冷鲜猪排骨假单胞菌生长预测模型的建立与验证

为快速预测和监控冷鲜猪肉中微生物的生长,建立和验证冷鲜排骨中0℃～20℃温度条件下假单胞菌的生长预测模型.结果表明:Gompertz方程能很好地描述不同温度下假单胞菌的生长,得到的假单胞菌一级生长预测模型,且其偏差因子和准确因子都在1左右;利用平方根模型描述温度与最大比生长速率和延滞期的关系,且呈现良好的线性关系,R2分别为0.9934和0.9263,从而得到假单胞菌生长预测的二级模型.初步说明生长预测模型能有效地预测0℃～20℃冷鲜猪排骨中假单胞菌的生长.     

基于预测微生物学的冷却牛肉货架期预测模型的建立

为实时监测冷却牛肉贮藏期间的品质变化与货架期,分别测定冷却牛肉0、4、7、10 ℃贮藏过程中假单胞菌菌数、总挥发性盐基氮含量和感官评分。利用修正的Gompertz方程建立不同贮藏温度下假单胞菌生长的动力学模型,以Belehradek方程为二级模型,描述贮藏温度对假单胞菌生长的影响,并利用2、5、8 ℃条件下贮藏的冷却牛肉验证货架期预测模型的准确性。结果表明：所建立的Gompertz模型拟合相关系数均在0.99以上,预测结果准确度在1.013～1.126之间,偏差度在0.926～1.057之间,贮藏温度与μmax 1/2和（1/λ）1/2均呈良好的线性关系,说明建立的一级和二级模型能够真实、有效地预测0～10 ℃贮藏条件下冷却牛肉中假单胞菌的生长情况;货架期的预测值与实测值相对误差在±10%以内,该货架期模型可有效预测冷却牛肉在0～10 ℃贮藏条件下任意温度下的货架期。     

前腿猪肉丝中假单胞菌生长预测模型的建立

假单胞菌是冷鲜肉中的优势菌,利用Gompertz模型拟合了不同温度条件下前腿肉丝中假单胞菌生长变化的一级模型,得到了假单胞菌在前腿肉丝基质上的生长的模型参数,5个温度一级模型拟合的R2值都大于0.99.利用平方根模型描述温度与最大比生长速率和延滞期的关系,得到假单胞菌的生长预测二级模型,二级模型方差分析非常显著.模型可用于预测0℃～20℃范围内冷鲜前腿猪肉丝中假单胞菌的变化情况,为经过切分处理的冷鲜前腿肉丝腐败微生物的预测研究提供了支撑.     

冷却猪肉中腐败微生物鉴定及其消长规律的研究

目的对冷却猪肉中腐败微生物进行鉴定,研究其在0～4℃条件下贮藏时的消长规律。方法采用选择性培养基对冷却猪肉中的腐败微生物进行分离培养,利用Biolog微生物自动鉴定系统对菌株进行鉴定。结果共鉴定出11株具有代表性的细菌:肠杆菌4株,假单胞菌1株,热杀索丝菌1株,不动杆菌1株,乳酸菌2株,葡萄球菌2株。冷却猪肉中腐败微生物初始菌相结构为:热杀索丝菌54.9%,肠杆菌科8.7%,假单胞菌属3.6%,乳酸菌属29.5%,葡萄球菌/微球菌0.6%,霉菌/酵母菌2.7%。在0～4℃条件下贮藏时,热杀索丝菌、肠杆菌科和假单胞菌属是冷却猪肉中的优势腐败菌,假单胞菌属和肠杆菌科在菌相结构中的比例增长最高,特别是假单胞菌属的数量增长最快。结论鉴定出了冷却猪肉中的主要腐败微生物,确定了其初始菌相和优势腐败菌。     

高通量测序分析不同增菌温度下冷鲜鸡肉细菌的群落多样性

采用Ion Torrent个人化操作基因组测序仪高通量测序技术,对冷鲜鸡肉贮藏过程中的细菌在4?℃与37?℃两种增菌温度下群落结构、相对丰度及演替规律进行深入研究。结果表明：在门水平上,变形菌门、厚壁菌门、拟杆菌门为3?大菌门。在属水平,4?℃条件下,贮藏前期（0～4?d）以假单胞菌属、希瓦氏菌属、不动杆菌属为主要的优势菌属,其中假单胞菌占最大的比例,最高达44.03%;在贮藏中后期（6～12?d）,类香味菌属迅速增加,含量大于假单胞菌属,成为冷鲜鸡肉贮藏中后期的优势腐败菌。在37?℃条件下,柠檬酸杆菌属、变形杆菌属、乳球菌属及未知其他菌属在贮藏前期占主要优势;到贮藏中后期,以类香味菌属、污蝇杆菌属为主,对冷鲜鸡肉腐败变质有着重要的影响。两种增菌温度下细菌群落多样性及菌群结构变化,反映了冷鲜鸡肉潜在的卫生质量风险,为后期冷鲜鸡肉冷藏过程或贮藏中温度失控情况下有效实施冷鲜鸡肉质量安全监测提供技术参考。     

非真空包装烧鸡贮藏中品质变化和腐败菌分析

对非真空包装烧鸡在低温(0~4℃)贮藏过程中品质和腐败菌种群变化进行研究,通过分析贮藏期间微生物生长情况及pH值、TVB-N值、TBARS值变化,结合感官质量变化,确定低温条件下贮藏产品的货架期和腐败菌群。结果表明:低温贮藏条件下,初始菌数为4.95×103 cfu/g时,产品的货架期约为3 d;酵母菌、假单胞菌属、乳酸菌和葡萄球菌属是产品腐败时的主要微生物;酵母菌、假单胞菌属是优势腐败菌。     

气调包装冷鲜鱼肉的菌相分析

正通过研究比较气调包装、真空包装和空气包装对冷鲜鱼肉贮藏品质变化和菌相变化的影响,分析形成原因。结果表明:在4℃条件下,气调包装的鲜鱼肉冷藏品质最好,对H2S菌、假单胞菌等抑制效果最佳;贮藏15天后摘要:通过研究比较气调包装、真结果表明:在4℃条件下,气调包装的鲜基氮含量最低,仍在二级鲜度范围内,货和假单胞菌,而气调包装对西瓦式菌具有关键词:气调包装;冷鲜鱼肉;菌相     

气调包装冷却牛肉特定腐败菌生长模型的建立

以气调包装冷却牛肉为研究对象,研究储藏在0、5、10℃温度条件下气调包装冷却牛肉中特定腐败菌(假单胞菌)的生长变化规律。通过Matlab7.0 软件拟合不同温度条件下假单胞菌的生长情况,得到假单胞菌生长的Gompertz 模型参数;利用响应面方程建立假单胞菌生长的二级模型;由平方根方程建立了温度对假单胞菌生长动力学影响的数学模型。进而验证0～10℃低温条件下假单胞菌的生长动力学模型。结果表明：建立的Gompertz 方程拟合相关系数均在0.99 以上,二级模型偏差度和准确度均在0.90～1.05 之间,说明建立的一级和二级模型能够真实有效地预测0～10℃条件下气调包装冷却牛肉中假单胞菌的生长情况。     

真空冷却鸡胸肉优势腐败菌生长模型的预测

为探究真空冷却对鸡肉保质期的影响,预测鸡胸肉内的微生物生长规律。对鸡胸肉进行了冷风冷却和真空冷却,测量其在贮藏期间菌落总数变化,证明真空冷却有助于延长鸡肉保质期。采用巢式PCR-DGGE结合传统测定微生物的方法研究了真空冷却后的鸡胸肉在5℃冷藏期间,鸡胸肉的表面菌相变化,确定了假单胞菌为贮藏期间的优势腐败菌。并以菌落总数、优势腐败菌总数作为微生物指标,以TVB-N、pH作为理化指标,确定了冷鲜鸡胸肉中微生物的最小限量为5.373 (lg(CFU/g))。通过将冷却的鸡胸肉置于0～25℃不同的温度下,建立了微生物生长的一级模型和二级模型,并对其进行了验证和评价,结果表明,所建立的数学模型可以较好地预测优势腐败菌的生长趋势。     

基于宏转录组学解析不同贮藏时期冷鲜滩羊肉微生物代谢过程

以托盘密封包装的冷鲜滩羊肉表面微生物为研究对象,利用宏转录组学技术解析0、4、8 d三个贮藏时期微生物基因组差异转录、代谢途径与3 个贮藏时期微生物群落演替的关系。结果表明：3 个贮藏时期的冷鲜滩羊肉微生物差异表达基因数分别为429、15、1 529 个。通过对这些微生物差异表达基因进行KEGG代谢途径富集分析发现,参与核苷酸代谢、脂质代谢、能量代谢、碳水化合物代谢以及氨基酸代谢相关过程的差异表达基因显著富集,说明这几种代谢途径在滩羊肉微生物的演替过程中占据重要地位。在3 个贮藏时期,变形菌门都是优势微生物,变形菌门下的假单胞菌属和肠杆菌科利用贮藏环境中的氧气与滩羊肉中的葡萄糖为碳源,迅速生长繁殖,成为最主要的优势微生物。随贮藏时间延长,氧气被消耗殆尽,且滩羊肉的pH值降低,使得乳酸菌迅速生长,成为仅次于假单胞菌、肠杆菌的优势微生物。研究结果可以为冷鲜滩羊肉贮藏期间微生物及肉品质量预报、控制技术研发提供理论参考。     

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.     

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.     

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.     

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.     

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.