桉叶精油对水产品中4种微生物的抑菌效果及抑菌机理

本文研究了桉叶精油对水产品中4种微生物的体外抑菌活性及其抑菌机理。通过滤纸片法和倍比稀释法分别测定抑菌圈直径(DIZ)和最低抑菌浓度(MIC),分析植物精油(桉叶精油、薄荷精油、茶树精油、丁香精油)对水产品中4种常见微生物(大肠杆菌、金黄色葡萄球菌、腐败希瓦氏菌和副溶血性弧菌)的抑菌效果;进一步以腐败希瓦氏菌和金黄色葡萄球菌为研究对象,通过扫描电镜、透射电镜、电导率、核酸含量、细胞内ATP含量分析植物精油的抑菌机理。结果表明,桉叶精油对大肠杆菌、腐败希瓦氏菌、副溶血性弧菌和金黄色葡萄球菌的抑菌圈直径分别为33.33、27.87、38.88、39.61 mm,对大肠杆菌、腐败希瓦氏菌、副溶血性弧菌和金黄色葡萄球菌的MIC值分别为1.00、1.25、0.75、0.63 μL/mL,在4种植物精油中显示出最强的抗菌活性。桉叶精油改变了腐败希瓦氏菌和金黄色葡萄球菌的细胞形态和超微结构,加了细胞膜的通透性,破坏了细胞膜的完整性,造成细胞内容物的泄露及细胞生理功能紊乱,从而导致细菌的死亡。本实验将为桉叶精油作为一种天然抑菌物质应用于水产品行业提供理论依据。     

留兰香精油的抗菌活性研究

采用扩散法对留兰香精油的抗菌活性进行定性测定,用紫外可见分光光度法确定精油的最小抑菌浓度(MIC值)。结果表明留兰香精油对3种试验菌株的抑菌性是枯草芽孢杆菌>金黄色葡萄球菌>大肠杆菌。对枯草芽孢杆菌、金黄色葡萄球、菌大肠杆菌3种菌的最小抑菌浓度(MIC)分别为0.5、1.0μL/mL和3.5μL/mL。     

香樟精油的体外抑菌活性

采用抑菌圈实验和二倍稀释法研究了香樟精油对金黄色葡萄球菌的抑菌活性、最低抑菌浓度(MIC)。结果表明:香樟精油对金黄色葡萄球菌抑菌活性显著,当香樟精油的浓度大于12.5%时,可完全抑制金黄色葡萄球菌的生长。     

香辛料精油复配抑菌效果研究

研究香辛料精油复配的抑菌效果。利用丁香、肉桂、豆蔻、孜然、茴香5种香辛料分别对大肠杆菌、金黄色葡萄球菌、啤酒酵母、黑曲霉菌单一精油的抑菌试验;丁香、肉桂及二者复配3种精油验对4种菌的抑菌试验;复配精油在不同温度、pH下对大肠杆菌和黑曲霉菌的抑菌稳定性试验,得出丁香精油抑制细菌、肉桂精油抑制真菌的能力较强,均高于其他几种香辛料精油的抑菌能力;复配精油对大肠杆菌、黑曲霉的抑菌效果明显;且复配精油在不同温度和pH下抑菌性较为稳定,为复配精油作为抑菌剂在食品中的应用提供参考。     

肉桂精油气相熏蒸金黄色葡萄球菌的抗菌机理

该研究主要探讨了肉桂精油的抗菌活性及其对金黄色葡萄球菌的抗菌机制,实验采用气相熏蒸法研究精油的气相抗菌活性,通过TEM、电导率实验、FT-IR、荧光光谱等方法探讨肉桂精油的气相抗菌机制。结果表明肉桂精油具有显著的气相抗菌活性,对金黄色葡萄球菌的最低抑菌浓度(MIC)为0.25μL/m L,最低杀菌浓度(MBC)为0.5μL/m L。TEM观察显示,经肉桂精油气熏后的金黄色葡萄球菌菌体细胞膜破损溶解,细胞皱缩,从而引起内容物外泄。电导率实验进一步表明气熏后的菌体细胞膜通透性提高,并通过测试OD260发现核酸外泄与精油浓度变化的正相关关系。通过FT-IR图与荧光光谱图,发现肉桂精油引起金黄色葡萄球菌菌体蛋白构象的变化,并通过分析酰胺Ⅰ带推测在气熏过程中菌体蛋白二级结构发生无序变化,以及通过荧光强度和波长峰位的变化判断肉桂精油气熏后菌体蛋白发生了改变,暴露出更多的发色基团。由此可见,肉桂精油气相熏蒸金黄色葡萄球菌可能的抑菌机理是改变菌体细胞膜通透性和形态,并改变了菌体蛋白的二级结构和三级结构。     

香旱芹精油对金黄色葡萄球菌抑菌机理的研究

采用微波辅助水蒸气蒸馏提取出香旱芹精油,对其成分进行GC-MS分析,通过测试其对金黄色葡萄球菌的抑菌圈直径、最低抑菌浓度(MIC)和最低杀菌浓度(MBC)评价其抑菌效果。分别从菌体微观形态、细胞溶出物、蛋白质和钾离子泄漏等方面研究香旱芹精油对金黄色葡萄球菌的抑菌机理。实验结果表明香旱芹精油的主要成分为百里香酚(45.85%)、对伞花烃(20.72%)和γ-松油烯(23.57%),其对金黄色葡萄球菌的抑菌圈直径为75mm,MIC为0.25μL/mL,MBC为0.5μL/mL。香旱芹精油可使金黄色葡萄球菌细胞膜受到损伤,使细胞膜表面出现塌陷和破裂,并引起菌体细胞溶出物、蛋白质以及钾离子的泄露,从而导致菌体的死亡。     

茶多酚-肉桂精油复合保鲜剂抗氧化活性及抑菌作用

为了研究茶多酚-肉桂精油复合保鲜剂抗氧化活性和对金黄色葡萄球菌的抑菌作用。采用体外抗氧化法测定了复合保鲜剂抗氧化能力。通过抑菌圈大小确定抑菌效果和最小抑菌浓度(MIC),结合抑菌活力、细菌生长曲线、细胞壁完整性和细胞膜通透性,综合评价复合保鲜剂对金黄色葡萄球菌的影响。结果表明,复合保鲜剂清除DPPH自由基、羟基自由基和超氧阴离子自由基的IC50分别为4.02μg/m L、9.15μg/m L、0.61 mg/m L。复合保鲜剂能够有效抑制金黄色葡萄球菌的生长,MIC为0.5 mg/m L,且能够破坏细胞壁和细胞膜。综上所述复合保鲜剂具有很强的抗氧化活性,对金黄色葡萄球菌有很好的抑菌效果,其可能的抑菌机理是破坏细胞壁,影响细胞膜的通透性。     

七种精油对多重耐药鲍曼不动杆菌的抑制作用

本文研究了肉桂等精油对多重耐药鲍曼不动杆菌(MDRAB)的体外抑菌效果,采用药敏纸片扩散法和微量肉汤稀释法测定其对MDRAB的抑菌圈直径和最小抑菌浓度(MIC),筛选出抑制效果最好的精油和绘制出该精油对MDRAB的动态杀菌曲线。用棋盘稀释法研究MIC值最小的两种精油联合抗MDRAB的效果。结果表明肉桂精油对MDRAB的抑菌效果最强,抑菌圈直径为29.30±1.16 mm,MIC值为0.62μL/mL,且对MDRAB的抑菌活性存在浓度依赖性,另外肉桂精油与薰衣草精油联合抗MDRAB有相加作用,与薄荷精油联合抗MDRAB有部分协同作用;薰衣草精油和薄荷精油也有较强抑菌效果,MIC值依次为1.25μL/mL和2.50μL/mL;丁香精油对MDRAB有中度抑菌活性,MIC值为10μL/mL;冬青精油和绿茶精油对MDRAB的抑菌作用相对较弱,MIC值为20μL/mL;安息香精油对MDRAB的抑制作用很弱甚至无抑制作用。因此,肉桂精油对MDRAB的抑菌效果最强,且对MDRAB的抑菌活性与浓度正相关,另外与薰衣草精油和薄荷精油有联合抗MDRAB作用,为临床用药提供有效指导。     

香樟精油的体外抑菌活性

采用抑菌圈实验和二倍稀释法研究了香樟精油对金黄色葡萄球菌的抑菌活性、最低抑菌浓度（MIC）。结果表明：香樟精油对金黄色葡萄球菌抑菌活性显著,当香樟精油的浓度大于12.5％时,可完全抑制金黄色葡萄球菌的生长。     

茶槲寄生“螃蟹脚”正丁醇萃取相对金黄色葡萄球菌抑菌机理的研究

本文研究了茶槲寄生"螃蟹脚"醇提各萃取相的抑菌作用及正丁醇萃取相(NVBEs)对金黄色葡萄球菌的抑菌机理。采用滤纸片扩散法测定抑菌圈直径(DIZ)的大小,对倍稀释法测定最小抑菌浓度(MIC)和最低杀菌浓度(MBC),来评价"螃蟹脚"醇提各萃取相对金黄色葡萄球菌(S.aureus)、大肠杆菌(E.coli)、鼠伤寒沙门氏菌(S.typhimurium)、单核细胞增生李斯特菌(L.monocytogenes)4种食源性腐败菌的抑制性;通过光学显微镜和扫描电镜观察、胞膜通透性、胞壁完整性和酶活性等实验,研究了NVBEs抑菌机理。结果表明,"螃蟹脚"醇提各萃取相对S.aureus、E.coli、S.typhimurium和L.monocytogenes均有明显抑制效果,其中NVBEs抑菌活性较好,对S.aureus抑制效果最好,DIZ为9.84±0.57 mm,MIC为3.52 mg/m L,MBC为7.04 mg/m L。抑菌机理结果表明:NVBEs可增加S.aureus细胞壁及细胞膜的通透性,破坏菌体细胞结构,引起细胞内含物如核酸和蛋白质等外泄;引起遗传物质DNA的改变,使菌体细胞形态结构出现异常;影响菌体酶的代谢活动,从而抑制细菌的生长。     

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.