130 s to 70 °C, the barramundi meats obtained appeared to be fully cooked with microbial counts below the limits of detection. In addition, under both heating conditions, thermal imaging revealed a uniform distribution of temperature within treated samples. Furthermore, monitoring of temperature profiles at central points in fish samples revealed that maximum temperatures of 97 °C and 79 °C were reached in response to MAIH processing at 90 °C for 110 s and 70 °C for 130 s, respectively. Thus, on the basis of the quality considerations of appearance, microbial count, and texture, the recommended optimal heating conditions for barramundi meats produced using MAIH are 90 °C for 110 s and 70 °C for 130 s. Industrial relevanceThe MAIH equipment is a novel thermal processing technology and allows food to be heated and pasteurized simultaneously after the package is sealed, eliminates issues of secondary contamination due to the need for subsequent packaging, and extends the shelf life. MAIH technology, therefore, serves as a viable future alternative for thermal processing of manufacturing refrigerated ready-to-eat seafood.

Combination of microwave heating and transglutaminase cross-linking enhances the stability of limonene emulsion carried by whey protein isolate

In this study, we examined the effect of transglutaminase (TG) cross-linking time (0 h, 2 h, 4 h, 8 h, and 12 h) on the stability of limonene emulsion loaded by microwave-heated WPI (MWPI). Size exclusion chromatography results showed that molecular weight of TG-treated MWPI and WPI was enhanced with the increase in TG cross-linking time (0–12 h). Microwave and TG cross-linking decreased particle size (7.55%) and increased ζ-potential (5.33%) and protein adsorption (4.58%) of WPI emulsion at TG cross-linking time of 12 h. CLSM results showed smaller droplet size of MWPI-TG emulsion and its uniform size. The obtained limonene emulsion loaded by MWPI-TG at 12 h showed the lowest creaming index and the strongest oxidative stability under aerobic conditions after 10thdays of storage. Thus, the combination of microwave heating and TG cross-linking effectively enhanced the stability of limonene emulsion stabilized by WPI and facilitating the application of WPI in the fields of food, medicine, cosmetics, and other areas.

Solvent-Free Microwave Extraction of Thymus mastichina Essential Oil: Influence on Their Chemical Composition and on the Antioxidant and Antimicrobial Activities.

Solvent-free microwave extraction (SFME) is a combination of microwave heating and dry distillation performed at atmospheric pressure without the addition of water or organic solvents that has been proposed as a green method for the extraction of essential oils from aromatic and medicinal herbs. In this work, SFME and the conventional techniques of steam distillation (SD) and hydrodistillation (HD) were compared with respect to the extraction and antioxidant and antimicrobial activities of Thymus mastichina essential oil. The main constituent of essential oils obtained using different methods was 1,8-cineole (eucalyptol). The results showed that the essential oils extracted by means of SFME in 30 min were quantitatively (yield) and qualitatively (aromatic profile) similar to those obtained using conventional HD over 120 min. In addition, SFME generates less waste and less solvent, consumes less energy, and provides a higher yield for a shorter extraction time, which is advantageous for the extraction of the T. mastichina essential oil compared to SD. The antioxidant and antimicrobial activities of the T. mastichina essential oil obtained from either SFME or conventional extraction methods (SD or HD) showed a similar pattern. Large-scale experiments using this SFME procedure showed a potential industrial application.

Extraction of nano-metals with judicious combination of microwave heating and acid leaching process from E-waste

The main aim of the present investigation is to develop and synthesis the precious nano-metals such as nano gold and its by product components such as nano copper, nano silver etc. The investigations were basically consisting of two level environmental friendly process i.e., recovering of the gold from discarded E-waste components and secondly with the proper reaction after boiling. The precious nano materials so obtained will be very much useful for sensors, organic photovoltaic materials, other electronic conductors, probes, drugs and medicines in bio-medical applications, catalysis and reagent in bio-chemical applications etc. The results with XRD, FESEM-EDX and UV analysis studies from present investigations clearly confirm about the presence of nano gold particles and its by products. All the investigations were performed with microwave heat treatment as an environmental friendly method.

Reduction of the Heterocyclic Amines in Grilled Beef Patties through the Combination of Thermal Food Processing Techniques without Destroying the Grilling Quality Characteristics.

In order to reduce the formation of heterocyclic amines in grilled beef patties without destroying their unique quality characteristics, the effects of different thermal processes, including charcoal grilling, infrared grilling, superheated steam roasting and microwave heating, on the production of heterocyclic amines in beef patties and grilling quality characteristics were systematically analyzed. The results showed that infrared grilling can significantly (p < 0.05) reduce the content of heterocyclic amines in grilled patties, and the combination of microwave heating or superheated steam roasting with infrared grilling could further reduce the content of heterocyclic amines, with a maximum reduction ratio of 44.48%. While subtle differences may exist in infrared grilled patties with/without superheated steam roasting or microwave heating, a slight change will not affect the overall quality characteristics of grilled patties. The combined thermal processing will not visually affect the color of the grilled patties. Correlation analysis and regression analysis showed that the reduction in heterocyclic amines caused by microwave heating and superheated steam roasting are related to the moisture content and lipid oxidation of grilled patties, respectively. Using combined thermal processes to reduce the formation of heterocyclic amines is advisable.

Microwave-Assisted Urea-Based-Hydrotropic Pretreatment of Rice Straw: Experimental Data and Mechanistic Kinetic Models.

The three major lignocellulose components can be transformed into various biomass-derived platform fuels, chemicals, and materials upon pretreatment and chemical upgrading. Lignocellulose pretreatment is an important step to obtain an eco-friendly, economical, and effective biomass utilization process. The combination of microwave heating and hydrotropic pretreatment is considered as a green method of lignocellulose pretreatment. Experimental data and two mechanistic kinetic models of microwave-assisted pretreatment of rice straw are presented. Here, the use of urea solution as the hydrotropic agent was examined to facilitate the degradation of three major lignocellulose components. The first kinetic model assumes that the soluble lignin does not undergo condensation, while the second one assumes that part of the soluble lignin condenses to a solid product. The mechanistic models were validated with a series of experimental data obtained from microwave-assisted hydrotropic pretreatment of rice straw. The results show that both models could generally describe the experimental data well. However, based on the evaluation of the results of the kinetic models, it turned out that the rate of lignin condensation was relatively slow compared to the rate of lignin degradation to soluble lignin (the value of kc is relatively small compared to the value of kl1). Hence, the kinetic model with exclusion of lignin condensation is suggested more since it is mathematically simpler. The proposed mechanistic model can also predict the cellulose and hemicellulose dissolution and thereby can be used as a process optimization tool. The microwave-assisted urea-based hydrotropic pretreatment conducted at a solid–liquid ratio of 1:35, a urea concentration of 36.8%, a reaction temperature of 90 °C, and a pretreatment duration of 73.6 min is predicted to give a solid residue with low lignin content and high cellulose content which resulted in a cellulose to lignin ratio of 5.53. Cellulosic biomass characterization revealed that microwave-assisted hydrotropic pretreatment was able to produce higher crystallinity and thermally stable cellulosic biomass.

Combination of Microwave Heating and Transglutaminase Cross-Linking Enhances the Stability of Limonene Emulsion Carried by Whey Protein Isolate

Combination of Microwave Heating and Transglutaminase Cross-Linking Enhances the Stability of Limonene Emulsion Carried by Whey Protein Isolate

Efficient biocatalytic strategy for one-pot Biginelli reaction via enhanced specific effects of microwave in a circulating reactor

A one-pot efficient biocatalytic strategy for the synthesis of 3,4-dihydropyrimidin-2-(1H)-ones was developed in a circulating microwave reactor selecting α-chymotrypsin as the promiscuous biocatalyst. In the circulating reaction system, the combination of microwave heating and external cooling could avoid the denaturation and inactivation of enzyme, and greatly improved the radiation power of microwave, thus improving the specific effects of microwave. During the reaction process, the microwave radiation power was automatically adjusted by adjusting the speed of the reaction mixture circulation. When the microwave power was maintained at 110W, the best results could be obtained with the highest yield of 96% at 55°C in 50min, and the reaction had a wide range of substrates. But no obvious product was detected in a tank microwave reactor at 55°C for 100min, under this condition, the microwave power was maintained at about 3W. As a contrast, the reaction only obtained 63% yield in 55°C oil bath for 96h.

Effect of Microcracks on Graphite Anode Materials for Lithium‐Ion Batteries

AbstractModified graphite with microcracks was obtained by a combination of microwave heating and KOH activation. KOH enhanced the degree of order of the graphite, and K+ increased the spacing of the graphite layer. Microwave heating caused microcracks on graphite and promoted doping of K+ into the graphite. The microcracks could increase the contact area of electrode materials and electrolytes and decrease diffusion length. Furthermore, the uniform microcracks dispersed the pressure of the electrode wetted by the electrolyte, relieved stress during lithium removal and increased the degree of order of the graphite. The modified graphite has a capacity of 449 mAh g−1 at 0.1 C, 380 mAh g−1 at 0.25 C and 367 mAh g−1 at 0.5 C. In addition, the capacity retention rate was 96.1% after one hundred cycles at 0.25 C, and the average coulombic efficiency was 99.4%.

Purification Mechanism of Quartz Sand by Combination of Microwave Heating and Ultrasound Assisted Acid Leaching Treatment

Iron is a major impurity in quartz sand and must be strictly removed in many applications. However, the iron removal rate in most of the conventional purification process is not high enough. In this study, a fast, low-energy consuming, environment-friendly and simple process for purifying quartz is demonstrated by a combination of microwave heating and ultrasound-assisted acid leaching treatment. Using the characteristics of selective heating of microwave, the micro-inclusions burst and generate cracks in the surrounding quartz matrix far below the α/β phase transition temperature, which enables removal of the impurities in the subsequent processing steps and reduces iron diffusion into the quartz matrix. Microwave process sequence, time, and temperature are all important factors, and appropriate parameters need to be explored. Ultrasound can assist acid leaching removal of Fe impurities through the cracks. Under optimized conditions, the iron content can be reduced to below 0.167 ppmw with one single purification pass.

Synthesis of Nano/Microsized MIL-101Cr Through Combination of Microwave Heating and Emulsion Technology for Mixed-Matrix Membranes.

Nano/microsized MIL-101Cr was synthesized by microwave heating of emulsions for the use as a composite with Matrimid mixed-matrix membranes (MMM) to enhance the performance of a mixed-gas-separation. As an example, we chose CO2/CH4 separation. Although the incorporation of MIL-101Cr in MMMs is well-known, the impact of nanosized MIL-101Cr in MMMs is new and shows an improvement compared to microsized MIL-101Cr under the same conditions and mixed-gas permeation. In order to reproducibly obtain nanoMIL-101Cr microwave heating was supplemented by carrying out the reaction of chromium nitrate and 1,4-benzenedicarboxylic acid in heptane-in-water emulsions with the anionic surfactant sodium oleate as emulsifier. The use of this emulsion with the phase inversion temperature (PIT) method offered controlled nucleation and growth of nanoMIL-101 particles to an average size of <100 nm within 70 min offering high apparent BET surface areas (2,900 m2 g−1) and yields of 45%. Concerning the CO2/CH4 separation, the best result was obtained with 24 wt.% of nanoMIL-101Cr@Matrimid, leading to 32 Barrer in CO2 permeability compared to six Barrer for the neat Matrimid polymer membrane and 21 Barrer for the maximum possible 20 wt.% of microMIL-101Cr@Matrimid. The nanosized filler allowed reaching a higher loading where the permeability significantly increased above the predictions from Maxwell and free-fractional-volume modeling. These improvements for MMMs based on nanosized MIL-101Cr are promising for other gas separations.

A Comprehensive Review on Infrared Heating Applications in Food Processing.

Infrared (IR) technology is highly energy-efficient, less water-consuming, and environmentally friendly compared to conventional heating. Further, it is also characterized by homogeneity of heating, high heat transfer rate, low heating time, low energy consumption, improved product quality, and food safety. Infrared technology is used in many food manufacturing processes, such as drying, boiling, heating, peeling, polyphenol recovery, freeze-drying, antioxidant recovery, microbiological inhibition, sterilization grains, bread, roasting of food, manufacture of juices, and cooking food. The energy throughput is increased using a combination of microwave heating and IR heating. This combination heats food quickly and eliminates the problem of poor quality. This review provides a theoretical basis for the infrared treatment of food and the interaction of infrared technology with food ingredients. The effect of IR on physico-chemical properties, sensory properties, and nutritional values, as well as the interaction of food components under IR radiation can be discussed as a future food processing option.

Microwave self-healing technology as airfield porous asphalt friction course repair and maintenance system

A problem increasingly faced by airport authorities is the maintenance of runways. Due to their large aircraft loadings associated with take-off and landing operations, runways experience surface deterioration. Poor quality runway surfaces cannot be tolerated in such an environment. Maintenance issues must be carried out to maximise safety and minimise the risk of aircraft damage. A recent development has been the introduction of self-healing technologies such as rejuvenator encapsulation, induction and microwave heating to address these issues. This paper summarises a laboratory investigation to determine the effectiveness of microwave self-healing for crack repair of Porous Friction Course (PFC) used for airfields. Four mixtures containing varying percentages of conductive steel fibre were tested. Their relative performance was assessed using the Indirect Tensile Stiffness Modulus (ITSM) and Indirect Tensile Strength (ITS) test methods. The results show that the addition of conductive steel fibre increases initial stiffness and strength of the mix. A combination of micro-wave heating and steel fibre addition to the mix indicates that it is possible to significantly improve asphalt performance by making it self-healing to structural problems such as cracking.

Microwave-Assisted Aminolysis of Lactones Under Solvent- and Catalyst- Free Conditions

Background: Aminolysis of lactones is an important reaction for the synthesis of hydroxy amides. This reaction generally requires rather harsh conditions, such as high pressure and temperature or strong alkali metal catalysts. Microwave-assisted reactions have provided a great impetus to organic synthesis, especially for accelerating the reactions. The combination of microwave heating and solventfree conditions is a particularly attractive methodology in modern organic synthesis because it leads to enhanced conversion rates, easier work-up, higher yields and in general cleaner reactions. Keywords: Aminolysis, lactones, microwave irradiation, hydroxy amides.

Rapid synthesis of aurones under mild conditions using a combination of microwaves and deep eutectic solvents

The combination of microwave heating and the deep eutectic solvent formed from choline chloride and urea has resulted in a new, essentially neutral, yet rapid method for the synthesis of a wide range of aurone derivatives. While isolated yields remain somewhat variable, in virtually every case, a significant increase in yield has been observed on going from conventional thermal heating to microwave heating. In addition, some compounds inaccessible using prior methods have become reproducibly available using this modification. Further application of the combination of DES and microwave heating is expected to be highly promising and of general utility.

Creating hierarchies promptly: Microwave-accelerated synthesis of ZSM-5 zeolites on macrocellular silicon carbide (SiC) foams

Hierarchical ZSM-5 coatings supported on macrocellular β-SiC foams were prepared by a microwave-accelerated secondary growth method. Under microwave irradiation, differential heating was enabled due to the high microwave-adsorbing ability of SiC leading to the fast assembly of ZSM-5 zeolites on the SiC foams. The effects of crystallisation temperature, time and agitation on the growth of ZSM-5 zeolites on SiC foams were also investigated under microwave heating. A specific surface area of ca. 52m2g−1 was obtained under the optimum condition of 150°C and 4h. Comparative studies of conventional hydrothermal and microwave-accelerated synthesis were conducted and the resulting materials were characterised extensively using XRD, SEM and N2 adsorption. The combination of microwave heating, high microwave absorption of SiC substrates and agitation allowed a much more focused heating across the surface of SiC foams than conventional heating, which suppressed the formation of ZSM-5 crystals in the liquid phase and the consequent sedimentation. Additionally, for the first time, mesoscopic features of ZSM-5 coatings on SiC foam composites (>10μm) were studied in 3D by X-ray micro computed tomography (μ-CT), providing quantitative information on the quality of the ZSM-5 coating such as the global thickness and distribution of ZSM-5 across the SiC foam supports. It was concluded that microwave-accelerated secondary growth synthesis offered an efficient route to give high quality coatings on structured foams with the good crystal quality and uniform thickness as well as lower energy consumption, especially for the substrate with a high loss tangent.

Combined Microwaves/Ultrasound, a Hybrid Technology.

The combination of microwave heating and ultrasound irradiation has been successfully exploited in applied chemistry. Besides saving energy, these green techniques promote faster and more selective transformations. The aim of this review is to provide a practical overview of the complimentary and synergistic effects generated by the combination of microwaves and either ultrasound or hydrodynamic cavitation. This will begin with a brief history, as we outline pioneering achievements, and will also update the reader on recent developments. Such hyphenated techniques are able to offer reliable and efficient protocols for basic chemistry, organic and inorganic synthesis as well as processing. The development of dedicated hybrid reactors has helped scientists to find solutions to new synthetic challenges in the preparation of nanomaterials and new green catalysts. This research topic falls within the confines of process intensification as it facilitates the design of substantially cleaner, safer and more energy efficient technologies and chemical processes.

Solvent-free Microwave Extraction as the Useful Tool for Extraction of Edible Essential Oils

Solvent-free microwave extraction (SFME) is proposed as a method for “green” extraction of edible essential oils extensively used in the fragrance, flavour, and pharmaceutical industries and also in aromatherapy. It is a combination of microwave heating and dry distillation, performed at atmospheric pressure without adding any solvent or water. Isolation and concentration of volatile compounds are performed by a single stage. Basil (Ocimum basilicum L.) was extracted with SFME at atmospheric pressure and 373 K for 30 min. The extracted compounds were removed from the aqueous extract by simple decantation, identified by gas chromatography–mass spectrometry (GC-MS). Hydrodistillation (HD) of basil was performed with 400 ml of water for 4.5 h for comparison of the results with those provided by the proposed method. SFME method offers important advantages over HD, viz. shorter extraction times (30 min vs. 4.5 h); better yields (0.13 % vs. 0.11 %); environmental impact (energy cost is appreciably higher for performing HD than that required for rapid SFME), cleaner features (as no residue generation and no water or solvent used); and provides a more valuable essential oil. SFME is a green technology and appears as a good alternative for the extraction of edible essential oils from aromatic plants used in aromatherapy and food industry.