不同产地咸干鱼的电子鼻分析

以在市场中购买的7个不同地区的咸干鱼产品为研究对象,利用电子鼻技术对其挥发性成分进行检测,并对其进行主成分分析、线性判别分析和负荷加载分析,结合感官评价的结果,实现电子鼻对7种样品的区分。结果表明,青岛一卤鲜咸干鱼感官评价得分最高,主成分分析比线性判别分析能更有效地区分不同产地的咸干鱼,挥发性盐基氮含量对电子鼻技术在咸干鱼气味的区分中发挥重要作用。     

利用电子鼻技术预测冰温贮藏牛肉的新鲜度变化

将牛肉贮藏在其冰点温度范围内(-1.7℃±0.2℃),并对贮藏期间牛肉的品质指标(菌落总数、挥发性盐基氮、感官色泽、感官气味)进行测定,同时用PEN3电子鼻对相应的牛肉挥发性气体物质进行检测。结果表明:贮藏期间牛肉的挥发性气体成分越来越多,不同贮藏时间的特征响应之间存在明显的差异性;电子鼻的2号、7号和9号传感器对检测牛肉挥发性气体物质的作用大,基本可以涵盖所有的检测信息;利用PCA和LDA2种分析可以有效区分开不同贮期的牛肉。通过电子鼻建立的模型可以很好地预测冰温贮藏牛肉不同贮藏时间的TVB-N值、菌落总数、感官色泽评分值以及感官气味评分值。     

基于电子鼻技术对真空包装三文鱼片的新鲜度评价

采用电子鼻对(4±1)℃条件下真空包装三文鱼片的挥发性物质进行检测并进行主成分分析(PCA)、线性判别分析(LDA)、负荷加载分析(LA),同时研究了鱼片在冷藏期间的感官、挥发性盐基氮值(TVB-N)、质构、色差值的变化规律。结果表明,三文鱼片冷藏期间的感官评分逐渐下降,TVB-N值明显增加,12 d时达到28. 768 mg/100g,已超出淡水鱼TVB-N值小于20. 00 mg/100g的规定范围;鱼片硬度值变化先增加后下降,弹性值缓慢下降;色差L*、a*、b*值变化波动不大,ΔE值前期变化较小,第4天开始迅速上升,第8天ΔE值达到24. 37,与初始鱼片颜色差异显著;电子鼻PCA及LDA分析均对不同冷藏时间的三文鱼片区分度良好,LA分析发现其中主要挥发性物质为氮氧化合物、芳香物质、乙醇及无机硫化物,电子鼻分析结果与感官、TVB-N值、质构及色差分析结果基本一致,表明电子鼻技术可作为真空包装三文鱼片新鲜度的快速评价方法。     

基于电子鼻的冷藏大菱鲆品质变化研究

利用电子鼻技术检测不同贮藏温度下大菱鲆样品的挥发性气体变化情况,对所得数据进行主成分分析(PCA)、载荷分析(LA)和聚类分析(CA),并结合细菌菌落总数和挥发性盐基氮(TVB-N)含量变化进行分析,建立一种基于电子鼻的冷藏大菱鲆新鲜度判别方法。结果表明:电子鼻主成分分析、载荷分析和聚类分析能很好地区分大菱鲆0℃与4℃贮藏过程中的挥发性气味变化,气味发生变化的时间拐点分别是贮藏20 d和16 d;电子鼻分析结果与细菌菌落总数和TVB-N值变化预测的货架期终点基本一致。因此电子鼻技术可以用来判别大菱鲆冷藏过程中的新鲜度变化。     

基于电子鼻技术的秋刀鱼新鲜度评价

采用德国PEN-3型便携式电子鼻收集4℃冷藏条件的秋刀鱼挥发性风味信息,并对收集的风味信息进行传感器载荷分析(loadings analysis)、线性判别分析(linear discriminant analysis,LDA)和主成分分析(principal component analysis,PCA),其结果与秋刀鱼感官评价、p H值、挥发性盐基氮(total volatile basic nitrogen,TVB-N)值和菌落总数等指标进行相关性分析。结果表明:秋刀鱼的气味随着贮藏时间的延长发生变化,其中氮氧化合物、有机硫化物和无机硫化物等电子鼻传感器的响应值变化最为明显;电子鼻分析结果与感官、p H值、TVB-N值和菌落总数分析结果显著相关,表明电子鼻检测技术可用作秋刀鱼新鲜度快速判别的一种新型检测方法。     

基于电子鼻的牛肉复配保鲜剂效果评价及储存时间预测模型研究

牛肉以其丰富的营养价值而深受消费者喜爱,然而其鲜度易受环境因素影响。本文分别采用1.0%葡萄糖溶液(G)、1.0%壳聚糖(C)、1.0%葡萄糖溶液+1.0%壳聚糖(CGC)、去离子水(CON)浸泡处理牛肉样品,于低温(4℃)保存。每隔24 h测定不同试剂处理的牛肉样品的挥发性盐基氮(TVB-N)指标,判定牛肉的新鲜程度,同时测定牛肉样品的电子鼻响应。试验结果表明:葡萄糖和壳聚糖的复配保鲜剂相比其它试剂具有较好的保鲜效果,用电子鼻可灵敏地区分不同保鲜剂处理的牛肉样品。建立了葡萄糖和壳聚糖复配保鲜剂处理牛肉样品的储存时间预测模型,为牛肉新鲜度快速分析提供新思路。     

基于电子鼻的黑胡椒鸭胸肉调理产品品质评价

利用电子鼻检测黑胡椒鸭胸肉调理产品在贮藏期的品质变化,并结合感官指标、微生物指标和挥发性盐基氮指标,对检测结果进行比较分析。结果表明：微生物指标和挥发性盐基氮指标并不能准确反映样品的品质,电子鼻对已经发生轻微气味改变的样品具有非常高的辨识度,可以作为一种快速、有效的检测手段应用于肉制品的品质鉴别和评判。     

鮰鱼冷藏过程中气味和新鲜度的变化及相关性

以真空包装与空气包装鮰鱼为研究对象,采用固相微萃取-气相色谱-质谱联用结合电子鼻技术,对鮰鱼4℃冷藏过程中的挥发性成分进行分析,并对不同样品的电子鼻传感器信号进行分析,同时结合感官评分、K值、三甲胺含量、挥发性成分及电子鼻传感器信号进行相关性分析。结果表明：鮰鱼4 ℃冷藏过程中的特征风味物质主要为己醛、壬醛、苯甲醛和1-辛烯-3-醇;电子鼻可以区分不同冷藏时间、不同包装的鮰鱼;感官评定结果表明,鮰鱼冷藏4～5 d时开始腐败,且真空包装组较空气包装组变化缓慢;冷藏鮰鱼三甲胺含量和K值随冷藏时间延长而逐渐上升,真空包装样品新鲜度较空气包装组好;相关性及主成分分析结果表明,苯甲醛、1-辛烯-3-醇可作为表征鮰鱼腐败的挥发性化合物。     

基于电子鼻技术的鲈鱼新鲜度评价

采用电子鼻获取不同保藏时间鲈鱼(Lateolabrax japonicus)鱼鳃和鱼肉的气味信息,通过对数据进行主成分分析(PCA)、线性判别分析(LDA)和负荷加载分析,并结合感官评价、挥发性盐基氮(TVB-N)和菌落总数进行分析,建立一种基于电子鼻技术判别鲈鱼新鲜度的方法。结果表明,随着保藏时间的延长,电子鼻传感器的响应强度逐渐增大,鲈鱼鱼鳃和鱼肉的气味随之发生变化,且鱼鳃的气味响应强度大于鱼肉,其中2号传感器对第1主成分的贡献率最大;电子鼻分析结果与感官、TVB-N值和菌落总数结果基本一致。因此电子鼻可以用来区分不同新鲜度的鲈鱼,鱼鳃的区分效果优于鱼肉。     

电子鼻结合气相色谱-质谱联用技术分析贮存条件对马铃薯面包挥发性成分的影响

以常温、冷藏的马铃薯面包为研究对象,采用电子鼻结合顶空固相微萃取-气相色谱-质谱联用技术,分析常温第1天、第6天和冷藏第6天的马铃薯面包样品挥发性成分。结果表明,电子鼻分析结果能够很好地区分常温和冷藏1～9?d马铃薯面包的风味。采用主成分分析和线性判别分析可以量化主成分贡献率和样品间风味的区分度,并利用判别因子分析建立马铃薯面包识别库模型。顶空固相微萃取-气相色谱-质谱联用分析结果表明,3?种马铃薯面包共检测出28?种挥发性风味物质,其中常温第1天17?种,冷藏第6天4?种,常温第6天14?种;经贮藏后,风味物质变化明显,冷藏样品酸类、酯类、酮类和烃类物质消失,常温样品贮藏后醛类和醚类消失,醇类化合物相对含量都显著增加。因此,电子鼻结合气相色谱-质谱联用技术可对贮藏期马铃薯面包的风味进行综合评价。     

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.