乳脂制品和奶油——脂肪酸度的测定

<正> 1 范围 此方法适用于乳脂制品中脂肪酸度的测定。 2 参考标准 IDF 50B:1985——乳与乳制品-取样方法 IDF 68A:1977——无水乳脂肪、无水奶油、乳脂肪、半流体黄油——鉴别标准 FAO/WHO A-2:乳脂制品 ISO2446——乳-脂肪含量的测定(常规法)     

碱水解法测定乳及乳制品中脂肪的含量

目的建立简单、快速的碱水解法测定乳及乳制品中脂肪的含量。方法取0.5 g样品于离心管中,用10 mL纯水复溶后加入2 mL氨水(25%)水解并65℃水浴20 min。加入乙醇沉淀蛋白质并使用乙醚、石油醚提取样品中脂肪。将上清液提取至收集瓶中,蒸干提取液,称量收集瓶前后质量,计算样品中脂肪含量。结果此法测得样品脂肪含量为26.53 g/100 g,结果相对偏差为0.37%。测定值在质控样品值满意区间内,且符合国标规定的两次独立测定结果之差≤0.3 g/100 g的要求。结论本法测定乳及乳制品中脂肪的含量具有简便、快速、重现性好的优点,适合实验室日常样品测定及考核使用。     

乳及乳制品中脂肪含量测定方法的探究

GB 5009.6-2016《食品安全国家标准食品中脂肪的测定》中第三法碱水解法和第四法盖勃法比较适合乳及乳制品中脂肪含量的测定,其中碱水解法比较成熟,稳定性高,数据结果比较准确,适用范围广。与之相比,盖勃法检测快、成本低,适用于生产部门对产品的监控。这两种方法都有自己的优点和缺点,因此下面对于盖勃法和碱水解法的检测过程和数据结果进行分析,并提出改进意见。     

基于双波长紫外吸收的乳脂肪快速测定

为便于实施对乳品加工中乳品及管路残留乳脂肪含量的全面监控,建立一种基于双波长紫外吸收的乳脂肪快速定量方法。采用萃取-沉淀操作采集液态乳或加工管壁样本中的乳脂肪并直接测定204 nm和230 nm 2 个波长处的吸光度,再基于吸光度差ΔA204 nm－230 nm和乳脂肪标准曲线方程可确定样本中的乳脂肪含量。对于液态乳品样本,该方法的变异系数不大于3%,回收率在95.6%～102.9%之间,并可有效避免乳品热处理差异的干扰。此外,该方法也可成功用于不同加工条件下乳品加工管路中乳脂肪管壁残留量的测定。     

离子色谱法检测乳及乳制品中硝酸盐和亚硝酸盐方法的研究

目的改进国标法检测乳及乳制品中亚硝酸盐、硝酸盐的样品前处理方法。方法样品经乙腈沉淀脂肪蛋白质后,采用相应的方法提取和净化,以氢氧化钾溶液为淋洗液,阴离子交换柱分离,电导检测器检测。以保留时间定性,外标法定量。结果亚硝酸盐回收率80%~110%,硝酸盐回收率90%~110%,方法精密度在10%之内。结论本方法可提高检测准确性,缩小检测偏差,适合于乳及乳制品定量测定。     

乳与乳制品中锡质量浓度检测方法研究

针对锡器具乳与乳制品,建立相应的锡检测方法,为食品安全检测作检测依据。用微波消解处理乳与乳制品样品,原子荧光法测定锡;通过优化还原剂浓度、载流液等实验条件,能达到比较理想的检测乳与乳制品中锡的质量浓度。结果表明,在最优实验条件下,仪器的检出限为0.060μg/L;在0~200μg/L质量浓度范围中,锡的线性相关系数均大于0.999。采用锡标准溶液及不同种类样品进行了精密度测定,结果的相对标准偏差均小于10%,加标回收率在88.7%~115%之间,回收率的RSD皆小于10%。该方法切实可行、样品前处理简单、结果稳定性好,适用乳与乳制品中锡质量浓度的检测。     

含羧甲基纤维素钠的发酵乳中脂肪检测技术

目的:提高含有CMC-Na发酵乳中脂肪检测方法的准确性。方法:采用国家标准方法——碱水解法,对含有CMC-Na发酵乳中的脂肪进行测定;通过优化碱水解法中各关键参数、盐酸水解代替氨水水解以及碱水解法中加入金属离子等方式,探索适用于含有CMC-Na发酵乳中脂肪的检测技术。结果:① 随着CMC-Na添加量的增加,碱水解法测得含CMC-Na发酵乳中脂肪结果越低;② 碱水解法中氨水体积、水解时间、水解温度、提取次数4个关键条件的改变,并不会对含CMC-Na发酵乳中脂肪的测定产生有效影响;③ 采用2 mL盐酸水解代替氨水水解时,不同CMC-Na添加量(0.50%,0.75%,1.00%)的发酵乳中脂肪测定结果,与碱水解法测定不含CMC-Na发酵乳的结果基本一致;④ 碱水解法中加入金属离子Na⁺、K⁺、Ca²⁺时,Na⁺、K⁺的浓度越高,含CMC-Na发酵乳的脂肪测定结果越高,并在金属离子浓度达到0.5 mol/L 后达到正常值,而随Ca²⁺浓度的增加,脂肪测定结果先小幅提高后显著下降。结论:CMC-Na的添加会使得发酵乳中脂肪测定结果偏低,可采用盐酸水解或在碱水解法中加入Na⁺、K⁺,提高含有CMC-Na发酵乳中脂肪测定的准确性。     

碱解法测定乳与乳制品中L-羟脯氨酸的含量

目的 建立了使用聚四氟乙烯带盖水解管,以NaOH溶液为水解液的碱解法测定乳与乳制品中L-羟脯氨酸含量(L- Hydroxyproline, L-Hyp)。方法 将样品置于10 mL水解管中,加入6 mL 2.5 mol/L NaOH溶液在110℃烘箱中加热2小时,水解出的L-Hyp经氯胺T氧化后与与对二甲氨基苯甲醛反应生成红色络合物,在558 nm 处测定其吸光度。结果 在优化实验条件下,该方法的线性范围0-10 ug/mL（r=0.9993）,检出限 1.35 ug/g,样品测定的相对标准偏差在0.89%-2.5%,并成功应用于乳与乳制品样品的检测,加标回收率为90.5% - 98%。结论 相对酸解法,碱解法的水解效率和酸解法基本一致,样品前处理操作简单,缩短了测定时间,灵敏度、重复性和稳定性良好。     

乳品分析仪在乳及乳制品快速检测中的应用

由乳品分析仪对生鲜牛乳及发酵乳中的关键理化指标脂肪和蛋白进行检测,并与常规国标法检测结果进行比较,得出使用乳成分分析仪进行乳及乳制品理化指标快速分析时可以减少技术人员手工操作时间,提高工作效率。该方法具有快捷、简便的优点,日常通过国标法的校准监控,可以准确快速的进行乳及乳制品理化指标的检测。     

两种乳中脂肪球粒径、脂肪酶活性以及游离脂肪酸的比较分析

以萨能奶山羊乳和荷斯坦牛乳为研究对象,用罗兹哥特法和激光动态散射仪分别测定了两种乳的脂肪含量、脂肪球粒径大小以及分布;用脂肪酶活性的临床分析方法测定了脂蛋白脂肪酶在乳脂肪和脱脂乳中的分布;采用硅胶-氧化铝柱层析分离脂肪酸,用气相色谱质谱测定了两种乳中游离脂肪酸的种类及含量。结果表明:萨能奶山羊乳和荷斯坦牛乳中的脂肪含量分别为4.04、3.55 g/100 m L;平均脂肪粒径为3.46、3.16μm;脂肪球粒径与脂肪含量之间存在线性正相关关系。萨能奶山羊乳和荷斯坦牛乳脂蛋白脂肪酶的活性分别为229.62±9.31、(366.81±24.33)U/L,其中乳脂肪中脂蛋白脂肪酶的含量分别为51.35%、27.09%,脱脂乳中含量分别为48.65%、72.91%;萨能奶山羊乳和荷斯坦牛乳中总的游离脂肪酸分别为211.38、717.02 mg/kg;短链游离脂肪酸含量分别为205.51、20.05 mg/kg;其中辛酸和癸酸是影响萨能奶山羊乳风味的主效成分。     

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.     

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