多糖类食品添加剂抑制鲜湿面老化机理研究

探讨3种不同亲水多糖的添加量和储藏时间对鲜湿面淀粉热力学行为产生的影响。利用差示量热扫描(differential scanning calorimeter,DSC)、Avrami方程和Hyperchem 8.0软件对分别添加瓜尔胶、卡拉胶、魔芋胶3种亲水多糖的鲜湿面老化动力学方程与分子结构模型进行分析。结果表明:多糖/鲜湿面体系的糊化温度范围(T_(01)~T_(c1))为55.30~72.82℃,多糖/鲜湿面体系的糊化焓(ΔH_0)高于空白组;多糖/鲜湿面体系的融化支链淀粉重结晶所需的老化焓(ΔH)低于空白组;多糖/鲜湿面体系的成核方式(n_1)变化范围为:n_1=0.742~0.816,均大于空白组(n=0.732)且不断趋近于自发成核;多糖/鲜湿面体系的重结晶的变化速率常数(k_1)变化范围为0.251~0.309,且均小于空白组(k=0.388)。Hyperchem 8.0软件模拟图像显示:淀粉分子上的羟基和多糖分子上的羟基竞争性聚集大量水分子而延缓水分子在淀粉分子周围重新分布。添加0.4%的瓜尔胶抑制老化效果最好,储藏21d时最大老化度仅为45.21%(CK组为68.25%),老化动力学方程为Y=0.816x-1.382(R~2=0.947)。     

乳化剂抑制鲜湿面货架期内品质老化机理研究

研究探析乳化剂抑制鲜湿面货架期内品质老化的机理,利用差示扫描量热仪(DSC)分析了硬脂酰乳酸钠(SSL)添加组,β-环糊精(β-CD)添加组鲜湿面以及经脱蛋白或脱脂处理后的鲜湿面的热力学变化。结果表明:未处理组的鲜湿面,在4℃储藏14d后,第一个支链淀粉峰SSL和β-CD添加组的老化焓△H都低于CK组(P0.05);第二个复合物峰SSL和β-CD添加组的重结晶融化温度Tp和老化焓△H都高于CK组(P0.05);鲜湿面经脱蛋白处理组,在4℃储藏14d后,相比未处理组支链淀粉老化焓稍有增大但无显著差异;第二个复合物峰的重结晶融化顶点温度显著升高,老化焓也稍有增大,但变化也不显著;经脱脂组鲜湿面储藏14d后,相比未处理组支链淀粉热力学特征无显著差异;第二个复合峰重结晶融化顶点温度和老化焓都显著升高(P0.05)。两种乳化剂均能干扰直链淀粉与脂类的结合,形成直链淀粉-乳化剂-脂质络合物,抑制鲜湿面货架期内品质老化。     

乳化剂对鲜湿面货架期内水分迁移及热力学影响

为探析乳化剂对鲜湿面货架期内水分迁移及热力学特性的影响,利用低场核磁共振仪、扫描电子显微镜和差示扫描量热（differential scanning calorimeter,DSC）仪,检测硬脂酰乳酸钠（sodium stearyl lactate,SSL）添加组、β-环糊精（beta-cyelodextrin,β-CD）添加组及空白（control check,CK）组鲜湿面货架期内水分迁移、微观结构和热力学特征。结果表明：贮藏7?d,鲜湿面结合水含量A21和不易流动水含量A22逐渐减少,自由水含量A23逐渐增大;SSL和β-CD均增大了鲜湿面A21和A22（P＜0.05）,且减小了A23（P＜0.05）,增大了贮藏前期结合水弛豫时间T21和不易流动水弛豫时间T22,其大小均为：SSL＞β-CD＞CK（P＜0.05）;2?种乳化剂使得贮藏7?d的鲜湿面弛豫时间T2减小（P＜0.05）,且SSL和β-CD的影响效果有显著差异（P＜0.05）;贮藏7?d鲜湿面的重结晶融化温度Tp和T0及老化焓ΔH越来越大;SSL和β-CD减缓了Tp、T0和ΔH的增加速率（P＜0.05）,SSL和β-CD分别使CK组ΔH从（1.81±0.05）J/g减小到（1.37±0.12）J/g和（1.31±0.04）J/g;SSL和β-CD使得鲜湿面微观结构表面光滑,水分分布均匀,面筋结构稳定,且SSL和蛋白连接紧密,β-CD和淀粉形成了包裹结构。?     

湿面老化动力学研究

利用差示量热扫描仪测定在不同储藏温度条件下(-4、15、25、35℃)的湿面老化焓,应用Avrami模型描述淀粉在回生过程中的结晶行为,研究了贮存温度对湿面淀粉老化速率和淀粉结晶成核方式的影响。通过对模型线性回归后得到结晶速率常数k和Avrami指数n。结果表明,在本实验贮存温度区间内,湿面淀粉的老化结晶速率k随着贮存温度的升高而逐渐减小;在-4～15℃的贮存温度区间内,Avrami指数n均小于1,表明其结晶方式是瞬间成核,在25～35℃区间内,1相似文献   

β-环糊精抑制面包老化及其机制初步分析

对β-环糊精(β-CD)抑制面包老化特性进行了研究。结果表明:添加2.0%的β-CD能明显地改善面包物性,延缓面包老化;一定程度上改变面包老化过程中晶体成核模式以及延缓面包储藏过程中淀粉晶型由V型向更稳定的B型晶体转化。这主要是因为在面包烘焙冷却过程中,β-CD与淀粉作用形成复合物。该复合物增强面包的网络结构,改善淀粉老化结晶环境,从而延长面包的有效储藏期。     

胖大海胶对鲜湿面流变学特性及蒸煮品质的影响

以胖大海胶(胖大海的中层皮层吸水胀润后形成的胶状物)为对象,将胖大海胶以0%、0.2%、0.4%、0.6%、0.8%、1.0%(质量分数)的比例添加到面粉中,研究胖大海胶对面团热机械学特性、面粉糊化特性、鲜湿面质构特性、色泽以及蒸煮损失等品质的影响。结果表明,面粉中适量添加胖大海胶可增强淀粉糊化热稳定性,延缓淀粉老化速率;胖大海胶的添加可显著提高鲜湿面吸水率,使鲜湿面蒸煮损失率显著降低,改善鲜湿面滑口感;色泽方面,胖大海的添加使鲜湿面亮度减弱,但具有咖啡色色泽。综合考虑,当胖大海胶添加量在0.4%~0.6%时,鲜湿面的整体品质较为理想。     

米饭回生研究（Ⅱ）米饭回生动力学

回生动力学研究在淀粉及谷物食品的贮存保鲜方面具有重要意义。Avrami模型可用于描述淀粉回生过程中的结晶行为,通过对模型参数k（结晶速率常数）和n(Avrami指数）的确定与分析,可以了解在结晶过程中直链及支链淀粉分子对晶体的成核方式、晶核密度和晶体生长方式的影响。在此基础上,本文研究了含水量对米粉糊及米饭回生速率的影响。结果表明在实验范围内,体系中含水量的减少主要是通过提高瞬时成核的强度（使n降低）和提高晶核密度（使k提高）来提高淀粉回生速率的。     

黄原胶对大米淀粉长期回生的影响

研究了黄原胶(Xan)对大米淀粉(RS)长期回生的影响,黄原胶和大米淀粉可以形成质地更为柔软的凝胶,黏着性升高,内聚性下降。X-射线衍射结果表明黄原胶能降低淀粉的重结晶度,用Avrami方程拟合结晶动力学,大米淀粉/黄原胶体系支链淀粉的重结晶生长为一次成核(n<1),添加黄原胶后,结晶速率常数k降低,表明大米淀粉的成核速度和重结晶增长速度都降低,支链淀粉回生受到较大抑制。扫描电镜(SEM)显示黄原胶能填充于淀粉颗粒片段间,体系表面孔洞缩小,表面更加光滑,形成的结构更加致密。     

DSC法研究6种莲子淀粉糊化和老化特性

利用差示扫描量热仪(DSC)结合Avrami 方程研究在4℃、储存两周的条件下,6种莲子淀粉的糊化和老化特性,探讨直链淀粉以及贮存时间对其热力学行为产生的影响,并用SPSS软件计算其相关性。结果表明：6种莲子淀粉的糊化温度、ΔH、老化焓、老化度以及老化速率存在着一定的差异,老化速率的大小顺序为太空莲＞美人红＞大紫红＞武植2号＞鄂莲＞洪湖莲,太空莲淀粉的老化速率是洪湖莲淀粉的1.36 倍;6种莲子淀粉的成核方式均为瞬间成核;4℃条件下贮存两周的莲子淀粉的老化度随着贮存时间的增加而增大;直链淀粉含量与Avrami 指数n值呈负相关,与速率常数k值、ΔH、老化焓以及冰融溶焓呈正相关。     

亲水多糖对鲜湿面货架期内水分迁移及老化进程的影响

利用低场核磁共振、差示量热扫描、Avrami数学模型研究瓜尔胶、可溶性大豆多糖、卡拉胶对鲜湿面贮藏期间水分迁移、热力学参数、老化动力学的影响。结果表明：贮藏7 d的鲜湿面结合水含量：瓜尔胶＞可溶性大豆多糖＞卡拉胶＞空白组（P＜0.05）;不易流动水含量：瓜尔胶＞卡拉胶＞可溶性大豆多糖＞空白组（P＜0.05）;自由水含量：空白组＞可溶性大豆多糖＞卡拉胶＞瓜尔胶（P＜0.05）。多糖主要作用于淀粉及面筋蛋白表面极性基团所吸引的结合水;同时多糖对3 种水分流动性的束缚并非呈单一的线性关系,且能抑制鲜湿面淀粉老化过程中重结晶融化起始温度（T0）、重结晶融化终止温度（Tc）、老化焓（?H）的上升速率;老化动力学方程：Y空白组=0.732x－0.946,Y卡拉胶=0.744x－1.192,Y瓜尔胶=0.791x－1.328,Y可溶性大豆多糖=0.752x－1.114。     

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.