纯种强化发酵细菌型豆豉研究

研究以纯种强化发酵细菌型豆豉为基础,以氨基酸态氮为指标,通过正交试验确定了前发酵条件对豆豉感官评价的影响.结果表明,枯草芽孢杆菌RH3519和BJ1-3最佳前发酵条件为泡豆水pH值为8.0,水温40℃,泡豆12h,接种量1.5％,发酵温度37℃,发酵3d.其中RH3519发酵的豆豉,氨基酸态氮及总酸含量分别为1.12g/100g、0.27g/100g,显著高于枯草芽孢杆菌BJ1-3和自然发酵的豆豉,且色泽与风味最佳.经初步工业放大试验显示,RH3519发酵的豆豉色泽更接近于自然发酵的豆豉,拉丝丰富,豉香诱人,且质地均匀,酱香浓郁,可作为工业纯种强化发酵生产豆豉的优良候选菌株.     

传统大豆发酵食品中纳豆芽孢杆菌的分离及纳豆发酵

以我国传统大豆发酵食品和稻草样品为来源,根据蛋白酶和纳豆激酶活性、产聚谷氨酸(poly-L-glutamic acid,γ-PGA)性能和生物素依赖特性进行筛选,分离获得了8株具有纳豆芽孢杆菌特性的枯草芽孢杆菌菌株。利用16S～23S rRNA内转录间隔区(internal transcribed spacer,ITS)序列对分离菌株进行系统发育分析,结果显示其与已报道的纳豆芽孢杆菌菌株以较高的相似性(93%～97%)聚类一簇,独立于同种内的其他枯草芽孢杆菌。其中TC100和TC103菌株制作的纳豆粗酶液中的纳豆激酶活性最高,分别为550 U/mL和519 U/mL。HN48和TC100菌株发酵纳豆的感官效果最好,评价分数均为19分。综上所述,本研究根据纳豆芽孢杆菌特有的性状,有效分离获得了具有纳豆芽孢杆菌特性的8株菌株,通过菌株形态和ITS基因序列的系统发育分析确定分离菌株均属纳豆芽孢杆菌,8株分离菌株均能产纳豆激酶,发酵生产纳豆的感官效果良好,有望作为纳豆生产的工业菌株。     

纳豆芽孢杆菌的筛选与鉴定

纳豆是大豆经纳豆芽孢杆菌发酵制成的-种药食兼用的传统食品.本文以市售纳豆为原料,利用目标纳豆芽孢杆菌所应具有耐热性、显著的蛋白酶活性等生物学特性,筛选得到一株菌株.根据菌落形态和糖发酵、过氧化氢酶等生理生化试验,初步鉴定其为枯草芽孢杆菌(Bacillus subtilis).实验表明,此株菌株具有产γ-聚谷氨酸(γ-PGA)、产纳豆激酶的生理特性,从而证实了该菌株确实为纳豆芽孢杆菌(Bacillus natto).     

纳豆芽孢杆菌的筛选与固态发酵研究

根据纳豆芽孢杆菌水解淀粉的生物学特性,采用稀释平板分离法,从中国传统食品豆豉中筛选出两株纳豆芽孢杆菌优势菌株.通过比较这两个分离菌株与实验室保存的纳豆芽孢杆菌菌株的耐受性,从中选出一株最优益生菌株B2.以活菌数、芽孢数、蛋白酶及α-淀粉酶活力为指标,对益生纳豆芽孢杆菌B2固态发酵条件进行了初步研究,试验结果表明:玉米粉:麦麸为3:7,含水量60%,种龄15 h,接种量5%,温度37℃,时间5 d,发酵效果最好.     

枯草芽孢杆菌MX-6产纳豆激酶特性分析

分离鉴定溶栓酶高产菌株,对其所产溶栓酶的类型、相对分子质量及发酵曲线进行特性分析。从中国豆豉中分离一株纤溶酶高产菌株MX-6,经个体形态、菌落形态及16S r DNA基因同源性比对,确定该菌株为枯草芽孢杆菌。应用聚合酶链式反应(polymerase chain reaction,PCR)克隆到1 473 bp的纤溶酶编码基因apr N,根据推测氨基酸序列与同源序列的多序列比对及系统进化树结果显示该纤溶酶为纳豆激酶。SDS-聚丙烯酰胺凝胶电泳法(SDS-polyacrylamide gels electrophoresis,SDS-PAGE)确定枯草芽孢杆菌MX-6所产纳豆激酶的相对分子质量约28 ku,与预测的相对分子质量27 712. 72 u相吻合。枯草芽孢杆菌MX-6所产纳豆激酶的发酵曲线结果显示在72 h达到纳豆激酶最大合成量,在纤维蛋白平板上的溶圈直径高达21. 60 mm。为更好地实现纳豆激酶的开发及应用提供一定的理论依据和方法参考。     

纳豆枯草芽孢杆菌对老陈醋中阿魏酸的影响

以纳豆枯草芽孢杆菌为研究对象,用于以玉米为原料的老陈醋发酵.结果表明,糖化酒精发酵第3天接种5.0％的纳豆枯草芽孢杆菌种子液,醋酸发酵结束时的醋汁中阿魏酸含量高达59.36 mg/L.纳豆枯草芽孢杆菌分别接种于玉米、麸皮和谷糠浆液,阿魏酸含量随着发酵时间的延长均先显著增大而后缓慢减小,均在24 h时达到最大值,分别为3...     

纳豆芽孢杆菌发酵黑豆豆豉的前发酵工艺优化

以黑豆为主要原料,以总多酚含量和DPPH·清除率为指标,采用单因素试验与正交试验设计优化纳豆芽孢杆菌发酵黑豆豆豉的前发酵工艺条件。结果表明:其最优发酵工艺条件为发酵时间4d,发酵温度39℃,纳豆芽孢杆菌接种量2.5g/100g·黑豆,在该条件下得到的黑豆豆豉总多酚含量为4.24 mg/g,DPPH·清除率为79.86%,表明黑豆经纳豆芽孢杆菌发酵后能够获得具有较高抗氧化活性的黑豆豆豉。     

一株高产3-羟基丁酮枯草芽孢杆菌的构建

以产3-羟基丁酮枯草芽孢杆菌(Bacillus subtilis)TH-49(Val-)和产α-乙酰乳酸脱羧酶地衣芽孢杆菌(Bacillus licheniformis)AD-30为亲本菌株,以聚乙二醇为融合促进剂,进行原生质体融合获得融合子,融合子经再生、筛选等过程,最终获得高产3-羟基丁酮菌株HB-32,该菌株3-羟基丁酮产量高达49.64 g/L,比菌株TH-49(Val-)提高了61.8%,且遗传稳定性良好。进一步采用随机扩增多态性DNA(RAPD)技术,从分子水平上分析了高产3-羟基丁酮菌株HB-32与亲本菌株基因组的变化。结果表明,枯草芽孢杆菌(B. subtilis)TH-49(Val-)和地衣芽孢杆菌(B. licheniformis)AD-30原生质体融合成功,提高了融合子HB-32 3-羟基丁酮产量。     

高活性谷氨酰胺酶基因glsA2 在枯草芽孢杆菌BJ3-2染色体上的定点整合

以枯草芽孢杆菌BJ3-2 的glsA1 基因为同源序列,通过构建单交换整合载体,将高活性谷氨酰胺酶基因glsA2 定点整合入BJ3-2 菌株染色体中,获得能够稳定遗传的重组菌株BJ3-2A2。经检测重组菌株谷氨酰胺酶活力为BJ3-2 菌株的3.36 倍。利用重组菌株BJ3-2A2 发酵豆豉,全氨基酸检测显示,重组菌株发酵的豆豉谷氨酸含量比出发菌株高12.8%。说明枯草芽孢杆菌BJ3-2 可以转化且为RecE+ 菌株,glsA2 基因在BJ3-2 菌株染色体上可实现较高活性表达,并提高发酵豆豉的鲜味。     

高活性谷氨酰胺酶基因glsA_2在枯草芽孢杆菌BJ3-2染色体上的定点整合

以枯草芽孢杆菌BJ3-2的glsA1基因为同源序列,通过构建单交换整合载体,将高活性谷氨酰胺酶基因glsA2定点整合入BJ3-2菌株染色体中,获得能够稳定遗传的重组菌株BJ3-2A2。经检测重组菌株谷氨酰胺酶活力为BJ3-2菌株的3.36倍。利用重组菌株BJ3-2A2发酵豆豉,全氨基酸检测显示,重组菌株发酵的豆豉谷氨酸含量比出发菌株高12.8%。说明枯草芽孢杆菌BJ3-2可以转化且为RecE+菌株,glsA2基因在BJ3-2菌株染色体上可实现较高活性表达,并提高发酵豆豉的鲜味。     

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.