用于微生物培养基有机氮源的废酵母自溶液研究

为进一步降低聚 β 羟基丁酸酯 (PHB)的生产成本 ,考察并优化了酵母自溶的影响因素与条件 ,探索采用廉价的废酵母自溶液作为有机氮源替代酵母浸粉的可行性。结果表明 ,自溶反应的最佳初始 pH为 7 0 ;加水比不仅影响酵母细胞的自溶速度和自溶效率 ,而且影响自溶产品的氨基氮终浓度 ,因此最佳加水比的确定取决于最终的经济核算。乙酸乙酯可以成功替代甲苯作为自溶促进剂 ,其优化用量为 3 %～ 4%。进一步以自制的酵母自溶液对重组大肠杆菌VG1( pTU 14 )进行摇瓶培养 ,结果表明 ,当以酵母自溶液为有机氮源替代酵母浸粉时 ,PHB浓度可以提高 2 2 7%以上。因此 ,废啤酒酵母自溶液在PHB的大规模生产中具有广泛的应用前景。     

味精废水培养汉逊德巴利酵母的自溶条件优化

为了优化酵母细胞的自溶条件、提高细胞自溶的效果,本研究以味精废水为培养基,能耐高硫铵的汉逊德巴利酵母为原料,以细胞内容物溶出率为响应值,在时间、温度、pH、促溶剂种类的单因素实验基础上,利用响应面法优化细胞自溶条件。结果表明,汉逊德巴利酵母自溶的最佳条件为:自溶时间为23h,自溶温度为54℃、pH为5.5、木瓜蛋白酶的添加量为0.8%;在该条件下酵母自溶液中氨基酸态氮含量为14.76 g/L,与最佳预测值14.84 g/L较为接近。说明该模型可靠,响应面法优化酵母细胞自溶可行,可用于指导生产实践。     

啤酒酵母营养饮料的研制

以啤酒废酵母为原料经洗涤、除杂、自溶制得酵母自溶液,并进行调配制取啤酒酵母营养饮料。通过正交试验得到啤酒酵母自溶最适条件为：pH值6．0,温度55℃,NaCl添加量4％,蛋白酶添加量0.02％,自溶时间48h;饮料的最佳配方为：啤酒酵母自溶液的添加量为15％,白砂糖添加量4％,柠檬酸为0．3％。     

洋葱醋的酿造工艺研究

以洋葱汁为主要原料,分别采用葡萄酒酵母1450和醋酸菌As1.41进行液态酒精发酵和醋酸发酵。试验结果表明:酒精发酵的最佳条件为起始糖浓度11%,发酵温度26℃,酵母接种量5%;醋酸发酵起始酒精度6%(V/V),发酵温度30℃,醋酸菌培养液接种量10%。     

不同促溶剂对酵母细胞在发酵液中自溶的影响

通过添加不同促溶剂研究酵母细胞在发酵液中的自溶情况。对影响酵母细胞内容物的溶出率的各因素进行单因素试验,并设计正交试验进行各因素参数优化。正交试验结果表明,以NaCl为促溶剂的酵母发酵液内的自溶条件为pH5.0、温度50℃、时间48h、NaCl添加量为9%,测得酵母细胞在发酵液内自溶率达到49.30%;以β-葡聚糖酶为促溶剂的酵母发酵液内的自溶条件为pH6.5、温度55℃、时间24h、酶添加量为0.6%,测得酵母细胞在发酵液内自溶率达到49.98%;以木瓜蛋白酶为促溶剂的酵母发酵液内的自溶条件为pH 6.0、温度60℃、时间72h、酶添加量1%,测得酵母细胞在发酵液内自溶率达到51.53%。     

啤酒废酵母生产酵母浸粉及其应用的研究进展

全面系统阐述啤酒废酵母生产酵母浸粉及应用的研究进展.通过分析,指出原料的预处理、破壁方法和自溶技术是酵母浸粉生产工艺的核心.预处理一般通过稀释、过筛除杂和沉降分离完成.破壁方法有物理法、化学法、酶处理法等,综合破壁法已经成为研究的焦点.自溶的强化可以通过添加化学物质激活内源酶和添加外源酶实现.某些微生物的培养可以使用国产酵母浸粉替代部分进口产品,节约生产成本,达到其最优化使用.酵母浸粉的生产不仅具有可观经济效益,而且促进了企业清洁生产,社会效益也相当可观,所以利用啤酒废酵母生产酵母粉将成为酵母浸粉生产行业的趋势.     

不同自溶方式对啤酒废酵母甘露聚糖的降解作用

评价啤酒废酵母正常自溶,加盐自溶,加木瓜蛋白酶自溶条件下细胞壁甘露聚糖降解程度.利用紫外分光光度法测定啤酒废酵母和自溶液中甘露糖含量.在其他相同试验条件下,研究结果表明对于加木瓜蛋白酶,正常自溶和加盐自溶甘露糖的溶出量分别是15.85%、6.65%和4.93%.啤酒废酵母正常自溶对细胞壁甘露聚糖有一定的水解作用,加盐可减缓甘露糖的游离,外加木瓜蛋白酶可强烈的破坏甘露聚糖.     

基于功能性调味剂开发的啤酒废酵母自溶工艺条件的研究

为了设计利用啤酒废酵母生产功能性调味剂的工艺流程,试验对啤酒废酵母的脱苦工艺和自溶条件进行研究。结果表明:啤酒废酵母脱苦的最佳NaHCO3浓度为0.5%,最佳的自溶条件为0.3%NaCl溶液和0.05%的溶壁酶作促进剂、pH7.0、自溶温度55℃、自溶时间60 h。     

菠萝皮渣果醋高效发酵工艺

以菠萝皮渣为主要原料、果酒酵母和沪酿1.01 醋酸菌粉为菌种,采用半固态发酵和二次补糖工艺,对菠萝皮渣酒精发酵和醋酸发酵工艺进行研究,以确定最优酿造工艺参数和实现菠萝皮渣果醋的高效生产。结果表明：菠萝皮渣酒精发酵条件为酵母添加量0.3%、发酵温度22℃、糖度16°Brix、pH3.5、发酵时间6d;醋酸发 酵最佳工艺条件为添加的葡萄糖质量分数2%、初始乙醇体积分数8%、发酵温度29℃、醋酸菌粉添加量0.09%、发酵时间3～4d,得到总酸量(以醋酸计)达6.78g/100g 的菠萝果醋半固态混合物,醋酸转化率为82.5%。经浸泡、过滤和陈酿1～2 个月后,所得菠萝果醋成品总酸含量(以醋酸计)为3.672g/100mL,色泽金黄,清亮透明,既有酸香,又有菠萝果香,口味柔和爽口。半固态果醋发酵法与液态果醋发酵法相比,能明显提高总酸产量和缩短发酵时间。     

啤酒废酵母自溶制备氨基酸液的研究

本文对啤酒废酵母自溶条件进行了研究,得出自溶最优条件为：助溶剂NaCl2％、自溶温度50℃、自溶时间24小时、pH4．5～7。酵母自溶液对酵母的生长有促进作用。     

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.     

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.     

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.     

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.     

Announcing a new international peer-reviewed journal:Food Science and Human Wellness now accepting manuscript submission in English

<正>We are pleased to announce the launch of a new international peer-reviewed journal-Food Science and Human Wellness,ISSN 2213-4530,which is an open access journal,produced and hosted by Elsevier B.V.on behalf of Beijing Academy of Food Sciences.Food Science and Human Wellness is an international peer-reviewed English journal that provides a forum for the dissemination of the