奶酪中挥发性硫化物的风味贡献、检测方法及其生物合成调控的研究进展

奶酪中的硫化物主要包括甲硫醇、硫化氢、二甲基硫醚、二甲基二硫醚、甲硫基丙醛等,是奶酪关键气味物质之一,对于奶酪整体风味的形成有着重要贡献。本文在查阅相关文献的基础上,对常见奶酪中硫化物的组成、香气贡献进行了系统的综述,介绍了奶酪中测定硫化物的常用方法及其优缺点;总结了奶酪中硫化物的形成机理以及研究者们提出的生物合成调控策略,包括菌种筛选、微生物搭配组合、基因工程技术。最后对当前研究中存在的问题以及未来研究方向做了归纳与展望。为全面认知奶酪中硫化物风味及其形成和调控,开发更适合国人口味的奶酪产品和中国奶酪产业的转型升级提供理论参考。     

油桃采后衰老与病害发生中挥发性物质变化的主成分分析

采用固相微萃取与气相色谱-质谱联用技术,对油桃果实采后衰老与褐腐病害发生中近表皮和近果核的挥发性物质进行测定;用主成分分析(PCA)法研究不同样品挥发物谱的差异并对香气品质进行综合评价.结果表明,共检测到油桃果实挥发性物质14种,主要为C6化合物、酯类和内酯类物质.贮藏期间油桃果实挥发性物质逐渐由近果核处转向近表皮,褐腐病害发生后加速了这种转变.PCA结果表明,5-羟基-2,4-癸二烯酸-γ-内酯、γ-癸内酯、δ-辛内酯和乙醇可作为区分油桃果实贮藏4d时衰老与病害发生的标志性挥发物;C6醛类、乙醇和乙酸乙酯则可作为区分油桃果实贮藏0、2d与贮藏4、6d时的标志性挥发物.病害组贮藏2d后近表皮处香气品质最佳,贮藏4d后病害组香气品质远低于衰老组.     

板栗及其膨化制品的挥发性香气成分分析

采用顶空固相微萃取结合气相色谱-质谱联用技术对生板栗粉、煮板栗和3种膨化板栗制品的挥发性香气成分进行分离鉴定。共鉴定出68种挥发性物质,初步认定吡嗪类物质中的甲基吡嗪、2,3-二甲基吡嗪、2-乙基-6-甲基吡嗪、2,6-二甲基吡嗪;呋喃类物质中的2-戊基呋喃、γ-丁内酯、2-糠醇、2,5-二氢-3,5-二甲基-2-呋喃酮和γ-辛内酯及芳香族类物质中的苯甲醛是板栗的特征风味物质。煮制可提升板栗的香气。膨化板栗片的膨化加工方式对其香气成分影响显著,挤压膨化板栗片的香气物质组成和煮板栗比较相似,微波膨化板栗片中易产生具有枯焦气息的2,4-二叔丁基苯酚,油炸膨化板栗片的挥发性成分最复杂,醛类物质较多。     

不同凝乳方式加工的硬质奶酪特性分析

通过比较酶凝法、盐析法、酸凝法和内酯凝法的凝乳作用,分析不同凝固方式加工的硬质奶酪工艺特点和品质差异;通过不同凝乳方式加工的奶酪水分测定表明,酶凝法和内酯法得到的凝乳持水性较好,但内酯法凝乳过程中需再次对牛奶进行高温加热,不利于奶酪的正常色泽呈现;盐析法获得的奶酪质地紧实,含水率最低;通过黏度测试可知,酶凝法和酸凝法所得凝乳黏度较低,所需的凝乳时间相对较长;结合电子鼻技术对4种不同凝乳方式的奶酪进行分析,结果显示,不同凝乳方式加工的奶酪香气成分差异较大,香气成分的构成和比例均有较大不同。     

SPME-GC-MS和GC-O鉴定3种不同生产工艺马苏里拉奶酪的特征香气物质

利用固相微萃取-气相色谱-质谱联用法对3种不同工艺制备的马苏里拉奶酪中挥发性风味组分进行鉴定。利用气相色谱嗅觉测量技术进行嗅闻分析,共得到109种化合物进行半定量分析,并且结合香气活力值进行主成分分析,结果表明:新鲜水牛奶马苏里拉奶酪的主要挥发性风味物质为己醛、庚醛、己酸乙酯、(E)-2-壬烯醛、糠醛和丁酸乙酯;新鲜牛奶马苏里拉奶酪的主要挥发性风味物质为1-辛烯-3-醇、2-十一酮和δ-十二内酯;半硬质牛奶马苏里拉奶酪的主要挥发性风味物质为正癸酸、苯乙醛和乙酸乙酯。主成分分析检测结果能将这6种马苏里拉奶酪分为三大类,说明这些挥发性风味物质能很好地描述不同类别奶酪的风味差异。为马苏里拉奶酪的种类鉴别和水牛奶马苏里拉奶酪的掺假提供一定的理论指导。     

内源性脂肪酶对奶酪风味的作用及风味成分分析

研究了内源性脂肪酶对奶酪风味的影响,采用气相色谱-质谱法(GC-MS)对风味成分进行分析.利用电子鼻分析添加和未添加脂肪酶的奶酪的香气组成,利用主成分分析(PCA)和统计质量控制分析(SQC)多元统计方法对电子鼻传感器响应值进行数据分析.结果表明,添加内源性脂肪酶后,奶酪中酸、酯(十四酸乙酯除外)等挥发性成分物质增加,奶酪风味得到很好的改善.     

刺梨皮渣和籽仁中游离态和键合态香气物质的比较

采用顶空-固相微萃取法提取刺梨皮渣、籽仁中游离态香气物质和酶法释放刺梨皮渣、籽仁中键合态香气物质,结合气相色谱-质谱法分析技术对刺梨皮渣和籽仁中的游离态和键合态香气物质进行定性和定量研究。结果表明,检出的刺梨皮渣中游离态香气物质有21 种,萜烯类物质最丰富,其次是酯类物质和酮类物质;检出的键合态香气物质有23 种,其中酸类物质最为丰富,其次是酚类物质和醇类物质。皮渣中游离态和键合态香气物质有很大差异,只有辛酸1 种物质都以游离态和键合态的形式存在。刺梨籽仁中检出游离态香气物质有9 种,萜烯类物质最为丰富,其次是醇类物质和酚类物质;检出的键合态香气物质有18 种,包括酸类8 种、酚类3 种、醇类3 种、羟基醛类2 种,羟基酯类和羟基酮类各1 种。籽仁中被释放出来的香兰素（3-甲氧基-4-羟基苯甲醛）和异香草醛（3-羟基-4-甲氧基苯甲醛）2 种羟基醛是重要的键合态香气物质。     

内酯类化合物在食品中的风味贡献及形成机制

食品中的内酯类物质主要包括γ-内酯、δ-内酯、葫芦巴内酯、威士忌内酯,它们对食品整体风味的形成具有重要作用,能赋予食品奶香、水果香、坚果香、焦糖香等优良的风味特征,研究食品中内酯类化合物的风味贡献及形成机制具有重要意义。该研究综述了食品中常见的内酯类化合物,食品中内酯类化合物的组成及香气贡献,总结了对食品风味贡献较大的内酯类化合物的形成机制包括：δ-内酯和γ-内酯的羟基脂肪酸-内酯生成途径、一步分子内酯交换反应途径、葫芦巴内酯的羟醛缩合反应途径、果实中脂肪酸-酰基CoA-内酯形成途径、果实中不饱和脂肪酸-羟基脂肪酸-内酯形成途径等,并对当前研究中存在的问题和未来研究方向做了归纳与展望。为全面认知食品中内酯类风味化合物及其形成,改善食品风味并提高食品品质,实现食品产业转型和升级提供理论参考。     

SPME Arrow-GC-MS鉴定3种不同杀菌乳中特征香气物质

利用新型箭型固相微萃取-气相色谱-质谱联用法（Solid-phase Microextraction Arrow-Gas chromatography-Mass spectrometry,SPME Arrow-GC-MS）对3类杀菌乳中挥发性风味组分进行研究,并结合香气活性值（odor activity values,OAV）与热图分析进一步探究3种杀菌方法对牛乳中特征香气物质的影响情况。3类杀菌乳中共检测到78种挥发性风味物质,其中脂肪酸类11种、酯类4种、内酯类7种、酮类12种、醛类18种、醇类14种、含硫化合物2种、芳香及杂环类化合物10种。对萃取到的风味组分进行热图分析,结果表明：不同杀菌乳中特征香气物质存在明显差异,其中巴氏杀菌乳中特征香气物质是辛醛和壬醛;UHT灭菌乳中特征香气物质是γ-十二内酯、顺式-4-羟基-6-十二烯酸内酯、2-壬酮、2-十一酮以及辛醛、壬醛;INF杀菌乳中则是1-辛烯-3-酮和壬醛。     

不同成熟时间切达奶酪中挥发性香气成分及其电子鼻判别分析

采用溶剂辅助风味蒸发法和固相微萃取法,结合气相色谱-质谱联用与电子鼻判别技术,对3种不同成熟时间的切达奶酪中挥发性风味成分进行鉴定及判别分析。结果表明:3种不同成熟时间的切达奶酪样品中共检测出78种化合物,脂肪酸类13种、酯类9种、内酯类8种、酮类9种、醇类5种、醛类12种、芳香及杂环类19种、含硫化合物3种。对3种奶酪风味组分主成分分析结果表明,淡味切达奶酪中主要挥发性化合物是脂肪酸类、甲基酮及杂环类;中味切达奶酪中主要挥发性物质有脂肪酸类、甲基酮及内酯类;浓味切达奶酪主要挥发性物质有脂肪酸类、酯类、甲基酮及内酯类;并且这3种不同成熟度的切达奶酪在电子鼻上也可以得到很好的区分。     

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.