培养条件对植物乳杆菌LIP-1抗冷冻活性的影响

以前期优化的MRS培养基为基础培养基,采用二次响应面分析法优化植物乳杆菌LIP-1的培养条件（温度、接种量、初始培养pH）,研究改变培养条件是否可提高植物乳杆菌 LIP-1高密度发酵培养后的活菌数以及对冷冻干燥后菌株的冻干抗性的影响。结果显示：最佳培养条件：培养pH6.7、培养温度36 ℃、接种量8.8%,在此培养条件下,植物乳杆菌LIP-1高密度发酵后活菌数为10.1855 lg（CFU/mL）,冷冻干燥后的存活率达83.40%,与未优化的培养条件相比,发酵培养后活菌数及冻干存活率显著提高（P<0.05）,分别提高0.2935 lg（CFU/mL）和8.46%。结轮：通过改变培养条件可显著提高植物乳杆菌LIP-1的高密度发酵活性和冷冻干燥存活率。     

发酵乳杆菌的生长限制性因素分析及高密度培养工艺优化

为提高发酵乳杆菌的增殖浓度,对其高密度发酵培养基成分及培养工艺进行优化以提高其活菌数。结果表明,酵母粉复合大分子肽的蛋白胨是发酵乳杆菌的最适氮源,缓冲盐在恒pH培养时对菌株生长无促进作用,Mn²⁺和Mg²⁺均是发酵乳杆菌的限制性微量元素。另外,中性条件下酸根的积累不会对发酵乳杆菌有特异性毒害作用,其生长主要是受到渗透压的抑制。以菌株生长速率被抑制时的碳氮消耗比作为培养基中的碳氮源比例,基于菌株生长速率被抑制时的渗透压确定碳氮源的添加量。进一步优化恒pH分批培养和恒pH自动反馈补糖培养工艺,得到各菌株的最优培养策略:发酵乳杆菌FXJCJ6-1、发酵乳杆菌FGDLZR161、发酵乳杆菌CCFM422分别在恒pH 6.0、5.5、5.5分批培养时,活菌数分别达到(1.3±0.1)×10¹⁰、(1.1±0.1)×10¹⁰、(9.5±0.5)×10^(9 )CFU/mL,较在MRS培养基静置培养时的活菌数提高了3.1、3.8和4.6倍。该研究结果的应用将显著提高发酵乳杆菌的工业化生产效率。     

基于pH下降速率的反馈补料策略高密度培养保加利亚乳杆菌NQ2508

保加利亚乳杆菌是酸奶发酵剂和益生菌制剂的重要菌种,其高密度培养对于提高菌种在应用产品生产中的效率具有重要的现实意义。葡萄糖浓度和发酵pH是影响保加利亚乳杆菌生长的关键因子,底物葡萄糖被转化为细胞菌体和主要代谢产物乳酸,探究葡萄糖消耗速率与表征乳酸生成的发酵pH下降速率的关系,是研究保加利亚乳杆菌代谢流方向的重要方法。该实验通过培养基组成和培养条件对保加利亚乳杆菌生长的影响进行研究,同时对葡萄糖消耗速率-pH降低速率相关模型研究,并基于底物质量守恒定律建立了一条基于pH下降速率的保加利亚乳杆菌高密度培养的反馈补料发酵策略。通过化学中和法控制发酵pH为6.0～5.0,基于pH下降速率进行反馈补料将葡萄糖质量浓度控制在8～2 g/L,发酵液的活菌数达到3.6×10⁹ CFU/mL,是批次分批培养的2.4倍。该策略的应用结果为提高保加利亚乳杆菌的工业化生产效率提供参考。     

蔬菜汁的乳酸菌发酵

为制备不含任何动物性来源成分的纯植物性的乳酸菌发酵产品,采用双歧乳杆菌、植物乳杆菌、保加利亚乳杆菌、嗜酸乳杆菌4种乳酸菌,在豆角、香菇、番茄、青瓜、胡萝卜和包菜6和蔬菜培养液中进行发酵。实验结果证明,4种乳酸菌可以在不添加其他营养物质的纯蔬菜培养液正常生长,但是不同菌种适合的蔬菜培养液也不相同,且混合蔬菜培养液培养效果要好于单一蔬菜培养液。番茄和青瓜混合培养液适合双歧乳杆菌生长,包菜和青瓜混合培养液适合植物乳杆菌生长,包菜和番茄混合培养液适合保加利亚乳杆菌生长,豆角和青瓜混合培养液适合嗜酸乳杆菌生长。蔬菜的乳酸菌发酵产品,在4℃下冷藏2周后,4种菌体的存活率均在106CFU/mL以上。在不添加其他营养物质的条件下,蔬菜汁可以用来生产活性乳酸菌产品,满足素食主义者、乳糖不耐症者的消费需求。     

植物乳杆菌发酵苹果汁及菌体活性保持

为实现植物乳杆菌在苹果汁中的发酵增殖及低温贮藏期间的活性保持,测定苹果汁先后添加无机盐、营养因子和微量元素后菌株的增殖浓度,并比较发酵果汁在添加不同保护剂后4℃冷藏期间的活菌数。发现KH_2PO_4、柠檬酸钠、酵母粉和MnSO_4是植物乳杆菌在苹果汁中发酵增殖的关键因子,其添加量分别为5、7、5和0.05 g/L时菌株发酵12 h活菌数达(3.4±0.2)×10~9CFU/mL,且抗性糊精更有利于菌体的活性保持。发酵结束离心收集菌体,以不同浓度的抗性糊精为保护剂制备粒径大小不同的海藻酸钠微胶囊,测定其在果汁中冷藏期间的活菌数。结果表明,抗性糊精浓度为200 g/L,粒径为4 mm的微胶囊显著提高植物乳杆菌在发酵苹果汁中的活性保持,冷藏21 d后存活率达(81±3.1)%。该研究解决了植物乳杆菌在发酵苹果汁高密度增殖的难题,且为含活性菌发酵果蔬汁的研发提供了指导方法。     

传统发酵牦牛乳中2株高产胞外多糖乳酸菌在模拟消化道中耐受力的研究

从传统发酵牦牛发酵乳中分离出的2株高产胞外多糖乳酸菌,为了研究其在模拟消化道中耐受力,对2株乳酸菌(植物乳杆菌、干酪乳杆菌)分别在人工胃液、人工肠液、人工胆汁和高盐4个模拟人工胃肠道消化环境中进行培养,测其耐受力以及对Caco﹣2细胞的黏附能力。结果表明:植物乳杆菌和干酪乳杆菌在人工胃液中作用3 h的存活率随pH值的增大而增加。在pH4.5时,植物乳杆菌的存活率达到53.63%,干酪乳杆菌的存活率达到50.83%;在人工肠液中作用4h,植物乳杆菌的存活率达到了59.58%,干酪乳杆菌的存活率达到了51.42%;在胆盐环境中培养24 h后的植物乳杆菌和干酪乳杆菌活菌数随牛胆盐质量浓度的增加而降低,活菌数均保持在108cfu/m L以上;在高盐环境中培养24 h后的活菌数随盐质量浓度的增加而降低,活菌数均在108 cfu/mL以上;并且2株乳酸菌的黏附能力也很强,植物乳杆菌可以达到16.83%、干酪乳杆菌可以达到14.86%。结论:植物乳杆菌和干酪乳杆菌均能通过胃进入肠道并保持活力,而且能在肠道很好地定植,为植物乳杆菌和干酪乳杆菌作为益生菌应用在食品中提供了理论基础。     

植物乳杆菌ST-Ⅲ的生长特性与保存性能研究

对植物乳杆菌ST-Ⅲ与酸奶发酵剂在不同温度混合发酵时的生长特性以及在不同pH值发酵乳中的保存活性进行了研究。结果表明,与酸奶发酵剂在37℃或40℃混合发酵时,植物乳杆菌ST-III不出现明显生长,活菌数始终保持在5.0×106 mL-1左右;在酸奶冷藏(0~6℃)保存2周的过程中,植物乳杆菌ST-III具有良好的存活性能,酸奶的初始pH值(4.00~5.00)不影响其存活性能。     

预培养冷冻干燥制备植物乳杆菌发酵剂

为提高菌体冷冻干燥存活率,制备发酵活力高的植物乳杆菌发酵剂,通过在MRS培养基和蕉杆培养基中比较不同收获期的菌体发酵活力,确定菌体培养最佳收获期;通过单因素实验和正交实验考察预培养时间、温度和保护剂海藻糖浓度对冻干存活率的影响;比较冻干发酵剂和新鲜菌液在MRS培养基和蕉杆培养基中的发酵活力。结果表明:对数末期为培养植物乳杆菌S14的最佳收获期;预培养的最优条件为温度37℃,预培养时间45 min,海藻糖浓度10%,冻干存活率达89.9%;植物乳杆菌S14冻干发酵剂的发酵活力与新鲜菌液的发酵活力十分接近。该发酵剂适用于蕉秆青贮发酵。     

甘氨酸甜菜碱对植物乳杆菌YSQ18的渗透压胁迫耐受性的影响

从传统泡菜中分离出一株耐盐的酸菌,对其进行形态学、生理生化特性及16S rRNA序列分析鉴定,确定其种属地位;并初步研究相容性溶质甘氨酸甜菜碱在高渗透压环境下对所筛菌株的生长曲线和发酵糖耗速率的影响。结果表明:筛选出的乳酸菌中有一株符合乳杆菌属植物乳杆菌的鉴别特征,与16S rRNA序列鉴定和发育树分析结果一致。在含有1.2mol/L NaCl和1.5mol/L NaCl的化学合成培养基中,该植物乳杆菌的生长受到完全的抑制。在培养基中添加0.80mmol/L的甘氨酸甜菜碱对植物乳杆菌有较明显的保护作用,能减弱高渗胁迫,有效缩短迟滞期,提高耐盐能力。发酵中糖耗速率测定结果表明添加0.80mmol/L的甘氨酸甜菜碱能有效保持细菌活性。因此,在高渗环境发酵过程添加甘氨酸甜菜碱也许能有效提高微生物的活性,如传统的酿制酱油以及腌制泡菜等。     

低聚半乳糖对植物乳杆菌发酵乳特性及抗蜡样芽孢杆菌活性的改善

为探究低聚半乳糖对植物乳杆菌发酵乳特性及抗菌活性的影响,本文采用单因素法考察影响发酵乳特性的主要因素,并以响应面法优化发酵乳最佳发酵条件;以产肠毒素蜡样芽孢杆菌HN001为指示菌,探究低聚半乳糖的添加对植物乳杆菌ZDY2013发酵乳抑菌活性的改善作用。结果表明:植物乳杆菌能有效利用低聚半乳糖进行体外代谢,并抑制蜡样芽孢杆菌生长;牛奶中添加适量低聚半乳糖能够增加植物乳杆菌发酵乳中的活菌数、降低发酵乳的pH,并提高其持水力;响应面分析发现低聚半乳糖发酵乳的最佳制备条件为:2.0%的植物乳杆菌接种量、1.0%的低聚半乳糖添加量、发酵时间为24 h及发酵温度为42 ℃;添加低聚半乳糖的发酵乳能有效控制产肠毒素蜡样芽孢杆菌浓度在106 CFU/mL以下。该研究结果为低聚半乳糖及植物乳杆菌ZDY2013在发酵乳中的应用奠定了理论基础。     

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.     

Chlorohydrins of bisphenol A diglycidyl ether (BADGE) and of bisphenol F diglycidyl ether (BFDGE) in canned foods and ready-to-drink coffees from the Japanese market

BADGE.2HCl and BFDGE.2HCl were determined in 28 samples of ready-to-drink canned coffee and 18 samples of canned vegetables (10 corn, 5 tomatoes and 3 others), all from the Japanese market. HPLC was used as the principal analytical method and GCMS for confirmation of relevant LC fractions. BADGE.2HCl was found to be present in one canned coffee and five samples of corn, BFDGE.2HCl in four samples of canned tomatoes and in one canned corn. No sample was found which exceeded the 1mg/kg limit of the EU for the BADGE chlorohydrins. However the highest concentration was found for the sum of BFDGE.2HCl and BFDGE.HCl.H₂O at a level of 1.5mg/kg. A Beilstein test confirmed that all cans containing foods contaminated with BADGE.2HCl or BFDGE.2HCl had at lest one part coated with a PVC organosol.     

European priorities for research to support legislation in the area of food contact materials and articles

A strong science base is required to underpin the planning and decision-making process involved in determining future European community legislation on materials and articles in contact with food. Significant progress has been made in the past 5 years in European funded work in this area, with many developments contributing to a much better understanding of the migration process, and better and simpler approaches to food control. In this paper this progress is reviewed against previously identified work-areas (identified in 1994) and conclusions are reached about future requirements for R&D to support legislation on food contact materials and articles over the next 5 or so years.     

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.     

Influence des ions sur le pouvoir hydratant de l'ure e: e tude sur peau de porc ex vivo

This study deals with the influence of ions (NaCl and MgSO4) in a W/O emulsion containing 10% urea. Moisturization kinetics are assessed by corneometry on pig skin ex vivo. The formula's influence on urea penetration is measured by infrared spectrometry with an ATR device and the stripping method. Corneometry and spectroscopy were chosen to record simultaneously the hydratation levels and urea localization into superficial cell layers. Urea crystallization after evaporation of emulsions and aqueous solutions is described. Results show that urea does not hydrate nor penetrate when applied to the skin through an aqueous gel. In a W/O emulsion, sodium chloride increases the ability of urea to moisturize without improving penetration. In vitro urea crystallization is disturbed by sodium chloride or magnesium sulphate for solutions and emulsions. This stabilization by ions is correlated with good moisturization values. The stabilization of urea in the solute state provided by ions increases its water epidermal binding capacity without enhancing penetration.     

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.