大豆分离蛋白/葡聚糖溶液共混体系溶胶-凝胶转变数学模型选择

通过跟踪光学性质白度值变化对大豆分离蛋白(SPI)/葡聚糖(DEXT)溶液共混体系经葡萄糖酸内酯(GDL)诱导溶胶-凝胶转变过程色差亮度(L*)-凝胶时间(t)关系曲线特征进行分析发现,L*-t关系具显著的"S"型规律性。通过6类回归数学模型拟合比较发现不同超声强度处理或大豆分离蛋白-葡聚糖共价复合物(SPI-g-DEXT)添加条件下,Boltzmann函数数学模型L*=L*2+(L*1-L*2)/(1+exp((t-tg)/dt))均具有相关系数R2值最高、模拟值与实际值残差平方和最小、普适性强且函数模型参数对应物理意义明确。采用Boltzmann函数可以明确地界定出L*-t曲线的3个特征区域:下平台溶胶区、溶胶凝胶共存转变区和上平台凝胶区。提出了一种基于色差亮度值动态变化分析SPI/DEXT溶液共混体系GDL诱导溶胶-凝胶转变过程凝胶起始时间、凝胶完成时间和凝胶速度的定量化新方法。     

SPI-g-DEXT对SPI/DEXT共混溶液相行为及微结构的影响

研究大豆分离蛋白-葡聚糖共价复合物（soy protein isolate-dextran grafted conjugates,SPI-g-DEXT）对大豆分离蛋白（soy protein isolate,SPI）与葡聚糖（dextran,DEXT）溶液共混物相行为及微结构形貌的影响。结果表明：添加SPI-g-DEXT的接枝率为49.92%时,共混溶液表观黏度、黏弹模量、宏观相分离时间及形貌结构中多糖相分散度随添加量（0、0.10、0.20、0.30 g/100 mL）增加而呈先增加后降低趋势。SPI-g-DEXT添加量为0.20 g/100 mL时,共混溶液相容性随其接枝度（0%、30.73%、49.92%、62.84%）增加而增加。添加共价复合物SPI-g-DEXT于SPI/DEXT共混溶液后,稳态剪切及动态黏弹流变性、宏观相分离时间、微观形貌结构和尺度主要取决于SPI-g-DEXT加入后增容作用与空间位阻作用的竞争结果。     

β-葡聚糖对大豆分离蛋白酸致混合凝胶流变性的影响

采用乳酸菌对大豆分离蛋白(SPI)/β-葡聚糖混合体系进行发酵制备酸致凝胶,研究β-葡聚糖浓度(0.4~1.6 mg/100 m L)和分子质量(OGL80~OGL360)对SPI(4、6、8 mg/100 m L)酸致混合凝胶流变性的影响。结果表明:在SPI中添加β-葡聚糖不会改变大豆蛋白的变性温度,但会使表面疏水性由81.97降低至71.83。一定浓度β-葡聚糖会使SPI酸致凝胶的起点由1 Pa降至0.01~0.1 Pa,甚至降低凝胶终点G'至10 Pa以下不能形成凝胶。而高分子质量β-葡聚糖通过增加体系黏度而减少分层现象并保持体系稳定,从而降低或消除β-葡聚糖对SPI酸致混合凝胶的弱化作用,甚至会改善混合体系凝胶强度。     

葡聚糖-大豆分离蛋白共混凝胶流变性质及微结构研究

采用pH监控,动态流变,激光共聚焦(CLSM)及图像分析技术研究葡萄糖酸内酯(GDL)诱导葡聚糖-大豆分离蛋白(SPI)共混体系形成凝胶的动态粘弹性质及微结构,并探讨凝胶形成动力学及形成机制。结果表明:添加葡聚糖可抑制SPI凝胶形成,使凝胶的粘弹性质降低并出现相分离现象,且葡聚糖浓度和分子质量对SPI凝胶结构具协同弱化效应;与对照样相比,加入葡聚糖后凝胶的微结构相分离程度随葡聚糖分子质量的增加而加剧,温度升高推动凝胶形成的速度弱于相分离的速度,并降低了凝胶的弹性模量值;凝胶形成动力学研究结果表明GDL诱导球蛋白-中性多糖共混凝胶形成动力学与模型方程G′(t)=G′f{1-exp[-k(t-t0)]}非常吻合,添加同浓度多糖条件下凝胶形成速率随葡聚糖分子质量的增加呈降低趋势。     

大分子拥挤体系中SPI-葡聚糖共价复合物制备

通过大分子拥挤体系发生Maillard反应制备大豆蛋白-葡聚糖共价复合物,系统研究了不同反应条件对制备产物的影响,得出最佳条件为:pH6.5的磷酸盐缓冲液中,反应物总浓度为40％,60℃反应30h,SPI与葡聚糖共价接枝效果最好,表现出了优越的乳化性质.采用十二烷基磺酸钠聚丙烯酰胺凝胶电泳法(SDS-PAGE)证实了大豆分离蛋白与葡聚糖之间发生共价结合,产生了共价复合物.该方法制备的产物色泽良好,褐变颜色较少,反应时间大大缩短,只需30h即可完成,而传统的干热制备反应一般需要几天或者数周才能完成.该实验模拟大分子拥挤环境,将多糖和蛋白质作为生物大分子处于该环境中,得到的产物大豆蛋白-葡聚糖共价复合物,可作为一种“绿色”乳化剂,可广泛应用到食品工业中.     

超声对大豆11S蛋白-葡聚糖共混溶液冷致凝胶流变性质的影响

本文采用稳态剪切和小变形振荡流变分析方法研究了超声时间、超声功率对大豆11S蛋白-葡聚糖共混溶液的稳态剪切粘度和及其冷致凝胶过程动态流变性质的影响。实验结果表明：对照样及超声处理后的共混溶液均为假塑性流体,共混溶液的表观粘度随超声时间或超声功率增加呈降低趋势。与对照样相比,经237.5 W超声处理6 min后,粘度的下降幅度达46.6%。当超声处理时间或功率分别位于0~9 min或0~142.5 W范围时,共混溶液经超声处理后均可冷致形成非共价三维网络共混凝胶,凝胶的G'和G"随时间或功率增加呈增加趋势。当超声时间或功率分别增加到12 min或237.5 W时,共混凝胶的G'分别由峰值的954.7 Pa和609.9 Pa降低为367.3 Pa和507.8 Pa,同时凝胶起始时间被迟滞。超声处理对凝胶线性粘弹区域影响不显著。     

大分子拥挤环境下多糖对蛋白肽的修饰研究

采用胃蛋白酶适度水解大豆分离蛋白得到蛋白肽,在大分子拥挤环境下通过Maillard反应制备蛋白肽-葡聚糖共价复合物(Hydrolated Soy Protein Isolated-Dextran Conjugates,HDC),采用十二烷基磺酸钠-聚丙烯酰胺凝胶电泳(SDS-PAGE)技术证实大豆7S球蛋白和葡聚糖发生了共价结合,并通过乳化剪切机、荧光分光光度计、差示扫描量热仪和粒度分布仪等对其接枝度、溶解性、热稳定性、抗氧化性和乳化性能进行系统分析。结果表明:大分子拥挤环境下大豆水解蛋白肽-葡聚糖60℃反应4 h就可以形成较高接枝度的共价复合物,溶解性较大豆分离蛋白(Soybean protein isolated,SPI)和大豆分离蛋白-葡聚糖(Soybean Protein Isolated-Dextran Conjugates,SDC)有所提高,热稳定性好,HDC的自由基清除率明显高于大豆水解蛋白和它与葡聚糖的混合物,达到66.39%,且羟自由基清除率高于维生素C,HDC的乳液粒径最小并具有优越的乳化稳定性。     

大豆蛋白-葡聚糖共价物酶法凝胶的冻融稳定性研究

研究了冻融循环过程中,谷氨酰胺转氨酶交联的不同质量浓度（30,40,50,60 mg/mL）大豆分离蛋白-葡聚糖共价物（SPI-D）凝胶的持水性、弹性、硬度、可溶性蛋白含量、微观形貌及结构的变化。SDS-PAGE试验证实大豆分离蛋白与葡聚糖发生美拉德反应,生成大豆分离蛋白-葡聚糖共价物。随着SPI质量浓度的升高,SPI-D的接枝度先增大后减小,50 mg/mL时达到最大值12.54%。表面疏水性和内源荧光光谱分析表明,随着美拉德反应的进行,蛋白柔性增大,无序性增加,朝有利于冻融稳定的方向转变。与对照相比,5次冻融循环后,SPI-D、SPI与D混合物（SPI+D）、SPI凝胶持水性分别降低了32.46%,42.81%,44.98%,硬度分别增加了124.66%,271.51%,343.38%,弹性分别升高了4.38%,9.58%,11.76%,可溶性蛋白含量分别降低了2.05%,3.61%,7.17%,SPI-D凝胶的各项指标变化幅度均最小,冻融稳定性最好。扫描电镜图表征了凝胶微观形貌,相比SPI+D和SPI,SPI-D凝胶孔隙更小且组织状态更均匀,说明美拉德反应是提升酶法大豆分离蛋白凝...     

卵白蛋白和大豆分离蛋白相互作用对凝胶结构及性质的影响

为了提高大豆分离蛋白(SPI)的凝胶性,通过在大豆分离蛋白中添加卵白蛋白(OVA)测定复合凝胶(OVA-SPI凝胶)的分子相互作用,研究其结构与性质.研究结果表明,与 SPI溶液相比,OVA-SPI溶液(复合蛋白质溶液)的游离巯基质量摩尔浓度增加;复合凝胶的分子间二硫键增加,α-螺旋与β-折叠结构的比例最低,表面疏水性...     

燕麦β-葡聚糖对大豆分离蛋白酸致凝胶物理性质影响的研究

采用乳酸菌发酵法对大豆分离蛋白/燕麦β-葡聚糖混合体系酸致凝胶的物理性质进行研究,将不同分子量燕麦β-葡聚糖添加到大豆分离蛋白中,探讨燕麦β-葡聚糖浓度和分子量对SPI凝胶的脱水收缩作用、质构特性和持水性的影响。结果表明:保加利亚乳杆菌发酵产酸速率较快,并且对混合凝胶性质的影响优于嗜热链球菌和嗜酸乳杆菌,为最佳发酵菌种。较高浓度或高分子量燕麦β-葡聚糖能降低SPI凝胶的脱水收缩作用,即减少乳清的析出;随着燕麦β-葡聚糖浓度的增加,SPI凝胶硬度和持水性呈下降趋势,而弹性和内聚性先增加后降低;高分子量的燕麦β-葡聚糖能够改善SPI凝胶的质构特性,并且增加凝胶的持水性。     

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