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（400 MPa/10 min）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55.75 kJ/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ΔE>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持蓝莓汁中酚类物质含量及抗氧化活性。     

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。     

蓝莓汁抗坏血酸体系非酶褐变反应动力学

通过构建蓝莓汁抗坏血酸非酶褐变体系,测定蓝莓汁在贮藏（4、25 ℃和37 ℃）过程中的相关指标,并相应分别用零级、一级和复合动力学模型拟合。结果表明：褐变指数（A420 nm）符合复合动力学模型;贮藏过程中抗坏血酸不断降解,符合一级动力学模型;5-羟甲基糠醛含量的变化符合零级动力学模型。根据Arrhenius方程进行线性拟合,反映各指标随温度变化情况,在各贮藏温度下5-羟甲基糠醛的产生与褐变指数的变化呈现良好线性关系（R2≥0.949）。     

紫薯花色苷在贮藏过程中的降解特性

本研究通过高效液相色谱-串联质谱（high performance liquid chromatography-tandem mass spectrometry,HPLC-MS/MS）法分析鉴定‘鄂薯12号’紫薯的花色苷成分,采用pH示差法和HPLC法研究该紫薯花色苷提取液在4、20、35 ℃贮藏98 d期间总花色苷和各单体花色苷的变化规律,并在此基础上研究了花色苷的降解动力学以及褐变指数和聚合物颜色指数。结果表明：从‘鄂薯12号’紫薯提取物中鉴定出13 种花色苷,主要为矢车菊素-3-槐糖苷-5-葡糖苷和芍药素-3-槐糖苷-5-葡糖苷与对羟基苯甲酸、阿魏酸或咖啡酸形成的酰基化花色苷;贮藏期间总花色苷和各单体花色苷的含量呈下降趋势,花色苷的降解符合一级动力学模型;4、20 ℃和35 ℃贮藏条件下总花色苷半衰期分别为228.8、48.1 d和32.6 d;在相同糖苷配体情况下,矢车菊素类花色苷的半衰期要短于芍药素;在相同花色素配体情况下,酰基化花色苷的半衰期要长于未酰基化花色苷,且二酰化花色苷的半衰期长于单酰化花色苷;褐变指数和聚合物颜色指数随贮藏时间的延长和贮藏温度的升高而增大,并且聚合物颜色指数与花色苷含量之间呈指数关系。     

蔗糖含量对牡丹花色苷贮藏稳定性和降解动力学的影响

研究蔗糖含量对牡丹花色苷贮藏稳定性的影响.花色苷降解动力学数据的分析结果表明,牡丹花色苷在20℃和37℃贮藏条件下的降解符合一级反应动力学模型,花色苷半衰期随贮藏温度降低而延长;褐变指数随贮藏温度的升高和贮藏时间的延长而增大.加入蔗糖,提高牡丹花色苷的贮藏稳定性,表现为花色苷的降解速率常数减小,半衰期延长,褐变指数减小.含糖花色苷样品液的降解速率常数和褐变指数依次为:62<30<45<11°Brix.     

紫薯酒花色苷在贮藏中的降解动力学研究

以紫薯酒为原料,探究了紫薯酒中花色苷在不同贮藏温度、p H和光照条件下贮藏的稳定性和降解动力学。结果表明:紫薯酒在贮藏过程中,花色苷受不同温度、p H和光照条件的影响,其降解规律符合一级反应动力学规律,反应速率常数k越大,半衰期t1/2越小。在5℃与25℃条件下较稳定,在37℃极易分解。p H为3.5时,紫薯酒花色苷稳定性最好。紫薯酒花色苷在避光条件下较稳定,在日光灯与室内散射光照射下易分解,在棕色玻璃瓶中贮藏可减少光照对花色苷的降解。因此紫薯酒在贮藏时应尽量保持低温和避光,将p H调整为3.5为宜。     

桑葚果浆中花色苷及其色泽的热降解动力学

为了研究桑葚果浆加工中花色苷和色泽的热降解规律,测定了不同温度(75、80、85、90℃)下桑葚果浆花色苷含量和色泽值的影响,并建立了花色苷与色泽值的相关性。结果表明:桑葚果浆中花色苷的热降解符合一级动力学反应,L*、a*和TCD*值的热降解符合联合动力学反应,b*值的热降解符合零级动力学反应。花色苷的降解与L*、a*和TCD*值正相关,与b*值负相关。     

桑葚果浆中花色苷及其色泽的热降解动力学

为了研究桑葚果浆加工中花色苷和色泽的热降解规律,测定了不同温度(75、80、85、90℃)下桑葚果浆花色苷含量和色泽值的影响,并建立了花色苷与色泽值的相关性。结果表明:桑葚果浆中花色苷的热降解符合一级动力学反应,L*、a*和TCD*值的热降解符合联合动力学反应,b*值的热降解符合零级动力学反应。花色苷的降解与L*、a*和TCD*值正相关,与b*值负相关。     

龙葵果花色苷降解动力学

通过研究4种龙葵果花色苷提取物在不同pH值和温度下的降解动力学过程,得出其降解规律。结果显示,龙葵果花色苷的降解符合一级反应动力学模型。相同pH下随着温度的升高,龙葵果花色苷的降解速率常数呈现指数型增长趋势,半衰期呈现指数型下降趋势。60℃和70℃时随着pH的增大,粗提物、一级精制物的降解速率常数呈现对数型增长趋势,而组分1和组分2的降解速率常数则呈现指数型增长趋势,4种提取物的半衰期均呈现指数型下降的趋势。而80℃和90℃时,4种花色苷提取物的降解速率常数和半衰期并未呈现规律性的变化。4种龙葵果花色苷提取物均在60℃、pH 1.0时降解最慢,稳定性最好,其中粗提物的稳定性最强。     

杨梅果汁花色苷及其色泽稳定性的研究

本文就氧、维生素C(Vc)、包装材料、贮藏温度以及光等因素对杨梅汁花色苷及其色泽稳定性的影响作了探讨。结果表明:杨梅汁花色苷的降解遵循一级反应动力学规律(r<0.98)。氧及Vc均不利于花色苷及色泽保存。复合铝箔袋装杨梅汁其花色苷和色泽稳定性很高,涂料罐则又不宜装杨梅汁。低温(4℃)贮藏八个月的杨梅汁花色苷及其色泽变化甚微,高温(37℃)贮藏对花色苷和色泽破坏严重,一个月内杨梅汁即失去原有紫红色而呈褐色,且瓶底有大量褐色降解物。曝光贮藏会促进杨梅汁花色苷降解和色泽的变化。     

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.     

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.     

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.