碱性蛋白酶Alcalase2.4 L酶解小麦麸皮蛋白制备小分子肽动力学研究

采用单因素实验分析法对碱性蛋白酶Alcalase2.4 L酶解小麦麸皮蛋白制备小分子肽的酶解条件进行了优化,并建立了酶解动力学模型。结果表明,Alcalase2.4 L酶解小麦麸皮蛋白最优条件为:酶底比6%,pH9.0,温度50℃。酶解过程中存在明显底物抑制和产物抑制作用,主要动力学参数为:Km=43.39 g/kg,Vmax=1.12 mmol/kg·min,Ks=58.82 g/kg,k2=3.73 mmol/min·g。     

酶解中国毛虾制备清除羟自由基活性产物的研究

研究以高产低值的中国毛虾为原料,通过测定酶解物对Fenton体系产生的羟自由基的清除效果,从风味酶、复合酶、中性蛋白酶、Alcalase2.4L等10种常用蛋白酶中筛选出Alcalase2.4L作为酶解中国毛虾制备清除羟自由基活性酶解物的水解酶;以羟自由基清除率为指标,利用正交实验对酶解条件进行优化,将优化酶解条件下的酶解产物进行SephadexG-15凝胶色谱分离(1.6cm×68cm),测定分子量分布并收集各吸收峰。结果表明:Alcalase2.4L在温度55℃、pH9.0、酶底物浓度比[E/S]为12.0AU/g、时间3h的水解条件下,酶解物对羟自由基清除率为84.6%,水解度为26.28%,平均肽链长为3.81。Alcalase2.4L酶解物凝胶色谱分离得到一个较强羟自由基清除活性的组分分子量范围是2259～869,IC50为0.385mg/mL,肽链长度在22.4～7.7之间。     

有限酶解花生蛋白的研究

研究了Alcalase酶对花生蛋白的有限水解作用,并讨论了pH、温度、酶用量、底物浓度和水解时间对该酶水解效果的影响;得出其最佳酶解参数为pH8.058℃、0.072AU/g、(E/S)5.0%(W/V)和120min。同时也探讨了Flavourzyme、酶对花生蛋白水解液的脱苦效果。     

Alcalase碱性蛋白酶水解棉籽蛋白动力学研究

采用pH-stat法对Alcalase碱性蛋白酶水解棉籽蛋白的动力学特性进行了研究,确定了Alcalase碱性蛋白酶水解棉籽蛋白的最佳反应条件:温度60℃、pH8.0、酶与底物比750 U/g、底物质量分数5%,水解300 min后水解度可以达到12.43%;动力学参数:Km=6.013 3 mol/L、vmax=9.549 3×10-3mol/(min·L).     

核桃蛋白酶法水解工艺条件研究

研究了核桃蛋白酶法水解的工艺条件,结果表明:蛋白酶种类对核桃蛋白水解作用影响较大,Alcalase 2.4L、Neutrase 0.8L对核桃蛋白水解作用较强;Alcalase 2.4L较适宜的酶解条件为酶与底物浓度比1000U/g,pH 8.0,温度60℃;Neutrase 0.8L较适合的水解条件为酶浓度为2000U/g,pH 6.0,温度45℃;Alcalase 2.4L、Neutrase 0.8L复合酶可以对核桃蛋白进行连续水解,并能提高核桃蛋白的水解度,产物肽链长度趋近于5。     

啤酒糟醇溶蛋白酶法水解及水解产物的抗氧化研究

用碱性蛋白酶(Alcalase)对啤酒糟醇溶蛋白进行水解,并使用正交试验设计以水解度为指标对酶法水解进行了优化。结果表明,啤酒糟醇溶蛋白的酶解最优条件为底物浓度2%,酶解温度60℃,pH9.5,酶浓度(E/S)0.096 AU/g,酶解时间3h。以DPPH自由基清除率和羟自由基清除率为指标,用抗坏血酸做对照,对酶解产物的抗氧化活性进行了分析。分别得到了两种自由基清除的最优酶解条件。啤酒糟醇溶蛋白酶解产物对不同自由基的最佳清除作用的水解条件不一致,可能与所产生的多肽对几种自由基的清除机理有关。     

大米蛋白的酶水解机制研究——Ⅰ酶反应进程及酶在反应体系中的分配

通过不同酶浓度和底物浓度下可溶出蛋白的分析表明,大米蛋白浓度约为8%、加酶量30AU/kg以下、反应时间150min以内是研究大米蛋白水解规律较合适的条件。水解过程中加酶量为30AU/kg的酶解物DH/蛋白质溶解度比值高于12AU/kg时的比值,且大分子组分(分子量为26100ku)的相对含量较低,而小分子组分(分子量为1350ku和220～660ku)的含量较高,说明反应体系中加入较多的蛋白酶时分配于水解已溶蛋白的酶比例增高。     

双酶法制备葵花籽肽的工艺研究

利用双酶法水解葵花籽分离蛋白（SPI）制备葵花蛋白肽,探讨各因素对水解度（Degree of hydrolysis,DH）和肽含量的影响,目的在于确定葵花蛋白肽制备的最佳酶解条件。结果表明：最佳酶解条件为底物浓度5.0?10-2 g/mL,温度为53.5 ℃,pH 8.5,按照[E/S]为1.0?10-2 g/g加Alcalase 2.4 L,酶解104 min,调整pH为7.5,按照[E/S]为0.44?10-2 g/g添加Flavourzyme酶解120 min。此工艺得到水解液中肽含量为4.25 mg/mL,DH为30.97%,与单酶法相比,肽含量显著提高。     

酶法水解小麦面筋蛋白研究

分别采用Alcalase、Neutrase、Protamex、Flavorzyme、胃酶、木瓜蛋白酶对小麦面筋蛋白进行水解研究,结果表明,Alcalase能有效水解面筋蛋白,并确定其最佳水解条件:pH 9．0,温度60℃,底物浓度5％,酶浓度E/S为1％,即0．03AU/g蛋白,反应时间4hr左右,在此条件下,水解度可达 20％左右。     

Alcalase 2.4L碱性内切酶和Flavourzyme风味酶酶解大豆分离蛋白及脱苦工艺优化

以大豆分离蛋白为原料,选用Alcalase 2.4L碱性内切酶和Flavourzyme风味蛋白酶对大豆分离蛋白进行酶法水解及脱苦工艺研究。以水解度和苦味分值为考察值,对酶解工艺进行优化,确定最佳条件。结果表明:Alcalase2.4L碱性内切酶最佳酶解条件为加酶量14 000 U/g、酶解温度60℃、酶解pH8.5、底物质量分数5%,酶解时间2h,最终水解度为45.34%,此时水解液苦味值为4。Flavourzyme风味蛋白酶对水解液进行二次水解的最优酶解条件为加酶量300 U/g、酶解温度55℃、酶解pH 7.0、酶解时间3 h,此条件下大豆分离蛋白水解液苦味值最低为1.2。Alcalase2.4L碱性内切酶和Flavourzyme风味蛋白酶水解大豆分离蛋白使水解度得到较大提高的同时也解决了水解液的苦味问题。     

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.