壳聚糖/聚乙烯醇改善纸基材料的水蒸气和氧气阻隔性能研究

研究了壳聚糖和聚乙烯醇在改善纸基材料水蒸气(极性气体)和氧气(非极性气体)阻隔性能上的应用效果,探讨了壳聚糖/聚乙烯醇不同质量比和不同复合方式(共混和分层)对纸基材料水蒸气和氧气阻隔性能、机械性能和涂层稳定性的影响。结果表明,随着壳聚糖和聚乙烯醇质量比的降低,纸基材料的水蒸气阻隔性能逐渐增强,同时氧气阻隔性能逐渐降低;壳聚糖/聚乙烯醇分层涂布纸的水蒸气和氧气透过量均低于壳聚糖/聚乙烯醇共混涂布纸。当壳聚糖和聚乙烯醇的质量比为1∶1时,壳聚糖/聚乙烯醇分层涂布纸的水蒸气透过量和氧气透过量分别为9.36 g/(m~2·d)和31.93cm~3/(m~2·d);与纯壳聚糖涂布纸相比,水蒸气透过量降低了约92%,与壳聚糖/聚乙烯醇共混涂布纸相比,水蒸气透过量降低了约68%,氧气透过量降低了约67%。     

不同增塑剂对结冷胶薄膜性能的影响

为开发新型食品包装材料，以结冷胶为成膜基质，以甘油、丙二醇和聚乙二醇400为增塑剂，采用流延法来制备生物可降解包装薄膜，研究膜的微观结构、热稳定性、力学性能、透光性能、水蒸气及氧气透过率。采用红外光谱、X-射线衍射和电镜扫描对3种增塑剂与结冷胶之间的相容性进行分析。结果表明：以甘油为增塑剂，成膜性能最佳，丙二醇次之。热重分析表明，3种基膜在0～100℃表现出良好、均一的热稳定性，热稳定性依次为：丙二醇、甘油、聚乙二醇400。物理学性能测试分析表明，3种增塑剂的添加均会提高基膜的厚度、断裂延伸率、抗拉强度、水蒸气和氧气透过率，降低膜的透光性能。采用甘油添加量为40%(质量分数，结冷胶基)来制备薄膜时，抗拉强度最大为32.46 MPa,断裂延伸率最大为8.33%,氧气透过率最大为2.11 cm³·mm/(m²·d·atm),水蒸气透过率最大为2.45×10^-10 g/(m·s·Pa),透光率最大为91.8%,满足包装薄膜的性能需求，为新型可降解包装膜的制备及应用提供理论基础。     

茶多酚-玉米胚芽粕蛋白膜制备及性能研究

以玉米胚芽粕为原料，通过醇法提取玉胚芽粕醇溶蛋白，以丙三醇作为增塑剂，添加壳聚糖提高复合膜液分子间距离，并向其中加入茶多酚，制成复合膜。首先，通过单因素正交试验，研究4个因素对复合膜拉伸强度、水蒸气透过率以及过氧化值指标的影响，以便确定最佳成膜条件，然后，通过测DPPH对其抗氧化性进行分析。试验结果表明：在玉米胚芽粕蛋白浓度为18%、丙三醇添加量为6 g、壳聚糖添加量为0.8 g、茶多酚浓度为2%时，拉伸强度9.24 MPa,水蒸气透过率为2.17 g·mm/(m²·d·kPa),过氧化值为4.23 meq/kg,所测复合膜的各项指标最佳，且成膜效果最好。同时，由于茶多酚的加入，DPPH高达32.57%,抗氧化性明显提高。向复合膜中加入丙三醇、壳聚糖以及茶多酚，使得复合膜各方面性能优化显著，且有效提高了膜的抗氧化性。     

淀粉-层状硅酸盐黏土复合薄膜的结构与性能研究

本研究通过溶液流延法制备了淀粉/层状硅酸盐黏土(LRD)共混物薄膜,考察了纳米黏土的添加量对薄膜的流变性能、水蒸气阻隔性能以及机械性能的影响。随着LRD的添加,储能模量G’和损耗模量G"均显著增加,且G’增速快于G"。静态流变特性表明,Herschel-Bulkley模型对混合体系具有较高的拟合度,并且高含量LRD下,混合体系具有更强的假塑性。X-衍射分析表明,当LRD添加量为5%时,LRD片层完全剥离脱落在淀粉基质里,当LRD添加量10%时,LRD在体系中的分散并不完全,甚至出现聚集。LRD的添加增强了薄膜的水蒸气阻隔性能,水蒸气透过率由0%LRD的1.595 g·mm/(k Pa·h·m~2)降低到10%LRD时的1.085 g·mm/(k Pa·h·m~2)。随着LRD添加量的增加,拉伸强度从0%LRD的8.987 MPa提高到15%LRD的21.180 MPa,而断裂伸长率从0%LRD的27.185%降低到20%LRD的8.008%。     

添加单宁对明胶可食膜性质的影响

如何提高明胶膜的机械性能和阻隔性能,一直以来是可食膜研究领域的重要内容。本文以不同剂量(0 mg/g、10 mg/g、20 mg/g、30 mg/g和40 mg/g)单宁添加于明胶液并以浇注法成膜,然后对膜的理化性质进行分析。研究结果发现单宁有效提高了明胶膜的拉伸强度,但降低了其断裂伸长率;当单宁添加量为30 mg/g(明胶干基)时,其拉伸强度最大(22.10 MPa),断裂延伸率最小(40.12%)。与对照膜相比,单宁的添加降低了复合膜水溶性,水蒸气透过率和氧气透过率。在单宁含量添加范围内,水蒸气透过性最低为1.49×10-11 g/(Pa·s·m);水溶性最低为27.76%,氧气透过率最低为21.63 meg/kg。同时,DSC分析表明单宁提高了明胶膜的热稳定性。FT-IR图谱表明单宁与明胶之间发生了以氢键和疏水键为主的物理交联作用。所以,单宁-明胶复合膜在食品包装方面具有潜在的开发价值。     

壳聚糖应用于纸张阻隔性涂布的研究

使用壳聚糖溶液对纸张进行涂布,研究了不同涂布量下纸张表面孔隙的封闭程度及涂布纸的阻氧性能与阻湿性能,探讨了壳聚糖/PVDC(聚偏二氯乙烯)复合涂布对涂布纸阻湿性能的改善情况.结果表明,涂布0.46g/m2壳聚糖能够将纸张表面原有孔隙填满,进一步增大壳聚糖涂布量,纸张表面完全被壳聚糖膜层覆盖,平整程度提高.壳聚糖涂布能够显著提高纸张的阻氧性能,当壳聚糖单层涂布量为1.96 g/m2时,涂布纸的氧气透过率相对原纸至少下降了99.3％,但水蒸气透过率相对原纸有所上升.使用壳聚糖/PVDC复合涂布时,在1.96g/m2壳聚糖涂层基础上二次涂布7 40 g/m2 PVDC,水蒸气透过率相对单独涂布壳聚糖下降了66.3％,降至原纸的44.8％,与此同时.阻氧性能及表面抗水性均有较大提升.     

肉桂醛浓度对浓缩乳清蛋白/壳聚糖复合膜性能的影响

为了研究新型高性能抗菌包装材料,本文将肉桂醛添加到浓缩乳清蛋白/壳聚糖复合膜中制成抗菌复合膜,采用FT-IR对复合膜的微观结构进行表征,研究了肉桂醛浓度对复合膜厚度、透光率、机械性能、水蒸气透过系数、氧气透过率等性质的影响,以及其对复合膜抗菌性能的影响。肉桂醛与浓缩乳清蛋白/壳聚糖复合膜有很好的相容性。结果表明:随着肉桂醛浓度的增加,膜的透光率和抗拉强度减小,当肉桂醛浓度为0.3%时,膜的水蒸气透过系数最小,为1.15×10-13 g/(cm·s·Pa),当肉桂醛浓度为0.4%时,膜的厚度和氧气透过率最小,氧气透过率为1.1×10-5 cm3/(m2·d·Pa),当肉桂醛浓度为0.5%时,膜的断裂伸长率最大,为57.5%,膜的抑菌效力随着肉桂醛浓度的增大而显著增大。该研究可为肉桂醛/浓缩乳清蛋白/壳聚糖复合抗菌膜的生产工艺参数的优化提供新的参考。     

响应面法优化壳聚糖/核桃蛋白复合膜的制备工艺

为了研究壳聚糖/核桃蛋白复合膜的制备工艺,采用响应面分析法对其进行优化。以壳聚糖/核桃蛋白质量比、甘油添加量、p H及戊二醛添加量为单因素,对膜的拉伸强度、断裂伸长率和水蒸气透过系数进行测定,得出各指标的二次回归模型。结果表明,壳聚糖/核桃蛋白质量比0.50、甘油添加量2.00 g、p H3.23、戊二醛添加量0.10 g时膜的各项性能最佳。该工艺参数下膜各性能指标分别为:(18.985±1.102)MPa、72.79%±2.172%、(4.41±0.125)g·mm/(m2·d·k Pa)。     

环保型PLA/CNF应用于纸张阻隔性涂布的研究

以聚乳酸（PLA）为基体、乙酰化改性纤维素纳米纤丝（m-CNF）为增强材料制得复合涂料,将其涂覆于A4纸表面制得PLA/m-CNF阻隔纸,探讨了复合涂料中m-CNF添加量对纸张阻隔性能、疏水性能、强度性能等的影响。结果表明,与原纸相比,当m-CNF添加量为3%时,PLA/m-CNF3%阻隔纸的抗张指数、耐破指数、疏水性能分别提高了30.6%、40.1%、24.8%,透气度降低了36.6%。原纸水蒸气透过量为1815 g/（m²·d）,PLA/CNF阻隔纸的氧气和水蒸气阻隔性能相较原纸显著提升;其中,PLA/CNF3%阻隔纸的水蒸气透过量为443 g/（m²·d）、氧气透过量为45 cm³/（m²·d·（0.1 MPa））;PLA/m-CNF3%阻隔纸的水蒸气透过量为385 g/（m²·d）、氧气透过量为35 cm³/（m²·d·（0.1 MPa））,与PLA/CNF3%阻隔纸相比,分别下降了13.1%和22.2%;表明PLA/m-CNF阻隔纸具有优异的保鲜效果。     

乳化剂提高大豆分离蛋白可食性膜透水性的研究

比较了11种乳化剂对大豆分离蛋白膜水蒸气透过率的影响,结果显示蜂蜡、斯潘60和斯潘40对膜阻水性能具有最佳改善效果.进一步研究了这3种乳化剂单一添加和复合使用时对大豆分离蛋白膜水蒸气透过率的影响,得出复合使用不如单一使用时改善效果好,且3 g/L质量浓度的蜂蜡对大豆分离蛋白膜阻水性的改善作用最好,使水蒸气透过率达到18.93 g · mm/(m2 · d · kPa),缩减为未加乳化剂时的54%.     

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.     

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.