桑蚕丝纤维低温处理后结构及活性染料染色

在回潮率为40%,冷冻时间为24 h,冷冻温度为-86~-10℃的条件对普通脱胶桑蚕丝纤维进行低温冷冻处理,通过SEM测试、FT-IR测试及XRD测试探讨了桑蚕丝纤维前低温冷冻处理前后结构变化,并对低温冷冻处理后桑蚕丝纤维进行力学性能测试。采用兰纳素蓝3G染料对处理前后桑蚕丝纤维进行染色,并进行染色性能测试。结果表明,低温冷冻处理后纤维表面出现明显的孔洞、裂痕结构;低温冷冻处理后的蚕丝蛋白结构仍以β-折叠结构为主,无规线团结构及α-螺旋结构有向更稳定结构转变的趋势;低温冷冻处理后桑蚕丝纤维仍以silkⅡ型结晶结构为主;低温冷冻处理后纤维的断裂强力有所下降,但伸长率明显提高;采用兰纳素蓝3G染料染色,上染率、固着率及总固着率均有所提高,染料的利用率大大提高。     

低温冷冻对桑蚕丝纤维表面结构和染色性能的影响

针对桑蚕丝纤维进行低温冷冻处理,利用扫描电镜和原子力显微镜对冷冻前后纤维表面结构的变化进行表征;采用活性染料兰纳素蓝3G对桑蚕丝纤维进行染色,测试了不同冷冻条件下桑蚕丝纤维的上染率、固着率和总固着率,分析了冷冻处理对桑蚕丝纤维表面结构和染色性能的影响。试验结果表明:经过低温冷冻处理后,桑蚕丝纤维表面结构发生变化,桑蚕丝纤维的染色性能得到改善,在回潮率40%,温度-86℃,冷冻时间48 h的冷冻处理条件下,桑蚕丝纤维上染率、固着率和总固着率分别提高27%、14%和35.3%。     

经纳米壳聚糖处理的桑蚕丝纤维聚集态结构

通过采用离子凝胶法制备的纳米壳聚糖处理桑蚕丝纤维,研究桑蚕丝纤维经不同质量分数纳米壳聚糖分散液处理后的聚集态结构变化。研究结果表明:桑蚕丝纤维经纳米壳聚糖分散液处理后,纤维内部聚集态结构呈现出β化趋势,结晶度和热稳定性提高;随着纳米壳聚糖质量分数的进一步提高,桑蚕丝纤维β化趋势增强,热稳定性更好。     

壳聚糖季铵盐处理桑蚕丝纤维的工艺研究

采用壳聚糖与2,3-环氧丙基三甲基氯化铵制备壳聚糖季铵盐:2-羟丙基三甲基氯化铵壳聚糖(简称HTCC),并将其用于桑蚕丝纤维的改性,探索了HTCC溶液处理丝纤维的工艺条件,并研究了经HTCC溶液处理前后桑蚕丝纤维表面微观形态和内部结构的变化情况。结果表明,丝纤维经HTCC溶液处理后有一定的增重现象,HTCC质量浓度和柠檬酸质量分数对丝纤维增重率的影响均非常显著;经HTCC溶液处理后桑蚕丝纤维表面有明显的纵向条纹和附着物,表面N元素周围的化学环境发生了变化,N元素含量明显降低,内部结构呈现β化趋势。     

冷冻贮藏对冻猪肉冰晶形态、TVB-N及TBARS的影响

研究了冻藏(-10、-15、-19、-22℃,150d)对猪肉品质的影响.结果显示:冷冻温度越低,形成的冰晶越小,冷冻结束时,各处理的冰晶面积的分布范围为4045.855～ 5509.739μm2,相当直径分布范围为69.381～ 81.439μm;经150d贮藏后,尽管温度越低,冰晶重结晶速度越慢,冰晶的体积仍显著增大(p<0.01),面积为7546.855～ 11273.890μm2,相当直径为98.945～ 106.670μm;而圆度和长度则没有显著变化(p>0.05).挥发性盐基氮含量(TVB-N含量)和硫代巴比妥酸还原值(TBARS值)同样也显著增大(p<0.05).冰晶体积、TVB-N含量和TBARS值变化显示了很好的时间相关性.实验说明冰晶形态也可用于反应猪肉的新鲜程度.     

基于碱脲溶剂体系胶化作用的湿强纸的制备

在低温及中高浓度条件下,利用氢氧化钠 硫脲水溶液浸渍处理由漂白硫酸盐慈竹浆抄造的纸张,经冷冻及洗涤后制备湿强纸,通过单因素实验探究碱浓、浸渍时间、冷冻温度、冷冻时间和洗涤时间等因素对纸张强度性能的影响,并利用傅里叶变换红外光谱仪、X射线衍射仪、热重分析仪、核磁共振波谱仪和扫描电子显微镜表征处理前后纸张性能的变化情况。结果表明,在碱浓7%、浸渍时间3 s、冷冻温度-7℃、冷冻时间15 min、洗涤时间15 min的处理条件下,制得的湿强纸强度性能最好。与处理前原纸相比,在该条件下处理后纸张的干抗张指数提高了66%,干耐破指数提高了183%,湿抗张指数提高了321%,湿耐破指数提高了980%;同时处理后纸张中单根纤维的含量显著降低,且处理前后纸张纤维的官能团结构、无定形区和结晶区结构、热力学性能以及碳骨架结构均没有明显变化。     

壳聚糖处理对真丝纤维结构与性能的影响

本文采用壳聚糖溶液对脱胶桑蚕丝进行处理，通过对处理后丝纤维的微观形态及力学性能等的测试，探讨了壳聚糖处理后丝纤维的结构和强力等方面的变化特征。并运用正交分析法得知壳聚糖的浓度、处理温度和时间对真丝纤维增重率及强力的影响程度。     

钙盐处理天蚕丝的结构与性能研究

对经钙盐处理后天蚕丝的质量损失率、力学性能及结构形态进行了研究,发现天蚕丝经钙盐处理后有质量损失现象,且其损失率随处理时间的延长而增大;纤维的断裂强度下降,断裂伸长随着处理时间延长先降低后增加;纤维的结晶度先增加后降低;纤维发生溶胀现象,微孔穴结构增强,但是分纤行为不如桑蚕丝严重.     

丝素肽增重处理对桑蚕丝结构与性能的影响

为了研究桑蚕丝增重处理的机理以及提高桑蚕丝的利用价值,通过对增重前后桑蚕丝纤维进行场发射扫描电子显微镜(FE-SEM)、红外光谱(FTIR)、X射线衍射(XRD)和热稳定性分析(TG)等表征,分析了丝素肽增重处理对桑蚕丝纤维结构与性能的影响。结果表明:经丝素肽增重处理后,桑蚕丝纤维的横截面结构变得松弛,有空隙;纤维的纵向表面变得粗糙,有条纹;桑蚕丝纤维中各特征吸收峰的强度增强,峰形相应变宽;增重前后桑蚕丝晶型结构没有变化,且增重反应主要发生在无定形区;增重后桑蚕丝热稳定性增加。     

不同冷冻方式对斑点叉尾鮰鱼片品质的影响

研究不同的低温冷冻预处理方式,即-20℃慢冻、-20℃、-40℃、-60℃速冻至-20℃,进行鮰鱼片的冷冻,随后于-20℃冻藏,考察储藏期间鮰鱼片理化性质的变化情况。结果表明,随着冻藏时间的延长,不同方式的冻结鮰鱼p H值、Ca~(2+)-ATPase活性、活性巯基均呈下降趋势,MDA值、TVB-N值、表面疏水性呈上升趋势,速冻处理组的样品各指标变化趋势明显低于或迟缓于慢冻组,且速冻温度越低,效果越显著。考虑到成本因素,可以结合其他保鲜手段适当提高冻结温度至-20℃~-40℃以保证产品品质。     

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.     

Detection of adulteration of locust bean gum with guar gum by capillary electrophoresis and polarized light microscopy

Capillary electrophoresis (CE) and polarized light microscopy (PLM) were utilized in the detection of the adulteration of locust bean gum with guar gum. For CE analyses, standards of locust bean and guar gums were extracted with 30% CH₃CN, removing the residual proteins from the gum matrix. A 8.75 mM NaH₂PO₄-20.6 mM Na₂B₄O₇ buffer, pH 9, was used to separate these proteins and to identify marker proteins that were present in the guar gum. These markers did not co-migrate with components in the extracts of mechanically processed locust bean gum, and are used as indicators of adulteration. Using PLM with toluidine blue and iodine staining techniques, unadulterated locust bean gum samples were distinguished from mixed samples through the differential staining of components in locust bean versus guar and tara gums. These experiments in the use of CE and PLM provide orthogonal and complementary methods for the verification of 'true' positives and the elimination of 'false' positives.