不同盐/甲酸溶解体系下丝素膜的制备及性能表征

采用盐/甲酸新型溶解体系对丝素进行溶解成膜,探讨氯化钙、溴化锂和溴化钙三种盐对丝素溶解和再生丝素膜结构性能的影响,通过扫描电镜、原子力显微镜、流变、红外光谱、X射线衍射和力学拉伸等测试技术表征再生丝素溶液及膜的结构与性能特征。结果显示,在相同条件下,脱胶蚕丝可快速溶解于三种盐/甲酸溶剂中,氯化钙溶解丝素溶液的颜色为浅黄色,溴化锂为黄色,溴化钙为深黄色;溶解液颜色的变化与溶解后丝素纳米结构相对应,随颜色加深丝素纳米纤维的长度和直径下降,说明溶解程度逐渐加重。结构分析表明,该盐/甲酸溶解体系制取的再生丝素膜以β折叠结构为主,盐种类不会对丝素结构产生明显影响。力学测试表明,该盐/甲酸体系获得的再生丝素膜具有良好的湿态力学强度和伸长,其中以氯化钙获得的膜性能最优。     

氯化钙-甲酸溶解体系再生丝素长丝的制备及其性能

为改善再生丝素长丝力学性能差的问题,选用氯化钙-甲酸溶解体系获得丝素溶液并采用湿法纺丝技术制备再生丝素长丝。研究结果表明:与传统的三元溶剂溶解丝素至分子水平有所不同,氯化钙-甲酸可在常温条件下溶解蚕丝,更重要的是在溶解过程中保留了原纤结构,在牵伸作用下再生丝素长丝的断裂应力较传统溶解方法提高了近1倍,纤维表面均匀光滑,在放线菌蛋白酶溶液中表现出相对缓慢的降解速度。该方法工艺简单,环境友好、高效,并可实现再生丝素长丝的连续制备。     

酸-醇体系丝素蛋白水凝胶制备与性能表征

针对再生丝素蛋白水凝胶形貌不可控、凝胶速度慢、压缩性能差的问题,提出了一种乙酸-乙醇体系共同促进丝素蛋白快速凝胶的方法。通过研究相同酸性条件下,不同质量分数乙醇对水凝胶形貌、聚集态结构、热稳定性、压缩性能等的影响,探索水凝胶内部纤维结构的成形条件以及不同形貌下水凝胶的结构与性能差异。结果表明:相同酸性条件下随着乙醇质量分数的提高,水凝胶的结构与性能均得到改善,凝胶时间由12~14 h缩减到1 h 左右,水凝胶形貌逐渐由几十到几百微米的孔洞结构向纤维结构转变,水凝胶中丝素蛋白结构以β-折叠为主;当乙醇质量分数为5.0%时,纤维直径为(1.09±0.5) μm,在干态下应变为60%时的压缩强度为(75.16±3.79) kPa,在湿态下压缩回复率达到伸长的63%。     

桑/柞蚕丝不同溶解体系再生丝素蛋白性能研究

通过对凝胶时间、蛋白质分子质量测试、氨基酸分析、FT-IR等方法的分析,研究了不同溶解体系下制备的再生桑蚕丝素、柞蚕丝素蛋白溶液稳定性差异和再生丝素膜组分、结构的变化。结果表明:桑蚕丝素的溶解以CaCl_2-H_2OC_2H_5OH体系为佳,Ca(NO_3)_2-4H_2O体系则更有利于对柞蚕丝素的溶解;丝素蛋白不同溶解体系下制备的丝素溶液分子量大小与稳定性成反比关系;在制备的再生丝素中桑蚕蛋白膜以非极性小侧基氨基酸为主;柞蚕蛋白膜以极性和非极性混合侧基氨基酸为主;再生桑蚕丝素蛋白分子构象为无规卷曲和β-折叠,并有由前向后的结构转化,再生柞蚕丝素蛋白以无规卷曲、α-螺旋和β-折叠的共存结构为主,并有按前序的结构转化。     

预拉伸对不同盐质量分数再生丝素膜的影响

丝素材料被广泛应用于生物医药领域,这是由于丝素材料具有低免疫源性,可降解且具备良好的力学性能。很多文献表明相比于传统溶解丝素的方法,甲酸/盐溶解丝素制备的再生丝素材料具有更好的机械性能,然而,当再生丝素应用于对力学性能要求更高的骨填充材料时,甲酸/盐溶解丝素制备的再生丝素材料力学性能还是不足的。文章采用甲酸/氯化钙溶解丝素制备再生丝素膜,然后对其进行预拉伸处理。结果表明,通过预拉伸处理的再生丝素膜具备更高的力学性能,选用4%的盐质量分数溶解时,可以得到稳定的二级结构(silk II)。研究结果对丝素材料应用于生物医药领域具有潜在的应用价值。     

剪切作用下高浓度再生丝素蛋白水溶液性质的研究

研究了不同剪切作用下高浓度再生丝素蛋白水溶液的性质，并利用拉曼光谱分析了丝素蛋白分子受剪切作用后的构象变化。结果发现：浓度和剪切作用是影响再生丝素蛋白水溶液性质的两个重要因素。高浓度再生丝素蛋白水溶液经过一定的剪切作用后将呈现各向异性的性质，且随着溶液中丝素蛋白浓度的增加，溶液出现各向异性现象所需要的临界剪切作用力减小；而在相同浓度下，剪切作用越大，再生丝素蛋白水溶液中丝素蛋白分子沿剪切作用方向的有序程度也随之增加。在一定的剪切作用下，高浓度再生丝素蛋白水溶液中部分丝素蛋白分子可由原来的无规线团和(或)α螺旋结构转变成β折叠结构。     

涂覆丝素液防止柞丝原纤化的研究

用氯化钙溶解法可制取具有一定粘度的桑蚕丝素液,将这种丝素液涂覆到柞蚕生丝上,并经戊二醛固着处理,柞丝表面就包覆了一层不溶性的丝素膜。丝素液的浓度越高,柞丝涂覆增重率也越高。涂覆处理后,柞丝断裂强力显著提高。经水洗证明,丝素膜的存在对防止柞丝原纤化有一定作用。     

天然蚕丝及再生蚕丝作为生物材料的应用

以再生丝素蛋白为研究对象,综述了再生丝素蛋白的结构及其生物应用.再生丝素蛋白材料以其易加工性能通常被制成丝素膜、丝素水凝胶、无纺网、多孔丝素海绵等多种材料,应用在人造皮肤、抗凝血材料、药物缓释、传感器等领域.     

海藻酸钠/丝素蛋白复合水凝胶的制备及性能研究

将海藻酸钠与丝素蛋白共混制备海藻酸钠/丝素蛋白水凝胶,探讨水凝胶成形过程及不同参数对水凝胶凝胶时间的影响及药物在海藻酸钠/丝素蛋白水凝胶中的缓释情况。试验表明:氯化钙/甲酸溶剂体系溶解脱胶蚕丝可以获得纳米原纤结构的再生丝素溶液,在凝胶过程中,复合水凝胶的凝胶时间随海藻酸钠的含量增加而延长,丝素蛋白/海藻酸钠比例为50/50时,凝胶时间需要89 min;当凝胶温度由15℃升至55℃时,凝胶时间由150 min缩短到55 min,因此可以通过调整海藻酸钠的比例、凝胶温度来调节复合水凝胶的凝胶时间;载药复合水凝胶释药曲线表明,药物释放过程呈先快后慢规律。     

生物可降解再生丝素纤维的研究

以再生蚕丝丝素纤维为研究对象，探讨天然丝素纤维用中性盐溶解时分子量的变化，再生丝素纤维的聚集态结构及其与力学性能、降解性能的关系。指出，再生丝素纤维不能达到天然丝素纤维的力学性能，但其生物降解性能得到提高。     

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.     

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.     

Analysis for organic residues from aids to polymerization used to make plastics intended for food contact

Polymers intended for food contact use have been analysed for organic residues which could be attributed to a range of substances employed as polymerization aids (e.g. initiators and catalysts). A wide range of polymers was extracted with solvents and the extracts analysed by gas chromatography-mass spectrometry (GC-MS). The overwhelming majority of substances identified were not derived from aids to polymerization but were oligomers, additives and adventitious contaminants. However, a small number of substances were identified as initiator residues. These included tetramethylsuccinonitrile (TMSN) which was observed in two polymers and it derived from recombination of two azobisisobutyronitrile (AIBN) initiator radicals. Methyl benzoate, benzoic acid, biphenyl and phenyl benzoate were detected in one poly(methyl methacrylate) sample and in two polyvinylchlorides and they are thought to be derived from benzoyl peroxide initiator. TMSN was subsequently targeted for analysis of poly-(methyl methacrylate) plastics using proton nuclear magnetic resonance spectrometry (¹     

Tests of potential functional barriers for laminated multilayer food packages. Part II: Medium molecular weight permeants

Experiments were performed to characterize the kinetics of the permeation of different medium molecular weight model permeants: bisphenol A, warfarin and anthracene, from liquid paraffin, through a surrogate potential functional barrier (25 microns-thick orientated polypropylene--OPP) into the food simulants olive oil and 3% (w/v) acetic acid. The characterization of permeation kinetics generally observed the permeation models previously reported to explain the experimental permeation results obtained for a low molecular weight group of model permeants. In general, the model permeants exhibited behaviour consistent with their relative molecular weights with respect to (a) the time taken to attain steady-state permeation into the food simulant in which they were more soluble, (b) their subsequent steady-state permeation rates, and (c) their partition between liquid paraffin and the OPP membrane.     

The development of reference materials for paralytic shellfish poisoning toxins in lyophilized mussel. I: Interlaboratory studies of methods of analysis

This paper describes the first part of a project undertaken to develop mussel reference materials for Paralytic Shellfish Poisoning (PSP) toxins. Two interlaboratory studies were undertaken to investigate the performance of the analytical methodology for several PSP toxins, in particular saxitoxin (STX) and decarbamoyl-saxitoxin (dc-STX) in lyophilized mussels, and to set criteria for the acceptance of results to be applied during the second part of the project: the certification exercise. In the first study, 18 laboratories were asked to measure STX and dc-STX in rehydrated lyophilized mussel material and to identify as many other PSP toxins as possible with a method of their choice. In the second interlaboratory study, 15 laboratories were additionally asked to determine quantitatively STX and dc-STX in rehydrated lyophilized mussel and in a saxitoxin-enriched mussel material. The first study revealed that three out of four postcolumn derivatization methods and one pre-column derivatization method sufficed in principle to determine STX and dc-STX. Most participants (13 of 18) obtained acceptable calibration curves and recoveries. Saxitoxin was hardly detected in the rehydrated lyophilized mussels and results obtained for dc-STX yielded a CV of 58% at a mass fraction of 1.86 mg/kg. Most participants (14 out of 18) identified gonyautoxin-5 (GTX-5) in a hydrolysed extract provided. The first study led to provisional criteria for linearity, recovery and separation. The second study revealed that 6 out of 15 laboratories were able to meet these criteria. Results obtained for dc-STX yielded a CV of 19% at a mass fraction of 3.49mg/kg. Results obtained for STX in the saxitoxin-enriched material yielded a CV of 19% at a mass fraction of 0.34mg/kg. Saxitoxin could not be detected in the PSP-positive material. Hydrolysis was useful to confirm the identity of GTX5 and provided indicative information about C1 and C2 toxins in the PSP-positive material. The methods used in the second interlaboratory study showed sufficiently consistent analysis results to undertake a certification exercise to assign certified values for STX and dc-STX in lyophilized mussel.     

Focus on China's Paper Industry

In the English section of this issue, 〈China Paper Newsletters〉 will introduce ＂National Development and Reform Commission Issued Announcement for Selection of Major Preliminary Research Projects for the ＇13th Five-Year Plan＇＂, ＂2013 Annual Report of China＇s Paper Industry＂, and news of projects and other policies.     

Listen to downstream & search for innovation

正Nowadays,textile enterprises are all taking efforts in transformation and upgrading,like improving producing capacity and optimizing production structure to face market downturn.It claimed a higher request to the standard of textile equipments.In the upcoming of ITMA ASIA+CITME 2014exhibition,this magazine have interviewed several branch associations and a series of relative enterprises,to summarize industrial developing status