[Determination of 11 nutrients in liquid milk by ultra-performance liquid chromatography-tandem mass spectrometry].

OBJECTIVE: To establish an ultra-performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS) method for simultaneous determination of 11 nutritional components(thiamine, riboflavin, nicotinamide, nicotinic acid, pantothenic acid, pyridoxine, pyridoxal, pyridoxamine, biotin, choline, L-carnitine) in liquid milk. METHODS: Milk samples were shaken with 20 mmol/L ammonium formate solution and heated in a water bath at 100 ℃ for 30 min, then incubated with papain and acid phosphatase at 45 ℃ for 16 h, the lower liquid was collected after centrifugation for analysis. UPLC separation was performed on an ACQUITY~(TM) HSS T3(3.0 mm×150 mm, 1.8 µm) column, 2 mmol/L ammonium formate(containing 0.1% formic acid) solution and acetonitrile(containing 0.1% formic acid) were used as mobile phase. Quantitative detection was performed by internal standard method. RESULTS: 11 nutritional components can be effectively separated and detected in 12 min, and the linear correlation coefficients(R~2) were all above 0.995. The limits of detection(LODs) were between 0.05 and 0.50 µg/L, and the limits of quantification(LOQs) were between 0.20 and 1.25 µg/L. The recovery rates of three-level addition were 85.6%-119.3%, and the precision RSDs were between 3.68% and 7.82%(n=6). Based on the detection of 60 liquid milk samples from 5 different animals, it was found that the contents of 11 nutrients in liquid milk from different milk sources were significantly different, but pyridoxine could not be detected. CONCLUSION: The method can quantitatively detect 11 water-soluble nutrients, including free and bound forms, by effective enzymolysis. It is sensitive, reproducible and can meet the needs of quantitative detection.

[Determination of furosine in liquid milk by high performance liquid chromatography-quadrupole time-of-flight mass spectrometry].

Furosine is often used both domestically and internationally as an indicator of the degree of heating to evaluate milk quality. However, in actual detection, the complexity of the milk matrix may lead to the inaccurate quantification of furosine in liquid milk. Therefore, in this study, an efficient and accurate method based on high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (HPLC-Q-TOF/MS) was established to determine furosine in liquid milk. A 2.00 mL milk sample was hydrolyzed with 5 mL 12.00 mol/L hydrochloric acid solution and 1 mL water at 110 ℃ for 12 h. After hydrolysis, vortex-mixing and filtration were performed. The filtrate was diluted six times with 6.00 g/L ammonium acetate solution and then analyzed. Gradient elution was performed with 0.20% formic acid aqueous solution and acetonitrile solution as mobile phases, followed by chromatographic separation on an AQ-C18 column (150 mm×3.5 mm, 5 µm). The data were collected by Q-TOF/MS with an electrospray ionization source operated in positive-ion mode. The accuracy of the quantification of furosine in milk was assessed by investigating the effects of the hydrochloric acid concentration (0.30, 1.25, and 3.00 mol/L) in the furosine solution on the MS response. The results showed that high hydrochloric acid concentrations inhibited the response signals. A good linear relationship was obtained in the mass concentration range of 0.05-2.00 mg/L, with a correlation coefficient (r) of 0.994. The limit of detection of the method was 0.50 mg/100 g, which meets the requirements of actual sample detection. The average recoveries of furosine ranged from 79.9% to 119.7% at three spiked levels of 1.52, 3.03, and 15.17 mg/100 g, with relative standard deviations of 1.4%-2.6%. The method was applied to detect 303 samples from 101 batches of pasteurized milk sold in the market, and the contents of furosine in these samples ranged from 5.1 to 11.9 mg/100 g. The proposed method is characterized with high efficiency, recovery, sensitivity, and accuracy. Thus, it can be used for the determination of large quantities of samples and provides technical support for the continuous promotion of the high-quality development of the whole dairy industry chain.

Investigation of melamine and cyanuric acid concentration in several brands of liquid milk and its non-carcinogenic risk assessment in adults and infants.

In this study, the melamine and cyanuric acid concentration of widely used milk brands and the probability of non-carcinogenic risk of the brands for adults and infants were investigated. These values were 1.37 mg/L, 1.10 mg/L, and 1.09 mg/L, which corresponded to creamy sterilized sample, high-fat (creamy) pasteurized sample, and low-fat (less-creamy) pasteurized sample, respectively. Similarly, the highest amount of cyanuric acid occurred in brand A with the values of 0.79 mg/L, 0.65 mg/L, and 0.64 mg/L, which was reported in the same samples mentioned for melamine. The HQ (Hazard Quotient) of melamine in the brands of A, B, C and D for adults was 0.0025, 0.0011, 0.0006 and 0.0008 respectively. These values for infants were reported as 2.2280, 0.9444, 0.5714 and 0.6714 respectively. The risk probability of melamine for adults was less than 1. However, the HQ in brand A for infants was greater than 1 (2.380), which indicate the high probability of non-carcinogenic risk. Furthermore, the HI (Hazard Index) values of the brands of A, B, C and D for infants were 2.7913, 1.1737, 0.7067 and 0.838, respectively. The simultaneous melamine and cyanuric acid in the brands A and B in for infants increase the non-carcinogenic risk probability by approximately 2.8 and 1.2 times, respectively. The results revealed that the melamine and cyanuric acid concentrations in creamy milk samples (0.5%) were higher than in less-creamy milk samples (2.5%). Moreover, the amount of the compounds in sterilized milk samples was higher than pasteurized. In this study, a conversion factor (0.7) was proposed in order to find out the concentration of cyanuric acid in milk sample with the amount of melamine is known but the cyanuric acid concentration is unknown.

[Determination of 10 carbamate pesticide residues in liquid milk by ultra performance liquid chromatography-tandem mass spectrometry with pass-through solid-phase extraction purification].

Carbamates are used in broad-spectrum insecticides and herbicides, and have highly efficient, low-residue, and long-lasting characteristics. However, this type of pesticide exerts mutagenic, teratogenic, carcinogenic, and other adverse effects, and its frequent use can exceed the recommended scope and limits. Research on the determination of carbamate pesticides mainly focuses on foods of plant origin and pays less attention to foods of animal origin. The methods for carbamate determination described in the current national standards have complicated operating procedures and low efficiency. Therefore, highly efficient and accurate methods for carbamate detection in milk must be established. In this work, a rapid method based on pass-through solid-phase extraction (SPE) purification coupled with ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was developed for the simultaneous determination of 10 carbamate pesticides in liquid milk. The pretreatment and instrument methods were systematically optimized. The milk sample was extracted with acetonitrile, and then purified using a Captiva EMR-Lipid filtration kit. The purified extract was separated on an ACQUITY UPLC BEH C18 column with mobile phase of methanol and 0.1% formic acid aqueous solution in gradient elution. The flow rate was 0.3 mL/min. Column temperature was 35 ℃. Quantitative analysis was performed using the external standard method with matrix matching curves. The 10 carbamate pesticides showed good linear relationships in the mass concentration range of 2-200 µg/L, with correlation coefficients greater than 0.999. The limits of detection (LODs) and quantification (LOQs) for the 10 carbamate pesticides were 0.045-0.23 and 0.15-0.77 µg/kg, respectively. Recovery tests were conducted using the blank-matrix method at three spiked levels of 15, 50, and 100 µg/kg, and good recoveries for the 10 carbamate pesticides were obtained. In particular, the recoveries for the three spiked levels of 15, 50, and 100 µg/kg were 68.7%-93.3% with relative standard deviations (RSDs) of 1.8%-8.0%. The proposed method is efficient, convenient, accurate, and suitable for the rapid detection of the 10 carbamate pesticides in liquid milk. Compared with the conventional NH2 and ENVITM-18 SPE columns used in the national standard determination method, the proposed method demonstrated better purification effects. The recoveries for aldicarb sulfoxide, aldicarb sulfone, methomyl, and carbaryl after purification using the Captiva EMR-Lipid kit increased from 60% to 80%. Thus, the proposed method is suitable for targets with strong polarity and gives measurement results with good repeatability and accuracy.

Modelling potential human exposure to the urease inhibitor NBPT through the environment-food pathway.

The urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT) has recently attracted a lot of attention attributing to its efficiency in reducing ammonia loss from urea fertiliser applied to temperate grassland soils. Ammonia gas lost to the environment causes soil acidification, eutrophication and contributes to global warming through increased greenhouse gas emissions and ozone layer depletion. The active chemical NBPT blocks the soil microbial enzyme (urease) and reduces ammonia emission. Furthermore, NBPT's use in agriculture might benefit farmers by reducing reliance on expensive nitrate fertiliser and aiding in a shift to more urea-based fertiliser (using NBPT co-applied with urea is more cost-effective). The present study was carried out to characterise the potential transfer of NBPT from grass to liquid milk and compute the associated human health risks. Using probabilistic risk assessment techniques, an exposure assessment model was developed to calculate the Estimated Daily Intake (EDI) of NBPT from milk, following co-application of NBPT with a urea N-fertiliser. Results show that the predicted mean concentration of NBPT in milk is 2.5 × 10-8 mg NBPT/kg milk, while the mean daily intake (EDI) of NBPT is 5 × 10-11 mg NBPT /kg BW/day). Back-calculations revealed that, under the studied conditions, for the EDI to exceed ADI of 3 × 10-2 mg NBPT/kg BW/ day, the NBPT application rate would need to exceed the NBPT fertiliser limit (0.09-0.2% by mass of urea nitrogen) set in the Commission Regulation (EC) No 1107/2008, and the bio-transfer factor would need to be over 100% (implausible). Sensitivity analysis revealed soil pH (SPH), phytoaccumulation factor (PF), NBPT permissible levels in fertiliser (NBPT%), pasture cover (P), and grazing rotation length (t) as critical factors influencing the EDI of NBPT. The present study concludes that NBPT presents negligible risk to human health under the conditions and assumptions studied.

Qualitative and semi-quantitative analysis of melamine in liquid milk based on surface-enhanced Raman spectroscopy.

Melamine is one of the common limited contaminations in dairy products. The traditional detection method has a long period and complicated pretreatment process. The rapid detection method is the better method to solve the screening of limited contaminations. In this paper, taking melamine as the research object, the surface enhanced Raman spectrum of melamine in liquid milk were collected by portable Raman spectrometer, and melamine was qualitatively identified and semi-quantitatively analyzed by Raman characteristic peak and Raman intensity, and a simple and efficient rapid screening method for limited contaminations was developed. The limit of detection is 0.25 mg/kg. The probability of detection is 100% at 2.5 mg/kg, which is the same between the two laboratories, indicating that the semi-quantitative method has good repeatability. The method of melamine proposed in this study can meet the rapid screening requirements of limited contaminations at the maximum residue limit, and has a good application prospect.

Simultaneous Determination of Nine Quinolones in Pure Milk Using PFSPE-HPLC-MS/MS with PS-PAN Nanofibers as a Sorbent.

In this study, a packed-fiber solid-phase extraction (PFSPE)-based method was developed to simultaneously detect nine quinolones, including enrofloxacin (ENR), ciprofloxacin (CIP), ofloxacin (OFL), pefloxacin (PEF), lomefloxacin (LOM), norfloxacin (NOR), sarafloxacin (SAR), danofloxacin (DAN), and difloxacin (DIF), in pure milk, using high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS). Polystyrene (PS) and polyacrylonitrile (PAN) were combined to form PS-PAN composite nanofibers through electrospinning. The nanofibers were used to prepare the home-made extraction columns, and the process was optimized and validated using blank pure milk. The analytical method showed high accuracy, and the recoveries were 88.68-97.63%. Intra-day and inter-day relative standard deviations were in the ranges of 1.11-6.77% and 2.26-7.17%, respectively. In addition, the developed method showed good linearity (R2 ≥ 0.995) and low method quantification limits for the nine quinolones (between 1.0-100 ng/mL) for all samples studied. The nine quinolones in the complex matrix were directly extracted using 4.0 mg of PS-PAN composite nanofibers as a sorbent and completely eluted in 100 µL elution solvent. Therefore, the developed PFSPE-HPLC-MS/MS is a sensitive and cost-effective technique that can effectively detect and control nine quinolones in dairy products.

Au@Ag-TGANPs based SERS for facile screening of thiabendazole and ferbam in liquid milk.

Surface-enhanced Raman spectroscopy based on thioglycolic acid (TGA) functionalized silver-coated gold nanoparticles (Au@Ag-TGANPs) was developed for the facile screening of thiabendazole (TBZ) and ferbam (0.025-10 ppm) in liquid milk for the first time. Results showed that silver-coated gold nanoparticles (Au@AgNPs) with a core size of 32 nm and a shell thickness of 5 nm was successfully modified with 3 nm TGA. The sensitive Au@Ag-TGANPs could enhance TBZ and ferbam signals by factors of 6.4 × 104 and 9.8 × 104, respectively, and achieved the detection of TBZ and ferbam with limits of detection of 0.12 and 0.003 ppm, R2 of 0.988 and 0.9821, percent recoveries of 88-103% and of 87.2-103.5%, and relative standard deviations of 4.1-9.2% and 3.5-8.3%, respectively. The current simple and green method could thus be used to detect other unsafe chemicals in future studies.

Survey of Aflatoxin M1 in Commercial Liquid Milk Products in China.

ABSTRACT: The objective of this study was to investigate the occurrence of aflatoxin M1 (AFM1) in Chinese liquid milk products. A total of 190 liquid milk samples, including 168 ultrahigh-temperature-treated milk samples and 22 pasteurized milk (PM) samples, were collected in August 2019. A screening assay with the Charm rapid test kit and a confirmation method with high-performance liquid chromatography were used for AFM1 analysis. Nine (4.74%) samples were screened positive, of which 5 (2.11%) samples were confirmed with concentration levels of 0.022 to 0.049 µg/kg. The AFM1 levels confirmed were all below the maximum residue levels set by China, the European Union, the United States, and the Codex Alimentarius Commission. The detection rate of AFM1 in domestic milk samples was 3.39%, while no AFM1 was detected in samples of imported milk. The prevalences of AFM1 detected in three groups of brands were as follows: group I, the major brands of China, 2.70%; group II, the local city domestic brands, 4.55%; and group III, the brands imported into China, 0. The detection rate of AFM1 was significantly higher in PM samples (9.09%) than in ultrahigh-temperature-treated samples (1.19%) (P < 0.05). Although the residue level of AFM1 did not exceed the maximum residue levels in any of the samples, the higher detection rate in local Chinese brands, especially in PM samples, deserves the attention of the Chinese government and consumers.

A Survey of 61 Veterinary Drug Residues in Commercial Liquid Milk Products in China.

ABSTRACT: To investigate the drug residue status in commercial liquid milk products in China, 190 samples, including ultrahigh temperature milk (n = 168) and pasteurized milk (n = 22) samples, were collected in 2019. Milk samples were analyzed for the presence of any of the 61 veterinary drugs in them by using a screening assay combined with an ultraperformance liquid chromatography-tandem mass spectrometry analysis. Ten (5.26%) samples were found positive for ß-lactams, tetracyclines, and aminoglycosides, and six (3.16%) samples were confirmed residual for penicillin G (n = 6; 3.16%), tetracycline (n = 1; 0.53%), and oxytetracycline (n = 1; 0.53%), with the maximum concentration of 2.85, 40.64, and 12.35 µg kg-1, respectively. Drug residue detection rate in group II (4.55%; the local city domestic brands) was higher than that in group I (2.70%; the major brands of China) and group III (2.78%; the imported brands into China) and higher in domestic samples (3.39%) than that in imported samples (2.78%), and higher in pasteurized milk samples (9.09%) than in ultrahigh temperature milk samples (2.38%). All drug residue levels were far below the regulated maximum residue limits. However, based on some veterinary drug residues detected in the samples, there is a potential veterinary drug risk in liquid milk products in the Chinese market, and this situation deserves the attention of governments and consumers.

[Determination of A2 ß-casein and total ß-casein in cow milk and milk powder by capillary zone electrophoresis].

ß-casein (ß-CN) is one of the major casein proteins in cow milk. There are 13 different variants documented for ß-CN in cow milk, among which A1 and A2 are the major variants. The separation and quantitation of A2 ß-CN are imperative for A2 dairy products. A new capillary zone electrophoresis (CZE) method with UV detection at 214 nm was established for the separation and quantification of the A2 variant and total ß-CN content in cow milk and milk powders. The separation of ß-CN variants was achieved on bare fused silica capillaries (50 µm×30/40 cm (effective/total length)). The separation buffer was a mixture of 4 mol/L urea, 0.2% (mass fraction) hydroxypropyl methylcellulose, 140 mmol/L citric acid, and 50 mmol/L disodium hydrogen phosphate buffer (pH 2.7). The corrected peak areas and the concentrations of total ß-CN and the A2 variant showed good linearity, with correlation coefficients (r2) ranging from 0.9968 to 0.9997. The intra-day precisions for A2 ß-CN and total ß-CN determination in four samples (two pasteurized milk samples and two milk powder samples) were in the ranges of 2.4%-4.7% and 2.6%-4.8%, respectively. The inter-day precisions for A2 ß-CN and total ß-CN determination in four samples were in the ranges of 4.0%-6.3% and 3.9%-6.7%, respectively. The recoveries of A2 and total ß-CN ranged from 85.5% to 106.4%. With the established CZE method, the A2 ß-CN variant and total ß-CN protein in liquid and powder bovine milk products could be separated and accurately quantified. By calculating the A2 ß-CN content in the total ß-CN, the quality of A2 dairy products can be evaluated, and this in turn would aid in the protection of consumer rights.

Multi-mycotoxins analysis in liquid milk by UHPLC-Q-Exactive HRMS after magnetic solid-phase extraction based on PEGylated multi-walled carbon nanotubes.

A simple and rapid magnetic solid-phase extraction (MSPE) method using PEGylated multi-walled carbon nanotubes magnetic nanoparticles (PEG-MWCNTs-MNP) as absorbents is proposed for isolation and enrichment of aflatoxin B1 (AFB1), aflatoxin B2 (AFB2), aflatoxin G1 (AFG1), aflatoxin G2 (AFG2), aflatoxin M1 (AFM1), aflatoxin M2 (AFM2), ochratoxin A (OTA), zearalenone (ZEA), zearalanone (ZAN), α-zeralanol (α-ZAL), ß-zeralanol (ß-ZAL), α-zeralenol (α-ZOL), and ß-zeralenol (ß-ZOL) from liquid milk. Combined with ultra-high performance liquid chromatography Q-Exactive high resolution mass spectrometry, simultaneous qualification of these mycotoxins was achieved with sensitivity and specificity. The proposed method showed a good linearity (R2 ≥ 0.995), high sensitivity (limit of detection in the range of 0.005-0.050 µg/kg and limit of quantification in the range of 0.015-0.150 µg/kg), adequate recovery (81.8-106.4%), and good repeatability (intra-day precision in the range of 2.1-8.5% and inter-day precision in the range of 3.9-11.7%). It has been successfully applied to the determination of 13 mycotoxins in real liquid milk samples.

Health Consciousness and Its Effect on Perceived Knowledge, and Belief in the Purchase Intent of Liquid Milk: Consumer Insights from an Emerging Market.

This study is based on the influence of consumers' health consciousness (HC), perceived knowledge (PK) and beliefs affecting the attitude and purchase intent (PI) of the consumers. The outcome of this study is obtained through an exclusive survey conducted on a randomly selected sample of 712 households who purchase liquid milk (LM) in the cities of Dhaka and Chittagong in Bangladesh. A structured questionnaire is used to interview these participants to obtain data which are analysed employing descriptive statistics, Confirmatory Factor Analysis, and Structural Equation Modelling. The results of the analyses corroborate that consumers' health consciousness has a positive impact on perceived knowledge, belief, and attitude, but not on purchase intent. In addition, belief affects both the attitude and PI positively. Although consumers' perceived knowledge is too low to constitute their attitude towards LM, it has a positive, significant impact on the PI. The results also reveal that more than a third of the respondents consume LM several times per month, followed by more than a quarter of the sampled respondents who consume LM several times per week, and these consumption patterns have a positive and significant influence on the PI. Moreover, the monthly income of the family, age, and labelling preference are significantly correlated with PI.

[Simultaneous determination of six estrogens in dairy products by high performance liquid chromatography-triple quadrupole-ion trap mass spectrometry coupled with matrix solid-phase dispersion and solid phase extraction].

Matrix solid-phase dispersion (MSPD) and solid-phase extraction (SPE) were respectively developed for the pretreatment six estrogens in milk powder and liquid milk. It was implied that MSPD was suitable for the treatment of milk powder, while SPE was suitable for liquid milk treatment. Based on the optimized pretreatment procedures, the method for the simultaneous determination of the six estrogens in different dairy products was established by high performance liquid chromatography-triple quadrupole-ion trap mass spectrometry (HPLC-Q-TRAP-MS). The proposed method provided low limits of detection (LODs, 0.01-0.05 mg/L) and limits of quantification (LOQs, 0.05-0.10 mg/L), wide linearity range of 0.1-200 mg/L (except for estriol of 0.1-20 mg/L) with excellent correlation coefficients (R2)> 0.99. The average recoveries of the six estrogens in milk powder pretreated by MSPD ranged from 71.8% to 106.0% with RSD of 1.6%-9.2% (n=3), while the corresponding average recoveries in liquid milk pretreated by SPE ranged from 70.3% to 108.4% with RSD of 2.0% and 11.0% (n=3) with spiking levels of 1.0, 5.0, and 10 mg/kg, respectively. This sensitive and reliable method meets the demand for the analysis of trace estrogen residues in complex matrices.

[Liquid milk exposure and risk assessment of thiocyanate in Chinese populations].

Objective: To analyze liquid milk exposure of thiocyanate among Chinese population and preliminarily assess its health risk. Methods: A total of 2 059 raw milk samples were collected during 2013 and 2014 from 12 Chinese provinces, New Zealand and Netherlands. Farms were chosed according to the main sources of dairy companies, the distribution of farms and the yield of milk. Content of thiocyanate were detected by ion chromatography. Liquid milk consumption data were taken from Chinese beverage and alcoholic beverage consumption survey in 18 cities or counties in 9 provinces, including 16 775 subjects older than 3. A simple distribution model was used to estimate the exposure of thiocyanate from liquid milk. The tolerable daily intake (TDI) of thiocyanate was made 0.08 mg·kg(-1)·d(-1). Then the exposures of different age groups were compared with TDI. Results: Finally, 1 331 samples out of 2 059 were detected to contain thiocyanate. The detection rate was 65%. The average concentration of thiocyanate was 2.11 mg/kg, with a range of 0.10-16.20 mg/kg. The general population's consumption of thiocyanate by drinking liquid milk was 0.001 mg · kg(-1) · d(-1), which was lower than TDI. The P(95) of general population and consumers were 0.009 mg · kg(-1) · d(-1) and 0.020 mg·kg( -1)·d(-1) respectively, which were also lower than TDI. Mean exposures of population aged 3-6, 7-12, 13-17, 18-59 as well as elderly aged 60 and above were 0.007, 0.003, 0.002, 0.001 and 0.001 mg · kg(-1)·d(-1) respectively, which were all lower than TDI. Conclusion: The results suggested that the health risk of thiocyanate exposure by drinking liquid milk among Chinese population was at a low level. However, milk products for children deserve more concern.

Liquid milk exposure and risk assessment of thiocyanate in Chinese populations / 中华预防医学杂志

Objective@#To analyze liquid milk exposure of thiocyanate among Chinese population and preliminarily assess its health risk.@*Methods@#A total of 2 059 raw milk samples were collected during 2013 and 2014 from 12 Chinese provinces, New Zealand and Netherlands. Farms were chosed according to the main sources of dairy companies, the distribution of farms and the yield of milk. Content of thiocyanate were detected by ion chromatography. Liquid milk consumption data were taken from Chinese beverage and alcoholic beverage consumption survey in 18 cities or counties in 9 provinces, including 16 775 subjects older than 3. A simple distribution model was used to estimate the exposure of thiocyanate from liquid milk. The tolerable daily intake (TDI) of thiocyanate was made 0.08 mg·kg-1·d-1. Then the exposures of different age groups were compared with TDI.@*Results@#Finally, 1 331 samples out of 2 059 were detected to contain thiocyanate. The detection rate was 65%. The average concentration of thiocyanate was 2.11 mg/kg, with a range of 0.10-16.20 mg/kg. The general population's consumption of thiocyanate by drinking liquid milk was 0.001 mg · kg-1 · d-1, which was lower than TDI. The P95 of general population and consumers were 0.009 mg · kg-1 · d-1 and 0.020 mg·kg -1·d-1 respectively, which were also lower than TDI. Mean exposures of population aged 3-6, 7-12, 13-17, 18-59 as well as elderly aged 60 and above were 0.007, 0.003, 0.002, 0.001 and 0.001 mg · kg-1·d-1 respectively, which were all lower than TDI.@*Conclusion@#The results suggested that the health risk of thiocyanate exposure by drinking liquid milk among Chinese population was at a low level. However, milk products for children deserve more concern.

A novel ultra-high performance liquid chromatography method for the rapid determination of ß-lactoglobulin as heat load indicator in commercial milk samples.

The level of undenatured acid-soluble ß-lactoglobulin can be used as an indicator to assess the heat load applied to liquid milk, thus further allowing the discrimination between milk originating from different thermal production processes. In this work, a new UHPLC method for the rapid determination of bovine ß-lactoglobulin in 1.8min only (total runtime 3min) is presented using simple UV detection at 205nm. Separation selectivity for possibly co-eluting other major whey proteins (bovine serum albumin, lactoferrin, α-lactalbumin, immunoglobulin G) was verified, and the method validated for the analysis of liquid milk samples regarding linearity (20-560µg/mL, R(2)>0.99), instrumentation precision (RSDs<2.8%), limits of detection and quantification (7 and 23mg/L milk), repeatability of sample work-up (RSDs≤2.6%) and method recovery (103%). In total, 71 commercial liquid milk samples produced using different preservation techniques (e.g., thermal or mechanical treatment), hence featuring different applied heat loads, were profiled for their intrinsic undenatured acid-soluble ß-lactoglobulin levels. As expected, pasteurized milk showed the highest concentrations clearly above 3000mg/L due to pasteurization being the mildest thermal treatment, while in contrast, ultra-high temperature heated milk featured the lowest amounts (<200mg/L). For extended shelf life (ESL) milk, quite diverse levels were determined ranging from ∼100 up to 4000mg/L, thus clearly illustrating variable applied heat loads and impacts on the "nativeness" of milk essentially due to the fact that the production technologies used for ESL milk may differ significantly, and are currently not regulated in the EU.

Rapid screening of mycotoxins in liquid milk and milk powder by automated size-exclusion SPE-UPLC-MS/MS and quantification of matrix effects over the whole chromatographic run.

An automated, size-exclusion solid phase extraction (SPE)-UPLC-MS/MS protocol without pre-treatment of samples was developed to screen for four mycotoxins (OTA, ZEN, AFB1, and AFM1) in liquid milk and milk powder. Firstly, a mixed macropore-silica gel cartridge was established as a size-exclusion SPE column. The proposed methodology could be a candidate in green analytical chemistry because it saves on manpower and organic solvent. Permanent post-column infusion of mycotoxin standards was used to quantify matrix effects throughout the chromatographic run. Matrix-matched calibration could effectively compensate for matrix effects, which may be caused by liquid milk or milk powder matrix. Recovery of the four mycotoxins in fortified liquid milk was in the range 89-120% and RSD 2-9%. The LOD for the four mycotoxins in liquid milk and milk powder were 0.05-2 ng L(-1) and 0.25-10 ng kg(-1), respectively. The LOQ for the four mycotoxins in liquid milk and milk powder were 0.1-5 ng L(-1) and 0.5-25 ng kg(-1), respectively.

Colorimetric detection of melamine based on methanobactin-mediated synthesis of gold nanoparticles.

A simple and rapid field-portable colorimetric method for the detection of melamine in liquid milk was reported. Methanobactin (Mb) could reduce Au (III) to Au (0) and mediate the synthesis of gold nanoparticles (Au-NPs). Upon the addition of melamine, melamine interacted with oxazolone ring of Mb, which interrupted the formation of Au-NPs. Melamine could also stimulate the aggregation of formed Au-NPs. In this paper, these characteristics have been used to detect melamine in liquid milk by naked eyes observation with a detection limit of 5.56 × 10(-6)M (0.7 mg/kg). Further, the plasmon absorbance of the formed Au-NPs allowed the quantitative detection of melamine by UV-vis spectrometer. A linear correlation was existed between the absorbance and the melamine concentration ranging from 3.90 × 10(-7)M to 3.97 × 10(-6)M with a correlation coefficient of 0.9685. The detection limit (3σ) obtained by UV-vis spectrum was as low as 2.38 × 10(-7)M (i.e., 0.03 mg/kg).

Simple spectrophotometric method for determination of melamine in liquid milks based on green Mannich reaction.

A new and simple spectrophotometric method has been developed and validated for measuring the contamination of melamine in different milk products. The method is based upon measuring the absorption of the complex formed from melamine, 4-hydroxyacetophenone (Hap) and 1-pyrene carboxaldehyde (Pcd), which was adapted from the Mannich reaction. Quantitative analysis was done at a wavelength of 236 nm within a few minutes. The reaction was optimized by focusing on both obtaining high performance of the method and to concern the volatility and toxicity of used reagents. This method provided a linear dynamic range, limit of detection and limit of quantification of 0.100-3.78, 0.08 and 0.14 mg L(-1), respectively. The relative standard deviation (RSD) was 3.6% (n=10). The recoveries of melamine spiked liquid milk samples, with melamine concentrations of 0.63, 1.26, 1.89 and 2.52 mg L(-1), were 87.7±3.7%, 91.1±8.8%, 89.2±4.4% and 90.6±3.6% (n=3), respectively.