液相色谱质谱法测定食品中咪唑菌酮残留量

建立采用高效液相色谱串联质谱仪测定植物源食品中咪唑菌酮残留量的分析方法。样品经丙酮提取,固相萃取活性炭柱净化,C18色谱柱分离,以乙腈和5 mmol/L乙酸铵甲醇水(v∶v=40∶60)溶液为流动相进行梯度洗脱,电喷雾正离子(ESI+)模式电离,多反应选择离子监测(MRM)。结果表明:咪唑菌酮在0.05μg/m L~0.8μg/m L范围内呈现良好的线性关系,相关系数(r2)大于0.999。在此范围内加标回收率为80.08%~108.53%,相对标准偏差(RSD)为1.16%~6.03%,检测限为1.0μg/kg。该方法可以满足植物源食品中咪唑菌酮残留量监测的需求。     

高效液相色谱法测定米糠油中谷维素

建立固相萃取柱—液相色谱法测定米糠油中谷维素六种谷维素组分及总量的检测方法。采用二醇基固相萃取小柱提取净化样品,以谷维素混合标准品(γ-Oryzanol)进行定量,色谱柱为Agilent ZORBAX Eclipse Plus C18(250 mm×4.6 mm,5μm),流动相为含1%乙酸的乙腈∶异丙醇=95∶5,紫外检测器检测(波长321 nm)。六种谷维素组分及总量的平均回收率分别为95.6%~105.7%、97.8%~100.2%,精密度分别为0.1%~4.6%、0.7%~3.4%。该方法可用来测定米糠油中谷维素组分及总量,为深入研究谷维素提供技术支持。     

SPE-HPLC法测定橄榄油中角鲨烯的含量

该文建立了固相萃取(SPE)——高效液相色谱(HPLC)测定橄榄油中角鲨烯含量的方法。采用硅胶固相萃取小柱提取净化样品。色谱柱:Inertsil ODS–SP–C18(150 mm×4.6 mm,5μm),流动相为乙腈∶四氢呋喃=90∶10,流速1.2 m L/min,检测波长208 nm,柱温35℃。本方法的最低检测浓度为0.02 mg/g。标准曲线在20~500μg/m L范围内线性良好,相关系数R2=0.999 9。角鲨烯的平均回收率为92.2%,相对标准偏差(RSD)为1.47%(N=5),是一种快速、简便、准确、重复性好的检测橄榄油中角鲨烯含量的方法。     

山楂果实中活性成分的高效液相色谱法

建立了用高效液相色谱同时测定山楂中活性成分的方法。色谱条件:色谱柱HypersilBDSC18(46mmid×250mm,5μm),UV检测波长为280nm;流动相A:重蒸水,含500μL/L的甲酸;流动相B:甲醇∶乙腈=237∶7(vv∶),含500μL/L的甲酸,梯度洗脱,流速0.8mL/min。结果表明:RSD分别为1.16%~3.46%,各成分的回收率为97.6%~105.4%。     

固相萃取-高效液相法测定芝麻油中苯并(a)芘

建立一种快速、高效测定芝麻油中苯并(a)芘的固相萃取-高效液相色谱(SPE-HPLC)方法。样品前处理采用硅胶固相萃取柱串联氧化铝固相萃取小柱,稀释液和淋洗液选择正己烷,洗脱液选择二氯甲烷,在40℃下氮吹干后,乙腈复溶后检测。采用Waters RP C18色谱柱(4.6 mm×250 mm,5μm)分离,以乙腈-水(90∶10)作为流动相,用荧光检测器检测,外标法峰面积定量。结果表明,苯并(a)芘在1.00 ng/m L~20.00 ng/m L浓度范围内线性良好,相关系数r2为0.999 8,检出限为0.05μg/kg,定量限为0.16μg/kg,加标回收率达到92.2%~98.5%。     

苹果多酚的固相萃取纯化研究

研究了用固相萃取法纯化,高效液相色谱法测定苹果中多酚类物质的方法。以苹果冻干粉为原料,加标回收率为指标,从四种固相萃取小柱中筛选出分离效果较好的Waters Oasis HLB固相萃取小柱对提取液进行预处理。以phenomenex Luna C18色谱柱(150mm×4.6mm,5μm)为固定相,以0.1%的甲酸溶液(v/v)和乙腈为流动相梯度洗脱,紫外双波长扫描280、320nm条件下检测。结果:检测出七种中性多酚,三种酸性多酚。加标回收率为95%~104%,相对标准偏差均小于2.2%。结论:该方法快速、灵敏、简便、准确,杂质干扰少,10种多酚类物质峰分离度好。     

固相萃取-HPLC法同时测定肉制品中苋菜红、胭脂红、日落黄和诱惑红含量

建立了利用固相萃取-高效液相色谱法同时测定肉制品中4种合成色素的检测方法。样品经乙醇+氨水+水(7+2+1,v/v/v)提取后,固相萃取净化,经C18柱分离,用紫外检测器检测。4种合成色素分离良好,加标平均回收率为66.7%~99.7%,相对标准偏差1.9%~3.6%。该方法准确度和精密度较高,可应用于测定肉制品中的合成色素,结果令人满意。     

高效液相色谱法检测乳品饮料中四环素类抗生素

建立一种用固相萃取-高效液相色谱法测定乳品饮料中土霉素、四环素、金霉素、强力霉素的检测方法。样品前处理用乙腈沉淀蛋白后,采用HLB固相萃取小柱进行净化和富集,氮气吹干后用流动相复溶上机检测。采用Waters RP C18色谱柱(4.6 mm×250 mm,5μm)分离,以乙腈∶甲醇∶0.01mol/L草酸溶液(18∶5∶77)作为流动相,用PDA检测器检测,外标法峰面积定量。结果表明,4种四环素类抗生素在0.10μg/m L~1.00μg/m L浓度范围内线性良好,相关系数r2为0.994~0.999,检出限均为2.0μg/kg~5.0μg/kg,定量限均为6.0μg/kg~15.0μg/kg,加标回收率达到77.6%~90.6%。     

高效液相色谱法检测运动饮料中甜菊糖苷

建立一种用高效液相色谱-PDA检测法测定运动饮料中甜菊糖苷的检测方法。样品前处理采用硅胶固相萃取小柱进行富集和净化,氮气吹干后用流动相复溶上机检测。采用Waters RP C18色谱柱(4.6 mm×250 mm,5μm)分离,以乙腈∶水=30∶70(体积比)作为流动相,用PDA检测器检测,外标法峰面积定量。结果表明,9种甜菊糖苷组分在20.0μg/m L~200.00μg/m L浓度范围内线性良好,相关系数r2为0.991~0.999,检出限在1.0μg/m L~3.0μg/m L,定量限为3.0μg/m L~9.0μg/m L,加标回收率达到81.4%~90.5%。     

基质固相分散-HPLC法测定水产品中孔雀石绿和结晶紫

建立了基质固相分散-液相色谱法快速测定水产品中的孔雀石绿和结晶紫的新方法。将鱼肉样品粉碎后与C18填料研磨混合,装柱、淋洗,洗脱液浓缩后用高效液相色谱检测。色谱条件:色谱柱Inertsil ODS-SP(5μm,4.6 mm×150 mm),乙腈和乙酸铵缓冲溶液体积比80∶20作流动相等度洗脱,流速1.00 m L/min,检测波长254 nm。结果表明,孔雀石绿和结晶紫在0.30μg/L~30.00μg/L范围内,线性关系良好,相关系数(r)均大于0.999,检测限(S/N=3)分别为:0.18 ng/g和1.10 ng/g,样品加标回收率分别为86.28%~98.79%和82.51%~93.71%,其精密度RSD均小于5%(n=5)。     

Microwave phase control heating

Summary Food processors are increasingly looking towards new microwave-based technologies to deliver competitive advantage in the market place, reduce operational costs, allow greater product innovation and increase flexibility without the need for large capital investments. The technical barriers to the widespread exploitation of microwave heating, and opportunities for microwave heating in food processing, are discussed in the context of the need to understand the microwave field/material/process interaction. It is shown how a new application of interference techniques, called phase control microwave heating, may offer opportunities for enhanced heat transfer in food processing, especially for direct control of the spatial power deposition within a foodstuff. Simulations of phase control heating using a 3D FETD microwave model, validation of experimental findings and examples in other applications are presented.     

The intestinal phase of peptide absorption

Peptides and not amino acids are the prevailing degradation products of protein digestion which are formed in the intestinal lumen and are absorbed from the mucosa. These two families differ in absorption. The differences become manifest when the absorption of peptide mixtures is compared with that of equimolecular mixtures of free amino acids. The absorption of peptides occurs in two different ways: 1. Transport of intact peptides through the membrane into the mucosal cell and subsequent hydrolysis by intracellular peptide hydrolases. 2. Hydrolysis of the peptides by peptide hydrolases localized on the luminal side of the mucosal cell membrane and subsequent transport of the amino acids thus formed through the membrane. The two mechanisms of absorption do not exclude each other. The way by which energy is supplied for the transport is not yet elucidated. The transport of intact peptides is of nutritive importance only in case of dipeptides and tripeptides. It enables in particular the introduction of peptides that cannot be cleft by membrane-bound peptide hydrolases. The hydrolysis of peptides by membrane-bound peptide hydrolases and the subsequent transport of released amino acids is of importance for long-chain peptides. The difference in absorbing behaviour between the free amino acids released in the intestinal lumen and the amino acids released by peptide hydrolases at the mucosal membrane is discussed.     

Stochastic modelling of bacterial lag phase

In order to study the lag distribution of the individual cells in a bacterial population, a stochastic birth model is used in this study. An integral formula is applied to transform the assumed lag distribution into a growth function describing the transition between lag and exponential phase of the cell population. By means of this formula, it is pointed out that traditional viable count curves are not suitable to identify the distribution of individual cells' lag time.     

食品供应链中的肉品安全管理——从农场饲养到屠宰环节

我国肉制品质量与安全问题日益突出,如何在供应链的各个环节,采取措施保障肉品安全管理体系,具有现实的意义。构建肉类食品的原料安全生产系统、全面质量管理系统、溯源管理系统等安全保障措施是构成肉类食品安全保障体系的重点。并且本文从提高中国肉类加工食品的市场竞争力出发,针对目前中国肉类加工食品尚未形成完善的供应链管理模式这一现状,提出了在新型的肉类供应链安全管理模型,旨在推进我国肉类工业健康稳步发展。     

双液相溶剂浸取棉仁的甲醇相中棉酚含量测定

提出了紫外可见分光光度计测定双液相溶剂(甲醇相 石油醚)浸取棉仁的甲醇相中棉酚含量的方法。采用转化法将甲醇相中棉酚转移到丙酮溶剂中,经离心沉淀后取上层清液在370nm波长下测定棉酚含量。结果表明,该方法具有简便、重复性好、回收率高等优点,可用于双液相浸取棉仁的甲醇相中棉酚含量的测定。     

相转移法催化合成生物柴油

以大豆油和甲醇为原料,在K2CO3与相转移催化剂四丁基溴化铵(TBAB)作用下,合成生物柴油。考查相转移催化剂种类及用量、K2CO3用量、反应时间、醇油物质量比和反应温度对生物柴油产率影响;实验结果表明,制备生物柴油最佳条件为:TBAB用量为大豆油质量0.6%、K2CO3用量为大豆油质量1.5%、醇油物质量比为6∶1、反应时间为20 min、反应温度为40℃;在此条件下,制备生物柴油产率可达95%以上。     

Modeling the lag phase of Listeria monocytogenes

An estimate of the lag phase duration is an important component for predicting the growth of a bacterium and for creating process models and risk assessments. Most current research and data for predictive modeling programs initiated growth studies with cells grown to the stationary phase in a favorable pH, nutrient and temperature environment. In this work, Listeria monocytogenes Scott A cells were grown in brain heart infusion (BHI) broth at different temperatures from 4 to 37 degrees C to the exponential growth or stationary phases. Additional cells were suspended in a dilute broth, desiccated or frozen. These cells were then transferred to BHI broth at various temperatures from 4 to 37 degrees C and the lag phase durations were determined by enumerating cells at appropriate time intervals. Long lag phases were observed for cells initially grown at high temperatures and transferred to low temperatures. In general, exponential growth cells had the shortest lag phases, stationary phase and starved cells had longer, frozen cells had slightly longer and desiccated cells had the longest lag phases. These data were from immediate temperature transitions. When a computer-controlled water bath linearly changed the temperature from 37 to 5 degrees C over a 3.0- or 6.0-h period, the cells had short lags and grew continuously with declining growth rates. Transitions of 0.75 or 1.0 h had 20-h lag phases, essentially that of immediate transitions. When the transition was 1.5 h, an intermediate pattern of less than 1 log of growth followed by no additional growth for 20 h occurred.