真空微波辅助萃取大蒜素工艺的研究

大蒜素具有很高的保健和药用价值.采用真空微波辅助萃取大蒜中的大蒜素,与传统溶剂萃取方法相比,微波萃取法更简单,而且具有萃取时间短、成本低、萃取效率高等优点.该方法适用面更广,能大大提高提取物中大蒜素的含量,且溶剂损耗量较少.微波辐射10min后可以得到较好的效果,而且利用微波处理,提取率可达到0.243%.     

微波辐射提取大蒜素的工艺研究

在微波辐射作用下,以乙醇为提取剂,从大蒜中提取大蒜素,采用分光光度法测定大蒜素的提取率.考察了微波功率、乙醇的体积分数、料液比、微波辐射时间对大蒜素提取率的影响.得到了从大蒜中提取大蒜素的工艺条件为微波功率200W、乙醇的体积分数90％、料液比1:5(g/mL).微波辐射时间5min.在此工艺条件下,大蒜素的提取率为0.143％.     

真空微波辅助萃取大蒜素工艺的研究

大蒜素具有很高的保健和药用价值。采用真空微波辅助萃取大蒜中的大蒜素,与传统溶剂萃取方法相比,微波萃取法更简单,而且具有萃取时间短,成本低,萃取效率高等优点。该法适用面更广,能大大提高提取物中大蒜素含量,且溶剂损耗较少。微波辐射10min后可以得到较好的效果,而且利用微波处理,提取率可达到0．243％。     

微波辅助萃取黑蒜大蒜素及对小鼠血糖值影响

本实验主要研究微波辅助萃取黑蒜大蒜素,以及对黑蒜大蒜素溶液进行GC-MS分析。与普通大蒜提取大蒜素比较,对小鼠进行降血糖动物实验。实验表明,黑蒜大蒜素具有降血糖功能。将黑蒜用有机溶剂萃取法提取出来,采用同时蒸馏萃取黑蒜大蒜素溶液中的挥发性物质,通过气相色谱-质谱联用技术对其化学成分进行了分析。鉴定出黑蒜大蒜素溶液中含有7种含硫物质。     

大蒜素的提取工艺研究

大蒜素是大蒜中的主要活性成分,具有预防癌症、降血压、降血脂等功效,在临床上的应用也越来越广泛,作为药物或保健品开发具有广阔前景。目的:采用高效液相色谱法测定大蒜素的含量,研究有机溶剂提取大蒜素的方法。方法:在考察单因素对提取效果影响的基础上,选取酶解温度、酶解时间和提取时间3个影响因素,设计正交试验,筛选最佳提取工艺。结果:正交试验显示,大蒜中大蒜素提取的最佳提取工艺为:蒜泥在40℃下酶解80 min后,按料液比1:4(g/m L)加入95%的乙醇,温度为25℃下大蒜酶提取物提取100 min。其中酶解温度是最为重要的影响因素,其次为酶解时间、提取时间。结论:在该优化工艺条件下,获得大蒜素的得率为0.27%,该工艺可为大蒜素的工业化生产提供参考依据。     

大蒜多糖的酶法提取及其抗氧化性研究

本实验研究了大蒜多糖的提取方法,结果表明,采用纤维素酶解可显著提高多糖提取率,在加酶量5%,pH值5.0,酶解温度50℃时,提取1.5h,提取率达20.54%.本实验进一步对大蒜多糖的抗氧化性进行了测定,并与大蒜素进行了对比.结果显示,大蒜多糖具有清除超氧阴离子自由基和羟基自由基的能力,且在较高浓度下强于大蒜素,而大蒜素的还原能力则强于大蒜多糖.     

采用响应面法优化大蒜素的提取工艺

为了高效地从大蒜(Allium sativum L.)中获取活性物质大蒜素,实验选用市售新鲜大蒜作为原料,以95%乙醇作为提取液,辅以超声提取法。考察了酶解温度(℃)、酶解时间(min)、超声功率(W)和超声温度(℃)4个因素对大蒜素提取率的影响。在单因素试验的基础上,通过响应面法优化了大蒜素的提取工艺条件。结果表明:蒜泥在35℃酶解31min、超声功率49 W、超声温度29℃的条件下,大蒜中大蒜素的提取预测值能达到3.024mg/g,验证值是3.018mg/g,预测值与验证值基本吻合。     

超临界二氧化碳法提取大蒜素工艺研究

采用高效液相法为检测手段,研究确定了超临界二氧化碳法提取大蒜素的最佳工艺条件为萃取压力20MPa、萃取温度35℃、静态萃取时间75min、动态萃取时间45min。采用该工艺方法大蒜素的总萃取率可达61.2%。     

赛买提大蒜中大蒜素的提取工艺研究

文章研究了以乙醇为提取剂分离提取大蒜素的最佳工艺条件:破碎大蒜在35 ℃下酶解0.5 h,按料液比1 g∶4 mL加入95%乙醇于25 ℃下萃取1.5 h,然后控制蒸馏温度在45 ℃,压强在0.01 MPa,旋转蒸发仪转速在75 r/s进行减压浓缩,大蒜素的提取率可以达到0.25%.     

烹饪方法对大蒜素含量的影响研究

在空白试验的基础上,利用定硫法测定经过不同烹饪方法加工后,大蒜中大蒜素的含量.结果表明:大蒜油炸后大蒜辣素含量0.0677%,蒸制后大蒜辣素含量0.0684%,水煮后大蒜辣素含量0.0845%,微波加热后大蒜辣素含量0.1914%.破坏大蒜素最小的烹饪方法是微波加热法,破坏最大的是油炸烹调法.     

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.     

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.     

低温带皮菜籽粕微粉的不同粒级部分的功能特性

为研究低温带皮菜籽粕微粉的不同粒级部分的功能特性,以经低温脱脂的带皮菜籽粕为原料,经微粉碎后筛分成212~425μm、150~212μm和106~150μm的3个不同粒级的微粉样品,检测这些样品的吸水性、吸油性、乳化性和乳化稳定性、蛋白质体外消化率。结果表明:1 3个不同粒级的微粉样品之间的粗纤维含量存在显著差异,表明三者的结构组成成分有一定差异。23个微粉样品的乳化活性和乳化稳定性随粒度级别的减小而显著增加(P0.01)。33个微粉样品的蛋白质体外消化率随粒度级别的减小而显著增加(P0.01)。4不同粒级带皮菜籽粕微粉样品的吸水性与吸油性受其结构组成物质不同和粒度的双重影响,与粒度的相关性不明显。     

Microbiology of food taints

Fresh and processed foods are often spoilt by the presence of undesirable flavours and odours caused by microbial action. The aim of this paper is to review the current knowledge of microbiologically induced taints that occur in a wide range of foodstuffs, including meats, poultry, fish, crustaceans, milk, dairy products, fruits, vegetables, cereals and cereal products. Examples have been chosen where the compounds responsible for the taint have been identified and sufficient data obtained to demonstrate the involvement of microorganisms. However, in some cases the full identity of the causative organism may not have been elucidated. The types of microorganisms covered by this review include bacteria, fungi, yeasts, actinomycetes and cyanobacteria. Although cyanobacteria do not in general infect foods, their presence in aqueous systems and water supplies can lead to off-flavours in aquatic organisms and processed foodstuffs. Several examples of each of these processes are discussed. Wherever possible, the likely biosynthetic pathway used by the microorganism to produce the offending compound in a foodstuff is indicated.