石墨炉原子吸收光谱法测定皂树皮提取物中铅的不确定度评定

目的:探讨石墨炉原子吸收光谱法测定皂树皮提取物中铅不确定度的评定方法。方法:用原子吸收光谱仪测定皂树皮提取物样品中铅含量,根据该分析过程的测量数学模型从样品称量、样品定容、标准溶液配制、标准曲线测定、样品和空白测定等方面进行测量不确定度的计算。结果:样品X_1铅含量为1.28 mg/kg,扩展不确定度为0.090 mg/kg(k=2);样品X_2铅含量为3.90 mg/kg,扩展不确定度为0.250 mg/kg(k=2)。结论:测量过程中的不确定度主要来源于方法的回收率、样品空白变动性、消化液中铅浓度和重复性。通过建立测量数学模型,可对石墨炉原子吸收光谱法测定固体样品中铅测量的不确定度进行合理的评定。     

稻谷中铅含量测定的测量不确定度的评估

随机选取2007年广东省产的稻谷样品一份,用原子吸收分光光度计石墨炉法测定样品中铅含量,参考《化学分析中测量不确定度的评估指南》的方法,分析铅含量测定过程中的测量不确定度的主要来源,包括溶液定容体积、称量、样品溶液铅浓度测定和测量重复性,计算合成不确定度和扩展不确定度。在该样品铅含量测定中,稻谷样品中铅含量为0.097 mg/kg,其扩展不确定度为0.0024 mg/kg(置信度95%,包含因子K=2)。     

石墨炉原子吸收光谱法测定梭子蟹中镉的不确定度分析

本试验用石墨炉原子吸收分光光度计法对不合格的梭子蟹中镉含量进行不确定度评定。依据GB 5009.15—2014中原子吸收分光光度法检测方法,样品经微波消解赶酸后,使用石墨炉原子吸收分光光度计进一步测定镉含量,并以JJF 1059.1—2012《测量不确定度评定与表示》中不确定度评定方法为参考,计算各不确定度分量。评定结果显示梭子蟹中镉含量为2.324 mg/kg,扩展不确定度为0.090 mg/kg(k=2)。结果表明：石墨炉原吸光谱法测定不合格梭子蟹中镉含量的不确定度主要来自标准曲线拟合,其次是系统偏差。     

石墨炉原子吸收测定大米中的铅不确定度评定

评定石墨炉原子吸收光谱法测定大米中铅含量的不确定度,找出影响不确定度的主要因素。按GB 5009.12—2010建立不确定度的数学模型,根据《化学分析中不确定度评估指南》对石墨炉原子吸收光谱法测定大米中铅含量的不确定度进行评定。结果表明:大米铅含量0.100㎎/kg时,其扩展不确定度为0.009 mg/kg(k=2)。石墨炉原子吸收光谱法测定大米铅含量时,样品消解过程和测定样品消解液中铅的质量浓度产生的不确定度对总不确定度影响最大。     

全自动石墨加热消解-石墨炉原子吸收法测定麦苗粉中铅含量的不确定度评定

目的评定全自动石墨加热消解-石墨炉原子吸收法测定麦苗粉中铅含量的不确定度。方法麦苗粉样品经全自动石墨加热消解后,石墨炉原子吸收法测定,外标法定量,根据建立的数据模型对每个不确定度分量进行评定,最终得出对合成不确定度的贡献度。结果置信概率为95%,取包含因子k=2,湿法消解-石墨炉原子吸收法测定麦苗粉中铅含量结果报告为X=(0.17±0.01)mg/kg。结论该方法测量铅不确定度的主要因素是曲线拟合的不确定度。     

石墨炉原子吸收光谱法测定普洱茶包装用棉纸中铅含量不确定度的评定

目的评定石墨炉原子吸收光谱法测定普洱茶包装用棉纸中铅含量的不确定度。方法采用石墨炉原子吸收光谱法对普洱茶包装用棉纸中的铅含量进行检测,参照CNAS-GL06:2018评定其不确定度。结果其合成标准不确定度为0.0435 mg/kg。GB 4806.8-2016《食品安全国家标准食品接触用纸和纸板材料及制品》中规定铅的残留量不大于3.0mg/kg,本次测试结果表示为(0.66±0.09)mg/kg,k=2,结果判定为符合。结论其不确定度主要来自于标准曲线的拟合,其次是铅标准中间液的配制及样品的重复性测量。     

石墨炉原子吸收光谱法测定热封型茶叶滤纸中铅含量的不确定度评定

目的 评定石墨炉原子吸收光谱法测定热封型茶叶滤纸中的铅含量的不确定度。方法 采用GB31604.34-2016测定热封型茶叶滤纸中的铅含量。计算工作曲线、标准溶液、样品重复测定、仪器、吸光值量化误差、消解回收率、样品称量过程引入的不确定度,建立数学模型,计算合成不确定度。结果 石墨炉原子吸收光谱法测定热封型茶叶滤纸中铅的不确定度为0.10mg/kg。结论 影响检测结果的不确定度主要来源为校准曲线与消化回收率。     

石墨炉原子吸收分光光度法测定海蟹中镉的不确定度

根据测量不确定度的评定理论,分析石墨炉原子吸收分光光度法测定海蟹中镉的不确定度来源。方法 以GB/T 5009.15—2003《食品中镉的测定》为检验依据对海蟹中的镉含量进行定量分析,以JJF 1059—1999《测量不确定度评定与表示》为依据对测量过程中的不确定度因素进行评估。结果 石墨炉原子吸收分光光度法测定海蟹中镉的质量比可表示为w=(172±16) μg/kg,k=2。结论 通过推导计算,给出了扩展不确定度,为石墨炉原子吸收光度法测量重金属元素的质量控制提供了理论依据。     

石墨炉原子吸收光谱法测定鲜虾中镉含量的不确定度评定

目的 建立石墨炉原子吸收光谱法测定泰虾中镉的不确定度评定方法。方法 样品经微波消解后稀释,将一定量的样品消解液注入原子吸收分光光度计的石墨炉原子化器中。采用标准曲线法定量。分析了测定过程中的不确定度来源,对不确定度的组成进行了评定和量化。根据数学模型计算了样品中镉的含量,合成了标准不确定度和扩展不确定度。结果 石墨炉原子吸收光谱法测定泰虾中镉含量为1.6 mg/kg,扩展不确定度为0.2 mg/kg(k = 2),结果表达为 (1.6 ± 0.2) mg/kg,k = 2。结论 结果表明,不确定度的主要来源是样品溶液中镉浓度的测定,其次是重复测定和加标回收试验,其他因素引起的不确定度可以忽略。     

微波消解-石墨炉原子吸收光谱法测定食用植物油中痕量铅的不确定度评定

研究了微波消解-石墨炉原子吸收光谱法测定食用植物油中痕量铅的不确定度来源,并对其不确定度分量进行了定量评定,确定了相对标准不确定度和扩展不确定度。结果表明：微波消解-石墨炉原子吸收光谱法测定食用植物油中痕量铅的不确定度主要来源为计量器具校准、标准曲线拟合、实验人员读数和仪器测定重复性,其相对标准不确定度分别为0.048、0.022、0.016和0.013。当称样量为0.500 1 g时,铅含量为0.024 mg/kg,k=2（95%置信度）,扩展不确定度为0.003 mg/kg,测量结果可表示为（0.024±0.003）mg/kg。     

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.