非水相中酶法合成糖酯的研究

以固定化脂肪酶作为生物催化剂在非水相反应体系中初步合成了葡萄糖月桂酸酯,探讨了温度、pH、初始水活度、分子筛添加量等影响酯化反应的因素。结果表明最适反应条件:温度45℃、初始水活度0.75、分子筛1g,最高酯化率达65%。     

非水相中酶法合成糖酯的研究

以固定化脂肪酶作为生物催化剂在非水相反应体系中初步合成了葡萄糖月桂酸酯，探讨了温度、pH、初始水活度、分子筛添加量等影响酯化反应的因素。结果表明最适反应条件：温度45℃、初始水活度0．75、分子筛1g，最高酯化率达65％。     

有机介质中脂肪酶催化肌醇烟酸酯的合成

探讨了有机相中固定化脂肪酶催化肌醇和烟酸合成肌醇烟酸酯的可能性；系统地研究了有机溶剂特性、反应初始水活度、温度、pH值、加酶量、底物浓度及摩尔比等因素对酯化反应的影响。     

无溶剂体系糖酯的酶法合成

以固定化脂肪酶作为生物催化剂在无溶剂体系中初步合成了蔗糖月桂酸酯。探讨了底物摩尔比、pH、初始水活度、水合盐等影响酯化反应的因素，并研究了酯化反应的选择性。     

超声辅助酶法合成魔芋葡甘聚糖油酸酯研究

研究了超声辅助酶法合成魔芋葡甘聚糖油酸酯的工艺条件。以酯化率为评价指标,系统研究了超声频率、超声功率、反应温度、反应时间、反应介质初始水分活度、酶与底物浓度比对超声辅助酶法合成魔芋葡甘聚糖油酸酯的影响,并在此基础上进行了L_(18)(3~7)正交实验优化合成工艺。结果表明,最佳工艺条件为:超声频率20 k Hz,超声功率220 W,反应温度50℃,反应时间8 h,反应介质初始水分活度0.65,酶与底物浓度比1∶1。在最佳条件下酯化率达到83.40%。与无超声辅助酶催化工艺相比,反应时间8 h,酯化率由9.48%提高到83.40%,超声对提高酯化反应作用显著。     

无溶剂体系中毕赤酵母表面展示CALB全细胞催化合成肉桂醇酯

利用表面展示南极假丝酵母脂肪酶B(Candida antarctica lipase B,CALB)的毕赤酵母细胞(Pp-CALB)为全细胞催化剂,以不同脂肪酸作为酰基供体,在无溶剂体系中和肉桂醇发生酯化反应合成肉桂醇酯。探究了Pp-CALB对于不同酰基供体的选择性,并且对反应温度、摇床转速、酶加量、底物摩尔比、酶的水活度和反应体系等一系列影响酶催化反应的因素进行了优化,建立了无溶剂体系中肉桂醇酯的酶法合成工艺。结果表明,在底物摩尔比为2:1,摇床转速为120 r/min,反应温度为50℃的条件下,添加初始水活度为0.53的Pp-CALB 0.05 g,反应3h,肉桂醇的酯化率可达81.34%,在最适反应条件下,使用Pp-CALB连续反应8次后,肉桂醇的酯化率仍然能达到70.00%以上,具有较好的操作稳定性。     

微环境对脂肪酶催化乙酸甲基苯甲酯立体选择性氨解的影响

系统研究了反应介质、水活度、温度、p H等因素对脂肪酶 N ovozym 435催化乙酸甲基苯甲酯立体选择性氨解反应的影响。以正己烷为反应介质 ,酶表现出较高的催化活性和对映体选择性 ;适宜的反应温度为 2 5～ 35℃ ;最适反应体系初始水活度为 0 .33;较适宜的 p H范围为 6～ 7。     

植物甾醇酯制备方法的研究

研究了以氧化钙为催化剂,用植物甾醇与脂肪酸直接酯化合成植物甾醇酯的合成工艺,探索了不同反应物摩尔比、反应温度及时间对酯化率的影响,并且与其他催化剂(氧化铝,氧化锌,硅胶,4分子筛)的催化效果进行比较。结果表明:以氧化铝为催化剂,在氧化铝用量0.8%,酸醇摩尔比1.4∶1,反应温度190℃下反应10 h,酯化率最高,可达99.5%;氧化钙、分子筛和硅胶也有较好的催化性能。     

非水介质中脂肪酶催化合成正戊酸异戊酯的研究

德氏根霉菌(Rhizopusdelemar) 经固态发酵生产脂肪酶,以此酶为催化剂,在非水介质中合成了正戊酸异戊酯。研究了反应温度、溶剂、底物浓度、底物摩尔比、吸水剂用量等因素对酯化反应的影响,确定了正戊酸异戊酯的最佳合成条件为:反应温度为5 0℃,异辛烷为反应介质,底物浓度为0 15mol/L ,酸醇摩尔比为1∶1 4。在反应体系中需加入0 2 5 g/mL的5 分子筛,以吸收酯化反应生成的水。在优化的条件下,反应6h后,酯合成转化率达98%。     

无溶剂体系酶催化酯交换反应的研究

主要以乌桕脂与硬脂酸甲酯在固定化脂肪酶催化下的酯交换反应作为模型体系研究了无溶剂体系酶催化酯交换反应。考察了温度、底物配比、酶量、无机盐、初始水活度等因素对酯交换反应的影响,研究了酯交换反应历程,用水合盐对进行了体系水分的调控。     

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.     

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.     

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.     

Analysis of benzo[a]pyrene in spiked fatty foods by second derivative synchronous spectrofluorimetry after microwave-assisted treatment of samples

A simple, rapid and inexpensive method has been developed for the determination of benzo[a     

The development of reference materials for paralytic shellfish poisoning toxins in lyophilized mussel. II: Certification study

This paper describes the second part of a project undertaken to develop certified mussel reference materials for paralytic shellfish poisoning toxins. In the first part two interlaboratory studies were undertaken to investigate the performance of the analytical methodology for several PSP toxins, in particular saxitoxin and decarbamoyl-saxitoxin in lyophilized mussels, and to set criteria for the acceptance of results to be applied during the certification exercise. Fifteen laboratories participated in this certification study and were asked to measure saxitoxin and decarbamoyl-saxitoxin in rehydrated lyophilized mussel material and in a saxitoxin-enriched mussel material. The participants were allowed to use a method of their choice but with an extraction procedure to be strictly followed. The study included extra experiments to verify the detection limits for both saxitoxin and decarbamoyl-saxitoxin. Most participants (13 of 15) were able to meet all the criteria set for the certification study. Results for saxitoxin.2HCl yielded a certified mass fraction of <0.07 mg/kg in the rehydrated lyophilized mussels. Results obtained for decarbamoyl-saxitoxin.2HCl yielded a certified mass fraction of 1.59+/-0.20 mg/kg. The results for saxitoxin.2HCl in enriched blank mussel yielded a certified mass fraction of 0.48 +/- 0.06 mg/kg. These certified reference materials for paralytic shellfish poisoning toxins in lyophilized mussel material are the first available for laboratories to test their method for accuracy and performance.     

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.