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Published in last 1 year |  In last 2 years |  In last 3 years |  All Please wait a minute... For Selected: Download Citations EndNote Ris BibTeX Toggle Thumbnails Select Microbial Identification and Analysis of the Production Environment of Infant Formula in Fujian Province in 2024 QIU Xibin Journal of Dairy Science and Technology    2025, 48 (4): 28-35.   DOI: 10.7506/rykxyjs1671-5187-20250210-011 Abstract （97）   HTML （7）    PDF （3024KB）（31）       Knowledge map    Save Objective: To investigate the microbial community composition and structure of the processing workshop of infant formula in Fujian province in 2024, to reveal the microbial diversity present in the workshop as well as the changes in the distribution of microorganisms among different functional zones, and to unveil the drug resistance of the isolates. Methods: A stratified random sampling strategy was employed to collect surface microbiota, airborne planktonic bacteria and sedimentary microbes from the selected manufactures by aseptic swabbing, six-stage Andersen air sampling, and plate exposure methods, respectively. The purified isolates were analyzed by 16S rDNA gene sequencing and multi-sequence alignment and phylogenetic tree construction were carried out using the MEGA software. To ensure taxonomic accuracy, the VITEK? 2 Compact fully automatic microbial identification system was utilized for physiological and biochemical characterization, and phenotypic validation was performed by referring to the latest Bergey’s manual of systematic bacteriology. A dual verification framework integrating molecular and traditional phenotypic identification was thereby established. Antimicrobial susceptibility testing was performed using standardized protocols, and based on the data obtained, a heatmap was generated. Results: A total of 355 isolates were obtained, belonging to 19 genera. Out of these, 61.1% were Gram-positive bacteria, and 38.9% were Gram-negative bacteria, Staphylococcus, Bacillus, and Pseudomonas being the major ones, accounting for 72.95% of the total collected strains. Among them, Staphylococcus has the highest distribution rate, accounting for 33.80% of all isolated strains The phylogenetic analysis and spatial distribution pattern of Staphylococcus revealed personnel movement and material handling to be the principal contamination vectors. Antimicrobial susceptibility testing demonstrated that coagulase-negative staphylococci (CoNS) showed 100% susceptibility to teicoplanin, vancomycin and linezolid and 20%–90% susceptibility to penicillin G (benzylpenicillin), erythromycin, methicillin and clindamycin. Some of the environmental isolates showed multi-drug resistance. Conclusion: Staphylococcal species were the dominant microbial population in the infant formula production environment, with workshop operators being their largest vector. The identification of antimicrobial-resistant isolates underscores the need for enhanced personnel sanitation and air purification to reduce the risk of microbial contamination. Related Articles | Metrics Select Simultaneous Determination of Five Major Proteins in Whey Protein Powder by Reversed-Phase High-Performance Liquid Chromatography DAI Yuting, YANG Jinqing Journal of Dairy Science and Technology    2025, 48 (3): 38-42.   DOI: 10.7506/rykxyjs1671-5187-20250113-002 Abstract （207）   HTML （7）    PDF （2331KB）（356）       Knowledge map    Save In this paper, a reversed-phase high-performance liquid chromatography method was proposed to determine five major proteins including α-lactalbumin, β-lactoglobulin, glycomacropeptide, bovine serum albumin, and immunoglobulin G in whey protein powder. After dissolution and ultrasonication, samples were separated on ChromCore 300 C4-T chromatographic column (4.6 mm × 150 mm, 5 μm) with gradient elution using a mobile phase consisting of 0.1% (V/V) aqueous trifluoroacetic acid (TFA) and 90% acetonitrile (containing 0.09% TFA). These analytes were detected using a diode array detector scanning in the wavelength range from 200 to 700 nm at 214 nm. Under the optimal experimental conditions, the five major bovine whey proteins were well separated within 30 min. The average recoveries from spiked samples were in the range of 83.5%–95.3% with relative standard deviations (RSDs) of 2.03%–7.49%. The limit of detection was 0.25% (m/m) for all analytes. The established method is rapid, accurate and sensitive that enables the simultaneous detection of the major bovine whey proteins in whey protein powder. Related Articles | Metrics Select Determination of Ethephon Residue in Milk by Ultra-high Performance Liquid Chromatography-Tandem Mass Spectrometry BAI Yanmei, ZHANG Lijia, WANG Yang, LIU Lijun, MO Nan, GAO Yujie, LI Peizhen, HU Xue, WU Xiaoli Journal of Dairy Science and Technology    2025, 48 (3): 43-48.   DOI: 10.7506/rykxyjs1671-5187-20241223-112 Abstract （148）   HTML （4）    PDF （2536KB）（110）       Knowledge map    Save An ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method with solid phase extraction (SPE) was established for the detection of ethephon residue in milk. In the sample pretreatment stage, formic acid solution was selected as the extraction solvent, and the extract was purified on an amino SPE column. The target compound was separated on a Waters Anionic Polar Pesticide column (150 mm × 2.1 mm, 5 μm) using gradient elution with a mobile phase consisting of 0.1% formic acid containing 50 mmol/L ammonium formate and acetonitrile. The detection was performed using electrospray?ionization in the negative ion mode with multiple reaction monitoring, and the matrix-matched external standard method was used for quantification. The calibration curve for ethephon showed an excellent linearity (r2 > 0.99) in the concentration range of 2 to 100 ng/mL, and the limit of detection and limit of quantification of this method were 0.5 and 1.0 μg/kg, respectively. At spiked concentration levels of 1.0, 2.0 and 10.0 μg/kg, the recoveries were between 92.50% and 113.76%, and the precision, expressed as relative standard deviation, ranged from 3.04% to 4.60%. In conclusion, the UPLC-MS/MS method has the advantages of high accuracy, specificity, and repeatability, and is very suitable for the determination of ethphon in milk. Related Articles | Metrics Select Development and Evaluation of Standard Reference Material for Iodine Analysis in Milk-Based Infant Formula Food for Special Medical Purposes LI Qingqing, LIU Junyao, YAN Jing Journal of Dairy Science and Technology    2025, 48 (3): 49-46.   DOI: 10.7506/rykxyjs1671-5187-20250223-012 Abstract （129）   HTML （4）    PDF （2203KB）（51）       Knowledge map    Save To address the need for iodine quantification in infant formula food for special medical purposes, a reference material for iodine analysis was developed. Powered infant formula milk for special medical purposes (containing partially hydrolyzed milk protein) was used as the matrix and added with dietary supplement of potassium iodide initially diluted with whey protein powder to establish a stable preparation system using stepwise dry dilution. The homogeneity and stability of the prepared reference material were verified using alkaline extraction combined with inductively coupled plasma mass spectrometry, and characteristic value assignment was conducted through a multi-laboratory collaborative approach. Results demonstrated excellent homogeneity and stability of the material, showing a characteristic value for iodine of (67.8 ± 4.6) μg/100 g (k = 2). This reference material could be useful for method validation, laboratory quality control, and instrument calibration for iodine determination in infant formula food for special medical purposes, providing technical support for ensuring accurate measurement of iodine content in this specialized food product. Related Articles | Metrics Select Optimized Gas Chromatographic Method for the Determination of Iodine Content in Liquid Milk LIANG Lin Journal of Dairy Science and Technology    2025, 48 (2): 15-19.   DOI: 10.7506/rykxyjs1671-5187-20240930-090 Abstract （138）   HTML （6）    PDF （2120KB）（24）       Knowledge map    Save The iodine content in liquid milk was determined via gas chromatography (GC). Through systematic screening and optimization of derivatizing reagents and derivatization time, higher measured values of the iodine content in liquid milk were obtained while solving the problem of poor repeatability of the traditional method. The optimized method was more efficient than the national standard method National food safety standard-determination of iodine in food (GB 5009.267-2020). The optimal pretreatment conditions were determined to be 1.0 mL of sulfuric acid, 2.0 mL of butanone, 0.5 mL of 3.5% (V/V) hydrogen peroxide, and derivatization reaction for 30 min. This study provides a reliable basis for this optimized scheme to achieve efficient and accurate detection of iodine in liquid milk and holds significant application value in the control of the iodine content in liquid milk. Related Articles | Metrics Select Correlation between Feed Types and the Beany Odor of Raw Milk LIU Yuru, LI Xinyi, CHEN Xiaomin, ZHANG Shuli, ZHANG Dexi Journal of Dairy Science and Technology    2025, 48 (2): 20-29.   DOI: 10.7506/rykxyjs1671-5187-20241122-100 Abstract （131）   HTML （3）    PDF （2109KB）（29）       Knowledge map    Save To investigate the correlation between the beany odor of raw cow’s milk and feed types, this study selected two samples of raw cow’s milk with beany odor and five common feeds: soybean meal, alfalfa, flaked corn, oat grass, and corn silage, and measured their volatile flavor compounds by headspace solid phase microextraction-gas chromatography-mass spectrometry (GC-MS). Key flavor compounds were identified using relative odor activity value (ROAV). The results indicated that acids and aldehydes contributed primarily to the beany odor of raw milk. A total of 49 volatile substances were identified in the two milk samples, among which hexanoic acid, octanoic acid, decanoic acid, decanal, nonanal, (E)-2-octenal, and (E)-2-decenal were the main beany odor substances. A total of 257 volatile substances were detected in all feed samples, including decanal, nonanal, and (E)-2-octenal. According to ROAV analysis, the beany odor compounds were more abundant in the feed samples than in the milk samples. The relative contents of beany odor compounds in the feed samples followed the following decreasing order of alfalfa > oat grass > soybean meal > flaked corn > corn silage, and flaked corn exclusively contained vanillin, with a strong milky aroma. Related Articles | Metrics Select Evaluation of Measurement Uncertainty in Microbiological Determination of Vitamin B6 in Milk Powder LIU Lu, GU Shenglin, XIA Yawen Journal of Dairy Science and Technology    2025, 48 (2): 30-34.   DOI: 10.7506/rykxyjs1671-5187-20241018-096 Abstract （194）   HTML （5）    PDF （3831KB）（21）       Knowledge map    Save To evaluate the measurement uncertainty in the microbiological determination of the vitamin B6 content in milk powder, we estimated various uncertainty sources according to the National food safety standard for the determination of vitamin B6 in foods (GB 5009.154-2023) and the Evaluation and expression of uncertainty in measurement (JJF 1059.1-2012), and calculated combined standard and extended uncertainties. The results showed that the content of vitamin B6 in milk powder was (9.34 ± 1.23) mg/kg (k = 2, p = 95%). Through uncertainty component analysis, it was found that measurement repeatability and the preparation of standard solution had a significant impact on the determination of the vitamin B6 content in milk powder. Related Articles | Metrics Select Monitoring and Dietary Exposure Assessment of Benzalkonium Chloride and Didecyl Dimethyl Ammonium Chloride Contamination in Infant Formula Milk Powder YU Shu Journal of Dairy Science and Technology    2025, 48 (1): 7-13.   DOI: 10.7506/rykxyjs1671-5187-20240921-087 Abstract （157）   HTML （6）    PDF （2534KB）（74）       Knowledge map    Save Benzalkonium chloride and didecyl dimethyl ammonium chloride residues in infant formula milk powder sold from 2022 to 2024 were detected and statistically analyzed. Based on the European Union’s allowable daily intake for benzalkonium chloride and the German Federal Institute for Risk Assessment’s allowable daily intake for didecyl dimethyl ammonium chloride, a point estimation method was used to provide estimated values applicable to the percentiles of the available sample quantities. The detection rates of C12-benzalkonium chloride C14-benzalkonium chloride, C16-benzalkonium chloride, and didecyl dimethyl ammonium chloride in infant formula milk powder were 23.3%, 16.8%, 15.4%, and 16.0%, respectively; the average residue levels from lower bound (LB) to upper bound (UB) were 10.96–12.18 and 3.71–4.13 μg/kg, respectively. The average exposure levels (LB–UB) to benzalkonium chloride for infants and young children aged 0–6, 7–12, and 13–36 months were 0.281–0.297, 0.036–0.047, and 0.026–0.032 μg/(kg mb·d), respectively. The average exposure levels (LB-UB) to didecyl dimethyl ammonium chloride were 0.091–0.095, 0.007–0.011, and 0.013–0.016 μg/(kg mb·d), respectively. The hazard quotient (HQ) for both substances was less than 1. The contamination levels of benzalkonium chloride and didecyl dimethyl ammonium chloride in infant formula milk powder sold from 2022 to 2024 were found to be at an acceptable level. Related Articles | Metrics Select Establishment of a Rapid Detection Method for β-Lactoglobulin in Milk by Mid-infrared Spectroscopy HUANG Jianhui, ZHANG Yanhui, ZHANG Yaoguang, ZHAO Cuiqin Journal of Dairy Science and Technology    2025, 48 (1): 14-19.   DOI: 10.7506/rykxyjs1671-5187-20241011-094 Abstract （109）   HTML （6）    PDF （2943KB）（46）       Knowledge map    Save In this study, a prediction model based on Fourier transform mid-infrared spectroscopy was developed for the rapid detection of β-lactoglobulin in milk. The content of β-lactoglobulin in 260 different batches of milk samples was determined as reference by high performance liquid chromatography (HPLC), and the mid-infrared spectra of raw milk were collected using an Fourier transform mid-infrared spectrometer. The effective wavebands were selected, and the background noise was eliminated by Savitsky-Golay (SG) smoothing, first-order derivative or second-order derivative pretreatment before the establishment of the β-lactoglobulin prediction model by using partial least squares regression (PLSR). The results showed that SG five-point smoothing second-order derivative was the optimum preprocessing method. The PLSR model exhibited good prediction accuracy with correlation coefficient (R2) of 0.932 for the calibration set, root mean square error of calibration (RMSEC) of 0.049%, R2 of 0.923 for the calibration set, and root mean square error of prediction (RMSEP) of 0.057%. Related Articles | Metrics Select Simultaneous Determination of Five Fat-Soluble Vitamins in Infant Formula Milk Powder by Ultra-high Performance Liquid Chromatography-Tandem Mass Spectrometry LI Jiao, LI Qiaolian, ZHOU Changmin, YUAN Shuai, LUO Jingyang, CHEN Jiao, DING Ting Journal of Dairy Science and Technology    2025, 48 (1): 20-23.   DOI: 10.7506/rykxyjs1671-5187-20240708-058 Abstract （147）   HTML （3）    PDF （1735KB）（53）       Knowledge map    Save A method was developed for simultaneous measurement of the levels of vitamins A, D3, K2, E, and β-carotene in infant formula milk powder using ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The calibration curves for the five fat-soluble vitamins showed good linearity within the concentration range of 1–800 ng/mL. The average recoveries at three spiked levels were between 92.0% and 108.0% with relative standard deviations (RSDs) ranging from 0.4% to 2.6%. The limits of quantification (LOQs) of this method were 12.5–125 μg/100 g. The proposed method was characterized by simple sample pre-treatment, high quantitative sensitivity, and good accuracy and precision. Related Articles | Metrics Select Determination of 3-Monochloropropane-1,2-Diol Esters and Glycidyl Esters in Infant Formula Milk Powder by Gas Chromatography-Mass Spectrometry WANG Shengjie, LIANG Lin Journal of Dairy Science and Technology    2024, 47 (6): 31-36.   DOI: 10.7506/rykxyjs1671-5187-20240606-042 Abstract （135）   HTML （2）    PDF （2157KB）（59）       Knowledge map    Save An analytical method for the determination of 3-monochloropropane-1,2-diol esters (3-MCPDEs) and glycidyl esters (GEs) in infant formula milk powder was established using gas chromatography-mass spectrometry (GC-MS). Based on optimized lipid extraction and derivatization conditions, the method was evaluated for spiked recovery, linear relationship, precision, limit of detection (LOD) and limit of quantification (LOQ). Quantification was carried out using the internal standard method. The proposed method showed good linearity in the range of 5–500 ng (r > 0.999), with an LOD of 0.006 mg/kg and an LOQ of 0.015 mg/kg. The recovery rates at three spiked concentration levels of 10, 100 and 500 ng ranged from 95.6% to 100.9%, with relative standard deviations (RSDs) less than 5.03%. The results of GC-MS and gas chromatography-tandem mass spectrometry (GC-MS/MS) for 3-MCPDEs and GEs in several batches of infant formula samples did not significantly differ. In addition, compared with GC-MS/MS, the GC-MS method was simpler and easier to operate with lower cost and could be promoted in different levels of laboratories. Therefore, this method is suitable for determining the content of 3-MCPDEs and GEs in infant formula milk powder. Related Articles | Metrics Select Performance Evaluation of Colloidal Gold Immunochromatographic Test Strips for Identification of Bovine-, Ovine- and Caprine-Derived Components in Dairy Products XU Zhipeng, PAN Qiuli, XIAO Jing, ZHANG Shuang, SONG Jiasheng, WANG Jun Journal of Dairy Science and Technology    2024, 47 (6): 37-42.   DOI: 10.7506/rykxyjs1671-5187-20240814-077 Abstract （277）   HTML （6）    PDF （2784KB）（98）       Knowledge map    Save According to the opinions of the state administration for market supervision on standardizing the use of rapid food detection, the performance of commercial colloidal gold immunochromatographic test strips for rapid in situ identification of bovine-, ovine- and caprine-derived ingredients in dairy products were evaluated in terms of application scope, detection limit, cross-reaction rate, sensitivity, false negative rate, false positive rate and coincidence rate with the results of the reference method. The results showed that the application scope of the test strip for bovine-derived ingredients was raw milk, and the detection limit was 5% (V/V); the application scope of the test strip for ovine- and caprine-derived ingredients was raw ovine and caprine milk, and the detection limit was 0.3% (V/V). Both test strips had no cross-reaction with enrofloxacin, sulfamethazine, dexamethasone, tetracycline or aflatoxin M1. The sensitivity, false positive rate and false negative rate of the test strips were 100%, 0% and 0%, respectively. The coincidence rate with the results of the reference method was high. In conclusion, the colloidal gold immunochromatographic test strips have high accuracy, and can be used for rapid in situ screening of adulterated milk. Related Articles | Metrics Select Rapid Determination of 54 Pesticide Residues in Fresh Milk by QuEChERS Pretreatment and Ultra-high Performance Liquid Chromatography-Tandem Mass Spectrometry YANG Qi, JIAO Xinzhe, MENG Hu, FANG Zhongfang, ZHANG Yaowu, ZHAO Lili, ZHANG Qianting Journal of Dairy Science and Technology    2024, 47 (6): 43-50.   DOI: 10.7506/rykxyjs1671-5187-20240816-080 Abstract （194）   HTML （5）    PDF （2906KB）（40）       Knowledge map    Save A high-throughput method for the screening and quantitation of 54 pesticide residues in fresh milk was developed by quick, easy, cheap, effective, rugged, safe (QuEChERS) extraction followed by ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The study optimized the composition of mobile phase, extraction solvent, extraction solvent volume, extraction salt packet formulation, and purification packet formulation. Furthermore, the matrix effect was evaluated and methodological evaluation were carried out. The results showed that the linear range was 5.0–100.0 μg/L for all 54 pesticides, with correlation coefficients (r) higher than 0.999. The limit of quantification (LOQ) was 10.0 μg/kg for all target analytes, and the average recoveries from spiked samples were 67.78%–119.38%, with relative standard deviations (RSDs) (n = 6) lower than 9%. The method is simple, rapid, sensitive, and accurate. It can meet the requirements of the simultaneous detection and analysis of 54 pesticide residues in fresh milk. Related Articles | Metrics Select Determination of 54 Pesticide Residues in Milk by Solid-Phase Extraction Combined with Gas Chromatography-Mass Spectrometry BAI Xiaoyun, MA Xiaochong, QI Xiaoru, SU Yuncong, ZHANG Yaoguang, LI Fei Journal of Dairy Science and Technology    2024, 47 (5): 12-19.   DOI: 10.7506/rykxyjs1671-5187-20240627-047 Abstract （199）   HTML （4）    PDF （1802KB）（175）       Knowledge map    Save A high-throughput gas chromatography-mass spectrometry method was established for the analysis of 54 pesticide residues in milk. Samples were extracted with acetonitrile while shaking, and the extract was concentrated and purified using solid-phase extraction (SPE) on a C18 column using acetonitrile as the eluent. The external standard method was used for quantification. The results showed that good linearity was observed over the concentration range from 0 to 1.00 μg/mL, with correlation coefficient (R2) greater than 0.990. Recoveries were between 43.33% and 113.87% with a relative standard deviation (RSD) of 1.8%–19.8% (n = 6). This method is accurate, simple and suitable for large numbers of milk samples. Related Articles | Metrics Select Detection of Common Molds and Yeasts in Low-Temperature Yogurt by TaqMan probe Real-Time Fluorescence Quantitative Polymerase Chain Reaction ZHANG Jie, CHEN Boxu, DU Haikuan, ZHANG Zilun, YAN Taotao, CHEN Jia, ZHOU Wei Journal of Dairy Science and Technology    2024, 47 (5): 20-24.   DOI: 10.7506/rykxyjs1671-5187-20240703-049 Abstract （217）   HTML （3）    PDF （2127KB）（360）       Knowledge map    Save In order to improve the detection efficiency of molds and yeasts in low-temperature yogurt, primers and probes were designed according to the sequences of the conserved gene elongation factor-1α (EF-1α) for molds and yeasts, respectively. A real-time fluorescence quantitative polymerase chain reaction (real-time PCR) method with TaqMan probe was established for the detection of molds and yeasts, respectively. The genomic DNA of fungi and lactic acid bacteria commonly found in low-temperature yogurt, were used as amplification templates for specificity testing. The sensitivity and repeatability were also tested, and the standard curves were constructed. The results showed that the designed primers and probes had good specificity; the sensitivity of the method was 101 and 102 CFU/mL for yeasts and molds, respectively; the coefficients of variation within and between groups in the repeatability test were less than 2%, indicating good reliability and stability; the correlation coefficients of the standard curves were higher than 0.99. Therefore, the real-time PCR method enables the rapid detection of molds and yeasts in low-temperature yogurt. Related Articles | Metrics Select Top-down Evaluation of Uncertainties in Quantitative Assays for Microorganisms LI Tiantian, WANG Yi, LI Zhijun, SUN Yingli, LI Caiqing, DONG Xiufang, HU Min Journal of Dairy Science and Technology    2024, 47 (5): 25-31.   DOI: 10.7506/rykxyjs1671-5187-20240814-078 Abstract （281）   HTML （3）    PDF （2351KB）（277）       Knowledge map    Save On the basis of Microbiology of the food chain-Estimation of measurement uncertainty for quantitative determinations (ISO 19036) and Guidelines for the estimation of measurement uncertainty of food microbiological quantitative detection (RB/T 228-2023), the top-down method was used to design an experimental scheme for uncertainty evaluation in three different quantitative assays by using raw and fermented milk as samples. The uncertainty evaluation for total colony number included technical uncertainty (utech), matrix uncertainty (umatrix) and Poisson distribution uncertainty (upoisson); when the result was 9.4 × 104 CFU/mL, the extended uncertainty was 0.31 (lg (CFU/mL)). The uncertainty evaluation for maximum probable number (MPN) included utech, umatrix, and uncertainty based on the most probable number (uMPN); when the result was 24 MPN/g, the extended uncertainty was 0.94 (lg (MPN/g)). The uncertainty evaluation for total colony number that needs to confirm target microorganisms included utech, umatrix, upoisson, and confirmatory uncertainty (uconf); when the result was 22 CFU/g, the extended uncertainty was 0.29 (lg (CFU/g)). Related Articles | Metrics Select Development of Quantitative Loop-Mediated Isothermal Amplification for Rapid Detection of Streptococcus thermophilus and Lactobacillus bulgaricus in Fermented Milk ZHOU Shuaikang, HU Lianxia, WANG Mengyang, LI Miao, LU Han, WANG Shijie Journal of Dairy Science and Technology    2024, 47 (3): 9-15.   DOI: 10.7506/rykxyjs1671-5187-20240505-033 Abstract （270）   HTML （8）    PDF （2254KB）（159）       Knowledge map    Save In this study, a rapid and quantitative method for the detection of viable bacterial counts of Streptococcus thermophilus and Lactobacillus bulgaricus in fermented milk was established using propidium monoazide (PMA) combined with quantitative loop-mediated isothermal amplification (PMA-qLAMP). The PMA treatment conditions for S. thermophilus and L. bulgaricus were optimized. A linear relationship was fitted between the logarithm of bacterial concentration and cycle threshold (Ct) value. The limit of quantification for S. thermophilus and L. bulgaricus was 7.2 × 103 and 5.6 × 104 CFU/g, respectively. The PMA-qLAMP method was applied to measure viable bacterial counts in commercial fermented milk, demonstrating good sensitivity and practicality. Related Articles | Metrics Select Determination of 25 β-Receptor Agonist Residues in Milk and Dairy Products by PRiME MCX Solid Phase Extraction Column Combined with Ultra-high Performance Liquid Chromatography-Tandem Mass Spectrometry FAN Lixin, YANG Liqiong, REN Xiaowei, YANG Cengceng, MENG Zhijuan, FAN Sufang Journal of Dairy Science and Technology    2024, 47 (3): 16-25.   DOI: 10.7506/rykxyjs1671-5187-20240606-041 Abstract （202）   HTML （3）    PDF （3673KB）（509）       Knowledge map    Save A method for the determination of 25 β-receptor agonist residues in milk and dairy products was established based on ultra-high performance liquid chromatography-tandem mass spectrometry. Samples were enzymatically hydrolyzed in 0.2 mol/L ammonium acetate solution at pH 5.2 for 16 h. After the removal of fat and protein through glass fiber filter paper, the filtrate was purified by solid phase extraction (SPE) using a PRiME MCX solid phase extraction column, and separated on a Waters BEH C18 column (100 mm × 2.1 mm, 1.7 μm) by gradient elution using a mobile phase composed of acetonitrile and 0.1% formic acid in water. Mass spectrometry was performed using an electrospray ionization source (ESI) in the positive ion mode with multiple reaction monitoring (MRM), and quantitative determination was performed using the internal standard method. The proposed method showed good linearity for all analytes in the concentration range of 0.2–50.0 ng/mL with coefficients of determination (R2) greater than 0.996; the recoveries ranged from 80.3% to 106.2% with relative standard deviations (RSDs) of 0.6%–8.5% (n = 6). The limits of detection (LOD) were 0.05–0.10 μg/kg, and the limits of quantification (LOQ) were 0.10–0.20 μg/kg. This method is simple, efficient and suitable for the determination of the 25 β-receptor agonist residues in milk and dairy products. Related Articles | Metrics Select Electronic Nose Based on Gas Chromatography for Analysis of Flavor Changes of Milk with Different Fat Contents during Storage ZHANG Shan, LI Wen, ZHANG Yuting, WEI Xuetong, SUN Ying, XUE Lu, ZHAO Pei, NIU Tianjiao Journal of Dairy Science and Technology    2024, 47 (3): 26-34.   DOI: 10.7506/rykxyjs1671-5187-20240422-028 Abstract （223）   HTML （2）    PDF （2621KB）（284）       Knowledge map    Save During storage, milk is prone to different degrees of oxidative degradation of fat with varying storage conditions, which changes the aroma components of milk. In this study, electronic nose based on gas chromatography (GC) and sensory evaluation were used to compare the changes in the composition of volatile flavor compounds and sensory properties of pasteurized whole milk, low-fat milk and skim milk (fat contents of 4, 1.4 and 0 g/100 mL) during storage at different temperatures. The results showed that all three milks maintained good flavor characteristics during storage at 4 ℃. The composition of flavor substances in whole milk was more complex, where 43 volatile compounds were identified, and no obvious stale flavor was perceived. The decreasing order of difficulty of fat oxidation was whole milk > low-fat milk > skim milk. Nonanal, a marker of lipid oxidation, was detected in both skim milk and low-fat milk. Methyl ketones derived from lipid oxidization such as 2-butanone, 2,3-butanedione, 2-hexanone, 2-heptanone and 2-undecanone were detected in skim milk during storage. The results of sensory evaluation were basically consistent with those of electronic nose. The sweetness and milky flavor of whole milk were more prominent, the flavor of low-fat milk was relatively bland, and skim milk tasted slightly bitter after 21 days of storage at 25 ℃. The findings of this study will provide a scientific basis for monitoring the flavor changes of milk products during storage and improving the quality of milk products. Related Articles | Metrics Select Determination of Vitamin C in Formulas for Special Medical Purpose Intended for Infants by Liquid Chromatography WU Xiuping, CHENG Baiyu, XU Xiaoqian, JIANG Ruiyu Journal of Dairy Science and Technology    2024, 47 (3): 35-40.   DOI: 10.7506/rykxyjs1671-5187-20240521-036 Abstract （151）   HTML （3）    PDF （2232KB）（403）       Knowledge map    Save A liquid chromatography (LC) method for the determination of vitamin C in formulas for special medical purpose intended for infants was established and validated. The sample was reduced, purified using an HLB solid phase extraction (SPE) cartridge, filtered through a 0.45 μm filter, and analyzed by hydrophilic interaction liquid chromatography (HILIC). The calibration curve was found to be linear in the concentration range of 0–50 μg/mL with correlation coefficient over 0.999. The limit of quantitation (LOQ) was 3.0 mg/100 g. Recoveries of spiked samples ranged from 95.2% to 102.8% with relative standard deviation (RSD) between 1.22% and 3.62%. The method is characterized by simple operation, accurate results and good reproducibility and suitable to determine vitamin C in formulas for special medical purpose intended for infants. Related Articles | Metrics Select Determination of 21 Veterinary Drugs in Cow and Goat milk and Milk Powder by QuEChERS Combined with Ultra Performance Liquid Chromatography-Quadrupole/Orbitrap Mass Spectrometry ZHANG Shenping, QIN Yu, GU Yingjuan Journal of Dairy Science and Technology    2024, 47 (2): 24-29.   DOI: 10.7506/rykxyjs1671-5187-20240409-018 Abstract （130）   HTML （7）    PDF （2755KB）（670）       Knowledge map    Save A method for the determination of 21 veterinary drugs in cow and goat milk and milk powder was established by the QuEChERS (quick, easy, cheap, effective, rugged, safe) sample pretreatment method combined with ultra performance liquid chromatography-quadrupole/orbitrap mass spectrometry (UPLC-Q/Orbitrap MS). Chromatographic conditions, mass spectrometric parameters and pretreatment conditions were optimized. Samples were extracted with acetonitrile in the presence of anhydrous sodium sulfate, purified using a mixture of primary secondary amine (PSA) and C18, separated on an Accucore RP-MS column (100 mm × 2.1 mm, 2.7 μm), and detected by UPLC-Q/Orbitrap MS. Good linearity was observed for all the analytes in the investigated concentration ranges with correlation coefficients (r2) of greater than 0.99. The limit of quantification (LOQ) of the proposed method was 0.5 μg/kg. The average recoveries at spiked concentration levels of 0.5, 2.0 and 10.0 μg/kg were 67.2%–110.2% with relative standard deviations (RSDs) of 3.6%–17.4% (n = 6). The method is simple and sensitive, and suitable for simultaneous detection of the 21 veterinary drugs in cow and goat milk and milk powder. Related Articles | Metrics Select Comparative Analysis of Frozen Concentrated Milk and Whole Milk Powder: A Nutritional Perspective WEN Hongrui, LI Nan, LI Fengying, LIU Yunjun Journal of Dairy Science and Technology    2024, 47 (2): 30-41.   DOI: 10.7506/rykxyjs1671-5187-20240401-016 Abstract （259）   HTML （25）    PDF （7455KB）（10）       Knowledge map    Save To compare the differences in nutritional composition and functional properties between frozen concentrated milk and whole milk powder, this study measured changes in immunoglobulins (Igs), lactoferrin, B vitamins, and metabolomics. It was found that the frozen concentrated milk had significantly higher levels of IgA and IgG, lactoferrin, B vitamins, vitamin A, vitamin D, and vitamin C compared to whole milk powder. Non-targeted metabolomics analysis revealed that the main differential metabolites between frozen concentrated milk and whole milk powder were annotated to multiple key pathways involved in amino acid and peptide (isoleucine, levodopa, phenylalanine-tyrosine, creatine, D-proline, L-glutamate, L-arginine, asymmetric dimethylarginine, L-pipecolic acid, L-histidine, and N-methyl-L-glutamate) metabolism, and carbohydrate (maltotetraose, trehalose, D-maltose, and isomaltose) metabolism. These metabolites showed significantly higher relative expression levels in frozen concentrated milk compared to whole milk powder (P < 0.05). The results indicate that frozen concentrated milk is significantly superior to whole milk powder in terms of nutritional composition. Related Articles | Metrics Select Verification and Application of Biochip for Detection of Veterinary Drug Residues in Raw Milk QI Bing, CHEN Rouhan, YANG Xiaojun, JIANG Chunling, MA Yingqing, DENG Bo Journal of Dairy Science and Technology    2024, 47 (2): 42-48.   DOI: 10.7506/rykxyjs1671-5187-20240415-022 Abstract （134）   HTML （7）    PDF （2050KB）（102）       Knowledge map    Save In order to verify the efficacy of biochip technology in the detection of veterinary drug residues in raw milk and to promote its application, 80 common veterinary drugs in raw milk were detected by biochip and confirmed by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The results showed that the limit of detection (LOD) of the biochip method met the requirements of the national standard, and the LOD for some veterinary drugs was below the national standard limits. The linear range of the method was wide, with correlation coefficient (r) greater than 0.99. Recoveries for negative samples spiked at 2 × and 4 × LOD concentrations were 70%–130%, with coefficient of variation (CV) of 5%–10%. This method has the advantages of simple pretreatment, short detection period and high sensitivity and is suitable for rapid screening of large quantities of samples. Using the proposed method, 10 of 100 batches of raw milk collected from Shanghai during 2022–2023 were tested positive for veterinary drug residues. Streptomyci was detected in 4 batches at concentration levels of 5.86–10.26 μg/kg, sulfapyridine in 3 batches at 1.09–1.42 μg/kg, sulfamonomethoxine in 2 batches at 1.38–1.46 μg/kg, and avermectin in 1 batch at 1.75 μg/kg. These concentration levels were far lower than the maximum residue limits set by international organizations, an announcement of the Ministry of Agriculture and Rural Affairs, and the national standard. Compared with traditional HPLC-MS/MS, the biochip method has the advantages of high sensitivity, wide linear range and fast detection rate. It can be used as a supplementary means for rapid detection of veterinary drug residues in raw milk, and has high application value. Related Articles | Metrics Select Optimization of a Method for the Detection of 1,2-Propanediol in Infant Formula LIU Yuxuan, MENG Genhua, LIN Tingjuan, GUO Ruifang Journal of Dairy Science and Technology    2024, 47 (2): 49-55.   DOI: 10.7506/rykxyjs1671-5187-20240116-002 Abstract （164）   HTML （5）    PDF （3005KB）（190）       Knowledge map    Save According to the first method for the determination of 1,2-propanediol in foods specified by the national food safety standard GB 5009.251-2016, 1,2-propanediol was extracted from milk powder using acetonitrile and was detected using a gas chromatograph (GC). Extraction solvent and standing time were investigated by one-factor-at-a-time method. Furthermore, response surface methodology (RSM) was employed to optimize oscillation time and standing time based on 1,2-propanediol recovery. The optimum extraction conditions were determined as acetonitrile, 4 ℃, 94–102 s and 1.2–1.4 h for extraction solvent, standing temperature, oscillation time and standing time, respectively. Under these conditions, the spiked recovery range of 1,2-propanediol was 95.2%–99.8%. The coefficient of variation for repeatability of the method was 1.62%, and it had good selectivity. The optimized method is suitable for the determination of 1,2-propanediol in milk powder. Related Articles | Metrics Select Determination of Nitrite and Nitrate in Milk Products by Ion Chromatography YIN Jie, ZHENG Guojian, YE Yinying Journal of Dairy Science and Technology    2024, 47 (1): 14-18.   DOI: 10.7506/rykxyjs1671-5187-20240401-014 Abstract （229）   HTML （6）    PDF （2023KB）（734）       Knowledge map    Save An ion chromatography with conductivity detector (IC-CD) method was developed for the determination of nitrite and nitrate in milk products. Samples were dissolved in water and added with potassium ferrocyanide and zinc sulphate solutions for protein precipitation. The supernatant was cleaned up on C18, Ag, and Na solid-phase extraction (SPE) columns, and analyzed by IC-CD. An external standard method was used for quantification. The IC-CD method was validated. Good linearity between the concentrations of nitrite (NaNO2) and nitrate (NaNO3) in the range of 0.01–0.20 mg/L and 0.1–2.0 mg/L, respectively and peak area was observed with correlation coefficient equal to or higher than 0.99. The limits of quantitation for nitrite and nitrate were 0.2 and 0.4 mg/kg, respectively. The spiked recoveries ranged from 92.5% to 102.0%, and the relative standard deviation (RSD) for precision from 1.5% to 6.6%. This method is accurate, repeatable, simple and applicable to the determination of nitrite and nitrate in milk products. Related Articles | Metrics Select Evaluation of the Measurement Systems for Chromium Determination in Milk Powder by ICP-MS and GF-AAS FENG Hao, SU Ying, GENG Yawen, GUO Qingqing, LIN Jin, ZHOU Taohong Journal of Dairy Science and Technology    2024, 47 (1): 19-25.   DOI: 10.7506/rykxyjs1671-5187-20240409-017 Abstract （194）   HTML （4）    PDF （3240KB）（337）       Knowledge map    Save Chromium is an important analytical item in food quality and safety monitoring. Two common methods to detect chromium in food: graphite furnace atomic absorption spectrometry (GF-AAS) and inductively coupled plasma mass spectrometry (ICP-MS) are specified in the National Food Safety Standard Determination of Chromium in Foods (GB 5009.123-2023). This study systematically evaluated the stability, bias, linearity, repeatability, and reproducibility of the two methods using Minitab statistical tools by control chart, independent sample, t test and analysis of variance (ANOVA) methods. The results showed that no outliers were found in the range or mean plots for each method, with within-group errors under statistical control and good stability; the results of gauge linearity and bias analysis showed no significant bias or significant linear error; the gauge repeatability and reproducibility (R&R) analysis showed good repeatability and reproducibility. Two-way ANOVA showed that the sample was the only factor that significantly affected the measurement error. Research variation analysis showed that the measurement system error was acceptable. ICP-MS and GF-AAS can effectively ensure the reliability and repeatability of the detected data of chromium content in milk powder. The findings of this study can not only provide a scientific basis for laboratory analysis and control of measurement system errors, but also provide a reference for the evaluation of measurement systems for the determination of other heavy metals in dairy products and other foods. Related Articles | Metrics Select Analysis of Volatile Compounds in Three Milks with Different Fat Contents by GC × GC-TOFMS WANG Haitao, SHEN Xiao, YAO Lingyun, SUN Min, WANG Huatian, FENG Tao Journal of Dairy Science and Technology    2024, 47 (1): 26-32.   DOI: 10.7506/rykxyjs1671-5187-20240415-021 Abstract （192）   HTML （5）    PDF （2909KB）（851）       Knowledge map    Save In this study, headspace solid phase microextraction in combination with comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (HS-SPME-GC × GC-TOFMS) was used to analyze the volatile compounds in whole (WM), low-fat milk (LFM) and non-fat milk (NFM). Altogether 49 volatile compounds were detected, among which methyl ketones with odd-numbered carbon chain lengths such as 2-nonanone and 2-undecanone constituted the main flavor compounds of WM. Using partial least squares discriminant analysis (PLS-DA), a model which could well differentiate among the 3 milks was developed and it was found to have good variance and cross-validation predictive ability. Nine differential key aroma compounds were identified using variable importance in the projection (VIP) > 1, P ≤ 0.05 and their contents ≥ 1% as criteria, which may be the main factors contributing to the differences in flavor profiles among the 3 milks. The heatmap from clustering analysis indicated that NFM had poor sensory performance due to the presence of off-flavor compounds (e.g., hexadecanal), whereas WM and LFM contained more aroma compounds, having a full and rich sensory aroma profile. The HS-SPME-GC × GC-TOFMS method can provide theoretical guidance for dairy flavor improvement and dairy flavoring formulation. Related Articles | Metrics Select Uncertainty Evaluation for the Determination of Nicotinamide in Milk Powder by Ultra-High Performance Liquid Chromatography CUI Suxia Journal of Dairy Science and Technology    2024, 47 (1): 33-37.   DOI: 10.7506/rykxyjs1671-5187-20240401-013 Abstract （174）   HTML （1）    PDF （4369KB）（178）       Knowledge map    Save The uncertainty in the determination of nicotinamide in milk powder by ultra-high performance liquid chromatography was evaluated. According to the technical normal “Evaluation and Expression of Uncertainty in Measurement” (JJF 1059.1-2012), a mathematical model was established, and the source of each uncertainty component in the mathematical model was analyzed and calculated. The results showed that the uncertainty in nicotinamide determination mainly came from the dilution of the standard solution. In addition, the average content of nicotinamide in milk powder was 5 007 μg/100 g with an expanded uncertainty of about 197 μg/100 g (k = 2). Related Articles | Metrics Select Determination of 17 Mycotoxins in Milk and Dairy Products by High Performance Liquid Chromatography-Tandem Mass Spectrometry LIU Ling, YE Pei, ZHANG Qiaoyan, SHEN Ying, DONG Yuying, JIANG Mengyuan, LI Wenting Journal of Dairy Science and Technology    2023, 46 (5): 22-27.   DOI: 10.7506/rykxyjs1671-5187-20231011-050 Abstract （95）   HTML （2）    PDF （4254KB）（678）       Knowledge map    Save To establish a method for simultaneous detection of 17 mycotoxins in milk and dairy products based on high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Samples (5.000 0 g) were added to 20 μL of a mixed solution of isotope-labeled internal standards, extracted with 20 mL of acetonitrile-water-formic acid solution (70:29:1, V/V) by vortex shaking, salted out with 0.3 g of sodium chloride, and then centrifuged at high speed. The supernatant was passed through a 0.22 μm membrane filter, detected by triple quadrupole mass spectrometry in the multi-reaction detection mode and quantified by an internal standard method. Results: Under the optimized instrumental conditions, good linearity was observed for the 17 mycotoxins in the tested concentration ranges, with correlation coefficient (r) greater than 0.99. The limit of detection (LOD) was 0.05-6.20 μg/kg, and the limit of quantitation (LOQ) was 0.2-20.0 μg/kg. Good average recoveries (78.9%-119.5%) and precision (relative standard deviations (RSDs) 0.2%–8.4%) were achieved at three spiked levels. The method is convenient, stable, reliable and sensitive, can meet the requirements of qualitative and quantitative analysis of the 17 mycotoxins in milk and dairy products, and is suitable for laboratory monitoring of the contamination of these mycotoxins in milk and dairy products. Related Articles | Metrics Select Determination of Steviol Glycosides in Fermented Milk by High Performance Liquid Chromatography YUE Hong, TANG Shuo, NING Yuelian, HUANG Xiaoyan, HU Wenhui, LIANG Jianying, LIU Lijun, LI Cuizhi Journal of Dairy Science and Technology    2023, 46 (5): 28-34.   DOI: 10.7506/rykxyjs1671-5187-20230831-043 Abstract （117）   HTML （2）    PDF （2277KB）（350）       Knowledge map    Save A method for the determination of stevioside, rebaudioside A, rebaudioside B, rebaudioside C, rebaudioside F, dulcoside A, rubusoside and steviolbioside in fermented milk by high performance liquid chromatography (HPLC) was developed and validated. The chromatographic conditions and sample pretreatment conditions were optimized. Samples were ultrasonically extracted with water for 20 min and for another 10 min after addition of 30% acetonitrile in water bath at 45 ℃. Potassium ferrocyanide and zinc acetate were added to precipitate proteins. The chromatographic separation was achieved on a C18 with gradient elution using a mobile phase consisting of sodium phosphate buffer and acetonitrile, and the analytes were detected by an ultraviolet (UV) detector at 210 nm. The results showed that the method was linear in the concentration range of 1–50 μg/mL, the limit of detection (LOD, RS/N = 3) was 3.0 mg/kg, and the limit of quantitation (LOQ, RS/N = 10) was 10.0 mg/kg. The average recoveries of all analytes spiked at 15–200 mg/kg were between 92.0% and 103.1%, with relative standard deviation (RSDs) (n = 6) less than 3.0%. This method was rapid, accurate, stable, sensitive, and suitable for the analysis of the content of steviol glycosides in fermented milk. Related Articles | Metrics Select Determination of Pyramid and Its Metabolite Melamine in Milk by High Performance Liquid Chromatography DENG Xiaoqing, ZHENG Lijun, TANG Wanli, TANG Wenjie, CHEN Tongqiang Journal of Dairy Science and Technology    2023, 46 (5): 35-39.   DOI: 10.7506/rykxyjs1671-5187-20231229-065 Abstract （110）   HTML （2）    PDF （2273KB）（106）       Knowledge map    Save A high performance liquid chromatography method was established to determine the content of cyromazine and its metabolite melamine in milk. The external standard method was used to quantify figures of merit such as linear relationship, precision, recovery, detection limit, and quantification limit. The results showed that the method had good linearity in the concentration range of 0.0–1.0 mg/L (R2 > 0.999), with detection limits of 0.003 and 0.004 mg/kg and quantification limits of 0.008 and 0.010 mg/kg for cyromazine and melamine, respectively. The average spiked recoveries were in the range of 84.4% to 89.5% and 83.9% to 91.2% for cyromazine and melamine, respectively, with relative standard deviations (RSDs) less than 10%. This method is characterized by high sensitivity, high accuracy, and good reproducibility, and can meet the requirement of the determination of cyromazine and its metabolite melamine in milk. Related Articles | Metrics Select Analysis of Reasons for Protein Coagulation in Ultra-High Temperature Milk at the End of Shelf-life WANG Chuanbao, HE Xiong, LI Jiaxin, LIN Lin Journal of Dairy Science and Technology    2023, 46 (4): 16-21.   DOI: 10.7506/rykxyjs1671-5187-20230630-033 Abstract （147）   HTML （4）    PDF （2448KB）（297）       Knowledge map    Save The protein content, pH, color, colonies number, average particle size, zeta potential, degree of proteolysis and proteinase activity of ultra-high temperature (UHT) milk with and without protein coagulation and commercial pure milk samples were determined to analyze the reasons for protein coagulation in UHT milk at the end of self-life. The results showed that the total protein content of coagulated milk samples was 2.9 g/100 g, which was not significantly different from that of milk samples without protein coagulation, but the pH decreased slightly. The total color difference (ΔE) and brightness value (L*) decreased to 68.05 and 67.56, respectively, indicating that the color became dark, and the total bacterial count increased to 1.92 (lg(CFU/mL)). The proteinase activity was 2 565.33 U/L, the degree of proteolysis was 17.07%, the average particle size was 685.8 nm, and the zeta potential increased to ?19.97 mV; these data were all significantly higher than those of milk samples without protein coagulation and commercial pure milk. The trend of changes in proteinase activity was basically consistent with that of the degree of proteolysis, particle size and zeta potential for all samples tested. Protein coagulation in UHT milk at the end of shelf life may be attributed to protein hydrolysis due to increased protease activity and physical deposition caused by the enlargement of casein micelles during long-term storage at ambient temperature. Related Articles | Metrics Select Analysis of the Difference in the Quality Acceptance of Various Culture Media for the Detection of Coliform Bacteria in Raw Milk Using Different Standard Strains LIU Shuai, XU Miaomiao, CHEN Yiwen, ZHANG Jie, WANG Hui, LI Xian, LIU Yumeng, CUI Shenghui, ZHANG Yalun Journal of Dairy Science and Technology    2023, 46 (4): 22-27.   DOI: 10.7506/rykxyjs1671-5187-20230801-037 Abstract （172）   HTML （9）    PDF （1632KB）（339）       Knowledge map    Save In order to ensure the quality of raw milk and enrich quality control strains for the acceptance evaluation of culture media for the detection of coliform bacteria in raw milk, three brands of violet red bile agar (VRBA), violet red bile agar with 4-methylumbelliferyl-β-D-glucuronidehydrate (VRBA-MUG), lauryl tryptose broth (LST) and brilliant green lactose bile broth (BGLB) were selected and evaluated for their physical indicators such as appearance, pH and moisture content as well as microbial indicators such as growth rate and selectivity using the methods specified in China’s national standard for quality requirements for culture media and reagents in food microbiological examination (GB 4789.28-2013). Besides, using Citrobacter freundii ATCC 43864 as a reference strain, seven strains of C. freundii were selected for acceptance evaluation of the four media. The results showed that the color of all three brands of dry powdered media was normal. Their moisture content was 5%–6%, and their pH was in line with the national standard. The growth rate of the seven tested strains of C. freundii was greater than 0.7 on the three brands of VRBA and VRBA-MUG, while only CMCC 48098 and CICC 22910 achieved turbidity of 2 on the three brands of LST and BGLB, and produced gas in the catheter; the same results were obtained with ATCC 43864. In summary, the three brands of VRBA, VRBA-MUG, LST and BGLB all comply with GB 4789.28-2013, and CMCC 48098 and CICC 22910 can be recommended as supplements to quality control strains for the acceptance evaluation of the four media. Related Articles | Metrics Select Contamination Status and Sources of Chlorate and Perchlorate in Infant Formula Milk Powder LI Linyao, GAO Chao, CHU Xiaojun, LIU Xiaoping, HUA Jiacai, ZHENG Huayan Journal of Dairy Science and Technology    2023, 46 (4): 28-34.   DOI: 10.7506/rykxyjs1671-5187-20230602-030 Abstract （247）   HTML （4）    PDF （1954KB）（591）       Knowledge map    Save Our aim was to understand the pollution levels and sources of chlorate and perchlorate in infant formula milk powder and to evaluate the risk of dietary exposure to chlorate and perchlorate in infants and young children. A total of 165 batches of samples were collected from the water, cow milk, and ingredients used, as well as 131 batches of infant formula milk powder. Chlorate and perchlorate in each sample were detected using liquid chromatography-tandem mass spectrometry (LC-MS/MS), and the data obtained were statistically analyzed. The results showed that chlorate and perchlorate were undetectable in the water samples. Cow milk was more severely polluted by perchlorate than by chlorate. Some ingredients were also found to contain chlorate and perchlorate. Infant formula milk powder was contaminated with chlorate and perchlorate, with average contents of 34.3 and 14.5 μg/kg, respectively. The average dietary exposure levels to chlorate and perchlorate for infants aged 0–6 months were 0.71 and 0.28 μg/(kg·d), respectively, which were at an acceptable level. Infant formula milk powder and the raw materials used were found to be contaminated by chlorate and perchlorate. Related Articles | Metrics Select Determination of 6S-5-Methyltetrahydrofolate Calcium in Milk Powder by Reversed-Phase High Performance Liquid Chromatography LIU Lijun, CHEN Jing, DUAN Guoxia, LI Cuizhi*, LÜ Zhiyong Journal of Dairy Science and Technology    2023, 46 (4): 35-39.   DOI: 10.7506/rykxyjs1671-5187-20230417-019 Abstract （226）   HTML （3）    PDF （2238KB）（658）       Knowledge map    Save A reversed-phase high performance liquid chromatography (RP-HPLC) method was established for the determination of 6S-5-methyltetrahydrofolate calcium in milk powder. After protein precipitation with trichloroacetic acid solution, samples were extracted with ascorbic acid solution in a hot water bath, and the extract was separated on a C18 reversed-phase column by gradient elution using a mobile phase composed of 0.1% trifluoroacetic acid solution and methanol, and the detection wavelength was set at 280 nm. Quantitative analysis was carried out by the single standard method. The results showed that the limit of quantification and detection of 6S-5-methyltetrahydrofolate calcium in milk powder samples were 150 and 50 μg/100 g, respectively. The recoveries for samples spiked at levels ranging from 150 to 600 μg/100 g were 95.0%–109.1% with relative standard deviations (RSDs) between 1.26% and 4.04%. This method is simple, accurate, with high recovery and reproducibility, and suitable for the determination of 6S-5-methyltetrahydrofolate calcium in milk powder. Related Articles | Metrics Select Simultaneous Determination of 10 Water-Soluble Vitamins in Infant Formula by Ultra Performance Liquid Chromatography-Tandem Mass Spectrometry CHEN Xiumei, YAN Huijuan, ZHANG Xiaomin, LIN Tingjuan, MENG Genhua Journal of Dairy Science and Technology    2023, 46 (4): 40-47.   DOI: 10.7506/rykxyjs1671-5187-20230616-032 Abstract （143）   HTML （5）    PDF （3129KB）（274）       Knowledge map    Save To develop a method for simultaneous determination of 10 water-soluble vitamins (nicotinic acid, nicotinamide, vitamin B2, pyridoxine, pyridoxal, pyridoxine, pantothenic acid, biotin, folic acid and vitamin B12) in infant milk by ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Samples were dissolved in water, and adjusted to pH 1.7 with 5 mol/L HCl solution and then to pH 4.5 with 5 mol/L NaOH solution to precipitate proteins. The supernatant was added with a mixed solution of isotope internal standard, and separated on an ACQUITY UPLC HSS T3 column (2.1 mm × 50 mm, 1.8 μm) by gradient elution using a mobile phase composed of 10 mmol/L ammonium formate aqueous solution (containing 0.1% formic acid) and 10 mmol/L ammonium formate methanol solution (containing 0.1% formic acid). Detection was performed by electrospray ionization in the positive ion mode with multiple reaction monitoring (MRM). The external standard method was used for the quantification of pyridoxine, pyridoxal and pyridoxine, and the internal standard method for the other seven vitamins. Good linearity of the calibration curves for the 10 water-soluble vitamins was obtained in the range of 10–5 000 ng/mL with correlation coefficients (R2) above 0.99, and the recoveries for spiked samples ranged from 73.9% to 106.0%, with relative standard deviations (RSDs) of 0.9%–8.0%. The proposed method is simple, rapid, sensitive and accurate, and can meet the requirements for the determination of the 10 water-soluble vitamins in infant formula. Related Articles | Metrics Select Determination of Sulfonamide and Quinolone Residues in Infant Formula Milk Powder by Ultra-Performance Liquid Chromatography Tandem Triple Quadrupole Mass Spectrometry SUN Lei, ZHANG Chunlin, HE Liangna, FAN Lixin, ZHANG Xu, MA Junmei Journal of Dairy Science and Technology    2023, 46 (4): 48-54.   DOI: 10.7506/rykxyjs1671-5187-20230517-024 Abstract （108）   HTML （1）    PDF （3640KB）（267）       Knowledge map    Save An analytical method was established for the determination of the residues of 11 sulfonamides and five quinolones in infant formula milk powder using ultra-performance liquid chromatography tandem triple quadrupole mass spectrometry (UPLC-MS/MS). Acidified acetonitrile was used for sample extraction and the extract was purified and concentrated by solid phase extraction (SPE) using a PRiME hydrophilic lipophilic balance (HLB) column, then separated on an XBridge BEH C18 column, detected in the positive ion mode using an electrospray ionization source, and quantified by the calibration curve method with matrix matching. The calibration curves of all analytes showed a good linear relationship in the concentration range of 2–100 ng/mL with correlation coefficients greater than 0.995 0. The limit of detection (LOD) and the limit of quantification (LOQ) were 0.1-0.2 and 0.3-0.5 μg/kg, respectively. Recoveries for spiked samples were between 84.8% and 108.0%, with relative standard deviations (RSDs) between 0.36% and 5.41%. The proposed method is simple, efficient, reliable and sensitive. Related Articles | Metrics Select Determination of Six Quaternary Ammonium Disinfectant Residues in Food for Special Medical Purposes by Ultra-High Performance Liquid Chromatography-Tandem Mass Spectrometry SUN Lei, ZHANG Mingxing, ZHAI Hongwen, MA Junmei, ZHANG Chunlin, REN Xiaowei, CAO Meirong Journal of Dairy Science and Technology    2023, 46 (3): 12-16.   DOI: 10.7506/rykxyjs1671-5187-20230517-026 Abstract （176）   HTML （4）    PDF （1979KB）（1528）       Knowledge map    Save An ultra-high performance liquid chromatography tandem triple quadrupole mass spectrometry (UPLC-MS/MS) method was established for the determination of six quaternary ammonium disinfectant residues in milk-containing food for special medical purposes. The sample was extracted with 80% acetonitrile in water and the extract was separated on a RRHD Eclipse Plus C18 column, detected in the positive ion mode using an electrospray ionization source with multiple reaction monitoring (MRM), and quantified by matrix-matched standard calibration. The calibration curves for the six quaternary ammonium disinfectants was linear in the concentration range of 0.1–5.0 ng/mL with correlation coefficient higher than 0.996 0. The limit of detection (LOD) was 0.5 μg/kg and the limit of quantification (LOQ) was 1 μg/kg. The recoveries were 72.8%-102.3% for spiked solid matrix samples, and 71.8%–100.8% for spiked liquid matrix samples with relative standard deviations (RSDs) in the range of 0.25%–3.88% and 0.19%–2.51%, respectively. The proposed method is simple, efficient, rapid, sensitive, and suitable for the qualitative and quantitative analysis of quaternary ammonium disinfectant residues in food for special medical purposes. Related Articles | Metrics Select Determination of Dicamba Residues in Milk by High Performance Liquid Chromatography-Tandem Mass Spectrometry ZHANG Lijia, LIU Lijun, BAI Yanmei, WANG Yang, MO Nan, GAO Yujie, LI Cuizhi Journal of Dairy Science and Technology    2023, 46 (3): 17-22.   DOI: 10.7506/rykxyjs1671-5187-20230407-017 Abstract （208）   HTML （4）    PDF （2583KB）（118）       Knowledge map    Save The objective of this study was to establish a method for detecting the residue of dicamba in cow milk by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The sample was extracted with 0.5% formic acid in acetonitrile, and the extract was purified by sodium chloride salting out, and separated on an Acquity UPLC BEH C18 column (100 mm × 2.1 mm, 1.7 μm) by gradient elution using a mobile phase composed of acetonitrile and 0.01% formic acid aqueous solution. Identification and quantification were achieved using an electrospray ionization source in the negative ion mode with multiple reaction monitoring (MRM). Under optimized pretreatment and instrumental conditions, good linearity was observed in the concentration range of 5.0–250.0 μg/L with correlation coefficient (r) more than 0.999. The limit of detection (LOD) and limit of quantification (LOQ) of the proposed method were 5 and 10 μg/kg, respectively. The recoveries of dicamba at spiked concentration levels of 10, 20 and 200 μg/kg were 104.3%, 101.5% and 96.2% with relative standard deviations (n = 6) of 3.0%, 2.0% and 1.5%, respectively. This method is simple, accurate, repeatable, and suitable for the rapid detection of dicamba in milk. Related Articles | Metrics Select Optimization of Extraction Method for the Analysis of Nitrite in Milk Powder LI Yongjuan, HUANG Ke, ZHANG Jing, SUN Wenyi Journal of Dairy Science and Technology    2023, 46 (3): 23-26.   DOI: 10.7506/rykxyjs1671-5187-20230423-021 Abstract （206）   HTML （5）    PDF （1636KB）（257）       Knowledge map    Save This study aimed to select and optimize a sample extraction method for the determination of nitrite from milk powder. The absorbance of the experimental water stored for different periods of time was detected by three extraction methods, heat extraction, ultrasonic extraction and ultrasonic decolorization. The color and spiked recoveries of the filtrates from the three methods were evaluated. The nitrite content of quality control samples was determined by ultrasonic decolorization and the limit of detection (LOD) of this method was investigated. The results indicated that storage time did not affect the absorbance of the experimental water. The recoveries of the ultrasonic decolorization method were over 90%, with relative standard deviations (RSD) less than 10%. and the measured results of the quality control samples were within the characteristic value range with LOD of 0.4 mg/kg, which meets the laboratory quality control requirements. The ultrasonic decolorization method has good accuracy and accuracy, and it is recommended that it be used for the decolorization of colored substances in the national standard method. Related Articles | Metrics page Page 1 of 6 Total 207 records First page Prev page Next page Last page