梅奇酵母氨基甲酸乙酯酶分离纯化与酶学性质分析及其对葡萄酒香气的影响

为了研究梅奇酵母所产生氨基甲酸乙酯（Ethyl Carbamate,EC）酶的性质,通过硫酸铵盐析、离子交换层析的方法对EC酶进行分离纯化,并对纯化后EC酶的酶学性质进行了分析。结果表明,纯化后EC酶对比纯化前的酶活提高了约1.2倍。纯化后EC酶最适反应温度为35 ℃,在25~45 ℃之间热稳定性较强;最适pH为5.5,在pH5~6时该酶稳定性强,即酸稳定性强,碱稳定性较差。当乙醇体积分数为12%~14%时,EC酶具有一定酶活。底物特异性结果表明,该EC酶对EC及其前体物质（尿素）具有较高的降解能力,且对于成品葡萄酒挥发性香气成分影响不显著。     

蒸馏萃取-气相色谱-质谱联用对不同腌制工艺大头菜挥发性风味物质的分析

采用同时蒸馏萃取-气相色谱-质谱联用(SDE-GC-MS)对不同加工工艺大头菜和原料的挥发性风味物质进行分析。从大头菜原料、新工艺大头菜、传统腌制大头菜、脱盐大头菜4个样品中共检验出90种挥发性香气物质,其中从新工艺大头菜、传统腌制大头菜和脱盐大头菜中分别检测出68、56和28种挥发性香气物质;大头菜腌制可产生大量挥发性风味成分,且新工艺大头菜挥发性香气成分种类高于传统大头菜和脱盐大头菜,脱盐导致大头菜香气成分大量损失。     

2种韩国泡菜挥发性风味物质分析研究

采用顶空固相微萃取方法提取2种知名品牌的韩国泡菜A和B中挥发性风味物质,然后结合气相色谱-质谱联用技术对提取的挥发性风味物质进行分离鉴定。通过对固相微萃取的纤维头、萃取时间和解吸时间的选择来优化其实验条件。采用气-质联用技术从2种韩国泡菜A和B中分别鉴别出65和55种挥发性风味物质。2种韩国泡菜中含有34种相同的挥发性风味物质,主要包括乙醇、乙酸、烯类和硫醚类等。研究表明,顶空固相微萃取以及气-质联用技术可以很好来分析泡菜中挥发性风味物质,并说明不同品牌泡菜其挥发性风味物质存在一定差异。     

长白山野生山葡萄酒挥发性成分分析

以2016年、2017年和2018年3个垂直年份的长白山野生山葡萄酒为研究对象,采用了电子鼻和固相微萃取结合气相色谱-质谱联用技术,分析不同年份山葡萄酒挥发性成分的种类和含量,旨在研究野生山葡萄酒的挥发性物质的差异。结果表明,电子鼻对不同年份葡萄酒的挥发性成分敏感,能够将3个年份的葡萄酒区分开。固相微萃取结合气相色谱-质谱联用,测定3个年份的葡萄酒中共存在153种挥发性成分,其中酯类56种、醇类30种、醛类2种、酮类11种、酸类5种、烃类25种、苯环类16种,其他类物质8种; 3个年份的葡萄酒中含有24种相同成分;随着年份的增加,其挥发性物质的种类和质量浓度也增加,其风味更加丰富浓郁。酯类和醇类物质是山葡萄酒主要的风味成分。该研究为全面认识野生山葡萄酒的风味和典型性提供了依据。     

外源酶对发酵羊肉香肠挥发性风味物质的影响

研究外源酶对发酵羊肉香肠挥发性风味物质的影响.通过顶空固相微萃取-气相色谱-质谱联用技术测定发酵羊肉香肠中的挥发性风味物质.结果表明,发酵羊肉香肠中的主要挥发性风味物质为醛类、烃类、醇类和酯类等.对照组和试验组发酵香肠挥发性风味物质的种类和含量存在着一定的差别.     

高湿挤压技术制备持香型仿肉制品工艺

以大豆分离蛋白和谷朊粉为挤压原料、天然呈味粉末油脂为香气调味料,利用高湿挤压技术制备持香型仿肉制品。通过固相微萃取-气相色谱-质谱联用技术对仿肉制品挥发性风味化合物进行定性定量分析,确定谷朊粉质量分数、水分质量分数、挤压温度及螺杆转速对挥发性风味物质保留率的影响。在单因素试验结果基础上,采用响应面法对高湿挤压工艺制备持香型仿肉制品进行优化,确定高湿挤压最优工艺参数为谷朊粉质量分数20%、挤压温度150?℃、螺杆转速300?r/min,响应值总挥发性风味物质保留率有最优值,为44.07%。而总挥发性风味物质保留率随水分质量分数的增加而减小,为不影响仿肉制品的咀嚼性,固定原料水分质量分数为60%。     

黑曲霉β-葡萄糖苷酶对葡萄酒酶解增香调控及香气物质的影响

采用Kramer感官品评,并结合顶空固相微萃取气相色谱质谱(SPME-GC-MS)联用方法,研究黑曲霉β-葡萄糖苷酶对赤霞珠葡萄新酒酶解增香调控的最佳条件及香气物质影响。结果表明,酶解增香处理的最佳条件为酶解温度45℃、酶解时间4.0 h、加酶量4.0 U/m L。酶解样品经SPME-GC-MS检测分析,共定性出59种呈香物质,方差分析得知其中35种物质酶解前后具有显著性差异。香气物质相对含量总量增加24.59%,其中以萜烯及C13-降异戊二烯类物质增量最为明显,为118.54%。酶解处理对提高葡萄酒中典型性香气,进一步改善葡萄酒风味起到积极影响。     

利用SDE-GC-MS分析宜宾芽菜中挥发性风味物质的研究

采用同时蒸馏萃取技术(SDE)对宜宾老坛芽菜中的挥发性风味物质进行提取,优化蒸馏萃取条件,并用气相色谱-质谱联用技术(GC-MS)对其风味物质进行分析检测。结果表明:在蒸馏萃取溶剂为二氯甲烷、蒸馏萃取时间2.5h和萃取温度55℃的条件下,宜宾芽菜中风味物质提取效果最好。芽菜样品中共检测出28种挥发性风味物质。     

全二维气相色谱-飞行时间质谱解析黄土高原产区赤霞珠葡萄酒挥发性组分特征挥发性化合物

采用顶空固相微萃取结合全二维气相色谱-飞行时间质谱(headspace solid-phase microextraction combined-compre-hensive two dimensional gas chromatography-time of flight mass spectrometry, HS-SPME-GC×GCTOFMS)对黄土高原产区赤霞珠葡萄酒中挥发性成分进行分析。结果表明:全二维气相色谱具有强分离能力、高灵敏性、高峰容量等优势,可以较为全面地对葡萄酒挥发性物质进行解析,特别是一些痕量香气化合物。通过质谱库检索及保留指数比对,在黄土高原5个小产区赤霞珠葡萄酒中共定性到600种香气化合物,其中以酯类、芳香族、萜烯类和醇类为主,分别检测到128、113、85、83种,同时还检测到醛酮类、含硫化合物、呋喃、内酯、吡嗪、挥发酸等化合物,这些物质共同作用形成了该产区葡萄酒的风味特征。此外,5个小产区葡萄酒定性到的香气化合物总数及各类别的数量则均相差不大。该研究探讨了全二维气相色谱技术在葡萄酒香气解析中的应用,同时也为深入探究黄土高原产区葡萄酒的风味特征提供基础数据与理论依据。     

不同前处理方法对酱香型白酒挥发性风味成分的影响

以酱香型白酒为研究对象,采用固相微萃取（SPME）和液液萃取（LLE）对白酒样品进行前处理,并采用单因素试验优化其萃取条件,结合气相色谱-质谱联用（GC-MS）技术对其挥发性风味成分进行分析。结果表明,最适固相微萃取条件为：萃取时间45 min,萃取温度50℃,酒精度15%vol;最适液液萃取试剂为二氯甲烷;液液萃取优于固相微萃取。在最适液液萃取条件下,酱香型白酒中共检出挥发性风味成分162种,包括酯类58种,醇类37种,酸类7种,酚类4种,醛酮类25种,呋喃类4种,吡嗪类7种,其他类20种。其中酯类、醇类和酸类物质含量较丰富,分别占总含量的41.4%、11.4%和39.9%。     

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.     

Chlorohydrins of bisphenol A diglycidyl ether (BADGE) and of bisphenol F diglycidyl ether (BFDGE) in canned foods and ready-to-drink coffees from the Japanese market

BADGE.2HCl and BFDGE.2HCl were determined in 28 samples of ready-to-drink canned coffee and 18 samples of canned vegetables (10 corn, 5 tomatoes and 3 others), all from the Japanese market. HPLC was used as the principal analytical method and GCMS for confirmation of relevant LC fractions. BADGE.2HCl was found to be present in one canned coffee and five samples of corn, BFDGE.2HCl in four samples of canned tomatoes and in one canned corn. No sample was found which exceeded the 1mg/kg limit of the EU for the BADGE chlorohydrins. However the highest concentration was found for the sum of BFDGE.2HCl and BFDGE.HCl.H₂O at a level of 1.5mg/kg. A Beilstein test confirmed that all cans containing foods contaminated with BADGE.2HCl or BFDGE.2HCl had at lest one part coated with a PVC organosol.     

European priorities for research to support legislation in the area of food contact materials and articles

A strong science base is required to underpin the planning and decision-making process involved in determining future European community legislation on materials and articles in contact with food. Significant progress has been made in the past 5 years in European funded work in this area, with many developments contributing to a much better understanding of the migration process, and better and simpler approaches to food control. In this paper this progress is reviewed against previously identified work-areas (identified in 1994) and conclusions are reached about future requirements for R&D to support legislation on food contact materials and articles over the next 5 or so years.     

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.     

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.     

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.     

Influence des ions sur le pouvoir hydratant de l'ure e: e tude sur peau de porc ex vivo

This study deals with the influence of ions (NaCl and MgSO4) in a W/O emulsion containing 10% urea. Moisturization kinetics are assessed by corneometry on pig skin ex vivo. The formula's influence on urea penetration is measured by infrared spectrometry with an ATR device and the stripping method. Corneometry and spectroscopy were chosen to record simultaneously the hydratation levels and urea localization into superficial cell layers. Urea crystallization after evaporation of emulsions and aqueous solutions is described. Results show that urea does not hydrate nor penetrate when applied to the skin through an aqueous gel. In a W/O emulsion, sodium chloride increases the ability of urea to moisturize without improving penetration. In vitro urea crystallization is disturbed by sodium chloride or magnesium sulphate for solutions and emulsions. This stabilization by ions is correlated with good moisturization values. The stabilization of urea in the solute state provided by ions increases its water epidermal binding capacity without enhancing penetration.     

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.