高效液相色谱测定食品中抗坏血酸含量的方法优化

本文通过对样品提取方式、提取剂、流动相等条件进行改进和优化,建立了一种同步测定食品中 L-抗坏血酸、D-抗坏血酸和脱氢抗坏血酸的方法。针对果蔬样品,采用液氮冷冻研磨进行预处理,相比机械匀浆,可以显著提高提取率,减少化学试剂用量,简化前处理操作。为保护 L-抗坏血酸不被氧化,在偏磷酸提取液中加入 0.019 mol/L 硫代硫酸钠作为保护剂,结果表明,实验无需避光操作,提取物可在 4 24 h℃ 内保持性质稳定;采用磷酸二氢钾-癸胺缓冲盐混合溶液作为流动相,可以使不同构型抗坏血酸在较高浓度时依然达到基线分离。抗坏血酸在 0.5 mg/L~200 mg/L 范围内呈良好线性关系,检出限为 0.04 mg/100 g。样品回收率为99.7%~107.3%,相对标准偏差为 3.80%。对于准确测定食品中活性抗坏血酸的组分含量、建立标准化操作规程具有重要意义。     

高效液相色谱法同时测定食品中18种食品添加剂

建立高效液相色谱同时测定食品中18种食品添加剂的高通量分析方法。对于不含油脂或油脂含量低的样品采用含抗坏血酸棕榈酸酯的正己烷饱和乙腈-6mol/L HCl溶液-饱和氯化钠混合溶液一次提取净化,对于油脂样品采用含抗坏血酸棕榈酸酯的正己烷饱和乙腈-乙腈饱和正己烷液液萃取。采用Ecosil C18色谱柱(250mm×4.6mm,5μm),乙腈-0.6%乙酸溶液作为流动相,梯度洗脱,用紫外检测器检测,检测波长280nm,外标法峰面积定量。18种食品添加剂在1.0～25mg/L范围内线性良好,相关系数r均大于0.99,样品在10、25mg/kg和50mg/kg三个添加水平的平均回收率为88.9%～99.9%之间,相对标准偏差为2.43%～11.7%(n=6),方法的定量限为10mg/kg。方法简便、准确,适用于食品中18种食品添加剂高通量的检测。     

HPLC法测定橙子中L-抗坏血酸含量的研究

建立高效液相色谱(High Performance Liquid Chromatography,HPLC)法对橙子中L-抗坏血酸进行含量测定研究。20 g/L偏磷酸溶液作为橙子中L-抗坏血酸的提取剂,超声5 min提取。液相色谱柱采用Inertsil ODS-3C_(18)(5μm,4.6 mm×250 mm),柱温25~℃,0.05 mol/L磷酸溶液-甲醇(90∶10)作为流动相,流速0.800 m L/min,检测波长245 nm。L-抗坏血酸标准品以不同浓度进样,获得标准曲线Y=60 408.6x+38 583.7,相关系数R~2=0.999 6;在1μg/m L~50μg/m L范围内L-抗坏血酸有良好的线性关系;检出限为0.5μg/m L;精密度相对标准偏差RSD=0.67%。     

高效液相色谱法测定食品中胭脂红酸

目的 建立高效液相色谱法测定食品中胭脂红酸含量的分析方法。方法 用2 mol/L盐酸提取样品中的胭脂红酸, 经混合型阴离子交换固相萃取柱净化后, 以0.02 mol/L磷酸二氢铵和甲醇作为流动相, 采用二极管阵列检测器进行检测。结果 胭脂红酸在0.2~100 μg/mL的范围内, 浓度与峰面积的线性关系良好, 相关系数(r2)为0.9999; 方法检出限为0.3 mg/kg, 方法定量限为1.0 mg/kg, 在10、50、200 mg/kg 3个添加水平时, 平均加标回收率为84.8%~97.3%(n=6), 相对标准偏差为2.7%~7.9%。结论 该方法操作简单, 具有较高的灵敏度和准确性, 适用于食品中胭脂红酸的测定。     

高效液相色谱法测定乳与乳制品中 L-羟脯氨酸的含量

目的建立高效液相色谱法测定乳与乳制品中L-羟脯氨酸的含量。方法样品水解衍生后采用C18色谱柱,以乙腈和10 mmol/L乙酸钠(p H=5.0)为流动相,梯度洗脱,流速为1.0 m L/min,柱温35℃,荧光检测器进行检测。结果 L-羟脯氨酸检出限为0.5 mg/kg,线性范围为1.0~100.0μg/m L,加标回收率在95.3%~102.7%之间,相对标准偏差在1.46%~7.56%之间。结论该方法操作简便、准确、快速,提高了样品检出灵敏度,适用于测定乳与乳制品中L-羟脯氨酸的含量。     

高效液相色谱法测定功能性食品中维生素C的含量

目的建立高效液相色谱法测定功能性食品中维生素C的含量。方法采用Venusil XBP C_(18)(L)柱(4.6mm×250 mm,5mm)为色谱柱,0.1%的草酸溶液为流动相,流速为0.5 m L/min,柱温为25℃,检测波长为245nm,样品经L-半胱氨酸-三乙胺溶液还原后,测定维生素C的含量,进样量20mL。结果维生素C在2.056~30.84mg/m L浓度范围内呈良好线性关系(r=0.9999),定量限为0.03726mg/m L,检出限为0.01242mg/m L,回收率为99.89%,RSD为0.31%(n=6);样品经L-半胱氨酸-三乙胺溶液还原后稳定性、重复性好。结论本方法简便快捷、适用范围广、准确度高、精密度好,可广泛用于功能性食品中维生素C含量的测定。     

高效液相色谱法检测运动饮料中的L-肉碱

建立一种快速、有效的高效液相色谱法测定运动饮料中L-肉碱的方法。样品经1.0 mmol/L盐酸提取后,采用MCX固相萃取小柱进行净化和富集。采用RP C18柱(4.6 mm×250 mm,5μm)分离,以乙腈∶辛烷磺酸钠(50 mmol/L)=25∶75(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,L-肉碱标液在1.0μg/m L~20.0μg/m L浓度范围内线性良好,相关系数r~2为0.999,检出限为0.1 mg/kg,定量限为0.3 mg/kg,加标回收率达到82.3%~84.1%。     

离子排斥液相色谱法测定食品中木糖醇的含量

本实验建立了离子排斥高效液相色谱测定各类食品中木糖醇含量的方法。样品用水提取,含油样品加入正己烷除去油脂;以离子排斥机理的Sugar-PakTM 1 为分离柱,柱温90℃,超纯水做流动相,示差折光检测器进行检测。结果表明：糕点中木糖醇的平均回收率为97.0%,RSD 为4.3%;果汁中木糖醇的平均回收率为100.1%,RSD 为2.4%,检出限为50mg/L。该方法具有操作简便、检测准确的特点,适合于各类食品中木糖醇的常规测定。     

微波消解-连续流动法测定食品中的硼酸

建立一种微波消解-连续流动法测定食品中硼酸含量的方法。方法采用浓硝酸和过氧化氢+微波消解食品样品,消解液经蒸干后,用水复溶残渣得到样品溶液,然后用连续流动分析仪进行硼酸的测定。结果表明:方法的检出限为0.35 mg/kg,回收率在95.0%～104.0%之间,相对标准偏差小于1.7%;建立的方法具有操作简便、快速、灵敏度高等优点,适用于食品中硼酸含量的快速测定。     

高效液相色谱-原子荧光光谱法测定水产品中 不同形态汞含量

目的建立高效液相色谱-原子荧光光谱法(high efficiency liquid chromatography-atomic fluorescence spectroscopy,HPLC-AFS)测定水产品中不同形态汞的含量,并以高效液相色谱-电感耦合等离子体质谱法(high efficiency liquid chromatography-inductively coupled plasma-mass spectrometry,HPLC-ICP-MS)进行方法确证。方法样品中的汞元素经5 mol/L HCl溶液提取,用6 mol/L Na OH溶液中和样品,L-半胱氨酸作为流动相中的汞配位剂,用于样品中不同形态汞的分离。结果汞化合物在质量浓度为1.0~20.0μg/L范围内,浓度和光谱峰面积间呈良好的线性关系。方法检出限分别为:无机汞0.009 mg/kg、甲基汞0.006 mg/kg和乙基汞0.009 mg/kg;加标回收率为81.0%~117.0%,相对标准偏差为3.59%~7.30%。用本方法对FAPAS质控样品蟹肉罐头T07231QC中的甲基汞进行测定,测定的结果值与参考值相符。结论该方法操作简单、灵敏度高、重现性好,适用于水产品中不同形态汞含量的测定及结果确证。     

Reliable identification of grapevine rootstock varieties using RAPD PCR on woody samples

Since grapevine ( Vitis spp .) rootstock material is being traded increasingly as disbudded woody material a lack of distinctive morphological features on such material necessitates an alternative and reliable means of identification. Methods described here were developed for rapid and efficient extraction of DNA from woody samples rich in phenolic compounds and polysaccharides, and for subsequent identification of varieties by RAPD PCR. Using these methods, and with the application of only one selected RAPD primer, we were able to differentiate sixteen rootstock varieties, including the seven varieties most commonly used in Germany. Problems commonly encountered with reproducibility of RAPD patterns were avoided by choosing primers with a dinucleotide sequence and a high G/C content that allowed a rather high annealing temperature of 45°C. Methods described here should also be useful for other horticultural crops, especially those with woody tissues rich in phenolic compounds and polysaccharides.     

An internet compendium of analytical methods and spectroscopic information for monomers and additives used in food packaging plastics

An internet website (http://cpf.jrc.it/smt/) has been produced as a means of dissemination of methods of analysis and supporting spectroscopic information on monomers and additives used for food contact materials (principally packaging). The site which is aimed primarily at assisting food control laboratories in the European Union contains analytical information on monomers, starting substances and additives used in the manufacture of plastics materials. A searchable index is provided giving PM and CAS numbers for each of 255 substances. For each substance a data sheet gives regulatory information, chemical structures, physico-chemical information and background information on the use of the substance in particular plastics, and the food packaging applications. For monomers and starting substances (155 compounds) the infra-red and mass spectra are provided, and for additives (100 compounds); additionally proton NMR are available for about 50% of the entries. Where analytical methods have been developed for determining these substances as residual amounts in plastics or as trace amounts in food simulants these methods are also on the website. All information is provided in portable document file (PDF) format which means that high quality copies can be readily printed, using freely available Adobe Acrobat Reader software. The website will in future be maintained and up-dated by the European Commission's Joint Research Centre (JRC) as new substances are authorized for use by the European Commission (DG-ENTR formerly DGIII). Where analytical laboratories (food control or other) require reference substances these can be obtained free-ofcharge from a reference collection housed at the JRC and maintained in conjunction with this website compendium.     

Aroma characterization of various apricot varieties using headspace–solid phase microextraction combined with gas chromatography–mass spectrometry and gas chromatography–olfactometry

The characterization of the aromatic profile of several apricot cultivars with molecular tracers in order to obtain objective data concerning the aromatic quality of this fruit was undertaken using headspace–solid phase microextraction (HS–SPME). Six apricot cultivars were selected according to their organoleptic characteristics: Iranien, Orangered, Goldrich, Hargrand, Rouge du Roussillon and A4025. The aromatic intensity of these varieties measured by HS–SPME–Olfactometry were defined and classified according to the presence and the intensity of grassy, fruity and apricot like notes. In the six varieties, 23 common volatile compounds were identified by HS–SPME–GC–MS. Finally, 10 compounds, ethyl acetate, hexyl acetate, limonene, β-cyclocitral, γ-decalactone, 6-methyl-5-hepten-2-one, linalool, β-ionone, menthone and (E)-hexen-2-al were recognized by HS–SPME–GC–O as responsible of the aromatic notes involved in apricot aroma and considered as molecular tracers of apricot aromatic quality which could be utilized to discriminate apricot varieties.     

Textural Properties of Cold-set Gels Induced from Heat-denatured Whey Protein Isolates

A 9% whey protein (WP) isolate solution at pH 7.0 was heat-denatured at 80°C for 30 min. Size-exclusion HPLC showed that native WP formed soluble aggregates after heat-treatment. Additions of CaCl2 (10–40 mM), NaCl (50–400 mM) or glucono-delta-lactone (GDL, 0.4–2.0%, w/v) or hydrolysis by a protease from Bacillus licheniformis caused gelation of the denatured solution at 45°C. Textural parameters, hardness, adhesiveness, and cohesiveness of the gels so formed changed markedly with concentration of added salts or pH by added GDL. Maximum gel hardness occurred at 200 mM NaCl or pH 4.7. Increasing CaCl2 concentration continuously increased gel hardness. Generally, GDL-induced gels were harder than salt-induced gels, and much harder than the protease-induced gel.     

Tests of potential functional barriers for laminated multilayer food packages. Part I: Low molecular weight permeants

The advent of the functional barrier concept in food packaging has brought with it a requirement for fast tests of permeation through potential barrier materials. In such tests it would be convenient for both foodstuffs and materials below the functional barrier (sub-barrier materials) to be represented by standard simulants. By means of inverse gas chromatography, liquid paraffin spiked with appropriate permeants was considered as a potential simulant of sub-barrier materials based on polypropylene (PP) or similar polyolefins. Experiments were performed to characterize the kinetics of the permeation of low molecular weight model permeants (octene, toluene and isopropanol) from liquid paraffin, through a surrogate potential functional barrier (25 μm-thick oriented PP) into the food simulants olive oil and 3% (w/v) acetic acid. These permeation results were interpreted in terms of three permeation kinetic models regarding the solubility of a particular model permeant in the post-barrier medium (i.e. the food simulant). The results obtained justify the development and evaluation of liquid sub-barrier simulants that would allow flexible yet rigorous testing of new laminated multilayer packaging materials.     

Occurrence of bisphenol-F-diglycidyl ether (BFDGE) in fish canned in oil

The levels of bisphenol-F-diglycidyl ether (BFDGE) were quantified as part of a European survey on the migration of residues of epoxy resins into oil from canned fish. The contents of BFDGE in cans, lids and fish collected from all 15 Member States of the European Union and Switzerland were analysed in 382 samples. Cans and lids were separately extracted with acetonitrile. The extraction from fish was carried out with hexane followed by re-extraction with acetonitrile. The analysis was performed by reverse phase HPL C with fluorescence detection. BFDGE could be detected in 12% of the fish, 24% of the cans and 18% of the lids. Only 3% of the fish contained BFDGE in concentrations considerably above 1mg/kg. In addition to the presented data, a comparison was made with the levels of BADGE (bisphenol-A-diglycidyl ether)analysed in the same products in the context of a previous study.     

Contribution of European research to risk analysis

The European Commission's, Quality of Life Research Programme, Key Action 1—Health, Food & Nutrition is mission-oriented and aims, amongst other things, at providing a healthy, safe and high-quality food supply leading to reinforced consumer confidence in the safety of European food. Its objectives also include the enhancing of the competitiveness of the European food supply. Key Action 1 is currently supporting a number of different types of European collaborative projects in the area of risk analysis. The objectives of these projects range from the development and validation of prevention strategies including the reduction of consumers risks; development and validation of new modelling approaches; harmonization of risk assessment principles, methodologies, and terminology; standardization of methods and systems used for the safety evaluation of transgenic food; providing of tools for the evaluation of human viral contamination of shellfish and quality control; new methodologies for assessing the potential of unintended effects of genetically modified (genetically modified) foods; development of a risk assessment model for Cryptosporidium parvum related to the food and water industries; to the development of a communication platform for genetically modified organism, producers, retailers, regulatory authorities and consumer groups to improve safety assessment procedures, risk management strategies and risk communication; development and validation of new methods for safety testing of transgenic food; evaluation of the safety and efficacy of iron supplementation in pregnant women; evaluation of the potential cancer-preventing activity of pro- and pre-biotic ('synbiotic') combinations in human volunteers. An overview of these projects is presented here.     

低温带皮菜籽粕微粉的不同粒级部分的功能特性

为研究低温带皮菜籽粕微粉的不同粒级部分的功能特性,以经低温脱脂的带皮菜籽粕为原料,经微粉碎后筛分成212~425μm、150~212μm和106~150μm的3个不同粒级的微粉样品,检测这些样品的吸水性、吸油性、乳化性和乳化稳定性、蛋白质体外消化率。结果表明:1 3个不同粒级的微粉样品之间的粗纤维含量存在显著差异,表明三者的结构组成成分有一定差异。23个微粉样品的乳化活性和乳化稳定性随粒度级别的减小而显著增加(P0.01)。33个微粉样品的蛋白质体外消化率随粒度级别的减小而显著增加(P0.01)。4不同粒级带皮菜籽粕微粉样品的吸水性与吸油性受其结构组成物质不同和粒度的双重影响,与粒度的相关性不明显。     

Microbiology of food taints

Fresh and processed foods are often spoilt by the presence of undesirable flavours and odours caused by microbial action. The aim of this paper is to review the current knowledge of microbiologically induced taints that occur in a wide range of foodstuffs, including meats, poultry, fish, crustaceans, milk, dairy products, fruits, vegetables, cereals and cereal products. Examples have been chosen where the compounds responsible for the taint have been identified and sufficient data obtained to demonstrate the involvement of microorganisms. However, in some cases the full identity of the causative organism may not have been elucidated. The types of microorganisms covered by this review include bacteria, fungi, yeasts, actinomycetes and cyanobacteria. Although cyanobacteria do not in general infect foods, their presence in aqueous systems and water supplies can lead to off-flavours in aquatic organisms and processed foodstuffs. Several examples of each of these processes are discussed. Wherever possible, the likely biosynthetic pathway used by the microorganism to produce the offending compound in a foodstuff is indicated.