明胶改性壳聚糖膜性能研究

根据壳聚糖与明胶的相容性,制备了壳聚糖膜、壳聚糖/明胶共混膜,研究了增加明胶含量对膜的强度、拉伸位移、溶出率、吸水率的影响.采用FT-IR谱图和XRD谱图分析,研究了膜的微观结构,探讨了共混体系中壳聚糖与明胶的相容性以及分子间的相互作用.当明胶含量在30%时,改性壳聚糖膜的抗拉强度达到最大值;在10%时,它的拉伸断裂伸长达到最大值;20%时,改性膜的吸水率达到最低;改性膜的溶出率则随着明胶含量的增加而增大.     

苯甲酸钠对多糖共混膜吸湿性和抗菌性的影响研究

苯甲酸钠是常用食品添加剂,它起着防腐的目的.利用天然高分子聚合物壳聚糖和环糊精为原料,添加苯甲酸钠,研究制备具有良好相容性和可降解性的用于食品包装的多糖共混膜.经对壳聚糖膜及共混膜的吸水率测试和抗菌试验,结果显示由于苯甲酸钠的加入而在共混物的分子链上引入了憎水的苯环,从而使得共混膜的吸水率下降,同时改善了多糖共混膜的抗菌性;共混膜的壳聚糖含量在60%时其吸水率控制在63.08%;在一周内,共混膜对葡萄球菌的抑制率分别比单纯CS壳聚糖膜和CSβC壳聚糖-β-环糊精二元混合膜平均提高约20%和48%.     

疏水改性生物胶乳的膜性能

制备了疏水改性生物胶乳,并以拉伸强度、断裂伸长率、吸水率为指标考察了疏水改性生物胶乳与苯丙胶乳共混液的膜性能。结果表明:疏水改性剂能有效提高生物胶乳与苯丙胶乳的膜性能。改性剂用量为0.5%时,膜的拉伸强度、断裂伸长率最大,吸水率最小;疏水改性生物胶乳与苯丙胶乳的质量比为3.5∶6.5时,膜的拉伸强度和断裂伸长率最大。     

HMMM共混改性水性聚氨酯的制备和性能研究北大核心

以异佛尔酮二异氰酸酯(IPDI)、聚醚二醇等为基本原料,合成水性聚氨酯(WPU)乳液,通过调节六甲氧基亚甲基三聚氰胺树脂(HMMM)的用量,制备共混改性水性聚氨酯。通过T-型剥离强度、力学性能、热性能和耐水、耐溶剂性能分析,探讨了HMMM含量对薄膜性能的影响。研究结果表明:与未改性的聚氨酯膜进行比较,共混改性的聚氨酯薄膜的综合性能有所提升。当HMMM含量为6%时,其共混改性阳离子型聚氨物(YWPU)胶膜的拉伸强度达到11.32MPa;当HMMM含量为10%,其共混改性非离子型聚氨酯(FWPU)胶膜的拉伸强度达到14.23MPa。     

HMMM共混改性水性聚氨酯的制备和性能研究

以异佛尔酮二异氰酸酯(IPDI)、聚醚二醇等为基本原料,合成水性聚氨酯(WPU)乳液,通过调节六甲氧基亚甲基三聚氰胺树脂(HMMM)的用量,制备共混改性水性聚氨酯。通过T-型剥离强度、力学性能、热性能和耐水、耐溶剂性能分析,探讨了HMMM含量对薄膜性能的影响。研究结果表明:与未改性的聚氨酯膜进行比较,共混改性的聚氨酯薄膜的综合性能有所提升。当HMMM含量为6%时,其共混改性阳离子型聚氨物(YWPU)胶膜的拉伸强度达到11.32MPa;当HMMM含量为10%,其共混改性非离子型聚氨酯(FWPU)胶膜的拉伸强度达到14.23MPa。     

疏水改性生物胶乳的膜性能

制备了疏水改性生物胶乳,并以拉伸强度、断裂伸长率、吸水率为指标考察了疏水改性生物胶乳与苯丙胶乳共混液的膜性能。结果表明,疏水改性剂能有效提高生物胶乳与苯丙胶乳的膜性能。改性剂用量为0．5％时,膜的拉伸强度、断裂伸长率最大,吸水率最小;疏水改性生物胶乳与苯丙胶乳的质量比为3．5：6．5时,膜的拉伸强度和断裂伸长率最大。     

偶联剂对超细羊毛粉体与聚氨酯共混膜性能的影响

用偶联剂对超细羊毛粉体进行了表面改性，然后制成羊毛粉体与聚氨酯共混膜．探讨了偶联剂的加入对共混膜力学、透湿、防水等性能的影响．并摸索出偶联剂的最佳改性条件．结果表明：偶联剂能明显改善共混膜的力学等性能．     

酸性染料对羊毛粉体/粘胶共混纤维染色研究

采用湿法纺丝制备羊毛粉体含量分别为0、5%、10%、15%、20%的羊毛粉体/粘胶共混纤维,利用酸性染料对共混纤维进行染色,分析温度、元明粉用量、pH值和不同羊毛粉体含量对共混纤维上染率的影响,得出最佳工艺参数。结果表明,酸性大红GR上染羊毛粉体/粘胶共混纤维时,在不同温度、元明粉用量和pH值下,不同羊毛粉体含量的共混纤维上染率曲线形状相似,表现出相似的上染规律;其中羊毛粉体含量为15%的羊毛粉体/粘胶共混纤维的上染率相对较高。     

非水溶性丝素粉体与聚氨酯共混膜的性能

采用浸没沉淀相转化法制备非水溶性丝素粉体与医用聚氨酯共混膜。研究共混膜中非水溶性丝素粉体质量分数不同时共混膜的表面形貌、吸水性、透汽性、水接触角及力学性能和红外光谱图的变化。实验结果表明:随着非水溶性丝素粉体质量分数的增加,共混膜的表面形貌由致密逐渐变得疏松,并逐渐出现微孔,且粉体在共混膜中分布均匀并没有明显的团聚现象,这表明二者的相容性好;另外,共混膜的断裂伸长和拉伸模量较纯PU膜虽有不同程度下降,但其吸水性和透汽性逐渐得到提高;膜的水接触角逐渐下降,表明其亲水性逐步得到提高。     

明胶/L-聚乳酸共混膜的制备与性能表征

L-聚乳酸(PLLA)和明胶共混改性后成膜,分析了共混膜的热性能、力学性能、形貌和亲水性。试验结果表明:明胶与PLLA共混对PLLA的热性能影响较小;当共混膜中明胶质量分数<20%时,可使共混膜保持较好的力学性能;加入甘油可降低共混膜的Tg,并提高其断裂伸长率,起到了一定的增塑作用;聚乳酸与明胶共混后可增加聚乳酸膜的亲水性并降低明胶膜的亲水性,明胶/PLLA共混膜为疏松多孔的结构。     

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.