冰温贮藏过程中蟹味菇几种营养成分变化的动力学特征

为研究冰温贮藏减缓蟹味菇营养成分降解的机理,以采后蟹味菇为试材,基于反应动力学理论研究了25℃、15℃、4℃及-0.5℃4个贮藏条件下蟹味菇抗坏血酸、可溶性糖和可溶性蛋白质等3种营养成分的降解表观动力学及热力学特征。结果表明,蟹味菇抗坏血酸、可溶性糖和可溶性蛋白质的降解均符合一级动力学反应模型,降解活化能分别为81.51 kJ/mol、83.88 kJ/mol、100.52kJ/mol;冰温贮藏条件下3种营养成分的降解半衰期、分子有效碰撞百分比、降解活化焓、降解活化自由能均高于其他温度处理组;降解过渡态平衡常数K≠均小于其他温度处理组。此外,可溶性蛋白质的降解活化熵及位阻因素为4℃贮藏时最大,而抗坏血酸及可溶性糖的降解活化熵和位阻因素则为冰温贮藏时最大。故,冰温贮藏改变了蟹味菇营养成分降解的动力学及热力学特性,从而表现为其减缓了蟹味菇营养成分的降解。     

黄金芽茶鲜叶加工过程中色泽变化及内在原因分析

探究黄金芽茶鲜叶加工过程中的色泽变化及其内在原因,以期为黄金芽及此类白化茶树品种鲜叶的加工生产提供一定理论指导。以常规茶树品种鸠坑作为对照,分析黄金芽鲜叶在受热加工过程中外观色泽和内在呈色物质含量的变化,采用UPLC法分析叶黄素、β-胡萝卜素、叶绿素a、叶绿素b、脱镁叶绿素a及脱镁叶绿素b等6种脂溶性色素含量。研究结果表明,黄金芽鲜叶杀青后外观颜色由黄变绿,色差a*值由正值(红色)变为负值(绿色),以叶黄素为代表的黄色素含量显著降低,导致绿色素与黄色素含量比值显著上升,呈现鲜绿色;而后续的闷黄工序可使茶叶外观色泽恢复黄色,原因在于闷黄可使茶叶中的叶绿素a/b含量显著下降,绿色素与黄色素含量比值显著降低,使得闷黄后的成品茶外观色泽和色素含量均与鲜叶更为接近,黄金芽鲜叶的色泽优势由此得以凸显。     

贮藏温度对红肉脐橙(Citrus sinensis Osbeck)果实类胡萝卜素含量的影响

研究贮藏温度(20℃和4℃)对红肉脐橙(C.sinensis Osbeck)果实类胡萝卜素含量的影响。结果表明:贮藏温度对红肉脐橙果皮和果肉类胡萝卜素含量的影响存在明显组织特异性。常温(20℃)对红肉脐橙果皮着色的积极作用只维持在贮藏的前5周,随着贮藏时间延长,果皮总类胡萝卜素含量基本保持不变;低温(4℃)能基本保持贮藏初期果皮类胡萝卜素含量,但含量低于常温贮藏。除贮藏10周时β-胡萝卜素、叶黄素、α-隐黄素含量有一个小幅增加外,常温对红肉脐橙果肉类胡萝卜素总体影响不大;低温贮藏的红肉脐橙果肉类胡萝卜素含量于采后1周达到峰值,随后含量基本保持稳定。     

成熟期温度对烟叶质体色素积累及香气成分的影响

为明确成熟期温度对烟叶品质风格的影响机制,以烟草品种K326为材料,采用盆栽试验在烟株打顶后将其分别转移至日均温度28.1℃和22.8℃的人工气候室中控温培养,在培养30 d后对中部叶片细胞结构、色素积累及烟叶香气成分进行分析。叶片超微结构观察结果显示,在烟叶成熟期高温条件下,叶片细胞核降解程度提高,淀粉粒含量(质量分数)丰富,嗜锇颗粒数量多、体积较大,叶绿体降解充分,类囊体片层不完整。LC/MS分析表明,成熟期高温处理的叶片中质体色素,包括β-胡萝卜素、新黄质、紫黄质、叶黄素、叶绿素a、叶绿素b等含量(质量分数)均低于低温处理的叶片。而在烤后烟叶中类胡萝卜素降解产物芳樟醇、异佛尔酮、β-二氢大马酮、二氢猕猴桃内酯、巨豆三烯酮4、法尼基丙酮、螺岩兰草酮等,叶绿素降解产物新植二烯含量显著高于低温处理的叶片。因此,烟叶成熟期高温促进了叶片细胞结构的降解和内含物质的积累,有利于质体色素降解和香气物质的生成,对烟叶品质和风格具有较大影响。     

冰温贮藏对生菜抗氧化能力及贮藏效果的影响

探讨冰温技术对生菜的贮藏效果以及对其抗氧化能力的影响,以采后生菜为试材,4 ℃预冷8 h后装入微孔聚乙烯保鲜袋中,置于温度为（－0.5±0.2）℃的冷库贮藏。贮藏过程中,每3 d测定生菜的抗氧化酶活性、抗氧化物质含量、H2O2含量、O2－•生成速率、丙二醛含量、细胞膜透性、呼吸速率、质量损失率以及叶绿素含量。结果表明：与传统冷藏相比,冰温贮藏显著抑制了生菜呼吸速率;降低了质量损失率;延缓了叶绿素含量的下降速度,并诱导H2O2含量增加,提高了抗氧化酶过氧化氢酶（CAT）、抗坏血酸过氧化物酶（APX）的活性,减缓了抗氧化物质抗坏血酸含量的下降速率;降低了O2－•生成速率;减缓了细胞膜脂质过氧化损害过程,延缓了丙二醛的积累速度。冰温贮藏可能通过抑制生菜自身代谢提高了生菜抗氧化能力,改善了生菜贮藏保鲜效果。     

2,4-表油菜素内酯处理对不同温度贮藏中小白菜品质和生理生化的影响

以'上海青'小白菜为试验材料,采用1.0 mg/L的2,4-表油菜素内酯(2,4-epibrassinolide,EBR)溶液进行采后喷洒处理,分别于2℃和20℃下贮藏,研究EBR处理对贮藏期间小白菜品质和生理生化的影响.结果显示,EBR处理能抑制2℃和20℃贮藏期间小白菜的L*上升和色调角H下降,减缓总叶绿素、叶绿素...     

食用植物油脂精炼过程中色素的定量分析

摘要：以精炼各工段大豆油、玉米油、菜籽油为原料,通过定量检测其中4种天然色素（β-胡萝卜素、叶黄素、玉米黄质及叶绿素）的含量,考察不同种类食用植物油脂的色素组成及在精炼各工段的含量范围,研究精炼过程中各色素的变化趋势。结果表明：原油中色素总量大小排序为菜籽油＞玉米油＞大豆油,3种植物油脂中色素组成也不相同。在中和工段,菜籽油中叶黄素、玉米油中叶绿素衰变较明显,其他色素衰变不明显;各色素在脱色工段衰变较为明显;脱臭工段叶绿素总去除率分别为大豆油85.7%～98.7%、菜籽油97.9%～99.9%、玉米油92.3%～98.9%,而脱臭油中β-胡萝卜素、叶黄素、玉米黄质含量均低于检出限。食用植物油脂精炼过程色素的定量分析,可以为植物油脂适度精炼及精准加工提供可靠的评估方式。     

低温贮藏和短波紫外线辐照对芥蓝采后叶绿素降解及脱镁叶绿素酶活性的影响

采后叶绿素降解造成绿叶蔬菜失绿,直接影响产品的感官品质和货架寿命.以研究芥蓝采后叶绿素降解和脱镁叶绿素酶(PPH)之间的关系为目的,考察了温度以及短波紫外线(uv-C)辐照对贮藏过程中芥蓝叶绿素含量及脱镁叶绿素酶活性变化的影响.结果表明常温22℃贮藏时,PPH活性在前期快速上升,第3d时约为第0d的200％,而在低温4℃时酶活仅为第0d的135％,第3d时叶绿素a的含量是常温时的2.8倍;UV-C辐照降低了PPH活性,第1dPPH酶活仅上升14％,而对照则上升50％,第5d时叶绿素a的含量是对照的1.3倍.因此低温和UV-C辐照抑制了贮藏过程中PPH酶活性的快速上升,从而降低了叶绿素降解的速度.     

6-BA、GA_3结合果蜡复合涂膜对槟榔果实失水和色泽的影响及其机理

以海南产新鲜槟榔为研究对象,研究了100 mg/L 6-BA+100 mg/L GA3+50%果蜡复合涂膜对采后槟榔鲜果在(25±0.5)℃和(7±0.5)℃条件下失水和色泽变化的影响及其机理。贮藏至21 d,低温结合涂膜处理的槟榔失重率为2.51%、电导率为15.09%、丙二醛为13.1%,含量均显著低于其他处理组(p0.05);贮藏至21 d,通过电镜观察,低温结合涂膜处理的槟榔组织结构保持平滑状态、没有破损,明显优于其他处理组,而且该组的槟榔果实表皮叶绿素含量最高、胡萝卜素含量最低、叶绿素酶活性最低。结果表明复配涂膜配合低温贮藏能有效抑制丙二醛的生成,维持细胞膜的完整性,降低了叶绿素酶对叶绿素的催化分解以及减缓了胡萝卜素的生成,相比常温贮藏和未涂膜处理可以更有效地降低槟榔果实失水,增加槟榔表皮叶绿素的积累,延缓槟榔果实黄化劣变。     

贮藏条件对超高压处理蓝莓汁酚类物质及抗氧化活性的影响

以经超高压处理（400MPa／IOmin）的鲜榨蓝莓汁为对象,研究其5周内在4℃、25℃、37℃贮藏条件下总酚、总黄酮、花色苷含量和抗氧化能力的变化。结果表明：随贮藏时间的延长,在以上三个贮藏温度下,总酚含量和抗氧化能力均呈显著下降趋势（p〈0．05）,总黄酮含量无显著变化,花色苷含量显著下降（p〈0．05）,且其降解过程符合一级反应动力学模型,其反应的活化能Ea为55．75kJ／mol;抗氧化能力与总酚和花色苷含量显著相关。4℃贮藏条件下抗氧化能力与总黄酮含量无显著相关,25℃、37℃下则呈负相关。此外颜色分析显示不同储藏温度下蓝莓汁a·值、b＋值、C值随贮藏时间的延长上升,L＋值下降,37℃下贮藏4周后蓝莓汁的色差△E〉2,已对其感官质量造成影响。由此表明低温短时贮藏有利于保特蓝莓汁中酚类物质含量及抗氧化活性。     

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.     

Chlorohydrins of bisphenol A diglycidyl ether (BADGE) and of bisphenol F diglycidyl ether (BFDGE) in canned foods and ready-to-drink coffees from the Japanese market

BADGE.2HCl and BFDGE.2HCl were determined in 28 samples of ready-to-drink canned coffee and 18 samples of canned vegetables (10 corn, 5 tomatoes and 3 others), all from the Japanese market. HPLC was used as the principal analytical method and GCMS for confirmation of relevant LC fractions. BADGE.2HCl was found to be present in one canned coffee and five samples of corn, BFDGE.2HCl in four samples of canned tomatoes and in one canned corn. No sample was found which exceeded the 1mg/kg limit of the EU for the BADGE chlorohydrins. However the highest concentration was found for the sum of BFDGE.2HCl and BFDGE.HCl.H₂O at a level of 1.5mg/kg. A Beilstein test confirmed that all cans containing foods contaminated with BADGE.2HCl or BFDGE.2HCl had at lest one part coated with a PVC organosol.     

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.     

European priorities for research to support legislation in the area of food contact materials and articles

A strong science base is required to underpin the planning and decision-making process involved in determining future European community legislation on materials and articles in contact with food. Significant progress has been made in the past 5 years in European funded work in this area, with many developments contributing to a much better understanding of the migration process, and better and simpler approaches to food control. In this paper this progress is reviewed against previously identified work-areas (identified in 1994) and conclusions are reached about future requirements for R&D to support legislation on food contact materials and articles over the next 5 or so years.     

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.