乙醇溶液中Tweens对猪胰脂酶的修饰作用

采用Tween系列表面活性剂在乙醇-水溶液体系中对猪胰脂酶进行修饰,以它们催化酯交换的交换量为指标评价修饰的效果,并且对修饰酶与未修饰酶的热稳定性进行了研究。结果表明:40℃下30 min即可完成Tweens对猪胰脂酶的修饰,但不同Tween的最佳条件并不相同。Tween 20修饰脂肪酶的最佳条件是无水乙醇与水的比例为1∶2(v/v),Tween 20用量为5%;Tween 40和Tween 65修饰猪胰脂酶的最佳条件是无水乙醇与水的比例为1∶2(v/v),用量均为15%;Tween 60修饰猪胰脂酶的最佳条件为无水乙醇与水的比例为1∶2(v/v),用量为20%;Tween 80修饰脂肪酶的最佳条件是无水乙醇与水的比例为1∶3(v/v),用量为5%;Tween 85修饰脂肪酶的最佳条件是无水乙醇与水的比例为1∶3(v/v),用量为15%。修饰后酶的热稳定性实验研究表明,在40～80℃间,修饰酶的催化反活性都高于未修饰酶。Tweens修饰猪胰脂酶能有效提高酶的活性及其热稳定性。     

无溶剂体系下表面活性剂修饰的猪胰脂酶催化酯交换反应的研究

在水溶液中,采用Tween40、蔗糖酯S970、Span60三种表面活性剂修饰猪胰脂酶(porcine pancreas lipase,PPLipase);再以修饰的猪胰脂酶(Tween40-PPLipase、S970-PPLipase、Span60-PPLipase)为催化剂,在无溶剂体系中催化茶油与亚油酸酯交换反应。结果表明,在酶促反应达到平衡前,随着加酶量的增加酯交换量也随之增加;在相同的加酶量下,Tween40-PPLipase、S970-PPLipase和Span60-PPLipase催化酯交换的速率均高于PPLipase催化酯交换的速率;加酶量5%时,2h时PPLipase催化反应的酯交换量为16.1%,Tween40-PPLipase、Span60-PPLipase和S970-PPLipase催化反应的酯交换量分别为20.4%、21.1%和22.4%。达到平衡时,Tween40-PPLipase、Span60-PPLipase、S970-PPLipase和PPLipase催化反应的酯交换量基本相同,均为25%左右。     

不同脂肪酶催化亚麻油水解反应性能的比较

从反应温度、水／亚麻油摩尔比、脂肪酶用量等方面比较了L-lipase和N—1ipase脂肪酶在无溶剂体系中对亚麻油水解反应的催化性能。得到了两种脂肪酶的最佳使用温度及催化亚麻油水解反应的适宜条件。结果表明，两种脂肪酶的最佳用量均为3％～5％，适宜的水／亚麻油摩尔比为30：1。L-lipase和N-lipase的最佳温度分别是35℃和67．5℃，与L-lipase相比，N—1ipase的热稳定性和催化活性相对较高。     

南海深海链霉菌Streptomyces sp.SCSIO 13580脂肪酶的酶学性质

对从南海深海链霉菌Streptomyces sp.SCSIO 13580中的新颖脂肪酶L-1进行了酶学性质鉴定。脂肪酶L-1对对硝基苯酚己酸酯的催化活性最高,最适反应温度为40℃,最适反应p H为8.0,在最适条件下的酶活力为51.5 U/mg。脂肪酶L-1对大部分有机溶剂和表面活性剂具有极好的耐受性。同时该南海深海微生物脂肪酶能在温和条件下催化制备多种短链酯食品香料产品,具有较好的工业应用前景。     

不同来源脂肪酶催化餐厨废油水解实验研究

研究不同来源的脂肪酶催化餐厨废油水解反应制备脂肪酸,通过单因素实验考察了酶用量对酶解率的影响,在此基础上采用正交实验对水解工艺参数酶用量、水解温度、油水比和水解时间进行优化。结果表明:猪胰脂肪酶L3621和假丝酵母脂肪酶LS20在适宜条件下均可实现餐厨废油的高效酶催化水解;L3621最佳水解条件为酶用量700 U/g、水解温度45℃、油水比1∶1.2、水解时间36 h,在此条件下酶解率达94.30%;LS20最佳水解条件为酶用量600 U/g、水解温度40℃、油水比1∶1、水解时间36 h,在此条件下酶解率达96.84%。     

有机相酶促反应中固定化脂肪酶的非共价修饰

在选用８种具有两亲性质的表面活性剂、２种胆汁盐和１２种金属盐，对庚烷中催化己酸乙酯合成的固定化米氏毛霉脂肪酶进行非共价修饰时发现：在一定的质量浓度范围内，阴、阳离子型和非离子型的表面活性剂对脂肪酶酶促催化活性有不同程度的促进；在底物浓度从０．２５ｍｏｌ／Ｌ提高至０．５ｍｏｌ／Ｌ时，气溶胶硫代琥珀酸２［２－乙己酸］酯钠盐、十二烷基磺酸钠和ＴｒｉｔｏｎＸ－１００对于脂肪酶保持稳定的催化活性有较大的提高作用。并从酶的活性中心和表面活性剂的结构和特性上对原因进行了分析。而胆汁盐和金属盐对脂肪酶的修饰作用不大，在高浓度时反而会抑制酶的活性。     

气单胞菌属JH菌株脂肪酶酶学特性的研究

从JH菌体中提取脂肪酶,并在不同的反应条件下对其酶学性质进行研究。该脂肪酶最佳反应温度和缓冲液pH制分别为40℃和7．0。该酶具有较强的热稳定性和pH稳定性：经过30℃、40℃处理60rain仍然保持90％以上的酶活;用pH3．5～9缓冲液处珲该酶,仍然保持80％以上的酶活。Ca2＋、Mg2＋对该脂肪酶具有明显的激活作用,尤其是Mg2＋作用最为显著,与对照组相比提高了38．8％,Zn2＋、Fe2＋对该脂肪酶有显著的抑制作用,Cu2＋对脂肪酶的影响不显著。用双倒数法作图得到Vmax=2．13×10^-2mol／L,Km=0．639（mmol／mL）min-1。表面活性剂吐温-80对脂肪酶有促进作用。该菌株产生的脂肪酶町以往温和的反应条件下作用。     

牡丹籽油微乳液的制备及其性质研究

采取相转变法和拟三元相图法制备牡丹籽油微乳液,从不同表面活性剂、亲水亲油平衡值（HLB值）、助表面活性剂中筛选最佳组分以确定制备牡丹籽油微乳液的体系组成。同时,通过单因素试验和正交试验优化牡丹籽油微乳液的制备条件。结果表明：牡丹籽油微乳液的体系组成为牡丹籽油/Tween 80/Span 80/无水乙醇/水;最优的制备条件为制备温度25 ℃,以Tween 80与Span 80（质量比为6∶ 4）为混合表面活性剂（HLB值为11）,混合表面活性剂与助表面活性剂无水乙醇比例（Km）为1∶ 1,先将混合表面活性剂相与牡丹籽油混合均匀,再逐滴加水。在最优条件下,随着加水量的增加,得到的牡丹籽油微乳液结构以W/O型向双连续相再到O/W型转变,最终得到的牡丹籽油微乳液为微黄澄清透明状液体,粒径为（40.63±1.77）nm,多分散系数稳定在0.218±0003,电导率为（681.75±19.15）mS/cm。同时发现,低浓度盐离子（≤1.0 mol/L）的存在可以促进牡丹籽油微乳液的形成,但盐离子浓度过高（≥1.5 mol/L）时会抑制微乳液的形成。     

混合办公废纸的酶法脱墨研究

将角质酶和实验室复配得到的表面活性剂协同应用于混合办公废纸脱墨领域,探讨其脱墨效果和最优工艺,并与常用商业脂肪酶进行脱墨效果比较。结果表明,角质酶在酶用量10U/g,酶处理时间30min,酶处理温度50℃,表面活性剂用量0.2%的条件下可以达到最优效果。与脂肪酶/表面活性剂以及单独用表面活性剂脱墨相比,角质酶脱墨后纸页的白度与油墨去除率更高,纸页的机械强度也较好。通过纸页性能的对比和扫描电镜(SEM)观察,角质酶的脱墨效果较脂肪酶更佳,角质酶/表面活性剂体系对混合办公废纸脱墨效果较好。     

基于响应面法优化脂肪酶水解涤纶织物工艺

酶处理改善涤纶织物的亲水性是目前涤纶改性中一种绿色环保的方法。本文通过改变猪胰脂肪酶(PPL)水解涤纶织物的反应条件(反应温度、反应pH、酶用量、反应时间),以及添加表面活性剂来增强PPL水解涤纶织物的效果。实验以水解产物释放量为评价指标,通过在单因素实验的基础上进行Box-Behnken优化实验。结果表明：PPL水解涤纶织物工艺中因素的影响作用大小顺序为反应时间(24 h)>表面活性剂(吐温80,2 g/L)>反应温度(60℃)>酶用量(80 U/mL)>pH(7)。经模型优化的最佳水解工艺条件为：反应温度59℃,pH 6.6,酶用量67 U/mL,反应时间31.2 h,表面活性剂质量浓度2.1 g/L,理论水解产物531.862 mg/L。最优条件下实验值与预测值的相对误差为5.3%。在此条件下,处理后织物表面的接触角下降了19.8%,力学性能良好。     

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.