基于S7-400PLC的啤酒发酵靶向温度控制系统

针对啤酒发酵温控系统非线性、大时滞的特点,提出将靶向控温思想与模糊PID控制算法相结合,设计了基于靶向控温点实现控温的模糊PID控制器,以提高啤酒发酵温度控制的精确性。以西门子S7-400PLC和Braumat软件平台为控制核心,设计啤酒发酵温度控制系统软硬件结构,实现对整个生产过程的控制与监测。现场实际应用表明:啤酒发酵温度控制误差为±0.3℃,控温效果好,满足实际生产要求。     

基于S7-1200PLC的啤酒发酵温度控制系统研究

针对啤酒发酵温度控制系统具有时变性、非线性和滞后性的特征,运用传统控制方法不能实现啤酒发酵温度精确控制的问题。引入论域伸缩因子,设计变论域模糊PID控制器,实现PID参数在线精细整定;以S7-1200PLC控制器和KTP1000触摸屏为硬件基础,开发啤酒发酵自动控制系统,实现人机交互。啤酒发酵试验结果表明:啤酒发酵温度控制误差为±0.09℃,控制精度为0.75%,温度控制系统稳定性好、精度高,提高了啤酒质量。     

啤酒发酵过程控制算法研究

针对啤酒发酵过程具有大惯性、大滞后和严重的非线性特性及其对微机自动监控系统的要求，引入以被调变量的偏差和偏差的变化趋势为依据的模糊智能控制算法，设计了啤酒发酵过程微机控制算法，并讨论了系统工程的软硬件实现的问题。系统实际运行效果表明该系统算法适应性和灵活性强，控制效果理想。     

基于模糊RBFNN-PID的啤酒发酵温度控制系统

基于模糊PID控制算法,结合RBF神经网络算法优点,设计具有逻辑判断和自我优化的模糊RBFNN-PID控制算法,实现PID参数在线最优整定。以CPU1214C和KP1500触摸屏为核心,设计啤酒发酵自动控制系统和人机交互界面,Matlab仿真和试验测试结果表明:该控制算法可以提升温度控制系统的稳定性、模型失配鲁棒性和抗干扰能力。     

基于模糊PID控制的窖池温度监控设计

目的：解决白酒入窖温度控制不精确的问题。方法：基于嵌入式平台构建了用于窖池参数集结的ZigBee无线传感器网络,通过NB-IOT与云平台实现窖池环境数据的传输、存储与显示,以酒醅表面温度为控制对象,运用模糊PID控制算法,实时优化输出参数Kp,Ki,Kd,实现窖池温度的精准控制。最后验证温度控制系统的性能。结果：模糊PID控制算法测定温度与设定温度最大偏差为0.25 ℃,超调量为1.6%,通过人工测量数据与监控系统采集数据对比误差在5%以内。结论：采用模糊PID控制策略可快速准确地控制入窖温度。     

基于Smith预估补偿的啤酒发酵温度控制策略

在啤酒发酵过程中,发酵液的温度控制具有大时滞、非线性和分阶段性等特点,这些特点造成发酵罐内发酵液的温度波动频繁,偏差较大。为了更好地对啤酒发酵温度进行控制,在常规PID控制的基础上,提出了基于Smith预估补偿的非线性PID控制策略。在对啤酒发酵温度控制系统的辨识模型进行Matlab仿真分析的基础之上,将该控制策略用于实际生产。结果表明:该控制策略可以有效改善控制系统的稳定性和抗干扰能力。     

PLC在啤酒杀菌控温中的应用

采用PLC对啤酒杀菌机进行改造,在调节温度方面采用模糊控制加区间加速的方式不但避免了PID调节过程的麻烦,提高了设备的启动速度,同时还减少了运行温差,使杀菌水温保持在±0.1℃的范围内.加上输送联动控制和远程监控系统,降低了啤酒杀菌系统的废品率和能耗,同时可对工艺参数进行记录分析.     

基于变论域模糊PID的啤酒发酵过程控制

针对啤酒发酵过程温度控制的大惯性、时滞及非线性等特点,在传统模糊PID控制算法的基础上引入变论域的思路,设计一种变论域模糊自适应PID控制器,可动态改变模糊控制器输入和输出的论域范围。实验数据表明,所设计的控制器具有超调量小、稳态精度高、动态调节能力强等优点。     

立式食品包装机袋材恒速供送控制系统研究

为提高立式包装机袋材长度控制精度和袋形外观质量,以模糊PID控制为基础,结合RBFNN算法优势,设计具有逻辑推理和自我学习能力的模糊RBFNN-PID控制算法,实现PID参数在线最佳整定,提升袋材恒速控制精度和稳定性.基于Siemens CPU1215C控制器和TP1500触摸屏,搭建立式包装机恒速监控系统,完成硬件选型和程序设计.MATLAB仿真和试验测试表明:模糊RBFNN-PID控制器性能优越、抗干扰能力和模型失配鲁棒性强,袋材长度偏差约为±0.15 mm.该控制系统实现包装机袋材供送的恒速精确控制,提高了袋材长度精度和袋形外观质量.     

基于模糊神经网络的PID张力控制系统

由于卷绕张力控制系统是一个复杂、联动、时变、非线性系统,采用传统PID控制不能解决系统的非线性时变和PID参数的在线整定难等问题,为此提出一种控制算法——模糊神经网络PID复合控制方式,可根据系统的偏差及其变化率实时对PID的3个参数进行优化,达到具有最佳组合的PID控制,从而实现PID控制的自适应和智能化性能。通过MatLab软件,进行传统PID控制与模糊神经网络PID控制动态性能的仿真比较,结果表明系统采用模糊神经网络PID控制具有更好的动、静态特性和自适应性。     

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.     

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.     

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.     

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.