Melamine Contamination Research Articles

Carboxyl-functionalized two-dimensional MXene-Au nanocomposites were prepared as SERS substrates for the detection of melamine in dairy products.

In the present study, we address the limitations of conventional surface-enhanced Raman scattering (SERS) techniques for sensitive and stable detection of melamine in food products, especially dairy. To overcome these challenges, we developed a novel SERS-active substrate by incorporating gold nanoparticles (AuNPs) onto carboxyl-functionalized two-dimensional (2D) MXene material doped with nitrides, specifically Au-Ti2N-COOH. Our strategy leverages the unique physicochemical properties of MXene, a class of atomically thin, 2D transition metal carbides/nitrides, with tunable surface functionalities. By modifying the MXene surface with AuNPs and introducing carboxyl groups (-COOH), we successfully enhanced the interaction between the substrate and melamine molecules. The carboxyl groups form hydrogen bonds with the amino groups on the melamine's triazine ring, facilitating the adsorption of melamine molecules within the 'hotspot' regions responsible for SERS signal amplification. A series of characterization methods were used to confirm the successful synthesis of Au-Ti2N-COOH composites.Using Au-Ti2N-COOH as the SERS substrate, we detected melamine in spiked dairy product samples with significantly enhanced sensitivity and stability compared to nitride-doped MXene alone. The detection limit in liquid milk stands at 3.7008 μg kg-1, with spike recovery rates ranging from 99.84% to 107.55% and an approximate RSD of 5%. This work demonstrates the effectiveness of our approach in designing a label-free, rapid, and robust SERS platform for the accurate quantitation of melamine contamination in food, thereby mitigating health risks associated with melamine adulteration.

Carbon dots derived from citric acid and urea as fluorometric probe for determining melamine contamination in infant formula sample

Melamine has been intentionally added into food products to increase the protein count at less cost, especially in dairy products for infant resulting in serious adverse effects on health of consumers. Therefore, this study aimed to develop a method to quantify melamine in dairy products based on the change of fluorescent properties of carbon dots (CDs) as sensing probe. CDs with green-fluorescent emission were synthesized from citric acid and urea under microwave irradiation. The synthesized CDs emitted fluorescence at the maximum wavelength of 538 nm with excitation wavelength of 410 nm. Thus, they provided high sensitivity and selectivity on melamine detection by which fluorescent emission of the CDs was increasingly quenched upon increasing melamine concentrations. Optimal conditions for melamine determination using the CDs was under pH 6, volume ratio between CDs and sample of 2:8 and reaction time of 15 min. The developed method provided high precision of melamine determination with less than 5% of %RSD (n = 5), wide detection range from 1.0 to 200.0 ppm, and high sensitivity with limit of detection (LOD) of 0.47 ppm and limit of quantification (LOQ) of 1.56 ppm, which is within the regulated level by the Food and Drug Administration of the United States for melamine in dairy products. Several analytical characterization techniques were conducted to elucidate the reaction mechanism between CDs and melamine, and the hydrogen bonding interaction was proposed.

Determination of melamine contamination in milk with various packaging: a risk assessment study.

Melamine is one type of monomer used as starting substance in manufacturing packaging lining in many countries worldwide. Environmental and food contamination is an issue constantly discussed. In the present study, the melamine content in milk samples with three package types was measured by HPLC/UV. Melamine is not a lipophilic compound. Therefore, the selected samples were low-fat milk. The melamine content in various packaged milk, including packet, polyethylene bags, and plastic packaging, is 790 ± 39.8, 50.7 ± 13, and 57.7 ± 24.54ppb, respectively. According to the existing standards, the measured values in all the milk samples were lower than the permitted limits. The risk assessment for adults and children showed that the HQ value for both age groups was less than 1. Therefore, milk consumption will not pose a health risk in terms of contamination with melamine.

Preparation of surface-modified electrode of copper(ii) oxide mixed with the molecularly imprinted polymer for enhancement of melamine detection with photoelectrochemical technique.

Melamine contamination in food and beverages affects short- and long-term health. In this work, enhanced sensitivity and selectivity in photoelectrochemical determination for melamine detection was achieved using copper(ii) oxide (CuO) combined with a molecularly imprinted polymer (MIP). A CuO nanomaterial was used to achieve MIP surface modification via co-precipitation synthesis. An MIP film was deposited by polymerizing the methacrylic acid monomer and a melamine template. The properties of the CuO nanomaterials, such as the surface morphology, chemical oxidation state, and crystalline structure, were characterized using field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction patterns (XRD), respectively. The diffuse reflection spectroscopy technique was applied to evaluate the optical properties of the CuO nanoparticles. The results indicated that the synthesized CuO nanomaterials had a monoclinic structure with an optical bandgap of 1.49 eV, which corresponds to absorbance in the visible light region. CPE electrodes with surface-modified CuO/MIP were measured using the photoelectrochemical techniques of cyclic voltammetry, differential pulse voltammetry (DPV), and amperometry. The modified CuO/MIP electrode for melamine detection in 7.4 pH PBS buffer solution exhibited a high sensitivity of 0.332 nA nM-1, with a linear range of 5.0-75.0 nM and a limit of detection of 2.45 nM. Moreover, real samples of various kinds of milk were applied to evaluate the sensing response of the prepared CuO/MIP electrode. The modified CuO/MIP electrodes could be reused seven times with good reproducibility and high selectivity for melamine detection.

DFT analysis on the adsorption of melamine in Ga12-N12/P12 nanocages: solvent effects, SERS analysis, reactivity properties

Due to its negative effects on people, melamine contamination in food products are detected and filtered. Amongst several sensory schemes for the screening of melamine poisoning, one of the most promising techniques is the use of nanomaterial based sensing for real time applicability in industries. In the current work, we have looked into the way melamine binds to Ga12-N12/P12 nanocages. Surface-enhanced Raman scattering (SERS), a successful spectroscopic technique is used to monitor melamine. Density functional theoretical (DFT) computations were used to study the sensing properties of melamine (Me) with Ga12-N12/P12 nanocages. Reactivity and Mulliken charge analyses show charge transfer from melamine to nanocage. Me-Ga12-N12 and Me-Ga12P12 clusters have adsorption energies of −47.54 and −33.12 kcal/mol, respectively. All nanocage-Me systems have a significant increase in polarizability. The electron densities revealed non-covalent interactions in the adsorbed systems. All adsorption energies in aqueous media are negative, indicating an attractive and exothermic reaction, with maximum value in water for Me-Ga12N12 and in acetone for Me-Ga12P12. Evidence of SERS is observed due to the enhancement of different vibrational modes. Communicated by Ramaswamy H. Sarma

Associations of Dietary Intake with Urinary Melamine Concentrations among Children aged 4-6 Years in the GAPPS Cohort

Describe how children are exposed to the environmental chemical melamine through their diets, and identify potential sources of contamination in children's diets. Melamine is an industrial chemical that may induce kidney injury at low dose exposures and kidney failure at high doses. Diet is a primary source of melamine exposure, yet little is known about exposure levels or dietary sources, particularly among children. Urinary melamine and metabolite concentrations were measured in 123 children aged 4-6 years in the Global Alliance to Prevent Prematurity and Stillbirth cohort. Children’s diets on the day preceding urine collection were assessed through 24-hour recalls. Associations of meat, fruit, and grain intakes with urinary melamine and metabolites were examined in primary analyses using generalized linear modeling. Remaining food groups were examined in secondary analyses. Melamine and ammelide concentrations were above the limit of detection (LOD) in 100% and 88% of samples, respectively. Ammeline concentrations were below the LOD in all samples. Mean urinary melamine and ammelide concentrations were 5.97 ng/mL (SD: 12.08) and 1.80 ng/mL (SD: 2.06), respectively. In minimally adjusted models, a doubling in fatty fish intake was associated with 74% (95% CI: 18%, 130%) greater melamine; this association was diminished in fully adjusted models. In full models, a doubling of yogurt intake was associated with 101% (95% CI: 33%, 167%) greater melamine; doubled dark green vegetable intake was associated with 59% (95% CI: 1%, 117%) lower ammelide. Exposure to melamine and ammelide was pervasive. Possible sources of melamine contamination including yogurt and fatty fish should be confirmed in larger samples. Additional study should clarify how chronic low-level melamine exposure affects children’s health.

Determination of melamine contamination in chocolates containing powdered milk by high-performance liquid chromatography (HPLC).

Melamine is widely being reported as a food adulterant. Although its toxicity is currently recognized, melamine adulterations of dairy products are ongoing to apparently increase the amount of protein. The study was conducted to investigate the determination of melamine amounts in chocolates containing powdered milk. In this study, 60 samples of chocolates containing powdered milk, both imported and domestic brands, were collected. The samples were prepared by solid phase extraction (SPE) and analyzed using high-performance liquid chromatography (HPLC). According to the results, melamine was found in about 94% of imported samples and about 77% of Iranian samples. Melamine concentration in imported samples ranged from 0.032 to 2.692mg/kg, while in Iranian ones it ranged from 0.013 to 2.600mg/kg. The mean melamine concentrations of foreign and Iranian samples were 0.685±0.68 and 0.456±0.73mg/kg, respectively. Moreover, the limit of detection (LOD) and limit of quantification (LOQ) values of melamine were 0.017 and 0.052μg/ml, respectively. The recovery rate (R%) at fortified levels of 1-2mg/kg was found to be 89.20-95.69% with an RSD (Relative Standard Deviation) of 1.8-2.7%. Based on the study results, melamine was present in 85% of all samples and the melamine level in one Iranian brand and one imported brand was higher than the Codex Organization standard. However, the consumption of chocolates containing these low levels of melamine does not constitute a health risk for consumers.

Melamine contamination and associated health risks: Gut microbiota does make a difference.

Melamine is a nitrogenous organic compound containing high amounts of nitrogen, which is interpreted as high protein in various standard protein measuring tests, therefore added to foods to boost the protein content. Illegal addition of melamine has been in practice by food manufacturers, which leads to toxicity and stone formation in kidneys of individuals consuming melamine-contaminated milk products. A focused and thorough structured search of bibliographic databases for peer-reviewed researches reported in the literature was carried out with a focused attention on melamine contamination, associated health risks, and the role of gut microbiota. The overall outcomes of the research and review articles pertaining to searched keywords along with analysis of the interventions have been described employing a deductive qualitative content analysis approach. Current review focuses on the various health risks associated with consumption of melamine-contaminated foods and the need to develop better and effective methods for its testing. Moreover, the importance of gut microbiota in mediating toxicity due to melamine has also been discussed as there is a link between toxicity and activities of gut microbiota.

Interrelationship of environmental melamine exposure, biomarkers of oxidative stress and early kidney injury

Melamine contamination has remained pervasive in the environment even after the 2008 toxic milk scandal. Exposure to chronic low dosages of melamine is known to induce renal tubular damage, increasing the risk of stone formation and early kidney injury. This damage may come about via increased oxidative stress, but no studies of this possibility have been performed in humans. We conducted two human studies in 80 workers from melamine tableware factories (melamine workers) and 309 adult patients with calcium urolithiasis (stone patients) to evaluate the relationships between urinary melamine levels and two urinary biomarkers of oxidative stress, 8-oxo-2′-deoxyguanosine (8-OHdG) and malondialdehyde (MDA). Both human studies showed urinary melamine levels to be significantly and positively correlated with urinary 8-OHdG and MDA, indicating melamine exposure can increase oxidative stress. Additionally, we used structure equation modeling to evaluate relative contribution of type of melamine-induced oxidative stress on renal tubular injury and found that MDA mediated 36 %–53 % of the total effect of melamine on a biomarker of renal tubular injury, N-Acetyl-β-d Glucosaminidase (NAG). In conclusion, our findings suggest exposure to low-dose melamine can increase oxidative stress and increase the risk of early damage to kidneys in humans.

Presence of melamine in human milk and the evaluation of the effects on mother-infant pairs in a cohort study.

Melamine contamination is a recent public health problem emerging globally. Present study aimed to detect the rate of melamine presence in human milk in a cohort study and to evaluate any possible differences in maternal-infant pair characteristics such as breastfeeding status, crying and sleep problems of infants, maternal postpartum depression, maternal-infant bonding, infant and maternal anthropometry, and maternal complete blood count caused by the melamine exposure. Mothers of infants born in Şanlıurfa were invited to participate in 'Urfa Child Cohort Survey'. Overall, two breast milk samples were taken between 5 days and 15 days postpartum and between 4 weeks and 10 weeks. Randox Food's InfiniPlex array was used to analyse the presence of melamine. Melamine was detected in 32.2% and 24.4% of the first and the second milk samples; 16.7% of mothers had two positive samples. z Scores for birth weight and z scores for height for age were detected to be significantly lower in cases with two positive samples compared to cases with negative samples. Mean maternal white blood cells counts were found to be lower in cases with repeated melamine contact. Melamine might have a detrimental effect on birth weight, infant height and maternal blood count. Further studies should be done to detect environmental contamination in different regions and countries.

Ripple effect of moral hazard: how does CSR misconduct impact firm performance in the dairy industry

In this article we study how collective corporate social responsibility (CSR) misconduct affects the market performance of enterprises in the dairy industry. We do this by revisiting the melamine-tainted milk powder event in China. By comparing pre- and post-event retail data of three different types of infant milk powder manufacturers, as well as by analysing the cumulative abnormal returns (CARs) of those milk powder companies listed on stock markets, based on an event study approach, the ripple effect of China's melamine incident as an exogenous shock was investigated. The results show that industrial CSR misconduct has a suppression effect on the enterprises involved, overlapping suppression and spillover effects on domestic enterprises that were not involved, as well as spillover effects for foreign peers. Lessons from the melamine contamination incident and its policy implications should be valuable in promoting the CSR level and sustainability of other similar fast-growing industries in developing countries.

Ripple effect of moral hazard: How do CSR misconducts impact firm performance in the dairy industry

In this article we study how collective corporate social responsibility (CSR) misconduct affects the market performance of enterprises in the dairy industry. We do this by revisiting the melamine-tainted milk powder event in China. By comparing pre- and post-event retail data of three different types of infant milk powder manufacturers, as well as by analysing the cumulative abnormal returns (CARs) of those milk powder companies listed on stock markets, based on an event study approach, the ripple effect of China's melamine incident as an exogenous shock was investigated. The results show that industrial CSR misconduct has a suppression effect on the enterprises involved, overlapping suppression and spillover effects on domestic enterprises that were not involved, as well as spillover effects for foreign peers. Lessons from the melamine contamination incident and its policy implications should be valuable in promoting the CSR level and sustainability of other similar fast-growing industries in developing countries.

INVESTOR RESPONSE TO FOOD NUTRITION LABELING REGULATION IN CHINA

INVESTOR RESPONSE TO FOOD NUTRITION LABELING REGULATION IN CHINA

Determinations of Melamine Residue in Infant Formula Brands Available in Iran Market Using by HPLC Method.

The contamination of melamine was evaluated in 69 infants along with follow up formula samples collected from the market for the first time in Iran using HPLC method. Since there are no previous data concerning the contamination level of melamine in all brands of infant formula samples consumed using the HPLC method in Iran, this study is the first investigation in this regard. Our results showed that melamine contamination was found in 65% of samples, where mean and maximum levels of melamine were 0.73 ± 0.71 mg/kg and 3.63 mg/kg, respectively. The level of melamine in 10 out of 69 samples was higher than the maximum level set by the Codex Alimentarius in infant food (1 mg/kg). Melamine was determined in 67.8% and 50% of domestic and imported samples, respectively. The estimated daily intake was designed in two scenarios: it was calculated based on the mean level of melamine contamination and maximum level of melamine in the samples. In both scenarios, our results showed that melamine intake across all age groups is lower than the tolerable daily intake (TDI) of 0.2 mg/kg body weight, suggested by WHO (0.2 mg/kg body weight). Thus, it seems that the current levels of melamine in infant and follow up formula purchased in Iran pose no health risk for infants.

Melamine and its derivatives in dog and cat urine: An exposure assessment study

Melamine is a nitrogen-containing organic compound that is used in a wide range of products, including paints, plastics, and paper, as a flame retardant. A few studies have reported the occurrence of melamine and its derivatives in pet food, following a number of deaths of cats and dogs from kidney failure in 2007, which was attributed to melamine contamination in ingredients used in pet food. Nevertheless, studies that report the occurrence of melamine and its derivatives in pet urine are scarce. In this study, we measured melamine and its derivatives (i.e., ammeline, ammelide, and cyanuric acid) in dog (n = 30) and cat (n = 30) urine collected from Albany, New York, USA, during March through July 2017. The mean (±SD) concentrations of melamine, ammeline, ammelide, and cyanuric acid in dog urine were 21.1 ± 51.2, 2.3 ± 3.8, 9.9 ± 1 0.4, and 79.0 ± 105 ng/mL, respectively; the corresponding concentrations in cats were 21.4 ± 26.1, 1.2 ± 2.5, 6.1 ± 3.9, and 105 ± 94.6 ng/mL, respectively. No significant difference was observed in urinary concentrations of melamine derivatives between cats and dogs. Age and gender were important determinants of the concentrations of the target chemicals in cats and dogs. Cumulative daily intake of melamine and its derivatives was calculated on the basis of urinary concentrations and was found to be 10–500-fold below the tolerable daily intake.

Rapid Detection for Toxicity of Melamine Contamination in Infant formula and Liquid Milk based on Fiber Chemical Sensor

Melamine has become as one of the major food adulterants. Therefore in this article, we developed a novel method for detecting the milk contaminants like toxicity of melamine and classified it based on data spectroscopy. The developed system based on optical fiber sensor, Optical spectroscopy and artificial neural network (ANN). The system consists of an optical source, refractive index sensor (RIS), optical detector (photodiode), spectroscopy data and neural package. Where the detection and classification process depends on the read out of the RIS sensor and near-infrared spectroscopies to achieve the detection and recognition of all the samples by using LM-BP neural network algorithm. The classification rate was reported at accuracy rate reach above 99.98%.

Effects of low-dose melamine exposure during pregnancy on maternal and fetal kidneys in rats.

Despite the previous reports on melamine contamination in high concentrations some years ago, there were not many studies on low-level exposure in daily life, particularly in pregnancy. We investigated the effect of low-dose melamine on the kidneys of the pregnant rats and their developing embryos/fetuses during various gestational stages namely implantation, gastrulation, organogenesis, maturation and whole pregnancy. Our results showed that the repeated low level of melamine (12.5, 25, and 50 mg/kg bw/d) during pregnancy did not cause obstruction of renal tubules although more precipitating crystals were found in the early gestational periods. Simple hyperplasia in the maternal tubules and pelvic epithelium were more prominent after exposed to melamine during the whole gestational period. Neonatal kidneys significantly suffered more from congestion in glomeruli and interstitium, dilated tubules and interstitial edema after melamine administration to the mother in the late and the whole gestational periods. A trend of advance of glomerular development in fetuses was also observed. We conclude that in utero exposure of low-level melamine could post a risk on the kidneys of the pregnant mother as well as the developing fetuses, which may further increase the possibility of other health problems later in life.

Melamine contamination in milk powder in Uruguay

ABSTRACTForty samples of milk powder purchased in Uruguay were analysed to assess melamine (MEL) levels. Trichloroacetic acid and acetonitrile were used to extract and precipitate milk proteins previously to clean up of the samples by solid-phase extraction and then were determined by liquid chromatography coupled to ultraviolet detection. The limit of detection (LOD) and limit of quantification (LOQ)of MEL were 0.006 and 0.019 mg kg−1, respectively. Milk was fortified with MEL at three levels, producing average recoveries higher than 83.8%. The values for positive samples ranged from 0.017 to 0.082 mg kg−1. Nine samples were positive. Three of them had concentrations between LOD and LOQ. The mean MEL contamination was 0.028 mg kg−1. Consumption of milk powder containing these levels of MEL does not constitute a health risk for consumers.

Sensors break out of the lab

Sensors break out of the lab

Determination of Melamine in Indian Milk and Dairy products by Reverse Phase Liquid Chromatography

The recent revelation of melamine contamination in food stuffs has rocked the international public health community, so a rapid and sensitive method to detect the presence of melamine in dairy products was essential. Therefore, we proposed the use of chromatographic data produced by HPLC in particular for melamine detection in complex dairy matrixes. A HPLC method for determination of melamine was reported, with acetonitrile 10% in water and formic acid 0.25% as mobile phase and UV detection at 240nm. The tested parameters include mobile phase composition, % of organic solvent, buffer concentration, pH value and UV detection λ. Good linearity was observed within the concentration range of 8–12μg/ml. The method was successfully applied to determine melamine in several dairy products, with acetonitrile as extract solvent of melamine and also as protein precipitant.