桉木发酵生产丁醇技术研究

为探索生物质能源树种发酵生产丁醇新技术。以桉木为原料进行稀酸预处理和纤维素酶解将纤维素、半纤维素转化为可发酵糖;采用Ca(OH)2、活性炭及离子交换树脂联合脱毒方法对酶解液脱毒;将脱毒后的酶解液用于丁醇发酵。结果表明:酶解最佳工艺为:纤维素酶用量60FPU/g干物质、酶解36h,纤维素酶解率高达91.55%。水解液脱毒后,甲酸、糠醛、羟甲基糠醛的脱除率分别为65.3%、76.79%和29.32%,木质素降解的醛类和酸类物质的降解率均大于80%;葡萄糖和木糖的损失率极小分别为2.97%和3.54%。脱毒后的水解液补加玉米浆进行丁醇发酵,丁醇和总溶剂产量分别达到11.9g/L和15.7g/L,葡萄糖和木糖的利用率可达95.4%和87.1%。利用桉木发酵生产丁醇效果理想,能够达到粮食发酵产丁醇水平。     

6种糖-酶解液模型体系中5-羟甲基糠醛的形成动力学分析

为研究糖-酶解液模型体系中5-羟甲基糠醛的形成动力学规律,以2 种糖（葡萄糖和蔗糖）和3 种肉（猪、牛、鸡肉）酶解液为研究对象,通过高效液相色谱分析研究了糖-酶解液模型体系中5-羟甲基糠醛的形成动力学模型。结果显示：加热温度90～110 ℃、加热时间0～6 h条件下,5-羟甲基糠醛的生成量与加热时间呈线性关系,符合零级动力学模型;5-羟甲基糠醛的生成量与加热时间、加热温度呈正相关,随着加热温度的升高、加热时间的延长,糖-酶解液模型体系中5-羟甲基糠醛含量呈持续增长的趋势,并且在葡萄糖-酶解液体系中5-羟甲基糠醛的含量远远高于蔗糖-酶解液体系。     

用备料苇渣发酵生产乙醇

以芦苇湿法备料废渣为原料,采用球磨预处理,进行纤维素酶解糖化发酵乙醇。结果表明:球磨预处理时间4 h、酶解时间24 h,其酶解转化率达61.7%,糖液中糠醛含量低,不影响发酵;在接种量1%、发酵时间24 h、温度35℃、pH值6,转速100 r·min-1的条件下,最终乙醇浓度为8.4 g·L-1,相当于乙醇产量为153 kg·t-1原料。     

玉米秸秆稀酸预处理对发酵抑制物产生的影响

研究了稀硫酸预处理玉米秸秆过程中,硫酸浓度、温度与时间对发酵抑制物甲酸、乙酸、糠醛、羟甲基糠醛以及乙酰丙酸产生的影响.结果表明,发酵抑制物甲酸、乙酸、糠醛、羟甲基糠醛与乙酰丙酸最大量分别为0.60、8.75、4.93、1.02、0.41g/L.随着硫酸浓度增大、温度升高、时间延长,各抑制物生成量增加.正交试验结果表明,影响乙酸生成的因素主次大小依次为硫酸浓度,温度,时间;而影响糠醛生成的因素主次大小依次是温度,硫酸浓度,时间.     

HS-SPME-GC-MS测定食醋中羟甲基糠醛衍生物的研究

利用顶空固相微萃取串联气相色谱质谱法（HS-SPME-GC-MS）测定食醋中羟甲基糠醛（HMF）衍生物,评估不同食醋中羟甲 基糠醛衍生物的含量差异及其对食品安全的影响。 从食醋中鉴定出糠醛,5-甲基糠醛和2-乙基-1-己醇共3种羟甲基糠醛衍生物,加标 回收率在81.62%～96.47%之间。 利用该方法测定的市售五种食醋中,糠醛含量最高为7 077.31 μg/L,最低为179.23 μg/L,5-甲基糠醛 含量最高为684.27 μg/L,最低为260.47 μg/L,2-乙基-1-己醇含量最高为107.21 μg/L,最低为62.13 μg/L。 以上结果表明,不同食醋中羟 甲基糠醛的含量具有显著差异（P＜0.05）,但日常的食醋量不会引起人体不良反应。     

酶法-乙醇辅助提取稻壳总黄酮工艺的研究

采用酶法-乙醇辅助提取稻壳总黄酮。对酶添加量、乙醇体积分数、p H、提取时间、提取温度和固液比对稻壳总黄酮提取率的影响进行考察,并在此基础上利用正交试验得到最优提取工艺条件为提取温度50℃、提取时间2h、p H5.5、乙醇体积分数35%、酶添加量1.5%、固液比1∶40(g/m L)。在此条件下,稻壳总黄酮提取率为0.72%。通过对比试验可知酶解-乙醇辅助提取的稻壳总黄酮提取率高于乙醇浸提法和纤维素酶预处理-超声提取法。     

Maillard反应体系中HMF和丙烯酰胺的含量分析

为了研究天冬酰胺和葡萄糖的Maillard反应体系中5-羟甲基糠醛和丙烯酰胺的含量,将天冬酰胺与葡萄糖在160℃条件下反应1.5 h,通过高效液相色谱和液质联用技术分别建立5-羟甲基糠醛和丙烯酰胺的测定方法,并进行验证。分析结果显示,丙烯酰胺测定方法的检测限和定量限分别为0.001、0.05μg/L,5-羟甲基糠醛的分别为0.3525、2.82μg/L,样品中丙烯酰胺的含量为6.64μg/L,5-羟甲基糠醛的含量为45.31μg/L。     

糠醛渣纤维素酶水解条件研究

以糠醛渣为原料进行纤维素酶水解研究,考察了水洗预处理、酶用量、转速、添加表面活性剂(tween80)及微波辐照对酶水解效率的影响.结果表明,水洗糠醛渣的酶解效率得到提高.优化后的三角瓶摇床酶解条件是:酶用量11FPU/g(酶活/底物)、间歇振荡转速140 r/min、添加tween80浓度1%(v/v),在此条件下水解48 h后,糠醛渣纤维素转化率达到61.6%,还原糖浓度达到53.7g/L.此外,对底物进行微波辐照(30min,210 W)后,水洗糠醛渣的酶解效率提高13%.     

常压甘油有机溶剂预处理甘蔗渣的浓醪酶解

为了实现木质纤维素浓醪酶解在低酶载量时的"三高"(高浓度、高转化率和高转化效率),通过利用常压甘油有机溶剂预处理甘蔗渣为底物,筛选合适的基质质量浓度(150 g/L)、纤维素酶添加量(6 FPU/g基质)和添加剂(吐温80,30 mg/g基质)。接着采用分批补料策略使基质质量浓度达到350 g/L,考察了不同加酶方式对分批补料浓醪酶解的影响。酶解72 h酶解液葡萄糖质量浓度达到132 g/L,葡萄糖转化率达到了理论值的60%。结果表明,常压甘油有机溶剂预处理基质具有较好的可酶解性,添加吐温80可以显著提高酶解效率。常压甘油有机溶剂预处理甘蔗渣的分批补料浓醪酶解推动了纤维素乙醇浓醪发酵工业化进程。     

过氧乙酸预处理对白酒丢糟纤维素降解效果的影响

为充分利用白酒丢糟资源,探讨过氧乙酸处理原料制备高浓度可发酵糖液的可行性.采用纤维素酶糖化、NaOH-过氧乙酸预处理白酒丢糟制备可发酵糖液,分别以单因素试验和正交试验考察了影响过氧乙酸预处理的条件.结果表明,预处理条件为过氧乙酸浓度2％,固液比1∶8,时间90 min,温度85℃时效果较好.该预处理条件下,酶解液中还原糖、葡萄糖及木糖浓度达到112.27 g/L、63.15 g/L和16.58 g/L,对应糖产率分别为692.33 mg/g、395.47mg/g和108.75 mg/g,较未优化前糖化酶解液糖浓度及产率提高了20％.糖化试验表明,利用过氧乙酸预处理白酒丢糟制备高浓度可发酵糖液具有可行性.     

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.