柱前衍生-高效液相色谱法测定食物和保健食品中维生素B_1

目的:建立柱前衍生-高效液相色谱法(HPLC)测定食品中维生素B1含量的方法。方法:样品以0.1 mol/L盐酸在120℃条件下高压提取,经2%碱性铁氰化钾溶液衍生后,以正丁醇液液萃取,用HPLC测定萃取物。采用Symmetry C18柱(150 mm×4.6 mm,5μm)分离,以0.05 mol/L乙酸钠溶液-甲醇(体积比65∶35)为流动相,荧光检测器检测(Ex=375 nm,Em=435 nm),外标法定量。结果:维生素B1在0.1~1.0 mg/L范围内线性关系良好,相关系数大于0.9990;不同食品中维生素B1的检出限为0.2~0.3 mg/kg,定量限为0.6~0.9 mg/kg;对鸡蛋等4种食品基质进行加标试验,维生素B1的回收率均值为90.1%~109%,相对标准偏差(RSD)为1.9%~8.5%(n=6)。结论:该方法简单快速,灵敏度高,准确性好,可适用于各类食品和保健食品中维生素B1含量的测定。     

高效液相色谱法测定饮料中的功能性成分

为测定功能饮料中的有效成分,建立了高效液相色谱法同时测定功能饮料中维生素B6、烟酸、叶酸、咖啡因、L-酪氨酸和L-苯丙氨酸的方法。对色谱分离条件做了试验并予以优化,以C18色谱柱(150 mm×416 mm ID,5μm)为分离柱,用甲醇(A)和体积分数0.1%乙酸/三乙胺水溶液(B)以不同比例混合进行梯度淋洗,以二极管阵列检测器在254 nm处测定。功能性成分的质量浓度在0.2~100 mg/L范围内与其峰面积呈线性关系。检测方法精密度相对标准偏差在2.3%以内,标准品加入样品后测得回收率在94.7%~97.6%之间,相对标准偏差(n=3)在0.5%~1.5%之间。建立的方法能够适用于市场中功能性饮料的检测与分析。     

蔬菜和水果中维生素C含量测定及其稳定性

建立一种高效液相色谱法测定蔬菜水果中维生素C含量的方法,样品经清洗匀浆后,并用草酸溶液定容。以ZORBAX SB-Aq (C_(18), 4.6 mm×150 mm, 5μm)为色谱柱, 0.1%草酸作流动相,流速1.0 mL/min,柱温箱温度25℃,检测波长254 nm,并将该法用于蔬菜水果不同贮存条件下维生素C稳定性及变化规律研究。结果表明,维生素C在0.5～250 mg/L范围内有良好线性关系,相关系数为0.999 9,方法检出限为0.060 mg/kg,对样品进行5.0, 20和150 mg/kg加标回收试验(n=8),回收率在98.00%～105.60%,相对偏差为0.22%～2.48%。该测定方法简便、快速、准确、稳定,适用于大批量蔬菜和水果中维生素C含量的测定。     

氨基酸自动分析仪测定游离L-半胱氨酸

目的对比讨论含硫氨基酸的传统测定方法过甲酸氧化法,针对添加了L-半胱氨酸的保健食品,提出一个操作简便、计算准确的测定游离L-半胱氨酸含量的方法。方法称取试样用上机缓冲液超声溶解,微孔滤膜过滤,应用氨基酸自动分析仪分析,用Na型离子交换色谱柱分离,L-半胱氨酸标准品定量计算其含量。结果L-半胱氨酸浓度在0.3861~3.0648 mg/m L的范围内与峰面积的线性良好,相关系数r0.999。在80%、100%、120%添加水平下,L-半胱氨酸的平均回收率为97.2%。结论该方法操作简便、准确、重现性好,适用于保健食品中游离L-半胱氨酸的含量测定。     

HPLC法测定草莓、蓝莓和黑莓中维生素C的含量

采用高效液相色谱法(HPLC)测定草莓、蓝莓和黑莓三种水果中的维生素C(VC)含量。色谱条件为0.1%的草酸溶液为流动相,Hypersil-C18色谱柱,检测波长为246 nm,流速为1.0 m L/min,柱温25℃。结果表明:维生素C在质量浓度为0~100 mg/L范围内有良好线性关系,线性回归方程为Y=10 765X-14 442,R2=0.996 8。高效液相色谱测得每百克草莓、蓝莓和黑莓中维生素C含量分别为68.84,19.44和34.10 mg。草莓、蓝莓、黑莓样品的回收率在95.53%~108.90%,94.00%~104.44%和95.32%~104.10%之间,高效液相色谱方法准确可靠,可用于其它水果维生素C含量的分析测定。     

柱前衍生法测定茶叶中L-茶氨酸的含量

本文研究了柱前衍生测定茶叶中L-茶氨酸含量的方法。茶叶中的L-茶氨酸用热水提取后,经2,4-二硝基氟苯衍生后上高效液相色谱法测定。色谱条件为:色谱柱(Kromasil C18柱4.6 mm×250 mm,5μm);流动相:乙腈︰磷酸盐溶液(pH=6.5)=15︰85梯度洗脱;检测波长:360 nm;流速:1.0 mL/min;柱温:35℃;进样:5μL。本方法检出限4 mg/kg,在1.0~50.0μg/mL呈现良好的线性关系(r=0.999 9),衍生后的样品室温25℃放置6天内稳定,重现性试验相对标准偏差0.16%(n=6),回收率为96.4%~102.2%。本高效液相色谱法可以准确地测定茶叶中L-茶氨酸的含量。     

亲水高效液相色谱法测定饮料中的维生素C含量

目的:建立一种简便、快速、灵敏的测定饮料中维生素C含量的方法。方法:采用氨基丙基色谱柱Agilent Zorbax carbohydrate(250mm×4.6mm,5μm),流动相为0.02mol/L磷酸二氢钾+甲醇=95+5,流速1.0m L/min,检测波长:249nm,柱温:25℃,测定饮料中的维生素C含量。该方法检测线性范围为1.46~146μg/m L,样品检出限为0.08μg/m L,加样回收率为99.34%。结论:该方法利用亲水色谱的原理,使用氨基丙基色谱柱分析饮料中维生素C的含量,克服了传统液相色谱方法维生素C在C18柱上保留不足的问题,能够实现样品中杂质与目标峰的有效分离,且前处理简单,测定准确、简便、快速,是一种更为实用快速的维生素C的液相色谱分析方法。     

气相色谱-质谱法测定食品中甲基汞的含量

目的建立气相色谱-质谱法(gas chromatography-mass spectrometry,GC-MS)测定食品中的甲基汞含量。方法样品经氯化钠盐析和甲苯萃取,经L-半胱氨酸水溶液反向萃取后采用四苯硼钠衍生,经Rxi-5MS毛细管色谱柱分离;质谱采用电子轰击源离子化,以选择离子扫描方式对样品中的甲基汞含量进行质谱分析。结果甲基汞在0.05~1μg/m L线性范围内具有良好的线性关系,相关系数为0.9998,检出限为10μg/kg。当甲基汞加标水平为0.2、0.5和1.0 mg/kg时,方法平均回收率为81.5%~95.2%,相对标准偏差为1.0%~2.3%(n=6)。结论该方法降低了甲基汞的活性,减少甲基汞在色谱柱上的吸附和峰拖尾的现象,具有操作简便快速、灵敏度高等优点,可适用于食品中甲基汞含量的测定。     

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。     

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。     

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.