ε-聚赖氨酸抑菌性能研究

分别采用分光光度法、菌体量法以及孔扩散法研究了ε-聚赖氨酸对细菌和真菌的抑菌活性及ε-聚赖氨酸浓度、pH值和温度对其抑菌活性的影响。结果表明,ε-聚赖氨酸对金黄色葡萄球菌、大肠杆菌、黄曲霉、枯草芽孢杆菌、酿酒酵母、保加利亚乳杆菌等6种供试微生物均有一定的抑制作用,对大肠杆菌、金黄色葡萄球菌、保加利亚乳杆菌抑制效果较好,对黄曲霉较差;对各种菌的最小抑菌浓度(MIC)为大肠杆菌、金黄色葡萄球菌、保加利亚乳杆菌12.5 mg/L;枯草芽孢杆菌25 mg/L;酿酒酵母800 mg/L;黄曲霉1 600 mg/L。ε-聚赖氨酸的抑菌活性随其浓度的增加而增强,热稳定性非常好,能耐100℃的高温,在pH5～8抑菌活性最强,与甘氨酸、Nisin都有协同增效的作用。     

国产Nisin部分特性的研究

研究温度、pH、蛋白酶、保存条件对国产Nisin抑菌活性的影响,以及抑菌谱等,结果表明温度、pH会显著影响Nisin活性,在酸性条件下,Nisin对温度较稳定,随PH值的增加,温度越高,Nisin活性下降越显著,温度越低越有利于保存,干制品比溶液易保存,国产Nisin对胃蛋白酶不敏感,但对胰蛋白酶敏感,国产Nisin对革兰氏阳性细菌有抑制作用,而对革兰氏阴性细菌、霉菌和酵母没有作用。     

连翘叶提取物抑菌作用以及稳定性研究

对连翘叶提取物(Forsythia Suspensa leaves extract,FSLE)抑菌性能进行研究,同时以大肠杆菌、枯草芽孢杆菌和金黄色葡萄球菌为指示菌研究FSLE抑菌成分的稳定性.结果表明:FSLE的抑菌活性具有良好的热稳定性;在中性和弱酸性环境中FSLE抑菌活性较强;在大于30min紫外线照射对FSLE抑制枯草芽孢杆菌和金黄色葡萄球菌活性有一定影响;H2O2对FSLE抑菌活性影响较大;金属离子Na+、K+对FSLE抑菌性能影响不大,Ca2+、Cu2+、Fe3+有增强FSLE抑菌能力作用.     

枫香叶精油抑菌活性及抗氧化活性研究

采用水蒸气蒸馏法提取枫香叶精油,用滤纸片法测定精油的抑菌活性,用平板涂布法测定其最低抑菌浓度(MIC),同时研究了枫香叶精油抑菌活性的酸碱稳定性、热稳定性、紫外稳定性和抗氧化稳定性。结果表明：枫香叶精油对5 种受试菌的抑制效果有较大差异,对革兰氏阳性菌和霉菌的抑制作用较强,对革兰氏阴性菌的抑制作用较弱;精油对枯草杆菌、金黄色葡萄球菌、大肠杆菌、黄曲霉、青霉的MIC 分别为1.25%、0.625%、5%、2.5%、2.5%;精油对温度和紫外照射具有良好的稳定性,在不同的pH 值条件下其抑菌活性不稳定,酸性环境下其抑菌活性强,碱性环境下抑菌活性弱;精油具有抑制食物氧化的作用,随着精油浓度增大其抗氧化性增强。     

茶多酚的制备及其抑菌活性的研究

以精制绿茶粉为原料,制备茶多酚。采用滤纸片法和平板计数法研究了制备所得的茶多酚对供试细菌和酵母的抑菌活性及茶多酚浓度、与菌种作用时间、pH值、温度和氯化钠浓度对抑菌活性的影响。结果表明:茶多酚对细菌有较强的抑菌活性,而对供试的酵母抑制作用不明显;茶多酚对金黄色葡萄球菌、枯草芽孢杆菌和大肠杆菌的最低抑菌浓度分别为6.25%、12.5%、25%;茶多酚的浓度越高,与菌种作用时间越长,抑菌活性越强;在弱碱性环境中的抑菌活性最强;一定温度内处理不影响茶多酚的抑菌活性;氯化钠能增强茶多酚的抑菌活性。     

Nisin和山梨酸钾对酸奶中乳酸菌及杂菌的体外抑菌实验

本文采用稀释平板法,在pH6.0条件下,测定Nisin、山梨酸钾及二者复配后对酸奶中的乳酸菌、芽孢杆菌、大肠杆菌、金黄色葡萄球菌、沙门氏菌、酵母菌、霉菌的抑制作用.结果表明培养相同时间,随着防腐剂浓度的升高,Nisin、山梨酸钾及二者复配对乳酸菌抑菌率上升;相同防腐浓度,随着培养时间的延长,Nisin、山梨酸钾及二者复配对乳酸菌抑菌率下降.Nisin对所试乳酸菌菌株具有一定的抑菌效果,而山梨酸钾在16h内具有一定的抑菌效果.Nisin、山梨酸钾二者复配抑菌效果明显优于单独使用,Nisin0.125g/kg、山梨酸钾0.5g/kg二者复配,16h、48h对乳酸菌的抑菌率分别为80.8%、46.7%.实验中的各个防腐浓度,Nisin、山梨酸钾单独或复配使用对芽孢杆菌等杂菌抑菌几乎无效果.     

防腐保鲜剂对牛肉火腿切片腐败菌抑制效果的研究

本文以牛肉火腿切片分离出的乳酸杆菌及肠杆菌为供试菌，采用滤纸片法对10种防腐保鲜剂：乳酸钠、双乙酸钠、山梨酸钾、EDTA二钠、Nisin、茶多酚、壳聚糖、水溶性壳聚糖、芦丁、苦荞壳提取液(黄酮)，以及部分复配剂的抑菌效果进行了筛选。结果发现Nisin对乳杆菌的作用效果明显；茶多酚、壳聚糖对肠杆菌有较强的抑制作用。实验表明可采用复合天然防腐保鲜剂-0．015％Nisin 0．5％茶多酚，对牛肉火腿切片的腐败菌进行控制，不同pH介质、热处理对其抑菌活性影响不大。最后对苦荞壳提取液的抑菌活性进行了探讨。     

玉米须多糖的超声辅助酶法提取及抑菌作用研究

为了研究玉米须多糖的提取工艺条件,在超声波作用温度、超声波作用时间、纤维素酶添加量、中性蛋白酶添加量4个单因素对多糖提取率影响的基础上,利用响应面分析法对超声波协同酶法提取玉米须多糖的最佳工艺条件进行优化。试验结果表明,玉米须多糖的最佳提取条件为超声波作用温度64℃,纤维素酶添加量1.35%,中性蛋白酶添加量1.14%,在此优化条件下多糖得率为4.48%。此外玉米须多糖经初步纯化后,采用琼脂平板扩散法进行抑菌试验,结果表明玉米须多糖对细菌、真菌均有一定的抑制作用,对真菌的抑制活性弱于对细菌的抑制活性,对革兰氏阴性菌的抑制作用稍优于对革兰氏阳性菌。     

苹果渣中多酚物质的纯化及其抑菌活性的研究

本实验运用静态吸附与解吸实验对10种大孔树脂进行筛选,筛选出效果最好的树脂对苹果渣中多酚物质进行动态吸附实验研究,并采用滤纸片法研究了多酚纯化物的抑菌活性及其质量浓度、pH值、温度对抑菌活性的影响。结果表明:D4020大孔树脂表现出良好的吸附性能与最好的解吸效果;苹果渣多酚纯化物对细菌的抑制作用较强,而对供试霉菌、酵母菌抑制作用不明显,其对大肠杆菌和金黄色葡萄球菌的最低抑制浓度(MIC)均为0.015%(W/W);在pH5～6环境条件下其抑菌效果最佳;一定温度内处理不影响苹果多酚的抑菌活性。     

艾蒿多糖抑菌活性及稳定性

采用水提法提取艾蒿多糖,用滤纸片法测定多糖的抑菌活性及最低抑菌浓度(MIC),同时研究艾蒿多糖抑菌活性的酸碱稳定性、热稳定性、紫外稳定性。结果表明:艾蒿多糖对3种常见细菌均有一定的抑制效果,对革兰氏阳性细菌如金黄色葡萄球菌和枯草芽孢杆菌抑制作用较强,对革兰氏阴性菌大肠杆菌的抑制作用较弱;艾蒿多糖对枯草芽孢杆菌、金黄色葡萄球菌、大肠杆菌的最小抑制质量浓度(MIC)分别为0.625、0.625、1.25 mg/mL;多糖的抑菌活性对温度和紫外照射具有较好稳定性,在不同的pH值条件下抑菌活性相对不稳定,酸性处理条件下抑菌活性较强,碱性处理条件下抑菌活性较弱。艾蒿多糖具有良好的抑菌活性,可用于天然食品防腐剂的开发利用。     

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.     

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.     

The development of reference materials for paralytic shellfish poisoning toxins in lyophilized mussel. I: Interlaboratory studies of methods of analysis

This paper describes the first part of a project undertaken to develop mussel reference materials for Paralytic Shellfish Poisoning (PSP) toxins. Two interlaboratory studies were undertaken to investigate the performance of the analytical methodology for several PSP toxins, in particular saxitoxin (STX) and decarbamoyl-saxitoxin (dc-STX) in lyophilized mussels, and to set criteria for the acceptance of results to be applied during the second part of the project: the certification exercise. In the first study, 18 laboratories were asked to measure STX and dc-STX in rehydrated lyophilized mussel material and to identify as many other PSP toxins as possible with a method of their choice. In the second interlaboratory study, 15 laboratories were additionally asked to determine quantitatively STX and dc-STX in rehydrated lyophilized mussel and in a saxitoxin-enriched mussel material. The first study revealed that three out of four postcolumn derivatization methods and one pre-column derivatization method sufficed in principle to determine STX and dc-STX. Most participants (13 of 18) obtained acceptable calibration curves and recoveries. Saxitoxin was hardly detected in the rehydrated lyophilized mussels and results obtained for dc-STX yielded a CV of 58% at a mass fraction of 1.86 mg/kg. Most participants (14 out of 18) identified gonyautoxin-5 (GTX-5) in a hydrolysed extract provided. The first study led to provisional criteria for linearity, recovery and separation. The second study revealed that 6 out of 15 laboratories were able to meet these criteria. Results obtained for dc-STX yielded a CV of 19% at a mass fraction of 3.49mg/kg. Results obtained for STX in the saxitoxin-enriched material yielded a CV of 19% at a mass fraction of 0.34mg/kg. Saxitoxin could not be detected in the PSP-positive material. Hydrolysis was useful to confirm the identity of GTX5 and provided indicative information about C1 and C2 toxins in the PSP-positive material. The methods used in the second interlaboratory study showed sufficiently consistent analysis results to undertake a certification exercise to assign certified values for STX and dc-STX in lyophilized mussel.