The Use of Microwave and Pulsed Electric Field as a Pretreatment Step in Ultrasonic Extraction of Polyphenols from Defatted Hemp Seed Cake (Cannabis sativa) Using Response Surface Methodology

The use of microwave and pulsed electric field (PEF) processing to optimize polyphenol extraction from defatted hemp seed cake in mixed solvent of methanol, acetone and water (MAW, 7:7:6 v/v/v) was investigated using the Box-Behnken response surface method. A variables combination for microwave processing of time, microwave power and liquid to solid (L:S) ratio and for PEF (ethanol concentration, time, frequency and voltage) were used in the investigation. Following microwave or PEF treatments, the polyphenols were extracted from the samples under ultrasound with fixed variables (200 W of ultrasonic power, water bath of 70 °C and 20 min of extraction time). The measured responses were total phenolics (TP), total flavonoids (TF), DPPH˙ scavenging activity and ferric reducing/antioxidant power (FRAP). The optimum variables combination for microwave processing (5 min treatment time, L:S ratio of 6, 700 W power and volume 30 mL) and PEF-assisted extraction (voltage (30 V), frequency (30 Hz), ethanol concentration (10 %) and time (10 s)) resulted in maximum yields in all measured responses. The results suggest that microwave processing and PEF can be integrated in processing defatted hemp seed cake to enhance polyphenol extraction and maximize the yield.     

Influence of microwave,the combined microwave/hot air and only hot air roasting on the formation of heat-induced contaminants of carob powders

ABSTRACT

This study aims to investigate the effects of microwave, combined microwave/hot air treatment and hot air-only roasting on the formation of heat-induced contaminants of carob powders. Moisture content, water activity and pH values of the product decreased with the increasing roasting time and microwave power, while browning index (BI) and ultraviolet absorbance (UV-A) values were increased. While L and b values of carob powders decreased with increasing the roasting time and microwave power, a and ΔE values were increased. Varying roasting conditions also significantly affected the content of Maillard reaction products (MRPs): 5-hydroxymethylfurfural (HMF) (0.69–28.32 mg/kg dry matter), furfural (<LOD-10.44 mg/kg dm), furan (6.65–10.26 mg/kg dm) and acrylamide (78.69–122.87 µg/kg dm). MRPs contents increased with increasing the roasting time and microwave power. The highest MRPs were found in the samples roasted at 140°C for 20 min by hot air. Significant correlations between the amount of MRPs and colour values were found, especially with a and b values.     

Sequential Microwave-Ultrasound-Assisted Extraction for Isolation of Piperine from Black Pepper (<Emphasis Type="Italic">Piper nigrum</Emphasis> L.)

Piperine is the natural bioactive component of black pepper (Piper nigrum L.) with several astounding therapeutic properties. In this study, sequential microwave-ultrasound-assisted extraction approach was used for isolation of piperine from black pepper. The effect of various factors such as extraction solvent, particle size of pepper, solvent to solid ratio, microwave power and time and ultrasound temperature and time on the extraction yield of piperine was considered. The maximum extraction yield was 46.6 mg piperine/g pepper which was obtained using ethanol as solvent at the particle size of 0.15 mm, solvent to solid ratio of 20:1, microwave power of 100 W for 1 min, and ultrasound temperature of 50 ^° C for 30 min. This extraction yield was higher than those obtained by Soxhlet (39.1 mg/g), microwave-assisted (38.8 mg/g) and ultrasound-assisted (37.0 mg/g) extractions. The purity of the extracted piperine was 81.4% as determined by HPLC analysis. The FTIR and UV-vis analyses confirmed that the structure of piperine remained intact after extraction and purification which is very important for medicinal applications.     

Microwave-Vacuum Drying of Lactic Acid Bacteria: Influence of Process Parameters on Survival and Acidification Activity

Freeze drying is one important step in downstream processing of probiotics and starter cultures production and requires a long duration of the drying step, which, therefore, often is the overall production bottleneck. Microwave accelerated vacuum drying already showed promising results in terms of product quality for various food products. However, poor information on drying microorganisms by microwaves is available. The aim of this work was to set up a suitable microwave-vacuum drying process for the conservation of lactic acid bacteria and to investigate the optimum process parameters to achieve dried cultures with high survival and activity. The probiotic Lactobacillus paracasei ssp. paracasei F19 was used as model strain. The influence of the process parameters chamber pressure (7–30 mbar), specific microwave power input (1–5 W/g), and maximum product temperature (30–45 °C) on the main quality parameters survival rate, metabolic activity, and water activity of the dried samples were analyzed. Continuous energy input was shown to act detrimentally to the cells due to extreme temperature rise in the second drying stage. Proper temperature regulation could be obtained by pulsed microwave input according to a maximum set temperature. Intermediate microwave power between 3 and 4 W/g, the lowest tested pressure level of 7 mbar and low product temperatures of 30–35 °C, resulted in the highest survival and activity of the bacterial cells. With these results, it could be shown that microwave-vacuum drying appears as a promising alternative drying technique for the preservation of starter and probiotic cultures.     

Application and Optimization of Microwave-Assisted Extraction and Dispersive Liquid–Liquid Microextraction Followed by High-Performance Liquid Chromatography for the Determination of Oleuropein and Hydroxytyrosol in Olive Pomace

In the present study, a new method based on microwave-assisted extraction and dispersive liquid–liquid microextraction (MAE–DLLME) followed by high-performance liquid chromatography (HPLC) was proposed for the separation and determination of oleuropein (Ole) and hydroxytyrosol (HyT) from olive pomace samples. The effective factors in the MAE–DLLME process such as microwave power, extraction time, the type and volume of extraction, and dispersive solvents were studied and optimized with the aid of response surface methodology (RSM) based on a central composite design (CCD) to obtain the best condition for Ole and HyT extraction. At the optimized conditions, parameter values were 220 W microwave power, 12 min extraction time, 60 μL extracting solvent, and 500 μL dispersive solvent. The calibration graphs of the proposed method were linear in the range of 10–500,000 μg L^?1, with the coefficient of determination (R²) higher than 0.99 for Ole and HyT. Repeatability of the method, described as the relative standard deviation (RSD), was 4.12–5.63% (n?=?6). The limits of detection were 35 and 20 μg L^?1 for Ole and HyT, respectively. The recoveries of these compounds in the spiked olive pomace sample were from 93 to 98%. The proposed method, MAE–DLLME–HPLC–UV, was an accurate, rapid, and reliable method when compared with previous methods.     

Puffing Characteristics of Parboiled Milled Rice in a Domestic Convective–Microwave Oven and Process Optimization

Microwavable products are gaining worldwide acceptance as convenience foods, where hygiene can be maintained when processed in small quantities at the domestic level. One such ready to eat products are puffed or popped starchy grains like corn, rice, sorghum, etc. Owing to its high starch content, rice has high expandability, and the puffed rice produce thence has better digestibility. Considering these aspects, an attempt was made to produce puffed rice in a domestic convective–microwave oven. Puffing characteristics were studied for Gurjari variety of rice at 14 % (wb) moisture content for different preheating temperatures of the glass base plate (180, 200, and 220 °C), microwave power level (300, 600, and 900 W), and residence time (10–100 s), from which the range of residence time was selected for the optimization study. It was found that the puffing of rice was better at higher power level and preheating temperature of the base plate, and puffing started only after certain residence time. Further study was carried out to optimize the process parameters by using response surface methodology, for a Box–Behnken design at three levels for four parameters, i.e., moisture content (12, 14, and 16 % wb), preheating temperature of the base plate (180, 200, and 220 °C), microwave power level (300, 600, and 900 W), and residence time (50, 60, and 70 s). The optimized conditions were found to be 14 % (wb), 220 °C, 900 W, and 60 s. The second-order polynomial model was validated by conducting three trials at the optimized point and found to be agreeing with the predicted values.     

A Rapid and Sensitive Method for Determination of Melamine in Fish,Shrimp, Clam,and Winkle by Gas Chromatography–Mass Spectrometry with Microwave-Assisted Derivatization

A method for rapid and sensitive determination of melamine in aquatic products by gas chromatography–mass spectrometry with microwave-assisted derivatization was proposed in this paper. Melamine was extracted from aquatic product samples using methanol, and the extract was cleaned with a mixed-mode cationic exchange solid phase extraction column. After elution with 5 % ammonia–methanol solution and drying with nitrogen, the residue was derivatized using N,O-bis(trimethylsilyl)trifluoroacetamide containing 1 % trimethylchlorosilane under microwave irradiation for 1 min with a power of 420 W, then detected with gas chromatography–mass spectrometry, and quantified by the external standard method. Some important parameters such as extraction solvent, microwave irradiation power and time, and derivatization reagent volume were investigated and optimized. The results showed that methanol could effectively extracted melamine from aquatic products as well as precipitated the protein in samples. Under the optimum conditions, the detection limit for melamine was as low as 0.006 mg/kg, and the linear range was from 0.02 to 50 mg/kg with a correlation coefficient of 0.9997. The proposed method was applied to the analysis of melamine in aquatic products (fish, shrimp, clam, and winkle), and the recovery for melamine was 89.65–105.16 % with relative standard deviation of 3.0–6.0 %.     

Effect of Microwave Treatments on Antioxidant Activity and Antigenicity of Fish Frame Protein Hydrolysates

Protein solubility, protein recovery, antioxidant activity, and antigenicity of microwave pretreatment and/or microwave-assisted hydrolysis of trout frame protein hydrolysates was investigated. Treatments consisted of (1) microwave pretreatment at low temperature (55 °C) followed by conventional enzymatic hydrolysis or (2) high temperature (90 °C) followed by conventional enzymatic hydrolysis; (3) microwave pretreatment at high temperature (90 °C) followed by microwave-assisted enzymatic hydrolysis, and (4) no microwave pretreatment followed by microwave-assisted enzymatic hydrolysis. Compared to controls, microwave treatments significantly improved (P < 0.05) protein solubility, protein recovery, degree of hydrolysis, and 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) free radical scavenging radical scavenging activity. Decrease of antigenicity (55–93 %) was obtained in all microwave-treated samples. Based on the results of this study, the use of microwave pretreatment for 5 min at 90 °C, followed by conventional enzymatic hydrolysis with alcalase for 2–10 min was the best treatment condition to produce fish peptides with antioxidant activity and the lowest immunoreactivity. These peptides have potential to be applied as hypoallergenic ingredients in food formulations and nutraceuticals.     

Effect of cooking procedures on tylosin residues in chicken meatball

Most information about drug residues is related to their concentrations in raw products. The objective of this study was to assess the effects of various microwave and boiling treatments on the stability of different concentrations of tylosin in chicken meatballs. The chicken meatball samples (75 g) were prepared and fortified by 3 concentrations of tylosin (100, 200 and 300 μg kg^?1) and were cooked by boiling (100 °C for 10, 20, 30 min) and microwave procedure (power 450 W for 1, 1.5 and 2 min). The tylosin content was measured in raw and cooked samples through the use of high performance liquid chromatography. The microwave and the boiling process significantly reduced the tylosin. In both procedures, there were negative correlations between the length of cooking time and the reduction percentage of tylosin. In addition, tylosin reduction percentage in chicken meatball cooked by boiling depended on its concentration in uncooked samples. There was a relationship between tylosin reduction percentage and the increase in the internal temperature and weight loss during the cooking process. The results of this study indicate that tylosin residues in the food are decreased during the cooking process. Thus, given that a food product is cooked to be consumed, the surveillance of data obtained from tylosin measurement in the raw tissues samples could not be considered as consumers’ exposure to tylosin via dietary intake.     

Microwave drying kinetics of jack pine wood: determination of phytosanitary efficacy,energy consumption,and mechanical properties

The aims of this study were to determine (1) the effects of microwave irradiation on the drying kinetics of jack pine wood, (2) the phytosanitary efficacy, and (3) the processing energy consumption and mechanical strength of the dried product. Microwave drying experiments were performed at 2.45 GHz frequency and at microwave powers ranging from 300 to 1000 W. Results indicate that higher microwave power and initial wood temperature and lower sample thickness increases the internal sample temperature, improves the drying rate, and reduces both drying time and energy consumption. The microwave irradiation efficacy to sanitize jack pine wood boards was determined in terms of temperature/time combinations based on actual drying kinetics according to standards for phytosanitary measures. The energy required to dry 12 mm thick wood board samples at microwave power ranging from 300 to 1000 W was in the range of 36.4–12.3 MJ/kg of water, respectively, for up to 65% energy consumption savings. The impact of microwave power on the mechanical properties was not statistically significant, although mechanical properties tended to decrease with increasing power.     

Impact of ultrasound on egg white proteins as a pretreatment for functional hydrolysates production

The objective of this study was to investigate the effects of different ultrasound pretreatment on enzymatic hydrolysis of egg white proteins (EWPs) by Alcalase as well as evaluating some functional and antioxidant properties of hydrolysates obtained by various proteases treatment and ultrasound technology. The effects of chosen ultrasound pretreatment parameters including frequency of ultrasonic waves (35 and 40 kHz), temperature (25 and 55 °C), time of pretreatment (15–60 min) and pH of egg white solution (7.00–10.00) were examined. It appeared that controlled ultrasound treatment can improved the hydrolysis process compared with untreated samples, but optimization of the power and length of sonication was important. The optimal ultrasound pretreatment at calorimetric power of 21.3 W and frequency of 40 kHz for 15 min at 25 °C and with naturally basic egg white (pH 9.25) resulted in increased initial rate and equilibrium degree of Alcalase hydrolysis by about 139.8 and 13.86 % compared with the control, respectively. EWP hydrolysates with ≈27.0 % degree of hydrolysis obtained with heat pretreatment and ultrasound pretreatments under optimal conditions were further separated by sequential ultrafiltration into 4 hydrolysate fractions (<1, 1–10, 10–30 and >30 kDa) which were investigated for protein content, peptide yield and antioxidant activity. The hydrolysis after heat pretreatment generated more peptides <1 kDa (19.04 ± 1.02 %) than ultrasound pretreatment did (11.90 ± 0.53 %), whereas the proportion of peptides <10 kDa were higher in the second case (28.80 ± 0.07 vs. 20.46 ± 0.39 %). The fraction obtained by the ultrasound pretreatment containing peptides with a molecular weight between 1 and 10 kDa demonstrated the strongest ABTS radical scavenging efficacy among the fractions (97.54 ± 0.30) with IC₅₀ value of 4.31 mg/mL. Compared with single-enzyme processes, the two-stage enzymatic processes did not significantly improve both antioxidant and functional hydrolysates’ properties.     

Optimization of microwave-vacuum drying of pomegranate arils

Pomegranate arils (Punica granatum L.) were dried in a microwave-vacuum drier up to a final moisture content of around 5–6 % (d.b.). The effect of microwave power level (25–95 W), vacuum pressure (25–195 mm Hg) and sample mass (65–235 g) on drying efficiency and some quality attributes (color, texture, rehydration ratio and sensory score) of dried pomegranate arils were analyzed by means of response surface methodology. A rotatable central composite design was used to develop models for the responses. Analysis of variance showed that a second order polynomial model predicted well the experimented data. All three process parameters microwave power, vacuum pressure and sample mass strongly affected quality attributes of dried pomegranate arils and drying efficiency. A lower vacuum pressure during drying resulted in better quality products. Optimum drying conditions of microwave power level of 80 W, vacuum pressure of 60 mm Hg and sample mass of 193.7 g were established for microwave-vacuum drying of pomegranate arils. Separate validation experiment was conducted at the derived optimum conditions to verify the predictions and adequacy of the models.     

Drying of Garlic Slices Using Convective Pre-drying and Vacuum-Microwave Finishing Drying: Kinetics, Energy Consumption, and Quality Studies

Garlic slices were dehydrated by convective drying (CD) and by a combined method consisting of convective pre-drying followed by vacuum-microwave finishing drying (CPD-VMFD). Drying of garlic using VMFD led to samples with high values of lightness and slightly lower values of the coordinates a* and b*. The treatment CPD-VMFD significantly decreased the drying time from 630 min for CD to 49 min and contributed to an important energy saving compared with CD (54.4–86.3 %). The total drying time was shorter when vacuum microwaves were introduced earlier and microwave power was higher. The highest temperature (114 °C) was found for samples pre-dried to a moisture content of 60 % and then dried at 360 W while showing the lowest energy consumption (98?±?1 kJ?g^?1). In general, the total antioxidant capacity increased after drying of garlic slices; however, the content of total phenolic compounds showed the opposite trend, and thus other compounds, such as allicin, should be involved in the antioxidant capacity of dried garlic. Garlic slices were CP dried until 30 % of moisture content followed by VMFD at 240 or 360 W showed the best results in terms of energy consumption and antioxidant capacity.     

Impact of Microwave-Assisted Heating on the pH Value,Color, and Flavor Compounds in Glucose-Ammonium Model System

The effect of microwave and oil bath heating on the evolution of Maillard reaction including pH, color and degree of glycation, and flavor compounds was investigated. Maillard reaction was induced by heating glucose-ammonium system for 10–30 min at 100–120 °C. Results indicated that microwave heating was more effective than traditional oil bath heating in Maillard reaction. The more decrease of pH values, higher A₄₂₀, lower whiteness and chroma, and stronger glycation were recorded in the model system heated by microwave. Moreover, microwave heating did not affect the contents of pyrazines extracted by dichloromethane but affect the formation of D-limonene extracted by ethyl acetate from model system. In addition, 2-hydroxy-3-methyl-2-cyclopentene-1-one, 3-methyl-2-pyrazinyl-methanol, and 6-methyl-2-pyrazinyl-methanol were firstly reported as flavor compounds in the glucose-ammonium system.     

基于Weibull分布函数的枸杞微波干燥过程模拟及应用

为了探究Weibull分布函数中各参数的影响因素及其在枸杞微波热风联合干燥中的应用,以枸杞在不同脉冲比(脉冲比1.5:2 min/1 min;脉冲比1.67:3 min/2 min;脉冲比2:1 min/1 min)、微波功率(185、200、215 W)、微波介入时枸杞含水率(30%,40%,50%)条件下的干燥过程为研究对象,利用Weibull分布函数对其干燥动力学曲线进行模拟并通过建立的Weibull模型对枸杞微波干燥过程中的水分有效扩散系数和干燥活化能进行分析。实验表明:Weibull分布函数能够较好地模拟枸杞的微波干燥过程;尺度参数α与微波脉冲比、微波功率以及含水率均有关,并且随着微波功率的升高而降低,随着微波脉冲比和含水率的升高而升高;而初始含水率、脉冲比和微波功率对形状参数β的影响较小;根据Weibull分布含水分析得到枸杞的水分有效扩散系数为1.7×10~(-5)~3.2×10~(-5)m~2/h以及枸杞的干燥活化能为54.78 k J/mol。     

Chemical Composition, Antioxidant Capacity, and Sensory Quality of Pomegranate (Punica granatum L.) Arils and Rind as Affected by Drying Method

The objective of this study was to evaluate the application of: (1) freeze drying, (2) convective drying (50, 60, or 70 °C), (3) vacuum–microwave drying (240, 360, or 480 W), and (4) a combined method of convective pre-drying and vacuum–microwave finish drying in the processing of pomegranate arils and rind. The quality parameters under study included sugars and organic acids, punicalagins and ellagic acid, total polyphenols, total antioxidant activity, and sensory quality. In general, drying led to a reduction in all studied parameters; however, the behavior of arils and rind was different. Vacuum–microwave drying at 240 or 360 W was the best drying treatment for arils, while rind required freeze drying or soft conditions of convective drying (50 °C). Further research is needed to obtain proper results with convective pre-drying and vacuum–microwave finish drying of arils and rind. With proper selection of the drying protocol, high-quality dried arils will be available for consumers; these arils will be characterized by high contents of fructose (25 g 100 g^?1), phytic acid (2.2 g 100 g^?1), punicalagins (0.57 mg g^?1), total polyphenols (1.6 mg eq gallic acid g^?1), high antioxidant capacity (0.6 mg eq Trolox g^?1), and high intensities of garnet color, sweetness, sourness, and fresh pomegranate aroma. Besides, dried rind with very high contents of active compounds (123 mg g^?1 of punicalagins and 108 mg eq gallic acid g^?1) and high antioxidant capacity (26 mg eq Trolox g^?1) will be also available as functional material.     

Effect of Carbonic Maceration Pre-treatment on Drying Kinetics of Chilli (Capsicum annuum L.) Flesh and Quality of Dried Product

A new pre-treatment — carbonic maceration (CM) pre-treatment — was presented in this paper. To study the effect of CM on microwave drying (MD) kinetics of Chilli flesh and quality of dried product, the fresh (control group, CK) and CM pre-treated samples were dried through MD at 100, 150 and 200 W, respectively. CM conditions were optimized by orthogonal test. The drying results indicated that, the average drying rate for CM samples were as much as 150–185 % of these for CK samples. For both CK and CM samples, the drying rate increased at the initial time (a warming-up period) and then decreased at the end time (a falling rate period) after reaching a plateau (a constant rate period). And the effective diffusivity, D _eff, increased gradually at the initial period and then rapidly at the final period with the diminishing moisture content. Elevated microwave power levels could lead to a linear increase in values of D _eff at the same moisture content. The activation energy, E _a, increased rapidly when moisture content was below about 1 g water/g dry mass, which was lower for CM samples than for CK samples, and can be well described with a logistic model. Scavenging free radical capability (DPPH), ferric reducing antioxidant power (FRAP), total phenol contents and vitamin C retention contents of the dried products for CM samples were as much as 170.1–190.9 %, 140.2–147.8 %, 140.1–160.0 % and 212.7–682.4 % of these for CK samples, respectively. The CM dried products were also better in terms of colour differences than CK.     

Optimization of Microwave-Assisted Extraction of Polyphenolic Compounds from <Emphasis Type="Italic">Ocimum basilicum</Emphasis> by Response Surface Methodology

Microwave-assisted extraction (MAE) was optimized by response surface methodology in order to enhance the extraction of polyphenols from basil (Ocimum basilicum L). Box–Behnken experimental design on three levels and three variables was used for optimization. Influence of ethanol concentration (50, 70, and 90%); microwave power (400, 600, and 800 W); and extraction time (15, 25, and 35 min) on each response were investigated. Experimental results were fitted to a second-order polynomial model, and multiple regression analysis and analysis of variance were used to evaluate model fitness and optimal conditions. Considering the maximum content of extracted total phenols, total flavonoids, and antioxidant activity, the optimal conditions for all investigated response were ethanol concentration of 50%, microwave power of 442 W, and extraction time of 15 min. Under the optimal conditions, obtained basil liquid extract contained 4.299 g gallic acid equivalents/100 g dry weight (DW) of total polyphenols, 0.849 g catechin equivalents/100 g DW of total flavonoids, and IC₅₀ and EC₅₀ values of 9.602 and 82.889 μg/mL, respectively. The development of simultaneous MAE procedure for extraction of total phenols, total flavonoids, and potential antioxidants from basil, represented valorization of basil as valuable source of bioactive compounds.     

Optimisation of microwave‐assisted extraction of phenolic compounds from broccoli and its antioxidant activity

The effect of independent variables of microwave‐assisted extraction (MAE), extraction temperature (50–90 °C), microwave power (100–200 W), solvent concentration (methanol/water, 50–90%, v/v) and extraction time (1–27 min) on total phenolics and flavonoids contents as well as antioxidant activity of broccoli extracts was investigated. Response surface methodology was successfully applied for optimisation and the high correlation of the mathematical model indicated that a quadratic polynomial model could be used for optimisation of investigated responses. Considering the maximum amount of extracted total phenolics, total flavonoids and antioxidant activity expressed as ORAC value, the optimal conditions for all three investigated responses were obtained (temperature ?71.11 °C; microwave power ?167.03 W; solvent concentration ?75.95%; and extraction time 16.34 min), which is in agreement with optimal conditions obtained for each investigated responses. The development of simultaneously MAE methods for total phenolics, total flavonoids and antioxidant activity of broccoli extracts might simplify assessment of broccoli as valuables source of antioxidants.     

Effects of microwave heating on the migration of substances from melamine formaldehyde tableware

Melamine formaldehyde (MF) tableware, after undergoing repeated heating in a microwave oven for 1, 2, 3 or 5 min, was tested for migration into 3% (w/v) acetic acid, a food simulant. Overall migration (OM) consistently increased with an increasing number of heating/washing cycles, while formaldehyde was found at low concentrations or was not detectable. Unexpectedly, the 1-min series caused the most rapid increase in OM; the European Union regulatory limit of 10 mg dm^–2 was exceeded after 25 cycles. The number of cycles required to reach the OM limit rose to 29 and 67 for the 2- and 3-min series, respectively. Only 37 cycles were needed in the case of the 5-min series; however, the cumulative exposure time to microwave irradiation was relatively close to that of the 3-min series. These findings indicate that microwave heating affects the migration of MF in a significantly different manner as compared with conventional heating reported in previous studies. Fourier transform infrared spectroscopy (FTIR) spectra of MF after completing the microwave heating series show that the plastic was not fully cured, as evidenced by the absence of methylene linkages. The majority of migrants obtained from OM tests consisted of low molecular weight methylol melamine derivatives. The results indicate that microwave heating allowed demethylolation, addition and condensation reactions to occur, which was not the case when using conventional heating. This study demonstrates that microwave heating for 1–2 min in a repeated manner is of high concern in terms of consumer health. It was found that the service terms of melamine ware under microwave heating were drastically reduced, by more than 10-fold, as compared with the service terms under conventional heating. Hence, it is strongly recommended that manufacturers of MF articles provide instructions for use, e.g. “Do not use in microwave”, which should be clearly visible to consumers and not easily detachable.