壳聚糖微球固定化葡萄糖氧化酶的研究

以壳聚糖微球为载体,戊二醛为交联剂,固定葡萄糖氧化酶,对葡萄糖氧化酶的固定化条件及固定化酶的各种性质进行了研究,确定了酶固定的最佳条件为0.1g壳聚糖微球与5ml5%戊二醛交联,固定6mg葡萄糖氧化酶,在此条件下酶活力回收可达60%。固定化酶的最适温度为50℃,最适pH为6.0,通过Lineweaver-Burk作图,确定动力学参数Km值为18.3mmol/L,表观米氏常数较游离酶有所降低,固定化酶的热稳定性较游离酶明显提高,该固定化酶具有良好的操作及保存稳定性。     

壳聚糖—戊二醛固定化木聚糖酶的技术研究

采用壳聚糖微球一戊二醛交联的方法固定木聚糖酶,探讨壳聚糖浓度、戊二醛体积分数和交联时间对固定化酶相对酶活力的影响.以正交试验确定木聚糖酶的最佳固定化条件,比较固定化酶与其游离酶的最适反应pH值、pH值稳定性、最适反应温度及热稳定性.结果表明,在壳聚糖质量浓度0.1g/mL、戊二醛添加量3％、给酶量2000U/g载体、交联时间2.5h时,固定化酶的回收率较高,可达到65.38％,同时固定化和游离酶的最适温度分别为60℃、55℃,最适pH值分别为4.5、5.0,热稳定性有不同程度的提高,pH稳定性两者变化不大.木聚糖酶的固定化能有效地提高其作用性能,从而为木聚糖酶的工业化应用提供了一定的理论依据.     

脂环酸芽孢杆菌α-葡萄糖苷酶固定化及酶学性质研究

以戊二醛为交联剂,壳聚糖为载体,优化脂环酸芽孢杆菌α-葡萄糖苷酶的固定化条件,探讨固定化对酶性质的影响。结果表明:当戊二醛浓度0.2mol/L、戊二醛交联时间12h、交联pH7.5和交联温度15℃时,酶的固定化效果最佳。此时,固定化酶的最适pH4.5,最适反应温度55℃,在pH4.5～8.0范围酶的活性不受损失。当温度为65℃时,固定化酶的活力接近100%。酶储存3周以上,可以保持80%以上的活力。重复使用6次后,酶活保持在80%左右,说明固定化酶优化了游离酶的部分酶学性质,具有一定的应用价值。     

壳聚糖小球共价固定化α-淀粉酶的研究

以壳聚糖小球为载体,采用戊二醛交联共价固定α-淀粉酶。试验结果表明,以1 g壳聚糖小球为载体,经5m L 2%戊二醛处理后,加入24 mgα-淀粉酶,30℃,在p H 6的磷酸缓冲液中固定化2 h,制备的固定化α-淀粉酶活力达1 407.6 U/g。固定化酶最适p H向酸性方向偏移,最适反应温度不变,固定化α-淀粉酶的酸碱稳定性和热稳定性均优于游离酶。     

磁性壳聚糖微球固定化脂肪酶研究

以磁性壳聚糖微球为载体,通过戊二醛交联进行脂肪酶固定化,对影响脂肪酶固定化各种因素进行考察,确定最佳条件,并比较游离酶与固定化酶pH和热稳定性。结果表明,固定化适宜条件为:脂肪酶加入量5.0 mg/100 mg载体、温度40℃、时间5 h、pH 8.04、戊二醛浓度10%、最高固载率可达90.56%,酶活4034 U/g载体;与游离酶相比,固定化酶pH和热稳定性都有较宽适用范围。     

壳聚糖固定化α-葡萄糖苷酶的研究

以粉末状壳聚糖为载体 ,采用吸附 交联的方法将α 葡萄糖苷酶固定化。在最适固定化条件下 ,室温吸附 6h ,然后与 3 5%的戊二醛在 4 5℃交联 6h ,可得到固定化酶的活力为1430 0U ,酶活力回收率为 59 6 %。通过实验发现 ,与游离酶相比 ,固定化酶的最适 pH向酸性方向移动 0 5pH单位 ,为 pH 4 5;最适作用温度达到 70℃ ,比游离α 葡萄糖苷酶提高 5℃ ;酸碱稳定性、热稳定性及贮存稳定性均有较大提高 ;在 6 0℃操作半衰期为 16 8h     

改性磁性壳聚糖微球固定化乳糖酶

通过反相悬浮聚合法,以甲基丙烯酸2-羟乙酯(HE-MA)与甲基丙烯酸缩水甘油酯(GMA)为单体,过硫酸铵为引发剂制备得到改性磁性壳聚糖微球。进一步以改性磁性壳聚糖微球为载体,通过吸附、共价结合以及戊二醛交联反应三方协同作用固定乳糖酶。对影响固定化的各种因素进行优化,确定固定化乳糖酶最适条件为:载体在0.1 mol/L、pH 7.0的磷酸缓冲液中充分溶胀后,按2.0 U/mg载体的添加量加入乳糖酶,4℃吸附3 h,再添加0.1%戊二醛交联4 h;最终所得的固定化乳糖酶活为685 U/g载体,酶活回收率为34.3%。固定化后的乳糖酶的pH稳定性和热稳定性都较游离酶有明显提高;连续操作10次后,固定化酶活仍保持在70%以上,具有良好的操作稳定性。     

几丁质固定化壳聚糖酶的研究

以几丁质为载体，戊二醛为交联剂，固定壳聚糖酶，对壳聚糖酶的固定化条件、固定化酶的性质进行了研究，确定了酶固定的最佳条件为0.1克几丁质与5ml5%戊二醛交联，固定2mg壳聚糖酶，在此条件下酶活力回收可达70％。固定化酶的最适温度和pH分别为60℃和4.0，动力学参数Km值为17.66g/L。将固定化酶于70℃水浴保温150min，酶活力未见明显下降。该固定化酶具有良好的操作和保存稳定性。     

壳聚糖固定化α-葡萄糖苷酶的研究

以粉末状壳聚糖为载体 ,采用吸附 -交联的方法将 α-葡萄糖苷酶固定化。最适固定化条件研究表明 ,0 .1 g壳聚糖与 2 4 ,0 0 0 U(0 .0 8ml) α-葡萄糖苷酶进行固定化 ,在p H6.0条件下 ,室温吸附 6h,然后与 3.5%的戊二醛在 45℃交联 6h,可得到固定化酶的活力为 1 4,30 0 U,酶活力回收率为59.6%。通过实验发现 ,与游离酶相比 ,固定化酶的最适 p H向酸性方向移动 0 .5p H单位 ,为 p H4.5;最适作用温度达到70℃ ,比游离 α-葡萄糖苷酶提高 5℃ ;酸碱稳定性、热稳定性及贮存稳定性均有较大提高 ;在 60℃操作半衰期为 1 68h     

戊二醛交联几丁质固定化青霉素G酰化酶及其性质研究

目的以几丁质为载体,戊二醛为交联剂固定化粪产碱杆菌青霉素G酰化酶。方法单因素优化固定化条件,以交联度、pH、温度、酶量4因素3水平正交试验,确定最佳固定化条件,并研究固定化酶的最适反应温度、pH及批次稳定性。结果最佳固定化条件为几丁质0.3 g,酶量6.0 mL,交联度1.5%,温度37℃,pH 8.0,时间48 h,固定化酶最高比活性为62.3 U/g湿载体,最适反应温度为65℃,最适pH 9.0,重复使用8批活性基本稳定。结论戊二醛交联几丁质固定化青霉素G酰化酶稳定性较好,具有一定的工业应用前景。     

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.     

The Ministry of Environmental Protection Issued "Feasible Technology Guidelines for Pollution Prevention and Control in Wood Pulping Process of the Paper Industry (Trial)" and Two Other Guiding Technical Documents

On December 27t＂, 2013, the Ministry of Environmenta Protection announced that, in order to implement ＂The Environmental Protection Law of the People＇ s Republic of China＂, improve the working system in environmenta protection technologies, and promote technologica advancement in pollution prevention, the Ministry of Environmental Protection sponsored the formulation of three guiding technical documents including ＂Feasible Technology Guidelines for Pollution Prevention and Contro n Wood Pulping Process of the Paper Industry （Trial）＂     

1~(st) Intelli-Tissue~ EcoEc Tissue Machine Supplied by PMP Group Successfully Put into Operation in China

正On April 29th,2014,Intelli-Tissue EcoEc tissue machine supplied by PMP Group successfully put into operation at Hebei Xuesong Paper Co.,Ltd.,this is the first such kind of paper machine of PMP Group in China.