利用微生物降解烟梗中细胞壁物质的响应曲面优化

细胞壁物质对烟梗抽吸品质有不利影响,为研究微生物发酵液对降解烟梗中细胞壁物质的作用效果,采用二因素三水平的响应曲面法优化了微生物发酵液添加量和处理时间对降解烟梗中纤维素、果胶、木质素较佳工艺条件。结果表明,微生物发酵液能有效降低烟梗中的细胞壁物质,发酵液添加量比处理时间作用效果更加显著,建立的二次回归模型均达到了显著性水平,能客观地描述发酵液添加量、处理时间与各响应值之间的关系。经优化,利用微生物降解烟梗中细胞壁物质的较佳工艺条件为发酵液添加量66.7 m L/kg、处理时间180 min,在优化条件下烟梗中纤维素、果胶、木质素含量较未处理烟梗分别降低了12.78%,8.77%和33.55%。     

造纸法再造烟叶原料的加酶萃取

为了减少造纸法再造烟叶中的不利成分,研究了在烟梗和烟末萃取过程中加入果胶酶、半纤维素酶和蛋白酶,以及酶添加量、酶解温度和酶解时间对烟末、烟梗中蛋白质、全纤维素和果胶含量及其萃取液中还原糖和氨基酸含量的影响.结果表明:①烟梗和烟末的适宜酶处理萃取条件为:复合酶用量:烟梗,0.5%果胶酶、半纤维素酶和蛋白酶[2∶2∶1(质量比)]、烟末,0.8%果胶酶、半纤维素酶和蛋白酶[1∶2∶2(质量比)];处理温度:50℃;处理时间:2h;②复合酶萃取后,烟梗和烟末的蛋白质、综纤维素和果胶的转化率分别比热水萃取高7.63,4.97,15.87和16.59,5.58,16.13百分点.烟末、烟梗萃取液中还原糖比热水萃取的分别高2.55和3.68百分点,萃取液粘度分别降低0.32和0.149 Pa·s.     

果胶酶对棉杆生物饲料发酵的影响

应用果胶酶对棉杆中的果胶类物质酶解处理后,可显著降低其生物饲料原料中的果胶含量,从而为后续的发酵工艺提供一定的营养成分。试验表明,对棉杆中果胶降解效果的影响因素中,降解温度影响最大,果胶酶添加量次之;酶解最佳工艺条件为：果胶酶添加量为0.6%,降解温度为45℃,保温时间为6 h。使用经过酶处理的棉杆原料进行发酵,所得饲料菌落总数增长到原来的2倍;pH值为6.01,与未加酶原料的6.84相比下降了12%。     

生物酶法降解烟梗末中果胶的研究

通过青霉产果胶酶降低烟梗末中的果胶的含量,从而提高梗末作为原料薄片工艺中的使用性能。首先通过正交实验确定了酶解的最佳条件为加酶质量分数6%,料液比1 g∶3 m L,酶解温度50℃,酶解时间2 h,果胶酶的最大降解率为38.92%。然后经热重分析表明,梗末经果胶酶降解后,最后的残重从24.46%下降至9.84%,说明酶解后的梗末的燃烧性得到提升。最后,利用热裂解-气相色谱/质谱联用分析酶解前后梗末的热裂解产物,发现酶解后裂解产中的乙酸含量降低,香味物质吡咯含量升高,这将有助于改善烟草薄片的吸食口感,本研究中为提高造纸法烟草薄片的品质提供了一个新的方法。     

外源酶改善糙米食味品质的研究

实验通过用纤维素酶、复合果胶酶来部分降解糙米中的粗纤维和果胶物质,改善糙米的食用品质。通过测定纤维素等物质的变化及糙米饭的感官,确定纤维素酶的作用条件为:反应温度45~50℃,加酶量0.11mg/mL,pH值4.8~5.2,作用时间4h;复合果胶酶的作用条件为:反应温度45~55℃,pH值5.0~5.6,加酶量0.6mg/mL,酶作用时间2h以上。实验发现经纤维素酶和复合果胶酶处理后的糙米食用品质较处理前有明显改善,其中纤维素酶作用好于复合果胶酶,混合酶作用效果最好。     

果胶酶酶解山楂浆工艺研究

以鲜山楂为原料,打浆后加入果胶酶进行酶解处理,通过优化加酶量、反应时间和料液比,考察果胶酶对山楂浆酶解效果的影响。经单因素实验,确定山楂浆酶解的最佳工艺条件。通过结果可知山楂浆最佳酶解条件为:果胶酶添加量0.4%,反应时间3h,料液比1∶4。结果表明,果胶酶对山楂浆进行酶解处理,酶解效果好,山楂果胶沉淀少,澄清度好。     

外源酶制剂对糙米蒸煮特性的影响

目的：使用纤维素酶、果胶酶来部分降解糙米中的粗纤维和果胶物质,改善糙米的食用品质。方法：选取温度、酶用量和作用时间3 个因素,以糙米的加热吸水率、米汤固形物质量、米汤碘蓝值等为考察蒸煮品质指标,通过单因素和正交试验考察酶作用的最佳条件。结果：确定纤维素酶作用的最佳作用条件为：反应温度50℃、加酶量10ml、酶作用时间120min;果胶酶的最佳作用条件为：反应温度55℃、加酶量10ml、酶作用时间120min。结论：经纤维素酶和果胶酶处理后的糙米食用品质较处理前有明显改善,其中纤维素酶作用好于果胶酶,而两种酶共同作用没有明显叠加效果。     

超声波辅助酶法提取柚子皮果胶的工艺研究

采用超声辅助酶法提取柚子皮中的果胶,在超声波为90?W的条件下,研究提取时间、提取温度、pH值、料液比和酶量对柚子皮果胶提取率的影响,并选取4因素3水平的Box-Behnken试验设计,以柚子皮果胶的提取率为响应值,利用响应面法对提取工艺参数进行优化.结果表明,柚子皮果胶提取率的最佳工艺条件:料液比1:26.30,pH...     

植物蛋白酶提取柠檬皮果胶

利用植物蛋白酶-醇析法对柠檬皮果胶的提取工艺进行研究。考察液料比、缓冲液pH、提取时间、提取温度、酶浓度对果胶得率的影响,采用单因素试验及正交试验得到柠檬皮果胶的最佳提取工艺条件:提取时间50 min,温度54℃,p H 7.0,加酶量3 mg/g,液料比20∶1。在此条件下进行了3次平行试验,在平行实验中其重现性很好,结果表明此工艺条件确实是稳定性良好的最佳工艺条件,果胶平均得率为27.60%。     

柿皮果胶纤维素酶法提取工艺

采用纤维素酶法辅助提取柿皮中的果胶,探讨提取过程中各因素对果胶提取率的影响。结果表明:柿皮果胶纤维素酶法提取的最佳工艺条件为提取温度45℃、加酶量3.0mg/g、提取液pH4.0、料液比1:35、提取时间2h,测得果胶的提取率为8.87%。该方法简便、快捷,可用于柿皮果胶的提取和测定。     

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.