乳酸菌发酵代谢合成叶酸的影响因素

对嗜酸乳杆菌以及乳酸乳球菌发酵合成叶酸的影响因素进行了研究。结果表明,乳酸菌代谢合成叶酸的产率为17~100μg/L,菌种、培养时间、pH值、对氨基苯甲酸(PABA)质量浓度会影响乳酸菌合成叶酸的产量。与乳酸乳球菌乳酸亚种相比,嗜酸乳杆菌CH-2生成的叶酸产量要高。不同菌株生成叶酸的能力与pH值有关,嗜酸乳杆菌在pH值为4.2叶酸产率明显下降,乳酸乳球菌乳酸亚种产叶酸的能力则不受pH值影响。添加PABA可以显著提高乳酸菌的叶酸产率。选择适宜的乳酸菌菌株,优化发酵工艺参数可以提高乳及相关食品中叶酸的质量浓度,达到生物方式强化叶酸的效果。     

铜和叶酸对奶公牛消化率和血液代谢的影响

为揭示铜和叶酸对奶公牛消化率和血液代谢的影响,试验将12月龄、体重(401±2.9)kg的8头荷斯坦奶公牛,随机分为4组,采用2(4 mg/kg日粮干物质的叶酸或过瘤胃叶酸)×2(10 mg/kg日粮干物质的硫酸铜或过瘤胃硫酸铜)因子的4×4拉丁方设计。结果显示,过瘤胃叶酸提高了干物质、有机物、粗蛋白质、中性洗涤纤维和酸性洗涤纤维的消化率(P0.05),但过瘤胃硫酸铜相反(P0.05)。过瘤胃叶酸较叶酸降低了粪氮、尿氮和总排泄氮以及血清中甘油三酯、乙酰乙酸和同型半胱氨酸浓度(P0.05),增加了沉积氮和沉积氮/消化氮以及血清中葡萄糖、白蛋白、总蛋白质、游离脂肪酸和叶酸浓度(P0.05)。过瘤胃硫酸铜较硫酸铜提高了粪氮和总排泄氮以及血清中游离脂肪酸和甘油三酯浓度(P0.05),降低了尿氮/总排泄氮以及血清中白蛋白、总蛋白质和总胆固醇浓度(P0.05)。两者对白蛋白、总胆固醇和乙酰乙酸存在交互作用(P0.05)。结果表明,过瘤胃叶酸和过瘤胃硫酸铜在蛋白质和脂质代谢中存在交互作用。过瘤胃叶酸的添加效果优于叶酸,而过瘤胃硫酸铜在本试验条件下可能造成了铜的过量摄入。     

叶酸的提取及抗氧化性研究

研究果蔬中叶酸的最佳提取条件及叶酸的抗氧化活性.以油菜,香菇,香蕉为原料,以提取温度、提取剂的浓度、提取时间为因素进行正交试验,确定最佳提取条件,用荧光光度法测定叶酸含量.采用Fenton体系、邻苯三酚自氧化体系,分别研究不同浓度的叶酸对羟自由基( ·OH)和超氧自由基(O2-·)的清除效果.结果表明果蔬中叶酸的最佳提...     

微生物法测定维生素矿物片中的叶酸含量

目的:在一定条件下,鼠李糖乳杆菌(ATCC 7469)繁殖速度与叶酸的含量呈正比关系,可定量测定维生素矿物片中的叶酸含量。方法:在含有除叶酸以外所有营养成分的合成培养基中,鼠李糖乳杆菌(ATCC 7469)的生长量随着叶酸浓度的增大而增大,且在一定浓度范围内呈线性关系。根据培养后菌悬液的吸光度与叶酸标准工作曲线进行比较,计算出维生素矿物片中的叶酸含量,并使用高效液相法测定其中3个样品与微生物法进行比较。结果:微生物法测定叶酸的线性范围为0.05～1 ng,其标准曲线多变量相关系数为0.99812,测定维生素矿物片中的叶酸含量的相对标准偏差(RSD)为3.25%,加标试验回收率在90.0%～108.5%。结论:微生物法测定维生素矿物片中叶酸的方法操作简便、稳定可靠、重复性好。     

叶酸抗苯并[a]芘致突变作用的实验研究

目的:探讨叶酸抗苯并[a]芘致突变作用。方法:用不同浓度的叶酸(6.25、12.5、25、50μmol/L)对苯并[a]芘致鼠伤寒沙门氏菌TA98、TA100产生回复突变作用进行抗诱变实验。结果:不同浓度的叶酸对苯并[a]芘致TA98和TA100回复突变有抑制作用,经SPSS 17.0统计学分析,与阳性对照组比较,高剂量叶酸(25、50μmol/L)对TA98菌株抑制效果显著(P<0.05);叶酸各剂量组(6.25、12.5、25、50μmol/L)对TA100菌株均有极显著抑制效果(P<0.01)。结论:叶酸对苯并[a]芘具有抗诱变作用。     

响应面法优化叶酸微胶囊制备工艺及其初步应用研究

以食用叶酸为芯材，明胶、阿拉伯胶为壁材，采用复凝聚法搭配真空冷冻干燥法对叶酸进行包埋，制备了一款叶酸微胶囊。以叶酸的包埋率和产率为评价指标，以壁芯比、壁材比、总壁材浓度、反应体系pH、反应时间和TG酶添加量为影响因素，通过单因素试验和响应面试验优化其制备工艺。结果表明，叶酸微胶囊最佳制备工艺条件为：以200 g反应体系总质量为基准，壁芯比1.8∶1、明胶：阿拉伯胶1∶1、总壁材浓度2.0%、反应体系pH 4.2、反应时间41.5 min、TG酶添加量150 mg，此时的包埋率和产率分别为86.8%、80.4%。叶酸微胶囊成品为浅黄色粉末，电镜下成囊情况良好，分布较为均匀，呈椭球形或短杆形，其长径为0.6～1.2μm、短径为0.3～0.5μm，整体饱满充实，无破裂、孔洞和褶皱出现。同时探究了叶酸微胶囊在馒头制作过程中的变化规律，结果表明微胶囊包埋的叶酸留存率为93.8%，比直接添加的叶酸留存率高21.4%，说明微胶囊对叶酸有很好的保护作用，可以通过添加叶酸微胶囊实现馒头中叶酸的营养强化。     

婴幼儿乳品中叶酸的微生物测定方法

按照GB 5413.16-2010、GB/T 5009.211-2008及Biostest叶酸检测试剂盒等不同方法,对同一乳制品样品叶酸含量进行测定,同时进行加标回收试验。结果表明,依据GB 5413.16-2010,在制备标准测试管时,使用两种浓度的含抗坏血酸的磷酸缓冲液稀释获得的叶酸标准工作液,同时样品测试液也由抗坏血酸的磷酸缓冲液稀释获得,测得叶酸质量分数为40.45μg/hg,回收率为71%。而参照GB/T 5009.211-2008,只使用一种浓度的用水稀释获得的叶酸标准工作液,同时样品测试液也由水稀释获得,测得同一样品的叶酸质量分数为70.5μg/hg,回收率为92.6%。使用Biostest叶酸检测试剂盒测得同一样品的叶酸质量分数为73.71μg/hg,回收率为99%。不采用含抗坏血酸的磷酸缓冲液而是用水稀释获得标准工作液和样品测试液,测试婴幼儿乳制品叶酸含量,加标回收率较高,测试结果可以接受。     

ELISA方法检测牛奶中叶酸含量

探讨牛奶中叶酸检测的酶联免疫反应(Enzyme-Linked Immunosorbent Assay,ELISA)方法建立及其叶酸本底含量测定。用竞争性酶联免疫,棋盘法确定最佳抗体包被条件、封闭条件、酶标抗原浓度等,并进行性能评价测定,检测80例牛奶样品中的叶酸本底含量。结果表明:1最佳ELISA条件为:叶酸抗体以2μg/m L浓度,碳酸盐缓冲液4℃过夜包被,用1%牛血清白蛋白(BSA)封闭,叶酸-辣根过氧化物酶标记物(叶酸-HRP)工作浓度1μg/m L。2该方法最低检测限2.22 ng/m L;精密度测试CV5%;特异性检测与叶酸类似物的交叉反应率均≤0.1%;本方法与对照方法具有良好的样本测值相关性(r=0.960,P0.05);该方法加标回收率在94.50%~108.00%之间,回收效果良好;样品基质效应对该方法测值无显著影响。3牛奶样本叶酸本底含量范围为12.55 ng/m L~68.72 ng/m L,均值37.93 ng/m L。本研究建立的ELISA方法能够满足牛奶样品中叶酸含量的检测。     

叶酸代谢抑制剂对小鼠骨髓基质细胞增殖和分化的影响

采用四甲基偶氮唑蓝（methyl thiazolyl tetrazolium,MTT）法、细胞形态分析法及诱导分化法结合油红O染色法研究叶酸代谢中二氢叶酸还原酶抑制剂甲氨喋呤（methotrexate,MTX）、甲氨苄啶（trimethoprim,TMP）和乙胺嘧啶（pyrimethamine,PTM）对OP9小鼠骨髓基质细胞增殖和分化的影响,探讨叶酸代谢与脂质合成的关系。MTT实验结果显示,在一定浓度范围内,3 种叶酸抑制剂均能抑制OP9细胞增殖,并呈现一定的剂量-效应依赖关系。且3 种叶酸抑制剂在高浓度时对OP9细胞有毒性作用。倒置显微镜观察和油红O染色检测结果显示,TMP在500～1 000 μmol/L浓度范围内对OP9细胞分化为脂肪细胞具有抑制作用。荧光定量聚合酶链式反应分析表明,TMP会使叶酸代谢途径中二氢叶酸还原酶和亚甲基四氢叶酸脱氢酶的转录水平发生下调,这可能是TMP抑制脂肪细胞诱导分化的原因。     

抗坏血酸浸渍后草莓中天然叶酸稳定性的变化

为研究抗坏血酸（Ascorbic Acid,AsA）浸渍后草莓中叶酸稳定性的变化,该研究采用真空（0.09 MPa）和常压两种方式浸渍AsA,对比浸渍速率以及浸渍后中天然叶酸的稳定性及草莓的新鲜度。同时探讨真空浸渍AsA的草莓在8 d冷藏过程中,天然叶酸的含量及质构的变化。结果表明,真空浸渍AsA的传质速率更快（k2=0.01）,浓度更高（1.24 mg/g）。草莓中总叶酸含量为100~128 μg/100 g,主要叶酸种类为5-甲基四氢叶酸、四氢叶酸、5,10-亚甲基四氢叶酸及叶酸降解产物或合成底物对氨基苯甲酸。草莓经8 d冷藏后,真空浸渍组和对照组的四氢叶酸分别下降了7.70%和42.51%,对氨基苯甲酸分别上升了57.13%和77.89%,5,10-亚甲基四氢叶酸均未出现显著性变化（p>0.05）,5-甲基四氢叶酸在第4天分别上升了24.47%和12.67%。质构结果表明,第8天时,真空浸渍组硬度（92.60 N）明显高于对照组（57.20 N）。因此,真空浸渍AsA处理可以抑制四氢叶酸降解（p<0.05）,从而提高叶酸在冷藏中的稳定性,保护草莓的质地。该研究为提高草莓叶酸稳定性提供了理论依据和参考。     

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.