酸性亚硫酸盐预处理桉木的分步和同步糖化发酵

本文以酸性亚硫酸盐预处理的桉木为原料,比较了不同固体浓度条件下进行分步(SHF)和同步(SSF)糖化发酵的水解与发酵产物得率。结果表明,SHF适合于固体浓度较低(2%和6%,w/w)的操作条件,当纤维素酶用量为20 FPU/g纤维素,酵母浓度为1g/L时,水解率可分别达到99.8%和94.8%,乙醇得率为94%和89%。SSF比SHF更适合于高浓的操作条件,当底物浓度为24%时,最高乙醇浓度可达56.7 g/L,是SHF得到乙醇浓度的1.7倍。     

菊芋原料同步糖化发酵生产丁二酸

对菊芋原料发酵生产丁二酸进行了研究,用 Actinobacillus succinogenes 和 Aspergillus niger 同步糖化发酵,发现同步糖化发酵效果优于糖化后再发酵,在同步糖化发酵过程中还原糖质量浓度始终保持在10～40 g/L,可以避免高浓度的还原糖对 A.succinogenes 的抑制.5 L搅拌罐中同步糖化补料分批发酵96 h产丁二酸98.2 g/L,对消耗糖产率95.4%,生产强度1.02 g/(L·h) .     

利用SSF制取纤维乙醇的工艺研究

利用同步糖化发酵（SSF）技术,以汽爆玉米秸秆为主要原料,对纤维乙醇的发酵工艺进行研究。玉米秸秆经蒸汽爆破预处理后,酶解得率增大到85.0%。进一步利用Box-Behnken实验设计方法,选取酶用量、发酵温度和发酵时间为影响乙醇产率的主要因素,通过响应面分析得到了较优的工艺条件：底物浓度15%（w/v）,酶用量35FPU/g（底物）,发酵温度37℃,发酵时间90h。在优化的工艺条件下,乙醇浓度为42.2g/L,达到理论产量的82.6%。和分步糖化发酵（SHF）工艺结果比较,SSF具有更高的生产效率。     

热醋酸梭状芽胞杆菌发酵葡萄糖和木薯粉产醋酸

在恒定pH值条件下,利用同型乙酸菌热醋酸梭状芽胞杆菌(Clostridium thermoaceticum)进行葡萄糖分批发酵、补料分批发酵和木薯粉发酵醋酸的初步研究.最适发酵葡萄糖模式:补糖的同时加入3倍量的氮源和微量元素补料分批发酵.醋酸产量40.2g/L,葡萄糖利用率98%,葡萄糖转化率0.82g/g,发酵时间为216h.结合葡萄糖发酵特点和木薯粉酶解条件摸索出木薯粉发酵条件:木薯液化后直接加入适量的糖化酶进行发酵并在发酵过程中补加适量糖化酶使醪液中葡萄糖浓度保持在一定范围内.醋酸产量47.3g/L,葡萄糖利用率94.75%,葡萄糖转化率0.89g/g,发酵时间192h.不添加过量的氮源和微量元素同时省略了糖化工段,底物转化率提高时间缩短,是比较理想的发酵模式.     

木薯粉酒精浓醪发酵条件的优化

以木薯粉为原料进行浓醪酒精发酵,在前期优化液化糖化条件的基础上,分析了培养基成分以及温度,pH值等条件对发酵的影响.实验结果表明,在优化的液化糖化条件下进行木薯粉浓醪酒精发酵,氮源和无机盐的最适添加量为尿素0.25%(w/w),MgSO4·7H2O 0.45g/L,KH2PO4 1.50g/L,CaCl2 0.20g/L,发酵最适温度为33℃,最适初始pH4.5,酵母接种量100,6(v/v),发酵时间48h.在此条件下发酵成熟醪酒精浓度高达17.2%(v/v),淀粉利用率达91%.     

木薯粉酒精浓醪发酵条件的优化

以木薯粉为原料进行浓醪酒精发酵,在前期优化液化糖化条件的基础上,分析了培养基成分以及温度,pH值等条件对发酵的影响。实验结果表明,在优化的液化糖化条件下进行木薯粉浓醪酒精发酵,氮源和无机盐的最适添加量为尿素0.25%(w/w),MgSO4·7H2O0.45g/L,KH2PO41.50g/L,CaCl20.20g/L,发酵最适温度为33℃,最适初始pH4.5,酵母接种量10%(v/v),发酵时间48h。在此条件下发酵成熟醪酒精浓度高达17.2%(v/v),淀粉利用率达91%。     

碱预处理秸秆同步糖化发酵生产丁二酸

研究了碱预处理秸秆及用琥珀酸放线杆菌Actinobacillus sucinogenes同步糖化发酵秸秆生产丁二酸。结果表明:用1.0%NaOH溶液于120℃分别预处理玉米、小麦和水稻3种秸秆2 h,其木质素的脱除率、纤维素与半纤维素的总保留率均在85%以上。以3种碱预处理后的秸秆为原料,在补加纤维素酶与纤维二糖酶的条件下,A.sucinogenes F3-21摇瓶厌氧发酵72 h,产丁二酸浓度分别为30.74 g/L、24.98 g/L和26.57 g/L;在7 L罐中厌氧发酵72 h,丁二酸浓度分别达到40.21 g/L,30.06 g/L和39.07 g/L,每克预处理秸秆产丁二酸分别为0.50g、0.38 g和0.49 g。并用钙盐法对玉米秸秆同步糖化发酵液进行提取,得到纯度为99.98%的丁二酸结晶。说明了玉米、小麦和水稻3种秸杆为原料进行同步糖化发酵生产丁二酸的可行性。     

小麦秸秆同步糖化发酵制取燃料乙醇

利用酿酒酵母Saccharomyces cerevisiae BY4742对小麦秸秆同步糖化发酵(simultaneously saccharification and fermentation,SSF)生产燃料乙醇的条件进行了研究,系统考察和研究了温度、固体含量、纤维素酶投加量、酵母菌浓度对SSF过程中乙醇浓度和产率的影响,并对以上参数做了初步优化,以提高最终乙醇浓度和产率。结果表明,小麦秸秆同步糖化发酵乙醇的最优条件为:温度38℃,固体含量16.0%(m/V),纤维素酶投加量35FPU/g底物,酵母菌浓度8 g/L。在此条件下,NaOH预处理后的小麦经过120 h同步糖化发酵,乙醇浓度达到最大值,为38.32 g/L,产率达理论产率的71.71%,木糖浓度为12.94 g/L。     

以白酒酒糟为原料发酵产丁二酸

以白酒酒糟为原料,经酶法糖化,由Actinobacillus succinogenes发酵生产丁二酸。纤维素酶或糖化酶分别水解白酒糟,在酶反应的最适温度和pH条件下,酒糟中的纤维素和淀粉的水解率分别为44.04%和92.26%,相应还原糖对酒糟的得率分别为110 mg/g和126 mg/g酒糟;但2种酶以分步或同步方式水解白酒糟时,酶水解反应受到产物抑制作用,总还原糖得率仅约为150 mg/g酒糟。采用分步糖化发酵工艺,400 g/L白酒糟经两种酶水解后,得到还原糖58.4 g/L,该水解液发酵产丁二酸28.8 g/L,丁二酸产率72 mg/g酒糟;而采用先用纤维素酶水解白酒糟,再用糖化酶和A.succinogenes同步糖化发酵的工艺,240 g/L白酒糟产丁二酸浓度为32 g/L,产率133 mg/g酒糟。以白酒酒糟为原料发酵生产丁二酸,利用了废弃物,无需外源添加氮源,无需对原料进行酸碱预处理,具有一定的应用前景。     

氧化去木质素玉米芯同步糖化发酵产2,3-丁二醇

2,3-丁二醇是一种重要的平台化合物。选取经过碱性高锰酸钾(APP)预处理后的玉米芯为底物,采用阴沟肠杆菌Enterobacter cloacae CICC10011通过同步糖化发酵工艺(SSF)发酵产2,3-丁二醇。通过对SSF主要工艺参数进行优化,确定最适宜工艺条件为:底物浓度120 g/L,纤维素酶添加量40 FPU/g,木聚糖酶添加量12 000 U/g,发酵温度35℃,初始发酵p H 5.5,转速180 r/min。在最优发酵条件下,以APP预处理后的玉米芯为底物连续发酵36 h,2,3-丁二醇的浓度为21.5 g/L,转化率为0.27 g/g(以纤维素和半纤维素为参照);分别是未处理的玉米芯为底物时的8.41倍和8.71倍。     

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.     

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.