高效液相色谱串联质谱法测定酱油中水解氨基酸

建立了高效液相色谱串联质谱(HPLC-MS/MS)法测定天然酿造酱油原油(FSS)和酸水解植物蛋白调味液(HVP)中多肽的水解氨基酸的组成的方法。FSS多肽总量约是HVP的10倍,其中FSS中多肽的总量为2378.76mg/L,HVP中多肽的总量为247.57mg/L。天然发酵酱油原油中赖氨酸在多肽中的含量21倍高于酸水解植物蛋白液。FSS多肽中赖氨酸、组氨酸、酪氨酸相对百分含量约是HVP的2倍,HVP中丙氨酸、脯氨酸相对百分含量约是FSS的2倍。该研究为鉴别天然酿造酱油与酸水解酱油提供依据。     

应用固定化胰蛋白酶制备大豆肽的研究

采用固定化胰蛋白酶水解大豆分离蛋白制备大豆低肽，对固定化胰蛋白酶水解工艺参数等进行了系统研究。结果表明：固定化胰蛋白酶的最适温度为60℃，最适pH为8．7，最佳底物浓度为2．0－3．0mg/mL，大豆分离蛋白的最佳流速为0．3mL/min，大豆分离蛋白的水解率达到45．6％，酶解液中大豆肽含量为1．462mg/mL。酶解液多肽分子量大部分在10000以下。     

双酶分步水解牛骨蛋白工艺的优化

以新鲜牛骨为原料,探讨牛骨粉的制备工艺。选用枯草杆菌中性蛋白酶与胰蛋白酶分步水解牛骨蛋白,以水解度为特征性指标,采用L9(34)正交试验设计优化双酶水解牛骨粉的工艺条件。结果表明：牛骨粉蛋白质含量高达30.72%,约为鲜骨蛋白质含量的3倍;采用胰蛋白酶先水解,中性蛋白酶后水解的方式分步水解牛骨蛋白,其效果优于两种酶同时水解及中性蛋白酶先水解,胰蛋白酶后水解;中性蛋白酶与胰蛋白酶分步水解牛骨蛋白的最佳工艺条件：固液比1:2,起始pH8.0,胰蛋白酶2000U/g蛋白质于45℃、150r/min振荡水解3h,然后用中性蛋白酶2000U/g蛋白质于45℃以150r/min振荡水解3h,水解度达18.34%;粒径小的活性炭对酶解液脱苦、脱色及除腥效果优于粒径大的活性炭。     

鱼露制品的研究开发

以市售鲫鱼为原料，经过前处理，应用正交试验法，并以酶解液中氨基氮的含量为指标，比较了中性蛋白酶、胰蛋白酶和木瓜蛋白酶的水解效果，并确定了它们的最佳作用条件。结果表明：胰蛋白酶是三种酶单独水解效果最好的，但酶解液透明度不够。考虑到鱼露制品澄清度的要求，决定使用胰酶和木瓜酶复合水解，并确定了复合酶的最佳作用条件如下：在温度50℃时，控制固液比为1：1，初始PH=7，先加1.5％（E：S）的胰蛋白酶作用6h，再加入2％（E：S）的木瓜蛋白酶作用2h。然后，经离心得到的酶解液晶莹剔透，通过后续步骤得到的成品鱼露，各项指标均达到国标要求，有效地缩短了生产周期，而且低盐、风味浓郁、色泽棕黄，得到了广泛的好评。     

水解大豆制备食用香精的工艺优化

以大豆为原料,通过酸解法制备植物水解蛋白(HVP),以HVP 为原料通过美拉德反应制取肉味香精。通过正交试验获得酸解大豆蛋白的最佳反应条件为水解时间7h、浓硫酸体积分数25%、固液比1:7(g/mL),此时蛋白水解度(DH)达65.26%。在此基础上研究美拉德反应的最佳工艺条件,正交试验结果表明：pH7.0、D- 木糖添加量0.4g/mL、L- 半胱氨酸盐酸盐添加量为0.05g/mL 时,获得的产物香味持久、浓郁。     

“水解植物蛋白液 葡萄糖”模型热反应中 3-氯-1,2-丙二醇的研究

通过设计“水解植物蛋白液 葡萄糖”模型热反应,考察了不同3-氯-1,2-丙二醇 (3-MCPD)含量的HVP液、葡萄糖用量、反应温度、反应时间等因素对热反应产物中 3-MCPD 含量的影响。结果表明：模型热反应产物中 3-MCPD 含量随着 HVP 液中 3-MCPD 的含量增加而增加;随着葡萄糖用量增加而减少;随着反应温度的升高,3-MCPD 的量先增加后减少;热反应时间越长,3-MCPD 的含量越高。     

乳蛋白水解产生肽工艺条件的优化

以肽含量为指标，确定了酶添加量及复合酶（胰凝乳蛋白酶、胰蛋白酶）的酶比，且分别考察了奶粉浓度、温度、pH、反应时间对酶解乳蛋白产生肽的影响。通过正交试验确定了复合酶酶解乳蛋白的最佳工艺条件：加酶量2500U/ml，胰凝乳蛋白酶：胰蛋白酶=1：3，奶粉浓度25%（W/V），温度45℃，pH8.0，水解时间2h。在此条件下，肽浓度可达1.82mg/ml。     

利用猪新鲜胰脏降解猪血蛋白的条件研究靠

研究了猪新鲜胰脏提取胰酶以及胰酶粗提液降解猪血蛋白获取蛋白水解液的条件。结果表明:加入提取溶剂乙醇和激活和稳定剂CaCl2能提高胰蛋白酶的得率。在E/S=6000U/ml加入胰酶、底物浓度8%、pH8.0条件下,45℃水解时间12h,猪血蛋白的水解率较高。     

固定化胰蛋白酶水解乌鸡肉制备功能肽的研究

以海藻酸钠为载体,戊二醛为交联剂固定化胰蛋白酶,考察胰蛋白酶的固定化工艺,固定化酶水解乌鸡肉的工艺条件及固定化酶的稳定性。结果表明：固定化胰蛋白酶的最佳条件为：海藻酸钠浓度4%、加酶量10%、pH7.5、温度70℃,酶活力回收率为38.84%;水解乌鸡肉的最佳条件为：固液比1:3(m/V)、pH7.5、加酶量10%、温度60℃,氨基氮含量最高为2.18mg/ml,固定化酶重复使用8 次,酶活力仍保持50% 以上。     

水解植物蛋白HVP的研制

以低配比(液∶料),低酸度盐酸催化,制备水解植物蛋白 HVP(Hydro lyzed Vege-table Protein)是一种新方法。HVP 含十七种混合氨基酸,总氮(TN)8%,氨基氮(AN),/TN70%左右;谷氨酸钠(MSG)/总氨基酸(TAA)20%,生物测试证实 HVP 无毒无害,它与小麦蛋白相混,蛋白质效价(PER)显著优于小麦蛋白。HVP 可以作为调味品和面食制品的风味和营养强化。本文着重介绍 HVP 工艺的选定和依据。     

Reliable identification of grapevine rootstock varieties using RAPD PCR on woody samples

Since grapevine ( Vitis spp .) rootstock material is being traded increasingly as disbudded woody material a lack of distinctive morphological features on such material necessitates an alternative and reliable means of identification. Methods described here were developed for rapid and efficient extraction of DNA from woody samples rich in phenolic compounds and polysaccharides, and for subsequent identification of varieties by RAPD PCR. Using these methods, and with the application of only one selected RAPD primer, we were able to differentiate sixteen rootstock varieties, including the seven varieties most commonly used in Germany. Problems commonly encountered with reproducibility of RAPD patterns were avoided by choosing primers with a dinucleotide sequence and a high G/C content that allowed a rather high annealing temperature of 45°C. Methods described here should also be useful for other horticultural crops, especially those with woody tissues rich in phenolic compounds and polysaccharides.     

An internet compendium of analytical methods and spectroscopic information for monomers and additives used in food packaging plastics

An internet website (http://cpf.jrc.it/smt/) has been produced as a means of dissemination of methods of analysis and supporting spectroscopic information on monomers and additives used for food contact materials (principally packaging). The site which is aimed primarily at assisting food control laboratories in the European Union contains analytical information on monomers, starting substances and additives used in the manufacture of plastics materials. A searchable index is provided giving PM and CAS numbers for each of 255 substances. For each substance a data sheet gives regulatory information, chemical structures, physico-chemical information and background information on the use of the substance in particular plastics, and the food packaging applications. For monomers and starting substances (155 compounds) the infra-red and mass spectra are provided, and for additives (100 compounds); additionally proton NMR are available for about 50% of the entries. Where analytical methods have been developed for determining these substances as residual amounts in plastics or as trace amounts in food simulants these methods are also on the website. All information is provided in portable document file (PDF) format which means that high quality copies can be readily printed, using freely available Adobe Acrobat Reader software. The website will in future be maintained and up-dated by the European Commission's Joint Research Centre (JRC) as new substances are authorized for use by the European Commission (DG-ENTR formerly DGIII). Where analytical laboratories (food control or other) require reference substances these can be obtained free-ofcharge from a reference collection housed at the JRC and maintained in conjunction with this website compendium.     

Aroma characterization of various apricot varieties using headspace–solid phase microextraction combined with gas chromatography–mass spectrometry and gas chromatography–olfactometry

The characterization of the aromatic profile of several apricot cultivars with molecular tracers in order to obtain objective data concerning the aromatic quality of this fruit was undertaken using headspace–solid phase microextraction (HS–SPME). Six apricot cultivars were selected according to their organoleptic characteristics: Iranien, Orangered, Goldrich, Hargrand, Rouge du Roussillon and A4025. The aromatic intensity of these varieties measured by HS–SPME–Olfactometry were defined and classified according to the presence and the intensity of grassy, fruity and apricot like notes. In the six varieties, 23 common volatile compounds were identified by HS–SPME–GC–MS. Finally, 10 compounds, ethyl acetate, hexyl acetate, limonene, β-cyclocitral, γ-decalactone, 6-methyl-5-hepten-2-one, linalool, β-ionone, menthone and (E)-hexen-2-al were recognized by HS–SPME–GC–O as responsible of the aromatic notes involved in apricot aroma and considered as molecular tracers of apricot aromatic quality which could be utilized to discriminate apricot varieties.     

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.     

Tests of potential functional barriers for laminated multilayer food packages. Part I: Low molecular weight permeants

The advent of the functional barrier concept in food packaging has brought with it a requirement for fast tests of permeation through potential barrier materials. In such tests it would be convenient for both foodstuffs and materials below the functional barrier (sub-barrier materials) to be represented by standard simulants. By means of inverse gas chromatography, liquid paraffin spiked with appropriate permeants was considered as a potential simulant of sub-barrier materials based on polypropylene (PP) or similar polyolefins. Experiments were performed to characterize the kinetics of the permeation of low molecular weight model permeants (octene, toluene and isopropanol) from liquid paraffin, through a surrogate potential functional barrier (25 μm-thick oriented PP) into the food simulants olive oil and 3% (w/v) acetic acid. These permeation results were interpreted in terms of three permeation kinetic models regarding the solubility of a particular model permeant in the post-barrier medium (i.e. the food simulant). The results obtained justify the development and evaluation of liquid sub-barrier simulants that would allow flexible yet rigorous testing of new laminated multilayer packaging materials.     

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.