基于响应面分析法对烟叶中果胶测定方法的优化

为了对酶解-连续流动法测定烟叶中果胶含量的方法进行优化,采用Box-Benhnken实验设计及响应面分析法对酶解过程中的酶解温度、酶解时间和缓冲液pH值进行优化。结果显示,酶解温度对果胶测定影响最大,缓冲液pH次之,酶解时间影响最小,且最优酶解条件为酶解时间1.9 h、酶解温度56 ℃、缓冲液pH 3.8;在此条件下,果胶具有良好的线性关系(R²=0.999),加标回收率在99.2%~100.9%,相对标准偏差RSD(n=6)<3%;说明Box-Behnken设计结合响应面分析法优化所得的果胶测定方法具有较好的精密度及准确度,适用于烟叶中果胶含量的批量测定。     

流动分析法测定烟草中的纤维素

建立了测定烟草中纤维素含量的流动分析法。采用纤维素酶酶解烟草中的纤维素,利用流动分析仪测定水解液中的葡萄糖。结果表明:①最优酶解条件为:烟粉0.25 g,缓冲溶液60 mL,酶用量0.25 g,水解温度37℃,水解时间24 h;②方法的相对标准偏差(RSD)为2.40%,回收率为96.7%～103.8%,检测限为0.11 mg/mL。该方法适合于烟草中纤维素含量的测定。     

柠檬酸-纤维素酶法提取塔罗科血橙皮中的果胶

以塔罗科血橙皮为原料,采用柠檬酸-纤维素酶法提取了其中的果胶。探索了料液比、酶用量、酶解时间、酶解p H、酶解温度、酸提取p H、提取温度、提取时间等因素对果胶产率的影响。以正交优化建立了纤维素酶法提取果胶的最优条件:料液比为1︰40(g/m L)、酶用量为9 U/m L、酶解时间为45 min、酶解温度为35℃。在最优提取条件下果胶产率29.97%,总半乳糖醛酸含量为79.77%,酯化度为72.29%,含水率为8.37%。研究结果对塔罗科血橙废弃物的综合利用具有一定的参考意义。     

纤维素酶促进菠萝皮果胶提取的研究

为了促进菠萝皮中果胶的提取,采用了纤维素酶处理菠萝皮的酸解液,对此工艺条件进行了初步研究。通过实验,确定了最佳的酶解工艺条件:酶解温度为55℃,酶解pH为pH 4.2,纤维素酶的适宜用量为15.5 U/ml,酶解时间为140min。在此条件下,酶解液中果胶含量达到7.4g/L,比菠萝皮酸解液的果胶含量提高了40.7%。     

酶解-流动分析法测定烟草中果胶前处理方法的改进

为提高烟草中果胶的分析速度,对酶解流动分析法中烟叶的前处理过程进行了改进,即用5%醋酸溶液萃取代替80%乙醇溶液回流抽提除去烟末中的水溶性糖,并采用两种方法同时测定了20个烤烟烟叶样品中的果胶含量.结果表明:①改进法果胶的回收率为99.5%～105.7%,变异系数2.08%;②改进法的检测结果稍高于原方法,但二者没有显著性差异.     

不同提取方法对黄秋葵果胶含量和结构特性的影响

本研究探讨了酸水热提、酶解、超声及酶解-超声四种提取方法对黄秋葵果胶含量及其结构特性的影响。酸水热提及酶解-超声联合法对黄秋葵果胶提取效果优于酶解和超声法;当干秋葵加入20倍pH 3 HCl水溶液,以70℃浸提1h(酸水热提法)或添加3‰果胶酶、50℃酶解90min后置于200W超声波处理10min(酶解-超声法)时,其果胶平均含量(以半乳糖醛酸质量分数计)达到43.61g/kg及32.59g/kg。四种提取方法所制果胶均为吡喃糖构型,但酸水热提及酶解法制备果胶的酯键易发生降解,其在1725cm~(-1)红外吸收峰有变弱甚至消失趋势;而超声或酶解-超声法处理则促进了果胶分子链断裂,其平均分子量由酸水热提法下533ku分别降至420～467ku、319ku。研究结果表明:采用酸水热提法(pH 3、70℃)制备黄秋葵果胶,其果胶得率高、分子量分布集中、外观呈片状且排列致密。本研究结果为高品质秋葵果胶的制备奠定基础。     

南瓜果胶不同提取方法的研究

以南瓜果肉为材料,采用咔唑比色的方法,通过正交试验,分别研究超声波法、纤维素酶法和离子交换树脂法提取南瓜果胶的最佳提取条件。结果表明：超声波法的最佳提取工艺条件为：超声波功率400W,时间35min,液料比10:1(ml/g),果胶得率5.98%;纤维素酶法提取果胶的最佳工艺条件为：酶解时间2.0h,pH4.5,酶解温度55℃,加酶量0.5%,果胶得率9.56%;离子交换树脂法提取果胶的最佳工艺条件为：树脂用量15%,料液比为1:20(g/ml),pH2.5,时间2.0h,温度80℃,果胶得率7.62%。三种提取方法进行比较,纤维素酶法果胶得率最高,为南瓜果胶的最佳提取工艺。     

山楂原液果胶酶解工艺

为改良山楂原液果胶的酶解效果,以山楂原液果胶脱除率为响应值,从四种商品酶中筛选出果胶去除率最高的Pectinex Yield MASH果胶酶。在单因素试验的基础上,对加酶量、酶解时间、酶解温度三个影响因素进行响应面优化。结果表明:山楂原液果胶最佳酶解工艺为加酶量12 U、酶解时间52 min、酶解温度45℃,在此条件下的果胶脱除率实际测定值为90.58%,与理论预测值90.18%接近,为山楂及其他水果高附加值产品生产工艺中果胶的脱除方法提供了科学的理论依据。     

再造烟叶中果胶降解条件优化及其应用研究

为降低造纸法再造烟叶中的果胶质含量(质量分数),以造纸法再造烟叶工艺生产线上经解纤和浸提处理的梗末混合物为研究对象,通过单因素及正交试验对黑曲霉产果胶酶降解的果胶工艺条件进行优化;采用在线裂解—气相色谱/质谱法(PY—GC/MS)对酶解前后样品的热裂解产物进行分析,采用硅烷化—GC/MS法分析果胶质酶解前后的单糖组成,并将处理前后的样品添加至卷烟中进行感官评价。结果表明:果胶降解最佳反应条件为酶活力3 700U/mL、料液比1∶1(m∶V)、酶解温度50℃、酶解时间1.5h,在该条件下果胶质降解率为32.47%;酶解后,样品果胶单糖组成中葡萄糖及半乳糖醛酸的含量降低。样品裂解产物的组成及含量有明显变化,酚类物质总量由(3.00±0.16)%降低至(2.46±0.11)%,醛酮类、醇类香味物质总量也有所降低,但杂环类、酯类香味物质总量增加;将酶解后的样品添加于卷烟后,卷烟烟气变得柔和,透发性好,刺激性降低,余味纯净舒适,但香气量及劲头略有不足。     

连续流动分析仪快速测定甘蔗植株全氮、全磷含量

为快速、准确测定甘蔗植株全氮、全磷含量,采用对比法,探讨连续流动分析仪测定甘蔗植株全氮、全磷含量的适用性和稳定性。结果表明,连续流动仪测定全氮、全磷标准溶液线性良好,相关系数(R2)均达0.9998以上;检出限均为0.01 mg/L,标准偏差分别在0.48%~0.68%、0.23%~0.63%之间,加标回收率分别为93.00%~106.44%、93.33%~109.00%;与常规法相比,利用连续流动分析仪测定甘蔗植株全氮、全磷含量的结果均在允许偏差范围内,说明利用连续流动分析仪快速测定甘蔗植株全氮、全磷是可行的。     

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.