固定化酶催化高酸废油脂合成生物柴油的研究

探讨了固定化C.antarctica脂肪酶催化高酸废油脂与甲醇合成生物柴油.通过脂肪酶酯交换工艺路线进行催化合成生物柴油的研究,系统研究了甲醇的加入方式、反应体系中的水、游离脂肪酸对反应的影响.结果表明,一次性加入等摩尔当量的甲醇,对脂肪酶的活性具有一定的抑制作用,两次等当量加入甲醇,最终酯化率可达90.6%;当反应体系中的水含量低于0.1%时,水对酶反应速率和甲酯产量影响甚小,而水含量高于0.1%时,酶反应速率和甲酯产率随着水含量的增加而降低;游离脂肪酸对反应的影响较小,固定化c.antarctica脂肪酶的催化稳定性和使用寿命至少达100 d.     

有机溶剂体系固定化脂肪酶催化合成生物柴油

探讨了有机溶剂体系固定化Candida antarctica脂肪酶催化大豆色拉油合成生物柴油的过程。将固定化Candida antarctica脂肪酶置于有机溶剂体系中催化合成生物柴油的效果较好。研究发现,在40℃下反应10 h,固定化Candida antarctica脂肪酶以石油醚作为有机溶剂转化率最高,当总醇油物质的量比为3∶1,固定化酶占5%(相对于油质量),加入5%质量分数的水时固定化酶反应活性最高,酯化率可以达到88.4%。固定化酶重复使用10次仍具有较高活性。     

固定化Enterobacter agglomerans脂肪酶生产菜籽油生物柴油的研究

用硅藻土对实验室筛选得到的成团肠杆菌脂肪酶干燥酶粉进行固定化,固定化酶在有机溶剂体系下催化生产生物柴油。在最佳反应条件,即菜籽油15.47 mL,固定化脂肪酶用量1 000 U,甲醇为酰基受体(7.15 mL,3次等量加入),5 mL正己烷,振荡速度180 r/min,35℃反应48 h时,转化率达91.03%。实验结果表明,油酸含量高有利于生产生物柴油,而芥酸有不利影响。固定化酶稳定性好,重复使用8次,转化率仍大于50%,同时还具有一定的适应性,可催化大豆油和葵花籽油生产生物柴油。研究表明,固定化酶可用于催化生产生物柴油,并有效降低酶催化法的生产成本。     

固定化脂肪酶催化活性影响因素的改变对生物柴油转化率的影响

本文考察了固定化脂肪酶催化活性的影响因素的改变对生物柴油转化率的影响,目的在于探索出固定化脂肪酶最适反应条件,降低生物柴油的生产成本,为生物柴油的产业化生产提供理论依据.结果表明,当固定化脂肪酶在豆油中浸泡8h,酶用量为原料油质量的6%,温度为40℃,振荡速率为200r/min,每隔4h按油醇摩尔比1:1添加甲醇1次,共3次,反应12h,生物柴油转化率最高可达到94.35%.并且每次反应后的脂肪酶用丙酮处理,可多次循环使用,9次循环使用后,催化效率还可达85.15%.     

预处理固定化脂肪酶催化合成生物柴油

探讨了预处理固定化Candida antarctica脂肪酶催化餐饮废油合成生物柴油的过程。将固定化Candida antarctica脂肪酶用叔丁醇处理3h后再用废油浸泡4h，用于催化酯交换反应，酯交换反应速率明显加快。研究发现，固定化Candida antarctica脂肪酶预处理后，过量甲醇对酶的抑制作用仍然存在。采用分步添加甲醇工艺，按总醇油摩尔比3：1，分别在0、0．5、1．0、1．5、2．0、2．5h等量加入甲醇，反应4h后，体系中甲酯含量达到97．86％，反应：效率是未处理固定化酶催化合成生物柴油体系的6倍。固定化酶重复使用仍具有较高活性。     

固定化脂肪酶Lipozyme TL IM催化菜籽油制备生物柴油稳定性的研究

研究了固定化脂肪酶Lipozyme TL IM催化菜籽油制备生物柴油的反应,探索了酶的预处理方式、后处理方式、反应温度、甲醇的加入方式等对酶活稳定性的影响.结果表明将酶在油酸甲酯中浸泡0.5h,过滤后用菜籽油淋洗,在菜籽油中浸泡12h可以提高酶活的稳定性;多批次反应温度40℃为适宜;用丙酮洗涤酶除去甘油可以提高酶的稳定性分三步加入甲醇的方式可以减轻甲醇对酶的毒害.Lipozyme TL IM经过预处理,40℃下进行多批次反应,每批反应24h,并在反应0、8、16h时加入1摩尔当量甲醇,并在8、16h以及反应结束时用丙酮洗涤固定化酶并重新投入体系,连续反应10批次,Lipozyme TL IM相对酶活仍有85%.     

固定化脂肪酶催化桐油制备生物柴油的研究

对磁性Fe3O4纳米粒固定化脂肪酶催化桐油制备生物柴油进行了研究,分步探讨了硼酸盐缓冲液用量、固定化酶用量、醇油摩尔比、反应温度、固定化酶清洗与否对转酯反应的影响,以及固定化酶的操作稳定性。结果表明：将正己烷与桐油体积比定为2∶?1,然后加入与桐油等摩尔的甲醇、桐油体积6%的硼酸盐缓冲液及7.5 mg/mL（以桐油体积计）固定化酶,反应5 h和12 h各加入与桐油等摩尔的甲醇（总的醇油摩尔比3∶?1）,并每次添加甲醇前用丙酮清洗固定化酶,45?℃、200 r/min 反应26 h后,甲酯转化率可达91.2%。该固定化脂肪酶连续催化10批次反应后,甲酯转化率仍然可达84.1%,具有一定的工业应用价值。     

固定化脂肪酶Lipozyme TL IM催化菜籽油制备生物柴油稳定性的研究

研究了固定化脂肪酶Lipozyme TL IM催化菜籽油制备生物柴油的反应,探索了酶的预处理方式、后处理方式、反应温度、甲醇的加入方式等对酶活稳定性的影响。结果表明：将酶在油酸甲酯中浸泡0.5h,过滤后用菜籽油淋洗,在菜籽油中浸泡12h可以提高酶活的稳定性;多批次反应温度40℃为适宜;用丙酮洗涤酶除去甘油可以提高酶的稳定性;分三步加入甲醇的方式可以减轻甲醇对酶的毒害。Lipozyme TL IM经过预处理,40℃下进行多批次反应,每批反应24h,并在反应0、8、16h时加入1摩尔当量甲醇,并在8、16h以及反应结束时用丙酮洗涤固定化酶并重新投入体系,连续反应10批次,Lipozyme TL IM相对酶活仍有85%.     

固定化嗜热嗜碱土芽孢杆菌T1脂肪酶的制备及其催化特性研究

以葡聚糖填料作为载体,采用共价结合法对嗜热嗜碱土芽孢杆菌T1脂肪酶进行固定化,在获得固定化酶制备的最佳方案的基础上进一步考察固定化酶的催化特性。在单因素实验中,2-碘酰基苯甲酸终浓度1.23%、固定化温度50℃、固定化时间2 h的条件下效果最好,酶活力达到50.25 U/mg基质。利用该固定化酶催化橄榄油和甲醇进行醇解反应生成脂肪酸甲醇酯,60 h后得率为14.08%。同时,对固定化脂肪酶的热稳定性以及有机溶剂耐受性进行了研究,结果发现固定化T1脂肪酶在60℃孵育7 h后依然保持70%以上的酶活性;且除甲醇、乙醇外,固定化T1脂肪酶在经过正丁醇、正丙醇、异丙醇处理后酶活力能够增加到120%~140%。以上催化特性研究的结果表明,该固定化酶具有催化甲醇生成生物柴油的潜力,具有良好的热稳定性和有机溶剂耐受性,是一种具有良好工业应用前景的脂肪酶。。     

有机溶剂系统中固定化脂肪酶催化废油脂制备生物柴油

在有机溶剂系统中,以固定化脂肪酶Novozym435为催化剂,对废油脂和甲醇的酯交换反应制备生物柴油的工艺进行了研究.结果表明,该反应的最佳工艺条件是以无水乙醚为溶剂、溶剂用量为0.8 mL/g-oil、酶用量为10%、醇油物质的量比为3.5:1、反应温度为40℃和反应时间为12 h;在此工艺条件下进行反应,转酯率为92.15%.采用分三步加入甲醇的方式可减轻甲醇对酶的毒害作用.但是酶在重复使用过程中存在失活现象,重复使用9次后的反应转酯率降至了15.84%.     

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.     

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.