Optimization of nuclear magnetic resonance and gas chromatography-mass spectrometry-based fingerprinting methods to characterize goat milk powder

This study is the first to provide a comprehensive characterization of the liquid and volatile fractions of whole goat milk powder (GMP). Robust nuclear magnetic resonance (NMR)- and gas chromatography-mass spectrometry (GC-MS)-based chemical fingerprinting methods were optimized and implemented. The untargeted ¹H-NMR analysis resolved 44 metabolites in the liquid fractions of GMP. The NMR fingerprinting technique effectively identified metabolites coming from the aliphatic, sugar, and aromatic regions that can be important in defining the technological properties and quality of the GMP. The untargeted headspace gas chromatography-mass spectrometry fingerprinting was able to detect a total of 50 volatiles including alkanes, ketones, alcohols, aromatics, alkenes, aldehydes, esters, acid, and sulfur compounds. The GMP was dominated by volatiles in the alkane group, while only a few esters were detected. Goat milk is a premium product and vulnerable to fraudulent activities such as adulteration or counterfeit. Therefore, proper characterization and identification is a crucial first step to verify its authenticity and quality.     

超高效液相色谱-四级杆-飞行时间质谱法与代谢组学技术分析牛乳与羊乳差异性

目的采用超高效液相色谱-四级杆-飞行时间质谱仪(ultra-performanceliquidchromatographyquadrupole time-of-flight mass spectrometry, UPLC-Q-TOF)高分辨质谱和代谢组学技术分析牛乳与羊乳差异。方法以小分子化学物质(分子量MW1000u)为研究对象,采用主成分分析、正交偏最小二乘法-判别式分析等多元统计分析手段,借助ProgenesisQI软件和数据库分析差异。结果初步鉴定出128种物质,其中在牛乳中含量高的物质有38种,在羊乳中含量高的物质90种。牛乳和羊乳在小分子代谢物上有明显差异(P0.05),主要为脂质、有机酸、糖类等,并剖析了伏马毒素B1、牛磺鹅去氧胆酸和乳清酸等典型的潜在生物标志物。结论本方法简单、便捷、且灵敏度高,为牛羊乳的真假鉴别以及牛羊乳差异性的进一步分析提供了理论支持。     

山羊奶与牛奶和人奶营养成分的比较

对山羊奶、牛奶和人奶中蛋白质、脂肪、维生素、矿物质等主要营养成分进行了比较,分析了3种奶中主要营养成分的差别。通过比较发现,山羊奶在总体营养成分方面优于牛奶,更接近人奶。但山羊奶存在铁、叶酸和维生素B12含量较低以及羊奶膻味的问题,应在营养上对这方面加以重视。     

羊乳与牛乳理化特性比较

以莎能奶山羊羊乳为样品,利用乳样自动分析仪,氨基酸自动分析仪、等离子发射光谱、色谱分析对其基本成分、氨基酸组成及含量进行了分析和检测,并与牛乳理化特性进行比较,为科学合理地利用羊乳,生产具有独特功能的羊乳制品提供了理论依据。     

气相色谱-质谱法测定奶粉中香兰素的不确定度评估

目的采用气相色谱-质谱法对奶粉中香兰素含量的不确定度评估。方法建立不确定度评估的数学模型,通过对不确定度的各主要分量进行分析计算,得出合成不确定度以及扩展不确定度。结果当香兰素的测定结果为57.1 mg/kg时,其扩展不确定度为4.4 mg/kg,k=2。结论采用气相色谱-质谱法测定奶粉中香兰素含量,其不确定度的主要来源为样品的回收率和最小二乘法拟合的标准曲线,该评估模型为检测奶粉中香兰素的不确定度评估提供了参考依据。     

中心复合设计法优化-气相色谱-质谱法检测奶粉中壬基酚

目的:建立气相色谱-质谱法测定奶粉中壬基酚的分析方法。方法:先通过对比实验选择合适的萃取剂和净化小柱,再以色谱峰面积为响应值,采用中心复合设计对壬基酚的衍生化温度,衍生试剂量和衍生化时间进行优化,采用气相色谱-质谱法进行测定。结果:选择乙腈为蛋白沉淀剂和萃取剂,Florisil柱为固相萃取柱,N,O-双三甲基硅基三氟乙酰胺（1%三甲基氯硅烷）为衍生试剂;当反应温度72℃,衍生试剂量为215μL,反应时间为27 min,壬基酚的衍生效果最佳。在此优化条件下,壬基酚浓度范围为10.70¹369 ng/m L时,其线性良好,检出限为24.0μg/kg,回收率为90.6%¹05.2%,RSD为2.7%。结论:该方法准确、灵敏、基质干扰小,适用于奶粉中壬基酚的测定。      

气相色谱串联质谱法快速筛查乳粉及巧克力中矿物油指标成分

目的建立基于普通气相色谱串联质谱(gas chromatography-mass spectrometry,GC-MS)的新检测方法确定乳粉和巧克力中25种矿物油残留成分。方法样品经正己烷提取,提取液经过硅胶固相萃取柱净化,浓缩定容后复溶待测,选取安捷伦DB-5MS毛细管柱(30 m×0.25 mm,1μm)为分析住,采用选择离子扫描(selective ion mode,SIM)模式,外标法定量分析。结果 25种指标成分在质谱上响应程度不一致,但在各自的浓度范围内线性关系良好,相关系数r均在0.990以上,乳粉的检出限(0.025～1.5 mg/kg)均高于巧克力的检出限(0.005～1 mg/kg)。加标回收率在25%～56%之间,相对标准偏差(relative standard deviation,RSD)在2.2%～9.4%之间。对国内外40批乳粉和25批巧克力产品中的矿物油进行检测,结果发现乳粉的检出率为12.5%,巧克力的检出率为100%。结论该方法前处理操作简单,分析时间短且能良好的分离25种污染成分,可作为矿物油快速检测方法。     

气相色谱-质谱联用法检测动物源性食品中的敌鼠

目的建立气相色谱-质谱联用法(gas chromatography-mass spectrometry,GC-MS)测定动物源性食品中敌鼠的方法。方法本研究考察了提取溶剂、萃取参数及净化小柱对检测结果的影响,样品用丙酮-正己烷(1:1,V:V)为提取溶剂进行微波萃取,采用C18小柱进行净化,以GC-MS进行检测。结果加标水平为0.001、0.002、0.01 mg/kg时,平均回收率为62%~90%,相对标准偏差为0.98%~9.04%,敌鼠的方法检出限为0.0008 mg/kg.结论该方法快速、简单,且灵敏度高,适用于动物源性食品中的敌鼠的检测。     

气相色谱-质谱法分析比较超高温灭菌乳和巴氏杀菌乳中的10种内酯类风味物质

目的 建立气相色谱-质谱法(gas chromatography-mass spectrometry, GC-MS)分析比较超高温灭菌乳(ultra-high temperature milk, UHT)和巴氏杀菌乳中10种内酯类风味物质的分析方法。方法 液体乳样品用乙腈提取、无水硫酸镁干燥、正己烷除脂后,经Stabile-WAX色谱柱分离,在单离子监测模式(single ion monitoring, SIM)下进行测定,采用基质匹配外标法进行定量。结果 10种风味物质在1~20 μg/L浓度范围内线性关系良好,线性相关系数均大于0.99,方法的检出限为0.2~4 μg/kg,定量限为0.7~13 μg/kg。各目标化合物在3个基质加标浓度（1、5、10 μg/L）下的平均回收率为85.94%-116.44%,相对标准偏差为1.06%~6.36%（n=6）。超高温灭菌乳样品中检出δ-癸内酯、γ-十二内酯、δ-十二内酯,巴氏杀菌乳样品中检出δ-癸内酯和δ-十二内酯,前者内酯类风味物质的种类和含量略高于后者。结论 建立的方法操作简单,适用于液体乳中内酯类风味物质的检测。     

掺假羊乳及其制品中牛乳的检测技术研究进展

羊乳具有营养价值高、蛋白质组成更接近人乳、脂肪球直径小及致敏性低等优点,更利于人体消化吸收,受到消费者和乳品企业的青睐.近年来我国羊乳产业发展迅速且潜力巨大,但由于受羊乳产量和养殖规模的限制,羊乳价格昂贵,市场中存在羊乳及其制品掺假牛乳的现象,且掺假手段多样,难以辨别.为了保证消费者的健康和权益,保障羊乳市场良性发展,...     

气相色谱-质谱法测定婴幼儿配方乳粉及原料中 15 种邻苯二甲酸酯

目的 建立婴幼儿配方乳粉及原料中 15 种邻苯二甲酸酯的气相色谱-质谱检测方法。 方法 样品经乙 腈提取后, 用 GC-MS 检测。采用外标法进行定量分析。结果 15 种邻苯二甲酸酯的线性范围除了邻苯二甲酸 二异壬酯为 0.01~1 mg/L, 其余均为 0.001~1 mg/L, 相关系数大于 0.99。方法检出限(S/N=3)为 0.006~0.2 mg/kg, 定量限(S/N=10)为 0.02～0.7 mg/kg。 在奶粉基质中 3 个加标水平的平均回收率在 88.6%~117.2%, 相对标准偏差 为 1.0%~9.3%。结论 本方法操作简单、精确、快速、廉价、稳定, 适用于奶粉中邻苯二甲酸酯类化合物的检测分析。     

Evaluation of the allergenicity of goat milk, cow milk, and their lactosera in a guinea pig model

The object of this study was to determine the allergenicity of goat milk (GM) and cow milk (CM) and that of their respective lactosera (GML and CML), by in vivo and in vitro assays. Two systemic tests for anaphylaxis were carried out in guinea pigs, the animals being sensitized orally with the 2 types of milk and lactosera. Sera were taken from the orbital sinus of the experimental animals at 0 and 22 d of the experiment to perform the serological study and the passive cutaneous anaphylaxis test. For the latter, the guinea pigs were sensitized passively with antibodies against the 4 antigen solutions. Enzyme-linked immunosorbent assay and Western blot were used to determine the specific antibodies of the isotypes immunoglobulin G1 and immunoglobulin G(Fc) developed against the same 4 antigen solutions. From these anaphylaxis and antibody-production tests, it was concluded that GM is hypoallergenic when compared with CM. The lactosera produced more closely grouped results, with values always below those of the corresponding milk. None of the proteins in the 4 immunizing solutions were identified as being their main allergen. These results show the hypoallergenicity of GM versus CM, and also that both casein and lactoserum proteins may be responsible for allergy in each case. To analyze the possibility of producing an innocuous food for those allergic to milk proteins, it would be of interest to identify the epitope(s) responsible for such allergenicity.     

拟干酪乳杆菌胞内代谢产物的GC-MS分析方法的建立

用气相色谱-质谱联用（GC-MS）技术建立了拟干酪乳杆菌发酵过程中胞内代谢物的代谢组学研究方法。考察了不同溶解剂（吡啶、四氢呋喃、二甲基甲酰胺）和衍生化试剂（N-甲基叔丁基二甲基硅基三氟乙酰胺（MTBDSTFA）、N,O-双（三甲基硅烷基）三氟乙酰+三甲基氯硅烷（BSTFA+TMCS）、N-甲基-N-三甲基硅烷基三氟乙酰胺（MSTFA））,对质谱峰的信号强度和个数的影响,确定使用吡啶作为溶解剂、BSTFA+TMCS作为衍生剂的两步衍生法效果最佳。以拟干酪乳杆菌为分析对象,共鉴定出38种胞内中间代谢物。方法学考察结果表明,该方法具有良好的精密度、稳定性和重现性。本方法已成功地应用于拟干酪乳杆菌发酵过程研究,并且发现了发酵过程中可能的生物标志物。      

牛羊乳酪蛋白制备及电泳分析比较

采采用新鲜和复原的牛羊乳为原料,等电点沉淀,通过洗涤、干燥等步骤分别制得牛乳和羊乳酪蛋白,用凯氏定氮法对其进行定量检测,应用十二烷基硫酸钠聚丙烯酰胺凝胶电泳（SDS—PAGE）分析比较牛羊乳酪蛋白组分差异。结果表明：牛乳酪蛋白得率为86．75％,羊乳酪蛋白得率为90．55％,高含量的酪蛋白主要集中在电泳图谱的中分子量组,可分为ds,CN、as2-CN、β-CN和K—CN,牛羊乳as2-CN分子量羊乳大于牛乳,牛乳a-CN含量比较多,羊乳β—CN含量比较多,鲜乳与复原乳全蛋白主要组分在电泳图谱中除酪蛋白差别外,上端的高分子量组清蛋白区羊乳IgG重链的分子量比牛乳小。应用蛋白质电泳分析技术可以区分羊乳和牛乳的蛋白质组分,等电点沉淀法制备酪蛋白的方法简单,易于操作。     

固相萃取-气相色谱-质谱法检测食品中 腐霉利的残留量

目的建立固相萃取-气相色谱-质谱法检测食品中腐霉利的残留量。方法样品提取采用浸渍-振荡法,采用石墨化碳黑固相萃取小柱和中性氧化铝固相萃取小柱对不同来源(植物源性和动物源性)的样品溶液进行净化和萃取,然后经气相色谱-质谱法分析腐霉利的残留量。结果在0.005~1.0?g/m L范围内,腐霉利呈现良好的线性关系(r=0.9998)。茶叶、葡萄酒、猪肝样品分别按0.01~0.10 mg/kg添加3个水平的标样,回收率在81.4%~103.6%之间,RSD为3.5%~8.2%,检出限分别为0.025、0.01、0.025 mg/kg。结论该方法可适用于食品中腐霉利残留量的检测。     

Monitoring the ripening process of Cheddar cheese based on hydrophilic component profiling using gas chromatography-mass spectrometry

We proposed an application methodology that combines metabolic profiling with multiple appropriate multivariate analyses and verified it on the industrial scale of the ripening process of Cheddar cheese to make practical use of hydrophilic low-molecular-weight compound profiling using gas chromatography-mass spectrometry to design optimal conditions and quality monitoring of the cheese ripening process. Principal components analysis provided an overview of the effect of sodium chloride content and kind of lactic acid bacteria starter on the metabolic profile in the ripening process of Cheddar cheese and orthogonal partial least squares-discriminant analysis unveiled the difference in characteristic metabolites. When the sodium chloride contents were different (1.6 and 0.2%) but the same lactic acid bacteria starter was used, the 2 cheeses were classified by orthogonal partial least squares-discriminant analysis from their metabolic profiles, but were not given perfect discrimination. Not much difference existed in the metabolic profile between the 2 cheeses. Compounds including lactose, galactose, lactic acid, 4-aminobutyric acid, and phosphate were identified as contents that differed between the 2 cheeses. On the other hand, in the case of the same salt content of 1.6%, but different kinds of lactic acid bacteria starter, an excellent distinctive discrimination model was obtained, which showed that the difference of lactic acid bacteria starter caused an obvious difference in metabolic profiles. Compounds including lactic acid, lactose, urea, 4-aminobutyric acid, galactose, phosphate, proline, isoleucine, glycine, alanine, lysine, leucine, valine, and pyroglutamic acid were identified as contents that differed between the 2 cheeses. Then, a good sensory prediction model for “rich flavor,” which was defined as “thick and rich, including umami taste and soy sauce-like flavor,” was constructed based on the metabolic profile during ripening using partial least squares regression analysis. The amino acids proline, leucine, valine, isoleucine, pyroglutamic acid, alanine, glutamic acid, glycine, lysine, tyrosine, serine, phenylalanine, methionine, aspartic acid, and ornithine were extracted as ripening process markers. The present study is not limited to Cheddar cheese and can be applied to various maturation-type natural cheeses. This study provides the technical platform for designing optimal conditions and quality monitoring of the cheese ripening process.     

气相色谱-质谱法测定食品包装行业用UV油墨中11种光引发剂的含量

目的建立气相色谱质谱法同时测定食品包装行业用UV油墨中11种光引发剂的方法。方法通过甲醇萃取油墨中的光引发剂,离心过滤后由气相色谱质谱仪测定11种光引发剂的含量。结果 11种光引发剂在0.10～5.0 mg/L范围内线性关系良好(r~2≥0.995),在低、中、高3个添加水平下,回收率在88.5%～100.5%,重复性相对标准偏差(n=6)为3.3%～6.5%,检出限为0.03 mg/L。结论该方法具有操作简单、响应良好、快速分析等特点,能够满足同时测定食品包装行业用UV油墨11种光引发剂的分析要求。     

固相萃取气相色谱-质谱联用法测定牛奶中的雌三醇

通过液液萃取和固相萃取提取、净化牛奶中添加的雌三醇，TMS衍生化试剂BSTFA衍生化。气相色谱-质谱联用（选择离子模式，选择离子为m／z311，m／z345，m／z414，m／zS04）对衍生物检测分析。确定了牛奶中雌三醇的定性、定量分析方法．该法栓出限为0．5μg／L，衍生物的峰面积与样品质量浓度在1—1000μg／L内呈良好的线性关系，线性回归系数为0．999。不同雌三醇加入量的加标回收率分别为78．2％-86．7％，变异系数为3．2％-3．6％。     

气相色谱-质谱法测定人体血液中的毒鼠强

目的建立气相色谱-质谱(gas chromatography-mass spectrometry,GC-MS)测定人体血液中的毒鼠强的方法。方法血液样品用乙酸乙酯提取后,用GC-MS进行测定。通过单离子检测扫描模式(single ion monitoring,SIM)确定毒鼠强的特征离子进行定性,并以毒鼠强的3个特征离子(m/z121、m/z212、m/z240)作为母离子,使用不同的碰撞能进行碰撞,得到相应的子离子。选择分别来自3个母离子的离子对,以响应值较高的离子对作为定量离子对,其余2个离子对作为定性离子对,采样选择反应监测(selective reaction monitoring,SRM)方式进行测定。结果毒鼠强浓度范围在0.01~0.2μg/m L范围内呈正相关,相关系数r为0.9998,回收率为92.0%~104.5%,相对标准偏差(relative standard deviation,RSD)为3.62%~5.32%,血液样品的检出限为0.0005μg/m L。结论该方法灵敏度高,选择性好,检出限低,适合食物中毒人体血液中毒鼠强的痕量检测。