酶法处理油茶籽壳制备低聚木糖工艺的优化

优化酶解处理油茶籽壳制备低聚木糖的工艺条件。以油茶籽壳为原料,经碱法制备木聚糖粗提液。以所得的木聚糖粗提液为原料,低聚木糖浓度为考核指标,酶解温度、木聚糖酶使用量、酶解时间和木聚糖底物浓度为变量因子,进行单因素试验。在单因素试验基础上,利用响应面法对酶法制备低聚木糖工艺进行优化研究。结果表明,最佳的制备工艺为:酶添加量5%、酶解时间10 h、酶解温度49℃、底物浓度2%。在此优化酶解工艺条件下,测得低聚木糖浓度为11.63 g/L,比未优化前提高4.63 g/L。试验所得到的酶解处理油茶籽壳制备低聚木糖的工艺条件具有实用价值,能为提高利用油料加工副产物油茶籽壳的附加值提供理论依据。     

重组木聚糖酶酶解玉米芯制备低聚木糖

研究了蒸煮法及碱提法对玉米芯木聚糖的提取效果,并利用重组木聚糖酶Xyn A对玉米芯低聚木糖的酶解制备条件进行了优化。对木聚糖得率及酶解产物进行了分析,确定碱提法所得玉米芯木聚糖适宜作为酶解底物制备低聚木糖。优化后得到酶解制备玉米芯低聚木糖的工艺条件:底物浓度0.9%,酶解温度49℃,酶解时间4.5 h,还原糖量可达33.9%。另外,对酶解成分进行分析,结果表明酶解碱提玉米芯木聚糖可产生以木二糖及木三糖为主要成分的低聚木糖。     

玉米芯碱法提取木聚糖及其酶解制备低聚木糖的工艺研究

采用碱法提取制备玉米芯木聚糖,以提取率为指标,研究了碱液浓度、提取温度、处理时间、提取振荡速度、醇沉p H等因素对提取率的影响,通过木聚糖酶酶解木聚糖提取低聚木糖,以酶解产物中还原糖含量、可溶性总糖含量及平均聚合度DP为指标,采用正交试验探讨了酶浓度、酶解温度、酶解时间、p H值、底物浓度对酶解产物的影响,得出酶解玉米芯木聚糖制备低聚木糖的最佳工艺条件为:底物浓度为12%(w/v),酶解p H为4,酶解温度为45℃条件下添加0.06%(w/v)的木聚糖酶,酶解8h,得到总糖含量为18.88mg/m L,还原糖含量为9.46 mg/m L,聚合度DP为1.85。     

超声波预处理棉籽壳酶法制备低聚木糖的工艺研究

本文以棉籽壳为原料制备低聚木糖。以超声温度、超声时间,料液比和Na OH浓度为单因素,采用正交实验设计确定了超声波预处理提取木聚糖的最优条件,即超声温度60℃,超声时间30 min,料液比为1∶15,Na OH浓度为8%,此时木聚糖得率为33.66%。在单因素料液比、加酶量、酶解时间、酶解温度的实验基础上,根据Box-Benhnken中心组合实验设计原理,采用4因素3水平的响应面分析法,以低聚木糖含量为响应值建立数学模型,确定了最佳酶解工艺条件:料液比1∶20,加酶量4%,酶解时间3.5 h,酶解温度64℃,此时低聚木糖含量为3.35 mg/m L。     

木聚糖酶Shearzyme 500 L对蔗渣木聚糖的特性研究

以木聚糖酶Shearzyme 500L水解蔗渣木聚糖制备低聚木糖,用DNS法测定酶解液中的总糖和还原糖,HPLC法测定酶解产物组成,其适宜的水解条件为底物质量浓度3g/100mL、pH5.0、60℃、木聚糖中酶用量50U/g、水解时间24h。在此条件下底物水解率约为63.1%,水解产物的81.5% 为低聚木糖,其中木二糖占54.8%,木三糖占26.7%。Shearzyme 500L 不能将一分子木二糖水解为两个木糖单糖,但能水解木三糖并相应生成木二糖与木糖。副产物木糖能显著抑制Shearzyme 500L 活性,降低木聚糖的水解率。     

超声波处理玉米芯制备低聚木糖的条件优化

考察了试验室规模下超声波处理玉米芯提取木聚糖经酶水解制备低聚木糖的影响因素,通过单因素试验和正交试验,优化了提取和水解条件。结果表明:以质量分数5%Na OH溶液为提取剂,超声功率为180 W,超声温度为60℃的条件下提取45 min,木聚糖产率可达到33.18%。所得提取液经脱色,调p H,调木聚糖底物浓度后酶水解制备低聚木糖。最佳酶解条件为:木聚糖底物质量浓度10 mg/m L,加酶量质量分数1.5%(相对于玉米芯干物料),酶水解时间为8 h的条件下,水解液中还原糖的质量浓度达到6.89 mg/m L。     

利用少动鞘氨醇单胞菌酶解制备棉籽壳低聚木糖

本文研究了利用自筛菌株酶法制备棉籽壳低聚木糖的基本工艺。低聚木糖是主要的功能性食品添加剂,棉籽壳是生产低聚木糖的良好来源。因此,如何有效的从棉籽壳中提取低聚木糖成为亟待解决的问题。本研究中通过筛选鉴定(法国梅里埃生物自动识别系统)得到一株新的产内切型木聚糖酶的菌株-少动鞘氨醇单孢菌。通过酶解木聚糖工艺的优化,结果表明:当酶解温度为30℃,酶解8 h,木聚糖酶的浓度15%,底木聚糖浓度为40 g/L时,低聚木糖的得率可达到53.20%,经HPLC分析,酶解野种木二糖和木三糖占低聚木糖总量的48.56%,低聚木糖占总糖的82%以上,以上研究可为工业生产低聚木糖工艺的优化提供依据。     

竹笋壳木聚糖酶法降解及产物的分离纯化

以自制笋壳木聚糖为原料,采用木聚糖酶将其降解制备低聚木糖,利用柱层析法分离纯化降解产物,并通过高效液相法(HPLC)测定了其纯度。研究结果确立了最佳酶解工艺为:木聚糖底物质量浓度为0.04g/mL,酶解pH4.8,在酶浓度为0.03%,反应时间为5h,摇床转速200r/min,温度为60℃。在上述条件下低聚木糖的平均聚合度为1.5。经高相液相色谱检测获得纯度为80.63%的木二糖。为利用竹笋壳生产低聚木糖奠定实验基础。     

酶解条件对麦麸低聚木糖含量及其性质的影响

采用酶法水解麦麸水不溶性阿拉伯木聚糖制备低聚木糖,研究酶解温度、酶解时间和加酶量对低聚木糖含量及其糖组成、平均聚合度以及益生元活性的影响。结果表明:随着酶解时间由1h延长至2 h、酶解温度由40℃增加至50℃和加酶量由0.125 g/L增加至1 g/L时,低聚木糖含量增加,平均聚合度减小,木二糖、木三糖和木四糖的相对含量比值减小;不同酶解条件下得到的低聚木糖培养青春双歧杆菌的菌体浓度含量均有不同程度的增加;青春双歧杆菌代谢不同酶解条件下得到的低聚木糖发酵液中代谢产物均含乳酸、乙酸和丙酸,乙酸含量最高,其产酸量变化趋势与菌体浓度和低聚木糖含量相一致,与低聚木糖平均聚合度相反。当酶解温度50℃,酶解时间2 h和加酶量1 g/L时,低聚木糖含量达到最大为101 mg/g,平均聚合度降至最小3.23,木二糖、木三糖和木四糖的相对含量比值也最小,菌体浓度增值倍数达到最大为5.65倍。     

烟草秸秆低聚木糖的制备和纯化

为优化烟草秸秆低聚木糖制备参数,采用碱解方法提取木聚糖、酶解法制备低聚木糖以及单因素实验法考察了常见因素对工艺的影响。结果表明,木聚糖提取条件为：2.000 g秸秆粉末（≤100目）浸没于20.00 mL浓度为24% NaOH（m/V）和1% NaBH₄（m/V）碱液中,70 ℃条件下浸提4 h,滤液加3倍乙醇体积用量进行醇沉以及0.2倍乙酸体积用量进行中和。制备低聚木糖的条件为：溶液pH为5.50,温度40 ℃,时间6 h,木聚糖溶液（20 mg/mL）10 mL,木聚糖酶液（0.6%,m/V,4.1 U/mL）20 mL。低聚木糖分离提纯条件为：阳离子树脂柱分离纯化,填充高度18.0 cm、直径为4.5 cm;纯化液用高效液相色谱进行定性定量分析。通过上述方法得到的低聚木糖产品纯度较高,对工业制备低聚木糖工艺优化有一定的参考价值。     

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.