ε-聚赖氨酸与纳他霉素复配剂抑菌性能的研究

研究了ε-聚赖氨酸(ε-PL)与纳他霉素复配剂的抑菌活性.以典型菌株大肠杆菌、伤寒沙门氏菌、金黄色葡萄球菌、枯草芽孢杆菌、酿酒酵母和热带假丝酵母为研究对象,采用二倍稀释法确定ε-PL和纳他霉素的最小抑菌浓度,96孔板法确定ε-PL与纳他霉素对酵母菌最佳复配抑菌浓度,通过测定胞内物质渗漏来反映酵母细胞膜的完整性.结果表明,二者抑制酿酒酵母的最佳复配浓度为ε-PL 100μg/mL、纳他霉素4μg/mL,抑制热带假丝酵母的最佳复配浓度为ε-PL 400μg/mL、纳他霉素2μg/mL,且两种复配剂均能抑制大部分细菌.通过测定抑菌剂作用于酿酒酵母在260nm、280nm的吸光度以及电导率的变化,可知复配剂对酿酒酵母细胞膜的破坏性最强.总之,ε-PL与纳他霉素复配使用,能够减少用量,拓宽抑菌范围,能更好的抑制食品中腐败微生物的生长.     

保鲜纸处理改善采后火龙果的贮藏品质

以红心火龙果为试材,在(20±0.5) ℃贮藏条件下,采用800 mg/L纳他霉素和800 mg/L ε-聚赖氨酸制成的保鲜纸处理,以蒸馏水制成的保鲜纸作为对照。研究纳他霉素和ε-聚赖氨酸保鲜纸处理对火龙果采后贮藏品质的影响。结果表明,与对照组相比,纳他霉素和ε-聚赖氨酸保鲜纸处理均能较好地降低采后火龙果贮藏期的呼吸强度,抑制果实腐烂率、失重率、丙二醛、霉菌及酵母菌和鳞片黄化率的增加,保持果实可溶性固性物、可滴定酸、Vc、甜菜素和鳞片叶绿素的含量。在贮藏末期8 d,纳他霉素保鲜纸处理组的腐烂率为8.30%,失重率为1.50%,丙二醛为4.30 μmol/g,均低于ε-聚赖氨酸保鲜纸处理组;Vc含量为15.53 mg/100 g,甜菜素含量为14.47 mg/100 g,均高于ε-聚赖氨酸保鲜纸处理组。因此,纳他霉素保鲜纸处理组的保鲜效果好于ε-聚赖氨酸保鲜纸处理。综上表明,纳他霉素保鲜纸可以有效地保持火龙果贮藏品质,延长其货架期。     

气调结合生物保鲜剂对葡萄冷藏品质及电子鼻判别的影响

为了提高无核寒香蜜葡萄的贮运品质,在箱式气调的基础上,研究800、1000 mg/L浓度的纳他霉素和500、1000 mg/L浓度的ε-聚赖氨酸对无核寒香蜜葡萄微环境气体含量、感官、质地、营养、生理品质及电子鼻判别的影响。结果表明:生物保鲜剂的添加可以维持箱内较高的CO_2含量和较低的O_2含量,且不同浓度的相同生物保鲜剂间具有显著差别(P0.05);1000 mg/L纳他霉素和500 mg/L的ε-聚赖氨酸均可在不同程度保证无核寒香蜜葡萄的品质,且1000 mg/L纳他霉素处理无核寒香蜜葡萄的贮藏品质最佳,至60 d时,其落粒率和腐烂率为12.00%,果皮强度和脆性保持在4.04 N、196.00 g/s,TSS、TA及Vc含量分别为15.80%、0.68%、4.2 mg/100 g,呼吸强度和乙烯生成速率分别为40.60 mg CO_2/kg·h、1.20μL/kg·h。PCA和LDA方法均适用于气调结合生物保鲜剂处理无核寒香蜜葡萄冷藏期的风味分析判别,NATA800、ε-PL1000处理与其余处理风味有一定的差异。     

纳他霉素在气调保鲜草莓中的应用研究

采用10、20mg/L和30mg/L的纳他霉素对草莓果实进行处理后,按30%O2+6%CO2密封包装,在(2±1)℃条件下贮藏。结果表明:纳他霉素处理可有效控制果实表面霉菌数量,减慢叶柄叶绿素含量下降的速率,抑制果实有机酸与糖分的下降,较好地维持果实的营养,延长贮藏期,改善其品质。20mg/L和30mg/L的纳他霉素处理草莓后贮藏21d,腐烂率仅3.3%,品质优良。     

不同防腐剂对盐鸡制品的抑菌性能及品质的影响

目的:研究防腐剂对盐焗鸡制品的抑菌性能及品质影响。方法:选取乳酸链球菌素(nisin)、双乙酸钠、脱氢乙酸钠、山梨酸钾、纳他霉素、ε-聚赖氨酸等作为防腐剂,菌落总数、p H、感官评定作为评价指标,考察防腐剂单独使用以及两两交互对盐焗鸡制品的抑菌性能及品质的影响。结果表明:单独添加4 g/kg的nisin或2 g/kg的ε-聚赖氨酸时,盐焗鸡制品的感官品质和p H达到最优,抑菌效果也较为显著;将5 g/kg的nisin和2.5 g/kg的ε-聚赖氨酸复配使用时效果最佳,菌落总数为5800 cfu/g,感官评分4.04,p H6.53,明显强于单独使用nisin的保鲜效果。     

纳他霉素对西兰花的保鲜效果

研究纳他霉素处理对西兰花冷藏保鲜品质的影响。纳他霉素处理浓度分别为800 mg/L、1 200 mg/L,在(0±1)℃冷藏期间每10 d取样测定西兰花理化指标及营养成分。结果表明:与冷藏对照相比,纳他霉素处理对于延缓西兰花可溶性固形物含量、VC含量及叶绿素含量的下降均有明显效果,并可抑制西兰花贮藏期间的呼吸强度;纳他霉素处理可提高西兰花SOD的活性和降低PPO活性,延缓了细胞膜相对透性的升高。说明冷藏结合纳他霉素处理对西兰花的成熟衰老有抑制作用,其中经1 200 mg/L处理的西兰花保鲜效果较好。     

ε-聚赖氨酸复配防腐剂在酱腌菜中的应用

为延长酱腌菜保质期,研究ε-聚赖氨酸（ε-ploy-L-lysine,ε-PL）与其他防腐剂和抗氧化剂复配对酱腌菜的防腐效果。结果表明,生物防腐剂乳酸链球菌素（Nisin）、纳他霉素和抗氧化剂茶多酚对酱腌菜中的腐败微生物有很好的抑制作用,并且同时使用具有协同增效的作用。通过响应面法复配防腐剂各成分配比为：ε-PL?0.06?μg/mL、Nisin?0.06?μg/mL、纳他霉素0.035?μg/mL和茶多酚0.40?μg/mL。经验证在酱腌菜拌料时添加复配防腐剂比在干制萝卜复水时添加防腐剂效果更好,可以延长其保质期至21?d,品质较好,总菌落数、大肠菌群数、总酸及氨基酸态氮含量符合国家标准,为ε-PL在酱腌菜中的应用提供了理论支持。     

ε-聚赖氨酸在冷鲜猪肉保鲜中的应用

研究ε-聚赖氨酸(ε-PL)保鲜冷鲜猪肉的处理条件,考察在优化条件下ε-PL对冷鲜猪肉感官、微生物、理化等指标的影响。结果表明:400mg/Lε-PL单独使用时就能显著抑制冷鲜猪肉感官品质的下降、微生物的生长繁殖、pH值的上升和TVB-N的积累,而当ε-PL和乙酸复配使用后抑制作用更佳,特别是对微生物的生长繁殖有明显的抑制作用,浸泡时间对ε-PL-乙酸助剂的抑菌效果影响很大,随着浸泡时间的增加,ε-PL-乙酸助剂抑菌效果逐渐加强。综合抑菌效果、处理成本以及处理效率考虑,优化组合为:ε-PL质量浓度400mg/L,助剂为0.2%乙酸,浸泡时间为5min。优化处理后冷鲜猪肉保质期从对照组2d延长至8d。结果揭示:ε-PL作为冷鲜肉生物保鲜剂,具有广阔的应用前景。     

乳酸链球菌素协同纳他霉素在豆腐保鲜中的应用

以豆腐为研究对象,通过添加乳酸链球菌素（nisin）和纳他霉素以提高豆腐的保鲜时间,以感官评分和菌落总数为评价指标,考察了乳酸链球菌素与纳他霉素添加量、杀菌温度和杀菌时间等对其的影响,通过正交试验得出最佳的优化条件为：nisin与纳他霉素添加量0.12 g/kg、杀菌温度90 ℃和杀菌时间20 min。此工艺条件处理后,冷却并在37 ℃恒温培养箱中保存7 d,测得试样的感官评分为93分,菌落总数为0.53×104 CFU/g。没有添加乳酸链球菌素和纳他霉素的对照组在同样条件下保存1 d,测得感官评分在50分以下,这为延长豆腐的保质期提供了实验基础和理论依据。     

纳他霉素在草莓防腐中的应用

研究了导致草莓腐败的主要病菌,用目前国内批准使用的2种天然防腐剂之一的纳他霉素对草莓防腐。结果表明,根霉、黑霉是导致草莓变质的主要病菌,用浓度为500mg/L的纳他霉素悬浮液喷洒的草莓,在温度为18℃～22℃,湿度为58%～65%条件下放置10d后腐败率仅为10%,而且纳他霉素还能使草莓具有甜中带酸的优良品质。     

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.