高酰基结冷胶与κ-卡拉胶复配胶的质构特性研究

用抗压实验和全质构测试对高酰基结冷胶(HA)与κ-卡拉胶(CA)复配胶的凝胶强度、形变性以及硬度进行分析。研究了Ca2+、Mg2+、K+、Na+四种离子以及HA与CA的质量比对复配胶质构特性的影响。实验中,总胶浓度控制为1%(w/v),离子浓度为2～80mmol/L,HA和CA的质量比为25:75、50:50、75:25。结果表明,二价离子较一价离子作用效果显著,其中Ca2+效果最为显著,复配胶在HA:CA=75:25时有显著的协同作用,HA与CA的复配胶有着较强的形变性。     

低酰基结冷胶流变行为研究

研究了浓度、温度、剪切速率、pH和离子浓度对低酰基结冷胶流变行为的影响。结果表明,低酰基结冷胶为典型的切力变稀流体,其表观黏度和剪切速率的关系符合幂律方程。在同一剪切速率下,表观黏度随温度的升高而降低。在同一温度下,结冷胶溶液的表观黏度则随着剪切速率的增加而减小。低酰基结冷胶凝胶强度随着Ca2+和Na+浓度的增加出现先增大后减小的趋势,相对于Na+而言,Ca2+形成的凝胶强度更高,且用量更少。     

高酰基结冷胶凝胶特性的研究

研究了高酰基结冷胶溶液的凝胶特性并对其凝胶机理进行了分析,通过对高酰基结冷胶在不同浓度、温度、pH值和Ca2+盐条件下流变特性和凝胶强度的实验研究,结果表明:胶体浓度、温度、游离的二价阳离子含量以及pH值的差异都会对高酰基结冷胶的粘度和凝胶强度产生影响。对高酰基结冷胶作用力的初步考察结果表明:疏水作用、氢键作用、静电作用在形成凝胶的过程中均起关键作用,疏水作用影响最大。     

高酰基结冷胶的溶胶和凝胶特性研究及结构初步分析

采用黏度计和质构仪对高酰基结冷胶的溶胶和凝胶性质进行研究。结果表明：高酰基结冷胶在质量浓度为 0.05～0.1g/100mL 时,表观黏度随质量浓度增加而增加,并呈现假塑性流体特性;在质量浓度为0.2～0.5g/100mL时形成凝胶,凝胶强度受胶体及 Ca2+ 质量浓度的影响明显,同时高酰基结冷胶比例增加,高低复配胶体的凝胶强度减小。并利用红外光谱扫描和核磁共振技术对高酰基结冷胶结构进行初步分析。     

激光共聚焦显微镜对结冷胶微观结构的观察研究

应用激光共聚焦显微镜研究了结冷胶的微观结构,阳离子、pH对结冷胶微观结构的影响。研究表明,含10mmol/LCaCl2,0.006%～0.01%浓度的低酰基结冷胶体系呈现弱凝胶网络结构,高酰基结冷胶不能形成类似的网络结构;Ca2+、K+对结冷胶的微观结构影响类似,但是要达到最大的网络密集度,所需的K+浓度是Ca2+的25倍;加酸改变pH会对结冷胶的微观结构产生影响。     

高酰基结冷胶/酪蛋白酸钠复合凝胶粘弹行为的研究

本文研究了酪蛋白酸钠浓度、结冷胶浓度、离子和测试条件对高酰基结冷胶/酪蛋白酸钠复合凝胶粘弹性的影响。结果表明:高酰基结冷胶/酪蛋白酸钠共混体系为典型的切力变稀流体,表观粘度随着酪蛋白酸钠浓度的升高而降低,而随着阳离子浓度的增大出现先增大后减小的变化趋势。压缩速度对复合凝胶硬度几乎无影响,而内聚性和弹性则随着压缩速度的增加而增大。内聚性随着压缩应变的增大出现先增大后减小的变化趋势。复合凝胶的硬度和弹性随着酪蛋白酸钠浓度的增加而下降,但复合凝胶的内聚性对酪蛋白酸钠浓度不敏感。高酰基结冷胶浓度越高,复合凝胶的硬度和弹性越大。相对于一价离子而言,二价离子形成的凝胶更强且用量更少。钾离子的添加对复合凝胶保水性影响较弱,而钙离子的添加则可以提高复合凝胶的保水性。     

无机盐对木瓜蛋白酶凝固大豆分离蛋白凝胶的影响

为研究食品中常见无机盐对木瓜蛋白酶凝固大豆分离蛋白凝胶的影响,以大豆分离蛋白(SPI)为原料,测定添加NaCl、KCl、CaCl2、MgCl2和MgSO4等常见无机盐后木瓜蛋白酶凝固SPI的时间、凝胶质构、凝固过程中pH值及蛋白质降解程度的变化。结果表明：添加一定浓度的无机盐可以缩短凝固时间并提高凝胶强度。相同离子强度下,Ca2+和Mg2+对凝固时间及凝胶强度影响均大于Na+和K+。添加无机盐可使SPI的pH值降低,加酶后pH值再次持续下降,但一定时间后趋于稳定。无机盐的种类和浓度对木瓜蛋白酶凝固SPI过程中蛋白质降解程度影响不明显。SPI中CaCl2的离子强度为15(CaCl2浓度为5mmol/L)时,将酶添加量从0.15%减少到0.1%,可使凝胶强度提高60%。因此,添加适量的一价及二价无机盐可显著缩短酶凝固时间并提高凝胶强度。添加Ca2+和Mg2+等二价阳离子盐类是提高木瓜蛋白酶凝固大豆蛋白凝胶强度的有效途径。     

阳离子对CMC溶液流变特性的影响研究

CMC具有典型的聚电解质效应,外源性离子强度及离子种类会使其流变性质产生影响.本文通过高级旋转流变仪详细研究了不同盐(包括一价阳离子Na+、K+及二价阳离子Ca2、Mg2+)及不同离子强度(离子浓度为0％～1％)对CMC水溶液流变特性的影响.通过实验发现,Na+、K+、Ca2+及Mg2+明显影响CMC溶液的零剪切粘度、黏度、剪切稀化指数、黏度衰减特性及黏弹性特性(包括弹性模量G,、黏性模量G”及损耗正切tan (ddlta)),并从微观结构上进行详细解析.同时,通过对CMC溶液进行频率扫描,研究了低频区与高频区的弹性模量与黏性模量随阳离子添加量的变化规律.另外,本文应用浊度仪及色度仪分别测定CMC溶液的浊度以及色度(包括L、a及b),研究了阳离子及其不同浓度对CMC水溶液浊度及色度特性的影响.     

糖醇对结冷胶凝胶质构的影响

利用物性分析仪研究赤藓糖醇、木糖醇、乳糖醇对结冷胶凝胶质构的影响。结果表明：3 种糖醇都能使结冷胶凝胶强度和硬度降低,且都随糖醇质量浓度的增加而降低,3 种糖醇的影响力为乳糖醇>木糖醇>赤藓糖醇,但对结冷胶凝胶脆性的影响不显著。其次,15 g/100 mL的复合糖醇对结冷胶凝胶质构的影响皆小于相同质量浓度的单一糖醇对质构的影响,复合糖醇间不存在正协同作用。最后,在以K+为成胶离子时（40～400 mmol/L）,乳糖醇对结冷胶凝胶质构有影响;在以Ca2+为成胶离子时,只在低浓度时（2～10 mmol/L）,乳糖醇对结冷胶凝胶质构影响明显,当Ca2+浓度升高时（10～50 mmol/L）,乳糖醇对结冷胶凝胶质构几乎不产生影响。     

二价离子对黄原胶溶液流变特性的影响研究

详细研究了不同盐(钙与镁)及不同离子强度对黄原胶溶液体系流变特性的影响。通过实验发现,Ca2+及Mg2+影响黄原胶的低剪切黏度、黏度、剪切稀化指数特性以及黏弹性,还对频率扫描及动态黏弹性温度扫描时G’与G"相交点的频率、松驰时间和凝胶点温度有影响。通过动态黏度温度扫描实验,发现盐的浓度影响黄原胶溶液的构象转变温度。实验还表明,在稳态流动扫描、应变扫描、频率扫描及动态黏温扫描中二价离子对黄原胶溶液流变特性的影响明显大于一价离子,同时Ca2+的作用大于Mg2+。     

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.     

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.     

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.     

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.     

Analysis of benzo[a]pyrene in spiked fatty foods by second derivative synchronous spectrofluorimetry after microwave-assisted treatment of samples

A simple, rapid and inexpensive method has been developed for the determination of benzo[a     

The development of reference materials for paralytic shellfish poisoning toxins in lyophilized mussel. II: Certification study

This paper describes the second part of a project undertaken to develop certified mussel reference materials for paralytic shellfish poisoning toxins. In the first part two interlaboratory studies were undertaken to investigate the performance of the analytical methodology for several PSP toxins, in particular saxitoxin and decarbamoyl-saxitoxin in lyophilized mussels, and to set criteria for the acceptance of results to be applied during the certification exercise. Fifteen laboratories participated in this certification study and were asked to measure saxitoxin and decarbamoyl-saxitoxin in rehydrated lyophilized mussel material and in a saxitoxin-enriched mussel material. The participants were allowed to use a method of their choice but with an extraction procedure to be strictly followed. The study included extra experiments to verify the detection limits for both saxitoxin and decarbamoyl-saxitoxin. Most participants (13 of 15) were able to meet all the criteria set for the certification study. Results for saxitoxin.2HCl yielded a certified mass fraction of <0.07 mg/kg in the rehydrated lyophilized mussels. Results obtained for decarbamoyl-saxitoxin.2HCl yielded a certified mass fraction of 1.59+/-0.20 mg/kg. The results for saxitoxin.2HCl in enriched blank mussel yielded a certified mass fraction of 0.48 +/- 0.06 mg/kg. These certified reference materials for paralytic shellfish poisoning toxins in lyophilized mussel material are the first available for laboratories to test their method for accuracy and performance.     

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.     

Announcing a new international peer-reviewed journal:Food Science and Human Wellness now accepting manuscript submission in English

<正>We are pleased to announce the launch of a new international peer-reviewed journal-Food Science and Human Wellness,ISSN 2213-4530,which is an open access journal,produced and hosted by Elsevier B.V.on behalf of Beijing Academy of Food Sciences.Food Science and Human Wellness is an international peer-reviewed English journal that provides a forum for the dissemination of the