河北省特种桑叶中游离氨基酸的含量测定

测定河北省特种桑叶中游离氨基酸的含量。超声辅助提取桑叶中的游离氨基酸,以异硫氰酸苯酯为柱前衍生化试剂,采用反相高效液相色谱法梯度洗脱测定。液相条件为Kromasil C18色谱柱(4.6 mm×250 mm,5μm),柱温40℃,流速1 m L/min,检测波长254 nm。16种氨基酸在0.03125~1μmol/m L浓度范围内呈现良好的线性关系,r均大于0.9961,平均回收率为92.2%~101.4%(n=6),RSD5.0%。此方法准确可靠,可用于桑叶及其他药食两用植物中游离氨基酸的含量测定。     

柱前衍生RP-HPLC法测定仙鹤草中氨基酸含量

采用柱前衍生RP-HPLC法对仙鹤草中游离及水解氨基酸进行测定。以异硫氰酸苯酯为柱前衍生化试剂。以异硫氰酸苯酯为柱前衍生化试剂;色谱柱采用Ultimate Amino Acid氨基酸柱(4.6 mm×250 mm,5μm);流动相A为80%(体积分数)的乙腈-水溶液,流动相B为7%(体积分数)的乙腈-CH3COONa溶液(p H=6.5);检测波长为254 nm。21种氨基酸在0.001 9μmol/m L~2.700μmol/m L内呈良好的线性关系(R20.999 0)。21种游离氨基酸平均回收率在95.84%~111.34%之间,RSD在1.23%~2.54%之间(n=6);水解氨基酸平均回收率在90.79%~111.23%之间,RSD在1.29%~2.21%之间(n=6)。柱前衍生RP-HPLC法灵敏、准确,具有良好的重复性和稳定性,适合仙鹤草中氨基酸含量测定。     

超高效液相色谱法测定不同黄酒中17种氨基酸的分析研究

建立一种快速准确的柱前衍生-超高效液相色谱法,同时测定黄酒中17种游离氨基酸含量。黄酒样以6-氨基喹啉-N-羟基琥珀酰亚胺基氨基甲酸酯(AQC)衍生化处理,以流速为0.7 mL/min经Waters AccQ·TagTM Ultra C_(18)(1.7μm,2.1×100 mm)的色谱柱梯度洗脱,利用二极管阵列检测器,在260 nm波长处检测。结果显示,17种游离氨基酸浓度在25～400μmol/L范围内,峰面积与浓度之间具有良好的线性关系(R~2≥0.9993),回收率在94.21%～104.82%。该方法可在11 min内将17种游离氨基酸完全分离,具有准确、快速、重复性好的特点,可用于黄酒中游离氨基酸含量的测定。     

异硫氰酸苯酯柱前衍生RP-HPLC法同时测定莲雾中15种游离氨基酸的含量

采用异硫氰酸苯酯(PITC)为柱前衍生化试剂,结合反相高效液相色谱法,建立了同时测定莲雾果实中15种游离氨基酸含量的方法。采用Atlantis T3柱为固定相,以0.1 mol/L乙酸钠缓冲液(pH6.5,含0.5%三乙胺)和乙腈-水(4:1)为流动相进行梯度洗脱,流速为1.0 mL/min,柱温35 ℃,紫外检测器波长254 nm。各氨基酸组分在2.0~500 mg/L范围内具有良好的线性关系,相关系数r均大于0.99,检出限为0.08~0.35 mg/L,定量限为0.35~1.25 mg/L,加标回收率为85.61%~106.68%,相对标准偏差RSD均小于5%。该方法使得15种氨基酸很好的分离,且准确度和精密度好,灵敏度和回收率高,适用于莲雾果实游离氨基酸含量的分析。     

柱前衍生-超高效液相色谱法同时测定虫草酒中17种游离氨基酸

建立一种快速、灵敏的柱前衍生-超高效液相色谱法同时测定虫草酒中17种游离氨基酸的方法。酒样经氮吹除醇,然后以6-氨基喹啉-N-羟基琥珀酰亚胺基氨基甲酸酯(AQC)为衍生试剂在硼酸盐缓冲溶液中衍生化。色谱柱为Waters Acc Q·Tag TM Ultra C18(1.7μm,2.1×100mm),Acc Q·Tag Ultra Eluent A及Acc Q·Tag Ultra Eluent B梯度洗脱,流速为0.7 m L/min,检测器为二极管阵列检测器,检测波长260nm。结果表明:17种氨基酸在25~400μmol/L内有浓度范围内,峰面积与浓度之间具有良好的线性关系(r2≥0.9950),回收率在83.21%~119.82%。该方法在10min内17种氨基酸能够完全分离,具有准确、快速、重复性好的特点。     

高效液相色谱法测定米渣复合氨基酸营养液中氨基酸含量

应用邻苯二甲醛(OPA)柱后衍生、离子交换高效液相色谱法同时测定20种氨基酸,氨基酸浓度在50~180μmol/L(色氨酸浓度为61.5~221.4μmol/L)时,其峰面积和氨基酸浓度的线性相关系数均大于0.96,20种氨基酸的加标回收率在95.7%~104.2%。用此法对米渣经多菌种发酵后制成的复合氨基酸营养液中游离氨基酸含量进行检测,取得了满意的结果。     

柱前衍生-RP-HPLC法测定蜂王幼虫冻干粉中16种氨基酸含量

目的:建立柱前衍生-反相高效液相色谱同时测定蜂王幼虫冻干粉中16种氨基酸含量的方法,并测定29批蜂王幼虫冻干粉中水解氨基酸含量。方法:以异硫氰酸苯酯为柱前衍生试剂,采用Waters Symmetry C18色谱柱(4.6 mm×250 mm,5μm)分析,以乙腈-水(4∶1)溶液和0.03 mmol/L醋酸钠-乙腈(355-15,ph=6.5)进行梯度洗脱,流速1.0 mL/min,在254 nm波长处测定氨基酸含量。结果:氨基酸在0.0625~1.2500 mmol/L范围内具有良好的线性关系(r≥0.9974),平均平均回收率在94.97%~99.50%之间;检出限为0.0005~0.0015 mmol/L,定量限为0.0075~0.0240 mmol/L。结论:该方法简便易行、准确性高、稳定性好,适于蜂王幼虫冻干粉中氨基酸定量检测。     

柱前衍生反相高效液相色谱法测定狭叶红景天中氨基酸含量

目的建立柱前衍生反相高效液相色谱法(reversed-phase high-performance liquid chromatography,RP-HPLC)测定狭叶红景天中游离及水解氨基酸种类及含量。方法以异硫氰酸苯酯为柱前衍生化试剂;色谱柱采用Ultimate Amino Acid氨基酸柱(4.6 mm×250 mm,5μm);流动相A为80%(V:V)的乙腈-水溶液,流动相B为7%(V:V)的乙腈-CH_3COONa溶液(pH=6.5);检测波长为254 nm。结果 21种氨基酸在0.0019~2.700mmol/L内呈良好的线性关系(r~20.9990)。游离氨基酸平均回收率在97.80%~116.82%之间,RSD在1.93%~2.47%之间(n=6);水解氨基酸平均回收率在99.26%~111.23%之间,RSD在1.70%~2.23%之间(n=6)。结论柱前衍生RP-HPLC法灵敏、准确,具有良好的重复性和稳定性,适合对狭叶红景天中氨基酸含量的测定。     

柱前衍生-高效液相色谱法测定保健食品中 16种氨基酸的含量

目的建立柱前衍生-高效液相色谱法测定保健食品中16种氨基酸的含量。方法优化GB/T5009.124-2003的前处理方法,样品经稀释或置于顶空瓶中直接酸水解;并采用OPA/FMOC柱前衍生法,色谱柱为Thermo ODS Hypersil,以醋酸钠缓冲液(含三乙胺、四氢呋喃)和醋酸钠缓冲液(含乙腈、甲醇)为流动相进行梯度洗脱,在338 nm和262 nm检测波长下进行高效液相色谱法检测。结果 16种氨基酸在4~250μg/mL范围内呈现良好线性关系,在10μg/mL水平下加标回收率为85.8%~115.2%,RSD为0.1%~9.1%(n=6),检出限在0.2~4.6 ng范围内。结论本方法操作简便、灵敏度高,可应用于实际样品的测定。     

PITC柱前衍生高效液相色谱法测定黄酒中17种氨基酸方法研究

建立了柱前衍生高效液相色谱法同时测定黄酒中17种氨基酸的方法。方法采用异硫氰酸苯酯(PITC)为柱前衍生试剂,色谱柱为C18(4.6×250mm,5μm),乙酸钠-乙腈-水混合体系梯度洗脱,紫外检测器,检测波长254nm,40min内17种氨基酸得到良好的分离。在0.025～1.25mmol/L范围内其浓度与响应值具有良好的线性关系,相关系数大于0.99;样品的平均加标回收率在78.6～118.1%之间,相对标准偏差在0.45%～3.30%范围;检出限为0.259～0.925μmol/L,定量限为0.863～3.083μmol/L。相对其他柱前衍生测定氨基酸的方法而言,该方法在可操作、低成本、易推广等方面具有明显优势,可供黄酒中氨基酸测定方法行业标准制定提供参考。     

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.     

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.     

The development of reference materials for paralytic shellfish poisoning toxins in lyophilized mussel. I: Interlaboratory studies of methods of analysis

This paper describes the first part of a project undertaken to develop mussel reference materials for Paralytic Shellfish Poisoning (PSP) toxins. Two interlaboratory studies were undertaken to investigate the performance of the analytical methodology for several PSP toxins, in particular saxitoxin (STX) and decarbamoyl-saxitoxin (dc-STX) in lyophilized mussels, and to set criteria for the acceptance of results to be applied during the second part of the project: the certification exercise. In the first study, 18 laboratories were asked to measure STX and dc-STX in rehydrated lyophilized mussel material and to identify as many other PSP toxins as possible with a method of their choice. In the second interlaboratory study, 15 laboratories were additionally asked to determine quantitatively STX and dc-STX in rehydrated lyophilized mussel and in a saxitoxin-enriched mussel material. The first study revealed that three out of four postcolumn derivatization methods and one pre-column derivatization method sufficed in principle to determine STX and dc-STX. Most participants (13 of 18) obtained acceptable calibration curves and recoveries. Saxitoxin was hardly detected in the rehydrated lyophilized mussels and results obtained for dc-STX yielded a CV of 58% at a mass fraction of 1.86 mg/kg. Most participants (14 out of 18) identified gonyautoxin-5 (GTX-5) in a hydrolysed extract provided. The first study led to provisional criteria for linearity, recovery and separation. The second study revealed that 6 out of 15 laboratories were able to meet these criteria. Results obtained for dc-STX yielded a CV of 19% at a mass fraction of 3.49mg/kg. Results obtained for STX in the saxitoxin-enriched material yielded a CV of 19% at a mass fraction of 0.34mg/kg. Saxitoxin could not be detected in the PSP-positive material. Hydrolysis was useful to confirm the identity of GTX5 and provided indicative information about C1 and C2 toxins in the PSP-positive material. The methods used in the second interlaboratory study showed sufficiently consistent analysis results to undertake a certification exercise to assign certified values for STX and dc-STX in lyophilized mussel.