微生物转谷氨酰胺酶改善谷朊粉凝胶特性研究

研究利用转谷氨酰胺酶的交联作用以改善谷朊粉的凝胶特性,分别探讨了酶浓度、谷朊粉质量分数、反应时间、反应温度和反应时间对谷朊粉凝胶特性的影响.结果表明:谷朊粉形成凝胶的最低质量分数为16%,且当酶浓度为7～9 U/(g谷朊粉),谷朊粉质量分数为20%,反应时间为1～2 h,反应温度为30～40℃,pH值为2.5～3.5 时,谷朊粉形成的凝胶质量最好.     

利用转谷氨酰胺酶提高谷朊粉乳化性研究

转谷氨酰胺酶是一种催化蛋白质分子交联酶类,利用其对谷朊粉乳化性进行改良,研究酶浓度、底物浓度、pH值、反应时间、反应温度对谷朊粉乳化活性和乳化稳定性影响;在此基础上通过正交实验,探索转谷氨酰胺酶酶解谷朊粉提高乳化性最佳反应条件。分析发现五个因素对谷朊粉乳化性影响由强到弱顺序为:pH值、谷朊粉浓度、温度、时间和酶浓度。最佳酶解条件为:谷朊粉浓度为6.0%,酶浓度1.0%,反应时间为1.0h,pH值为5.0,反应温度为45℃;此时谷朊粉乳化活性为84.9%,乳化稳定性为85.7%,比酶解前谷朊粉乳化性有明显提高。     

碱性蛋白酶水解提高谷朊粉乳化性的研究

利用碱性蛋白酶对谷朊粉乳化性进行改良，研究了酶浓度、底物浓度、pH值、反应时间、反应温度对谷朊粉乳化活性和乳化稳定性的影响，在此基础上通过正交实验，探索碱性蛋白酶水解谷朊粉提高乳化性的最佳反应条件。分析发现五个因素对谷朊粉乳化性的影响由强到弱的顺序为：底物浓度、反应时间、酶浓度、pH值和反应温度。最佳水解条件为：底物浓度为10．0％，反应时间为4h，pH值为8．0，反应温度为60℃；此时谷朊粉的水解度为3．2％，乳化活性为77．02％，乳化稳定性为78．56％，比水解前乳化性有明显提高。     

木瓜蛋白酶提高谷朊粉乳化性的研究

利用木瓜蛋白酶对谷朊粉乳化性进行改良,研究了酶浓度、底物浓度、pH值、反应时间、反应温度对谷朊粉乳化活性和乳化稳定性的影响,在此基础上通过正交实验,探索木瓜蛋白酶水解谷朊粉提高乳化性的最佳反应条件。分析发现五个因素对谷朊粉乳化性的影响由强到弱的顺序为:谷朊粉浓度、酶浓度、温度、时间和pH值。最佳水解条件为:谷朊粉质量分数11.0%,酶浓度25μl/g谷朊粉,反应时间为2.0 h,pH值7.0,反应温度55℃;此时谷朊粉的水解度3.5%,乳化活性72.4%,乳化稳定性75.5%,比水解前乳化性有明显提高。     

酶解小麦面筋蛋白及其组分功能特性研究

利用木瓜蛋白酶对谷朊粉功能特性进行改良,在pH7.0的条件下,研究时间对水解度的影响以及水解度对乳化活性和溶解度的影响,水解度为2.4%时,乳化活性可以达到72.5%.通过响应面实验,研究酶浓度、底物浓度、pH值、反应时间、反应温度对谷朊粉乳化活性和溶解性的影响,探索木瓜蛋白酶水解谷朊粉提高乳化性和溶解性的最佳反应条件,分析发现5个因素对谷朊粉乳化性的影响由强到弱的顺序为酶浓度、谷朊粉浓度、时间、温度和pH值.最佳水解条件为:酶浓度0.475%、反应温度60℃、反应时间1.63 h、pH6.6、底物浓度4%,此时的水解度为4.32%、乳化活性为63.4%、溶解度则为19.04%.经过超滤(10 ku)后得到的截留组分乳化活性与酶解面筋蛋白接近.     

有限酶解对谷朊粉功能性质的影响

为了改善谷朊粉在水溶液中的分散特性,又保留其蛋白质大分子的功能性质,利用碱性蛋白酶对谷朊粉进行了有限水解,研究了谷朊粉的有限酶解条件对酶解物全成分的分散特性、乳化性、发泡性等功能性质以及水解度的影响。结果表明,酶解后谷朊粉在水中的分散性大大提高,而乳化能力和起泡特性则依底物浓度、酶解温度、加酶量和反应时间等因素发生不同的变化。综合评价结果可知,在谷朊粉浓度0.30 g/mL、酶解温度50℃、酶对底物的质量分数为0.75%、反应时间20 min条件下所得酶解物具有较好的功能特性,分散性为0.962,乳化能力为84.3 mL油/g蛋白,起泡性为52 mL。     

谷朊粉的有限酶解对其分散性及胶黏性的影响

为了改善谷朊粉在水溶液中的物化性能,利用碱性蛋白酶对谷朊粉进行了有限水解。通过单因素实验,分析了底物浓度、反应温度、加酶量和反应时间对其分散稳定性、胶黏性的影响,并分析了酶解物中的蛋白质分子粒径。通过正交实验确定了以提高谷朊粉分散特性和胶黏性为目的的最佳酶解条件为:底物浓度0.30g/mL、温度50℃、加酶量0.50%、反应时间20min,此时可使谷朊粉的相对分散稳定性达到96.3%,黏度为3.2mPa.s,蛋白质平均分子粒径604.6nm。分析显示,不同酶解样品分散稳定性、黏度和蛋白质平均分子粒径三种指标之间的变化趋势并不完全一致。     

酶解谷朊粉-卡拉胶复合体系凝胶特性研究

采用物性仪研究了酶解谷朊粉-卡拉胶复合体系的胶凝条件和凝胶特性。结果表明,酶解谷朊粉为300 mg/mL时仍是松软的糊状形态,添加0.3%卡拉胶时凝胶成形较好;随着卡拉胶浓度或酶解谷朊粉浓度增加,凝胶的黏性和弹性持续提高,而硬度则在0.3%卡拉胶或250 mg/mL谷朊粉时达到最高点后逐渐下降;随着加热温度增加或加热时间延长,凝胶的质构特性均呈现先逐渐增加后又下降的趋势。综合分析可知,在酶解谷朊粉300 mg/mL、卡拉胶0.3%8、0℃加热30 min条件下形成的复合凝胶硬度(252.822 g)、黏性(128.112 g.s)和弹性(0.045)均达到了较高值。     

盐酸处理对谷朊粉理化性质改良的研究

利用盐酸处理改善谷朊粉的溶解度、乳化性、起泡性等理化性质,研究盐酸与谷朊粉的相对浓度、反应温度、反应时间、盐酸浓度对谷朊粉理化性质的影响。结果表明,盐酸处理改良谷朊粉理化性质的最佳条件:谷朊粉质量百分比为8%,盐酸∶谷朊粉为3.5∶100(质量比),反应温度65℃。试验证明,盐酸处理对谷朊粉的溶解度、乳化性及其稳定性、起泡性及其稳定性都有显著作用。     

谷朊粉糖基化改性及其工艺优化

该实验以谷朊粉和果糖为主要原料,采用干法制备其接枝耦联产物,从而提高谷朊粉的功能特性和应用价值。实验分析了反应时间、反应温度、谷朊粉/果糖(W/W)对糖基化接枝物的溶解度的影响。并利用响应面法优化了谷朊粉与果糖接枝反应的工艺参数。研究结果表明:最佳反应条件为反应温度51℃,谷朊粉/果糖(W/W)90%,反应时间2.5 d(60 h),此时的平均溶解度为4.21 mg/m L,比天然谷朊粉提高了约12倍。     

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.     

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.     

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.     

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.     

Announcing a new international peer-reviewed journal:Food Science and Human Wellness now accepting manuscript submission in English

<正>We are pleased to announce the launch of a new international peer-reviewed journal-Food Science and Human Wellness,ISSN 2213-4530,which is an open access journal,produced and hosted by Elsevier B.V.on behalf of Beijing Academy of Food Sciences.Food Science and Human Wellness is an international peer-reviewed English journal that provides a forum for the dissemination of the