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In recent years, microwave food processing has been increasingly utilized worldwide. Omega-3-rich oils, which have various health benefits, must be protected from heat treatment, including microwave heating, due to their thermosensitivity. In this study, we investigated oxidative stability of blends of omega-3-rich oils, such as flaxseed, sesame, and perilla oils, with extra virgin olive oil (EVOO) in order to reduce concentration of acrolein during microwave heating. Microwaving flaxseed oil increased the free acidity and the formation of undesirable and irritating odors (e.g., acrolein). In contrast, microwave treatment of EVOO resulted in a much lower level of free acidity and acrolein formation. Blending 10% EVOO in flaxseed oil enhanced the antioxidant capacity and effectively reduced free acidity and acrolein formation during microwave heating. The enhancing effect was also partially achieved in flaxseed oil blended with both 10% refined olive oil and a-tocopherol, which are bioactive components in EVOO. Similarly, blending 10% EVOO in other omega-3-rich oils, including sesame oil and perilla oil, also decreased free acidity and acrolein formation during microwave heating. These results suggest that blending with EVOO facilitates the use of omega-3-rich oils in microwave food processing while retaining their health benefits. [ABSTRACT FROM AUTHOR]

Highlights • Simulation of microwave rotating heating is realized by ALE method. • The simulation results compared with conventional methods is more accurate and efficient. • This method can be used for microwave heating simulation of other food movements. Abstract In a particular condition, moving elements are typically used to improve heating uniformity during microwave heating. However, due to the complexity of mathematical models, the simulation of moving elements during microwave heating process remains a challenge. In this paper, a novel continuous algorithm based on Arbitrary Lagrangian-Eulerian method is developed to compute this heating process. By introducing the ALE method, the mesh of moving domain are set as a function of space coordinate and time, the mesh of surrounding domain is free deformation under the action of the moving domain, ensuring the accuracy and continuity of calculation by remesh the deformed configuration. A 2-D model and a 3-D model with a rotating turntable are used to illustrate the proposed method in detail. The change of temperature was measured by experiments to verify the rationality and accuracy of the proposed method. This method can be used in microwave heating simulation of other food movements and assist microwaveable food product development. [ABSTRACT FROM AUTHOR]

The objective of this work was to evaluate the effect of microwave power on acrylamide generation, as well as moisture and oil fluxes and quality attributes of microwave-fried potatoes. Concretely, 25 g of potato strips, in 250 mL of fresh oil (at room temperature), were subjected to three different microwave powers (315, 430, and 600 W) in a conventional microwave oven. Microwave frying resulted in an acrylamide reduction ranged from 37 to 83% compared to deep-oil frying. Microwave-fried French fries presented lower moisture and higher fat content than deep-oil fried potatoes. Concretely, microwave-fried potatoes presented values of moisture and texture more similar to potato chips than French fries, nonetheless with lower fat levels (less than 20 g/100 g wb) and acrylamide content (lower than 100 μg/kg wb) at the reference time. This study presents an alternative way of frying to address the production of healthier potato chips. [ABSTRACT FROM AUTHOR]

The dielectric properties of starch based snack pellets have been measured in situ during microwave heating and expansion. The microwave setup consists of a single mode shorted waveguide, equipped with a six-port impedance analyser which measures the absorbed power and complex reflection coefficient during heating. The pellet is suspended in the electric field maximum, with an optic temperature sensor inserted in the centre. The dielectric properties of the pellet during heating and after expansion are obtained via an inverse mapping of the recorded reflection coefficient to dielectric properties, which are pre-computed via finite elements simulations. Experiments show that the dielectric properties of the starch pellets change significantly during heating, expansion and subsequent drying. The dielectric properties increase with increasing temperature up to the moment that the pellet starts expanding. Subsequently, the power absorption shows a sudden decline, which is mainly due to the sudden change in porosity. Addition of salt (2.5%) to the starch pellet composition results in a slight decrease of the dielectric constant and loss factor, as it apparently lowers the effective mobility of the dipoles. The dielectric properties as function of temperature and moisture content were fitted with a polynomial model. The strong effect of porosity for the dielectric properties of the expanded snack is well predicted with the effective medium mixing rule. [ABSTRACT FROM AUTHOR]

The Commission Regulation (EC) Regulation N. 488/2014, established the concentration limits for cadmium in specific products based on cocoa and chocolate products as from January 2019. Based on this information there is a need to determine ultratrace levels of elements that might be presents in cocoa and chocolate products. In this work, the concentrations of Arsenic, Antimony, Cadmium, Chromium, Lead, Selenium and Vanadium were evaluated in cocoa powder and chocolate by the validation of an ICP-MS method. Good selectivity/specificity, recovery, repeatability and within-laboratory reproducibility, LOD, LOQ, range of linearity, standard measurement uncertainty parameters for method validation were achieved, in accordance with Commission Regulation. The cocoa powder revealed the maximum metal concentrations of 0.303 ± 0.035 mg/kg for cadmium, 1.228 ± 0.146 mg/kg for lead and 0.094 ± 0.013 mg/kg for arsenic. A significant difference was found between cocoa powder and chocolate samples (p < .05). [ABSTRACT FROM AUTHOR]

A simple and very environmental friendly microwave assisted method to produce oleacein in good yield starting from the easily available oleuropein is here presented. The methodology is proposed to produce the appropriate amount of hydroxytyrosol derivatives to enrich a commercial oil for an oil which provides beneficial effects on the human health. [ABSTRACT FROM AUTHOR]

Optimizing the physicochemical properties of microwave-cooked meat needs a better understanding of the mechanisms responsible for protein changes. This paper explored the causes of aggregation of the denatured fish protein in ready-to-eat food by determining the changes in sarcoplasmic and myofibril proteins, which includes the effects of different microwave power levels (300, 600, and 900 W) and heating times (0-60 s) on the aggregation kinetics and physiochemical properties. The determination of aggregation kinetics that accurately describes microwave cooking characteristics is crucial for the optimization of operating parameters, performance improvement of the cooked food system, and product quality. The aggregation rate and turbidity of proteins increased with increasing microwave power and time. A negative correlation was observed between the protein solubility and microwave power and time. Protein aggregation induced by microwave showed a reliable and reproducible characterization of particle size distributions. At longer microwave heating time or higher microwave power, these protein particles formed larger aggregates. [ABSTRACT FROM AUTHOR]

The ubiquitous use of poly- and perfluoroalkyl substances (PFASs) in a variety of industrial and consumer products has resulted in chronic exposure in most industrialized nations, and led to measurable concentrations in blood and other tissues in humans across all life stages; however, behavioral attributes that relate to exposure are not well studied. To further investigate how behavior may relate to PFAS exposure, 37 adults were recruited from central North Carolina. Participants provided blood samples and behavioral questionnaires were administered, asking questions about a variety of household, dietary, and behavioral outcomes. Six PFAAs, including PFHxA (geometric mean: 0.14 ng/mL), PFOA (1.57 ng/mL), PFNA (0.67 ng/mL), PFDA (0.28 ng/mL), PFHxS (3.17 ng/mL) and PFOS (4.96 ng/mL) were detected in >50% of the samples. Generally, males had higher serum levels than females across all chemicals, and levels were very similar to NHANES levels; however, PFHxS and PFDA levels were higher in our study population. Several personal characteristics and behaviors were associated with serum PFAS levels. Reported use of filtration devices was associated with lower levels of PFOA (28% lower, p = 0.03), but higher levels of PFHxA (122% higher, p = 0.04). Serum PFHxS levels were also elevated in individuals that vacuumed less often, and in individuals that reported consuming more microwavable foods. These results suggest that personal behaviors may be important determinants of PFAS exposures. [ABSTRACT FROM AUTHOR]

Native waxy maize starch was treated at a moisture content of 30% by microwave irradiation for 5 min, 10 min and 20 min, respectively. The molecular structure and physical properties of waxy maize starch were characterized. Compared with native maize starch, lower population of short chains of amylopectin (A chain), higher proportion of short B 1 and long B 2 and B 3 were observed in irradiated starches. 1 H NMR data showed that α-(1,6) glycosidic linkages were destroyed more easily than α-(1,4) glycosidic linkages during microwave treatment. A increase in gelatinization temperatures and a decrease in the molecular weight, the relative crystallinity, ΔH, viscosities and syneresis were observed after microwave treatment. Gelatinization temperatures were positively correlated with long chains B 3 with DP > 36, while ΔH and syneresis were negatively correlated with them. The extent of the changes induced by microwave treatment for different times revealed that the major degradation occurred in internal chain (amorphous region) at the first stage (microwave treatment for 5 min), the external chain (crystalline region) mostly destroyed at the second stage (microwave treatment for above 10 min). The foregoing data indicated that the molecular structure of amylopectin is a critical factor determining physical properties. [ABSTRACT FROM AUTHOR]

Objective: To observe the effects of microwave oven exposed diet on spermatogenesis in the testis of mice and comparative effects of Mentha piperita and melatonin. Study Design: Laboratory based randomized controlled trial. Place and Duration of Study: Anatomy Department, Army Medical College Rawalpindi, in collaboration with National Institute of Health (NIH), Islamabad, from Apr 2015 to May 2015. Material and Method: Study comprised of 32 adult male mice (BALBc strain) weighing 25-30 gms. Selection criteria based on non-probability (purposive) simple random sampling. Mice were divided into four equal groups of 8 mice each. Group 1, taken as control, was given standard diet 5-10gm/animal/day daily for four weeks. Group 2 was given 5-10 gm/animal/day of microwave oven exposed mice pellets for four weeks. Group 3 received Mentha piperita leaf extract (1g/kg b.wt./day) along with microwave oven exposed mice pellets (5-10 gm/animal/day) for 4 weeks and group 4 received oral dosage of melatonin 12mg/kg/day along with microwave oven exposed mice pellets (5-10gm/animal/day) for 4 weeks. After four weeks animals were dissected. The shape, color and any abnormal finding of the testis were observed. Testis were processed, embedded and stained for histological study. Spermatogenesis was assessed by the Johnsons scoring. SPSS 21 was used for statistical analysis. Chi square test was applied for intergroup comparison. Results: Spermatogenesis was suppressed and Johnsons score was decreased from normal spermatogenesis (10) to (6-8) in the experimental group 2 and was more improved in the Mentha piperita treated group as compare to the melatonin. Conclusion: Microwave oven exposed mice pellets suppressed spermatogenesis and Mentha piperita had better ameliorative effects than melatonin on the testis of mice. [ABSTRACT FROM AUTHOR]

Measurement of the electromagnetic properties of food is important for its electromagnetic protection, microwave heating and sterilization. Much research had focused on describing the non-thermal mechanism of electromagnetism and locating its site of action. Amino acids are the basic units of proteins, and therefore their electromagnetic characteristics are central to understanding the transmission and loss of microwave energy in food and the non-thermal mechanism of electromagnetic effects. Herein, the dielectric properties and conductivity characteristics of solutions of basic amino acids, at an electromagnetic frequency of 2.45 GHz and at temperatures between 10 °C and 70 °C, have been measured. The results show that the dielectric constant and dielectric loss decrease with increasing temperature, for example, increase the temperature form 10 °C to 70 °C, the dielectric constant of lysine at 2% decreased from 77.259 to 68.601, and the dielectric loss decreased from 13.412 to 10.302, due to the decrease of the solution viscosity and the relaxation time, causing an increase of the dipole moment. Increasing the concentration of the basic amino acids leads to an increase of the dielectric loss, fix the temperature at 20 °C, the concentration of lysine increased from 0.5% to 10%, the dielectric loss increased from 10.191 to 23.232, which is related to the change of the conductivity. The conductivity has positive correlation with the concentration and temperature of the amino acid solution, fix the temperature at 20 °C, the concentration of lysine increased from 0.5% to 10%, the conductivity increased from 234 to 2840 μS/cm, and when the temperature was increased form 10 °C to 70 °C, the conductivity of lysine at 2% increased from 694 to 1347 μS/cm. The absorption properties of the solutions are characterized by the loss of reflection, and the absorption characteristics of the basic amino acids are related to the electromagnetic frequency, the concentration and the thickness of the absorbing layer, the variation of which affects the impedance matching. In this paper, through the study of the electromagnetic characteristics of basic amino acids in solution, a theoretical basis for the application of basic amino acids in microwave sterilization, as well as a mechanism for the microwave effect, are proposed. [ABSTRACT FROM AUTHOR]

The article talks about European Forum for Industrial Biotechnology (EFIB) event 'Pitchfest' held in Glasgow, Scotland in October 2016. Topics discussed performance of different biotech firms such as Embion Inc., Marine Biopolymers Ltd. and MetGen Co.; development of food and high value chemicals from seaweed. Also mentioned are the enzymatic process for the production of bio-based products.

Multiphysics based numerical model are promising tools to enhance understanding of microwave heating of foods. These models are specific for particular microwave oven and food configuration, which limits generalization. In addition, the models are computationally expensive limiting their utility in the food industry. In this study, we have developed a simple 1-dimensional (1-D) analytical model based on planar wave assumption to predict the average heating rate of a food product and to determine the thickness of multicompartment meals based on the dielectric, thermal, and physical properties. The model was benchmarked by comparing with earlier developed 1-D model. A numeric “vpasolve” solver in MATLAB was used to adjust the thickness of two compartments such that they would heat at the same rate and have better heating uniformity. To validate this approach of determination of thickness using the 1-D model, a 3-D multiphysics based numerical model and experimental microwave cooking were used to evaluate the average heating rate in the original equal and adjusted food designs. The validation using 3-D numerical model was also performed for three multicompartment meals, three top surface areas, three food shapes, and three microwave ovens. The meals with adjusted thicknesses showed that the average heating rates of two compartments were closer indicating improved heating uniformity. The average heating uniformity indices based on average final temperature difference and coefficient of variation of 21 scenarios are 57.6% ± 9.4% and 29.3% ± 5.3%, respectively. Therefore, the simple 1-D model can be used for preliminary design of microwaveable food products. [ABSTRACT FROM AUTHOR]

A first-ever theoretical model describing the cell rupture mechanism for microwave-assisted extraction (MAE) of bioactive compounds from plant samples is presented. This model incorporates the microwave heating of intracellular moisture within the plant cells using Lambert’s law. It then calculates the heating time and the intrinsic energy required to pressurize and stretch the plant cells until rupture using thermodynamic relations. The attainment of cell rupture is determined from elasticity theory for solids. The simulation requires the inputs of the effective shear modulus of the plant cell wall and the incident microwave irradiation flux entering the extraction mixture. The predicted cell rupture time by the intrinsic energy validated excellently against the optimum extraction time found in experiments. This model is generally applicable over a wide extraction parameters and microwave systems. [ABSTRACT FROM AUTHOR]

Several microwave power settings were applied to green beans in order to determine the effect on the drying kinetics along with the rehydration ratio and colour values. In the experiments, several microwave power settings were studied as 180, 360, 600, and 800 W. From the results, it is seen that the level of microwave power affected the drying kinetics, rehydration ratio, and colour of the beans slightly. The nine best known thin-layer drying models that were used in literature were applied to the experimental data and the results showed that Midilli et al. model best fits the experimental data for the drying kinetics of green bean slices. Effective moisture diffusivity was found to be between 1.387 x 10-8 and 3.724 x 10-8 m2/s. Using modified Arrhenius type equation the activation energy was found as 19.185 kW/kg. The rehydration ratio of samples dried at 800 W was higher than those of samples at other power settings. It was observed that an increase in the microwave power increased the brightness and yellowness, on the contrary, it decreased the greenness of the dried samples. [ABSTRACT FROM AUTHOR]

Relatively little work has been reported about flour changes during microwave irradiation. For this reason, maize flours were treated by microwave radiation at 400 W for 0.5, 1, 2 and 4 min, and their microstructure and physicochemical characteristics (X-ray diffractometry, differential scanning calorimetry and pasting properties) were analysed. Micrographs showed that maize flour treated by microwave radiation displayed less compacted particles and more swollen starch granules. Treated maize flours displayed higher V-type crystalline structure, indicating amylose-lipid complexes formation. Additionally, onset and peak temperature and gelatinization enthalpy increased when increasing treatment time of samples. Maize flours subjected to mild treatment (0.5 and 1 min) showed higher peak viscosity and breakdown than native maize flour, and maize samples subjected to severe treatments (2 and 4 min) displayed a lower peak viscosity and breakdown, which reflects an increase in shear stability, with respect to native maize sample. In general, microwave treatment fostered changes in starch crystallinity and the formation of amylose-lipid complexes affecting the functional properties of flour such as its pasting behaviour and its thermal properties. [ABSTRACT FROM AUTHOR]

Highlights: [•] A MA-NPS-DME system was assembled for determination of OPPs in cereals. [•] A microwave extractor was made and used to heat samples directly. [•] The microwave extractor can be reused. [•] The MAM can be recycled and was not in contact with the samples. [•] Only non-polar solvent was applied to the extraction of OPPs. [Copyright &y& Elsevier]

Heat treatment is a well-known process in food preservation. It is made to avoid and to slow down food deterioration. The process was developed by Louise Pasteur French scientist to avoid late among others wine further fermentation. The different heat treatments influence the shelf life in food production. In our article we present the process of grape must fermentation, as grape must is the base material of wine production. The treatment of harvested fresh grape juice has a big influence on end product quality. It is our experiments we examined the same grape must with four different methods in closed and in open spaces to determine CO² concentration change. There are four different methods for treatment of grape juice: boiling, microwave treatment, treatment by water bath thermostat and a control without treatment. As a result of the comparison it can be stated that the heat treatment delays the start of fermentation, thereby increasing shelf life of grape must. However, no significant differences were found between two fermentation of heat-treated grape must by the microwave and water-bath thermostat. The different heat treatment of grape must base materials was done at the laboratory in Faculty of Mechanical Engineering of Szent István University. The origin of the table grapes used for the examination was Gödöllő-hillside. [ABSTRACT FROM AUTHOR]

Drying kinetics of extruded, starch-based pellets with initial moisture content of 0.695 kg/kg d.b. were experimentally investigated in a microwave vacuum drying system. The influence of the initial sample amount (100, 200 and 300 g), microwave power (400, 600 and 800 W) and system pressure (20, 50 and 100 mbar) were examined in detail. An increase in microwave power and a decrease in initial sample amount significantly shortened the drying time. Among several thin layer models, the model of Balbay and Sahin best describes the experimental data for starch-based pellets. The activation energy was calculated to be 10.89 W/g and effective moisture diffusivity varied from 3.4 × 10−9 to 1.2 × 10−8 m2/s, depending on microwave power level and sample amount. Practical Application Third generation snacks provide an alternative to fully prepared puffed snack foods. In contrast to conventional extrusion, nonexpanded pellets are formed via extrusion, then predried and then expanded to achieve a crispy and porous texture. In this alternative process, the extrusion can be performed at high moisture content, moderate temperature and shearing conditions. This is beneficial for the preservation of thermally and mechanically sensitive ingredients and allows the production of snacks with high nutritional quality. A special feature of the process investigated in this study is that the expansion is achieved by microwave-vacuum processing which allows an indirect expansion without a time- and energy-consuming predrying process. In addition, due to the processing under vacuum, the temperature inside the product can be kept at desired moderate values. The drying kinetics, drying rate and diffusion coefficient in connection with the volume expansion allow process design and product quality improvement. [ABSTRACT FROM AUTHOR]

Abstract: The study evaluated the use of 915 MHz continuous microwave processing with a rotation apparatus for pasteurization of acidified vegetable packages. Broccoli florets, and 1.2 cm cubes of broccoli stems, red bell pepper, and sweetpotato were pre-equilibrated to 1 g/100 g NaCl and 0.38g/100 mL citric acid, and separately placed in 110 mL cups with a 0.5g/100 mL citric acid solution. Unsealed packages were placed on a conveyor belt and run through a 915 MHz microwave cavity operating at 3.5 kW (residence time = 4 min). After processing, cups were sealed with a lidding film, and held in insulating molds for 30 min. Infrared thermocouples, fiber optic temperature sensors, and infrared imaging were used to monitor product temperatures. Microbial stability and changes in color and instrumental textural properties were measured over a 60-day storage period at 30 °C. Good retention of color and texture of acidified vegetable pieces was observed after microwave pasteurization. Over storage, textural properties significantly degraded for all vegetables, but the brilliant color of red bell pepper and sweetpotato was relatively retained. Chemical indicators of microbial spoilage were not detected at the end of storage. This study demonstrates a successful continuous microwave pasteurization process for producing shelf-stable acidified vegetable packages. [Copyright &y& Elsevier]

Abstract: A modeling technique based on absorbed microwave energy was proposed to model microwave-assisted extraction (MAE) of antioxidant compounds from cocoa (Theobroma cacao L.) leaves. By adapting suitable extraction model at the basis of microwave energy absorbed during extraction, the model can be developed to predict extraction profile of MAE at various microwave irradiation power (100–600W) and solvent loading (100–300ml). Verification with experimental data confirmed that the prediction was accurate in capturing the extraction profile of MAE (R-square value greater than 0.87). Besides, the predicted yields from the model showed good agreement with the experimental results with less than 10% deviation observed. Furthermore, suitable extraction times to ensure high extraction yield at various MAE conditions can be estimated based on absorbed microwave energy. The estimation is feasible as more than 85% of active compounds can be extracted when compared with the conventional extraction technique. [Copyright &y& Elsevier]

Abstract: The purpose of this research is to study the stabilization effect of microwave on wheat germ using continuous microwave processing equipment. Results from the study indicated that microwave technique had a significant stabilization effect on wheat germ. When the on-line processing capacity of wheat germ was 20kg/h, the optimal conditions for wheat germ stabilization were microwave power of 4kW, the processing time of 8min and ventilation rate of 60Nm3/h. Under such conditions, the residual lipase activity decreased to 14.01% of that of the raw wheat germ. The lipoxygenase lost its activity completely under such intensity microwave processing. After 60days’ accelerated storage, the acid value increased only 6.56% of that of the stabilized wheat germ before storage. In addition, microwave could cause the death of harmful microorganisms. It was clear that the continuous microwave stabilization process was practicable for wheat germ stabilization. [Copyright &y& Elsevier]

Abstract: An important quality problem when cooking or warming battered and breaded foods in a microwave oven is the resulting lack of crunchiness due the way microwaves heat foods. In this regard products are beginning to be designed specifically for microwave heating, by using active packaging (with susceptors) or/and by changing the batter formulation. In this study, a completely new approach was undertaken to avoid that problem: a film of alginate gel with high salt concentration between substrate and batter was used as an edible susceptor. The performance of the proposed film was studied by Infrared Thermal Imaging (IRTI). A thermovision camera allowed to take thermographs after different heating periods in the microwave and to observe how heat was distributed once this new film of alginate plus salt was incorporated. The temperature histograms were also obtained from the thermographs to study the temperatures’ distribution and their evolution with heating time. It could be observed that the alginate films produced more even heating patterns in the samples and shorter cooking times. In addition, the IRTI technique resulted to be a valuable tool to study the edible susceptor performance. [Copyright &y& Elsevier]

The best enzyme to prepare peanut peptides, papain, coupled with microwave irradiation was selected from five common proteases according to the results of the yield of peanut peptides [nitrogen solution index (NSI) in trichloroacetic acid (TCA), TCA-NSI] and the degree of hydrolysis (DH). The main factors that influenced the microwavecoupled enzymatic digestion method were optimized by response surface analysis. The optimal conditions obtained were as follows: microwave extraction time, 9.5 min; power, 600 W; substrate concentration, 4%; enzymatic reaction temperature, 50°C; enzyme quantity, 6,500 U/g; pH, 7.1 (phosphate buffer, 0.05 mol/L). Under these conditions, TCA-NSI was 62.00% and DH was 25.89%, which is higher than that obtained with either protease hydrolysis or microwave hydrolysis alone. [ABSTRACT FROM AUTHOR]

Press residues formed during processing of berry fruits are regarded as valuable pectin sources. In this work, pectins were extracted from press residues obtained by processing of various fresh berry fruits: red and black currant, raspberry and elderberry. The extraction was carried out by conventional and microwave-assisted methods. Comparing the two methods, the microwave-assisted process gave significantly better results. The rheological behaviour of the pectins extracted was studied, and we found that the gels of pectins from berry press residues are somewhat weaker than gel of commercial citrus pectin, but stronger than that of commercially available apple pectin. Red currant pectin was found to possess outstanding values regarding gel-forming capacity and thickening effect. [ABSTRACT FROM AUTHOR]

Microwave reheating, compared to a conventional method, is notorious for lack of crust formation and severe toughening of flour and starch-based products. This review discusses how the typical thermal characteristics of microwave heating are involved in affecting the texture as well as the possible role of non-thermal effects. While low surface temperature is the well known mechanism why microwave heating is incapable of crust formation, the most severe toughening problems are caused by internal boiling. Beside moisture loss, the internally generated steam causes 2 main textural effects when it is vented out. The first is the replacing of non-condensable gases (air) in the product voids with a condensable one (steam). When the latter is condensed by cooling, a vacuum may be created in the voids causing their collapse and a formation of a more compact and tougher structure. The second textural effect involves amylose extraction from starch granules and its redistribution to eventually form a rich layer on the walls of the structural foam cells of the baked goods. Relatively fast crystallization of the amylose seems to be the main cause of toughening a short while after microwave heating. This mechanism is relevant mainly to products where starch is an important structural element. Structural disruptions by localize excessive steam pressure at hot-spots are also discussed in this review as well as methods of preventing or alleviating the most objectionable textural changes. The most effective ways of preventing these undesirable changes are by avoiding internal boiling and/or by manipulating the starch content and properties. [ABSTRACT FROM AUTHOR]

Abstract: Fluoride (F) intake is recognized to be important for dental health. Tea leaves are known F accumulators and brewed tea as well as the water used for brewing may contribute significantly to individual intake. The USDA''s Nutrient Data Laboratory determined the F content of brewed and microwaved teas using geographically matched tap water samples. Two brands of top-selling regular and one of decaffeinated teabags were purchased in 36 locations and brewed either by steeping in boiled water or with microwave heating followed by steeping. The mean F content for caffeinated regular brewed tea was 373±49μg/100g (n =63) and for decaffeinated tea was 270±46μg/100g (n =34). The overall mean for F in microwaved regular tea was lower than regular brew (364±40μg/100g vs. 322±30μg/100g (n =36)). In all cases, prepared tea using water from the Midwest had the highest F-values. The mean F content of the brewed teas was 3–4 times higher than the national mean of the tap water, analyzed separately (71±33μg/100g). These data are the first nationally representative F-values for brewed teas, and will provide valuable information to the dental and medical research communities in assessment of fluoride intake and impact on dental health. [Copyright &y& Elsevier]

The presence of endocrine disruptors bisphenol-A, bisphenol-A-dimethacrylate, bisphenol-A-diglycidyl-ether, phthalic-acid, dibutyl-phthalate, diethyl-phthalate and dioctyl-phthalate was determined in vegetable cans, baby bottles and microwaveable containers from the Mexican market. Gas-Chromatography-Mass-Spectrometry was used for the identification and High-Performance-Liquid-Chromatography with UV/Visible light and fluorescence detectors was used for the quantification. Endocrine disruptors were found in all samples. PA and DOP were the substances most commonly found, and maximum concentrations were 9.549 and 0.664 μg/kg, respectively from a jalapeno peppers can. Bisphenol A, phthalic-acid, bisphenol-A-dimethacrylate, bisphenol-A-diglycidyl-ether, dioctyl-phtalate and dibutyl-phthalate were found in baby bottles and microwaveable containers. [ABSTRACT FROM AUTHOR]

Abstract: The performance of a custom-designed, multimode 2450MHz laboratory-scale, batch type-converted to continuous microwave-assisted extraction (CMAE) system was investigated and the optimization results obtained were used to develop and test a pilot-scale 5kW, 915MHz focused cavity CMAE system. Oil was extracted from soy flour and rice bran at various time–temperature combinations with an ethanol: feedstock ratio of 3:1. Both processes were optimized to minimize extraction time while maximizing the quantity of oil extracted. Extraction yields were compared to conventional (CE) and Soxhlet extraction. Yields in the laboratory-scale system for soybean oil were highest at the highest temperature (73°C) and longest exposure time (21min), while for rice bran oil, the highest yields were obtained at 73°C and 17min. Using the pilot-scale extraction system, greater than 93.0% of total recoverable oil was extracted from both feedstock at all tested flow rates and extraction times, more than the oil recovered by the laboratory-scale unit. Time of extraction and flow rate did not have a significant influence on extraction yield at tested temperatures for the pilot-scale process for soybeans. For rice bran, extraction yield decreased slightly with increasing flow rate (from 0.6 to 1.0l/min) and extraction time also influenced oil yields. Analysis of oil quality indices (IV, AV, FFA content, wax and phospholipids) extracted by both CMAE processes indicate that the oil meets prescribed biodiesel feedstock quality standards, further justifying use of microwaves as a rapid tool for oil extraction. [Copyright &y& Elsevier]

Abstract: The effects of different gums on macro-structure of gluten-free rice cakes baked in conventional and infrared–microwave (IR–MW) combination ovens were investigated by using the images obtained by scanner and scanning electron microscopy in this study. The gum types used were xanthan, guar, locust bean, κ-carrageenan and xanthan–guar blend. Cake containing no gum was used as control. It was observed that both addition of different types of gums affected the pore area fraction and percent number of pores of the rice cakes. The highest pore area fraction was obtained in cakes containing xanthan and xanthan–guar blend. Cakes baked in IR–MW combination oven had higher porosity than those baked in conventional oven. Micro-structure of gluten-free rice cakes was also analyzed. According to these results, conventionally baked cakes showed more starch granule deformations. Both granular starch residues and deformed starch structure were observed together in cakes baked in IR–MW combination oven. All of the starch granules did not lose their identity and did not disintegrate completely. [Copyright &y& Elsevier]

Abstract: The knowledge of dielectric properties may hold a potential to develop a new technique for quality evaluation of milk. The dielectric properties of water-diluted cow’s milk with milk concentrations from 70% to 100% stored during 36h storage at 22°C and 144h at 5°C were measured at room temperature for frequencies ranging from 10 to 4500MHz using open-ended coaxial-line probe technology, along with electrical conductivity and pH value. The raw milk had the lowest dielectric constant when the frequency was higher than about 20MHz, and had the highest loss factor at each frequency. The highest linear coefficient of determination, 0.995, between the milk concentration and the loss factor at 915MHz was observed. The change tendency of the loss factor was inversed to pH during milk storage with the best linear correlation (R 2 =0.983) at 1100MHz. The loss factor can be an indicator in predicting milk concentration and freshness. [Copyright &y& Elsevier]

Abstract: Beetroot cubes were dehydrated by convective drying in hot air at 60°C and by the combination of convective pre-drying (CPD) until moisture content 1.6, 0.6 or 0.27kg/kg db and vacuum-microwave finish drying (VMFD) at 240, 360 or 480W. The control samples were obtained by freeze-drying (FD). The drying kinetics of beetroot cubes was described with an exponential function. VMFD significantly reduced the total time of drying and decreased drying shrinkage in comparison with convective method. A critical moisture content divided the temperature profile of samples during VMFD into increasing and falling periods. At the falling temperature period a significant increase in the colour parameters L ∗, a ∗ and b ∗ was found. VM treated samples as well as FD ones exhibited lower compressive strength, better rehydration potential and higher antioxidant activity than those dehydrated in convection. Increasing the microwave wattage and decreasing the time of CPD improved the quality of beetroot cubes dried by the combined method. [Copyright &y& Elsevier]

Abstract: There is a large market for microwave foods, with one of the most prevalent growth areas being low-density bakery products. The dielectric constant and loss factor of Madeira cake batter and its constituents (sugar, cake concentrate, margarine, flour, egg) were measured at a range of moisture contents (0.429–1.000kgkg−1, dry basis), temperatures (20–80°C), and over a frequency range of 915–2450MHz. In general, for a given material, the dielectric properties of samples increased with increasing frequency. Irrespective of frequency and sample moisture content, the dielectric constant of batter and flour was relatively independent of sample temperature, whereas that of the sugar samples increased with increasing temperature, particularly within the lower moisture range. At 2450MHz the loss factor of batter and flour samples decreased by a limited amount as temperature was increased, whereas at 915MHz they were relatively unaffected. The sugar samples showed a significant decrease in loss factor with increasing temperature, irrespective of frequency. During microwave baking, the dielectric properties of Madeira cake batter initially increased sharply and then decreased steadily until the end of the baking process. [Copyright &y& Elsevier]

Abstract: The dielectric properties of salted systems based on different hydrocolloids (native or modified starches, or on ι, λ, or κ carrageenan) as models for microwaveable white sauces were studied. Microstructural and rheological properties were also studied to better understand the dielectric behaviour. As expected, salt had a significantly positive effect (p <0.05) on both dielectric properties. Raising the starch concentration significantly lowered (p <0.05) the loss factor, whereas increasing the carrageenan did not. None of the hydrocolloids significantly affected the penetration depth. The decrease in the loss factor could be related to a decrease in the free water content which was observed by Cryo-SEM. Free water and salt content seemed to be the major factors to control for microwave heating of hydrocolloid-thickened systems. [Copyright &y& Elsevier]

With the development of the new Swiss Ventafresh technology (Steffen, 2007; Steffen et al., 2007a,b) that produces edible, packaged foods having much longer shelf-lives than are available by current technologies, new vistas in food service and restaurant service have become available. About 170 km outside of Madrid is a new food processing and packaging plant. Raw foodstuffs (spices, fruits, meats, vegetables, rice, potatoes, pasta, salads, etc.) are delivered to this plant where they are washed (in ozone-containing water), peeled, sliced, etc. Microwaveable packing trays are filled with ingredients of a complete meal and then sealed with a microwaveable plastic film (sometimes with modified atmospheres). Both the packing trays and the sealing film are disinfected using combinations of ozone and UV radiation. Individual meals are prepared and packaged, but are not precooked, then are delivered to five (currently) Crono Chef restaurants strategically located throughout Madrid (www.crono.tv). There are only waiters/waitresses. A customer entering a Crono Chef restaurant is seated, offered the usual libations, and given a menu of the meals stocked - in refrigerators, not frozen. The customer's selection is cooked fresh in one of many microwave ovens on the premises. Cheese and/or desserts follow, along with the usual after-dinner drinks, if desired. This new concept in food delivery can be extended to food service for large institutions, e.g., military installations, sporting events, hospitals, elder care facilities, schools, prisons, highway restaurants, and is available for franchising. [ABSTRACT FROM AUTHOR]

A new microwave heating process was developed for cooking microwaveable foods containing raw meats. A commercially available inverter-based microwave oven was modified for pasteurization of mechanically tenderized beef, inoculated with Escherichia coli O157:H7 (approximately 5 log10 CFU/g) and packaged in a 12-oz CPET tray containing 150-mL de-ionized water. The new microwave heating system was equipped with an infrared sensor and a proportional feedback mechanism to allow temperature controlled microwave heating. A 2-stage heating strategy was adopted to cook the product. In the primary heating stage, the sample surface temperature was increased to an initial temperature set-point (ITSP, 65, 70, 75, or 80 °C). In the secondary heating stage, the heating was continued with a small fraction of microwave power. The effect of ITSP, hold time (0 to 3 min), and sample elevation (0, 0.03, and 0.07 m above turntable) on inactivation of E. coli O157:H7 and background microflora was evaluated. It was observed that only a small number (approximately 1.3 logs) of E. coli O157:H7 and background microflora were inactivated in the primary heating stage. The elevation 0.07 m, which was in the proximity of the geometric center of the metal cavity, was more effective in inactivating both E. coli O157:H7 and background microflora. Substantially more bacteria were inactivated in the secondary heating stage. Complete inactivation of E. coli and background microflora was observed with heating at temperatures above 70 °C for more than 1 min. This study demonstrated a new approach for ensuring the safety of microwaveable products containing raw meats. [ABSTRACT FROM AUTHOR]

Fresh blue honeysuckle fruit slices were puffed in a microwave vacuum dryer up to a final moisture content about 5% (w.b.). The effect of initial moisture content (IMC) (25–45%), vacuum pressure (VP) (70–90 kPa) and microwave intensity (MI) (10–30 W g−1) on quality attributes, in terms of expansion ratio (ER), hardness (HD), crispness (CR) and colour of the products, were analysed by response surface methodology. Besides the effect of MI on chroma (CH), the high IMC and low VP had a significantly positive impact on the quality attributes of blue honeysuckle snacks. The optimum product qualities, which were ER (1.62 times), HD (5836.31 g), CR (4.48), and CH (28.7) were obtained at an IMC of 38.42%, VP of 82.02 kPa, and MI of 22.42 W g−1. The microwave vacuum method has obvious advantages when puffing the blue honeysuckle snacks. [ABSTRACT FROM AUTHOR]

Abstract: A theoretical analysis has been carried out to study the efficient microwave processing of discrete food sample ceramic composite attached with ceramic (Al2O3 and SiC) plates. Continuous food sample with a specific thickness corresponding to smaller power absorption is replaced by two discrete samples and processed with ceramic composite. The effective power and temperature distribution are found to be function of discrete food sample ratios, type of microwave incidence and ceramic layer thickness. The effect of ceramic material on various discrete sample ratios have been studied via effective average power vs. thickness of ceramic (Al2O3 or SiC) intermediate for one side and both sides microwave incidence. It is found that power absorption is enhanced significantly for beef sample due to specific thickness of ceramic composite corresponding to one side microwave incidence. The power enhancement is lesser and the temperature difference or thermal runaway is larger for bread samples as compared to beef samples. The enhancement of heat absorption is larger for one side incidence as compared to both sides incidence with identical total intensity of microwave incidence. The role of discrete samples with ceramic composites is significant for highly lossy substances (beef) whereas the composites do not play significant role on optimal processing of low lossy substances (bread). [Copyright &y& Elsevier]

A unique DNA isolation protocol based on microwave irradiation and density centrifugation for the simultaneous detection of porcine, chicken, and mutton meat species in food by PCR using newly developed primers is described. Emphasis is placed on the detection of pork, as it is considered unlawful in the diet in major religions such as Islam and Judaism. The method has been optimized using the primers designed from porcine mitochondrial DNA (mtDNA) sequence and tested in 96 samples. The method involves 35 seconds of high microwave irradiation of lysed sample homogenate followed by a 5- min centrifugation in 1.5 mL Eppendorf tubes until a clear supernatant is obtained. The design of this protocol makes it possible to process many samples in a short time. To evaluate the method pork and food spiked with different concentrations of pork together with unknown food samples were analyzed by PCR using the new set of porcine specific primers. The new set of primers and the method involved showed high sensitivity in detecting porcine and chicken content in food in addition as a marker for the detection of mutton. The present sample preparation method has the potential to be applied to other meat detection systems as well. [ABSTRACT FROM AUTHOR]

Abstract: The use of microwaves in the food industry is attributed to the lower time needed to increase the temperature of foodstuffs compared to the traditional heating methods. However, the heating is not uniform and the products show hot and cold spots. In order to analyze the behavior of microwaved foods a mathematical method was developed solving the unsteady state heat transfer differential equations. The model was applied to large systems for which Lambert’s law is valid because it leads to similar results as Maxwell equation. It takes into account variable thermal and electromagnetic properties. The numerical solution was developed using an implicit finite difference method in one dimensional systems (sphere, infinite cylinder and slab) and an alterning direction method in two- and three-dimensional conditions (finite cylinders and brick shaped products). It allows to predict temperature profiles and heating times. The model was validated with own data of mashed potato and meat products and with experimental data from literature obtained with agar gel, sodium alginate gel and whole potato. [Copyright &y& Elsevier]

This paper presents an integrated electromagnetic and thermal model for the microwave processing of food packages. The model is developed by combining the edge finite element formulation of the 3-D vector electromagnetic field in the frequency domain and the node finite element solution of the thermal conduction equation. Both mutual and one-way coupling solution algorithms are discussed. Mutual coupling entails the iterative solution of the electromagnetic field and the thermal field, because the physical properties are temperature-dependent. The one-way coupling is applicable when the properties are temperature independent or this dependence is weak. Mesh sensitivity and shape regularity for the edge element based formulation for computational electromagnetics are discussed in light of available analytical solutions for a simple wave guide. The integrated model has been used to study the electromagnetic and thermal phenomena in a pilot scale microwave applicator with and without the food package immersed in water. The calculated results are compared with the experimentally measured data for the thermal fields generated by the microwave heating occurring in a whey protein gel package, and reasonably good agreement between the two is obtained. [ABSTRACT FROM AUTHOR]

Summary Microwaves interact with polar molecules and charged particles of food to generate heat. There are differences between the heating mechanisms of microwave and conventional heating. The use of microwave heating has the advantage of saving energy and time, improving both nutritional quality and acceptability of some foods by consumers. Microwave ovens are successfully used both in homes and in the food service industry. However, there are still problems in perfecting microwave baking, therefore it is a popular research area. The main problems found to occur in microwave-baked food products are low volume, tough or firm texture, lack of browning and flavour development. Recent studies aim to improve the quality of microwave-baked products. This article reviews the basic principles of microwave baking, problems commonly occurring in microwave-baked products and finally studies published concerning microwave-baked products. [ABSTRACT FROM AUTHOR]

Summary A novel technique using microwave energy for roasting and drying or garification of fermented cassava mash is investigated. The quality of gari produced using this method compared favourably with the standards quoted in the literature and with those of commercial gari purchased from a London market, in terms of colour, swelling capacity, moisture, pH and total acidity. [ABSTRACT FROM AUTHOR]