储粮横向通风多尺度热湿耦合传递研究

温湿度是影响粮食安全储存的重要因素,为保证储粮安全,采用机械通风,使粮堆和粮粒的温度和水分含量可以得到有效控制。该文基于多孔介质的传热传质理论,建立了仓储稻谷通风过程中粮堆内部流动和热湿耦合传递的数学模型以及粮粒的热量传递和水分输运模型。采用计算流体力学的方法,从粮堆尺度和粮粒尺度,分析了机械通风过程中仓储粮堆和粮粒内部的温度、水分分布规律。研究发现,通风过程阶段,粮堆内部温度降温显著,粮堆整体平均水分呈降低趋势,且粮堆内部温湿度受外界环境温湿度的影响很大;研究还发现粮粒水分扩散速度远小于温度扩散速度。研究结果可以为储粮横向通风保水降温的工作以及粮堆局部霉变、发热和害虫的发育的预防提供参考。     

基于多尺度的稻谷干燥热湿耦合传递的数值研究

为保证稻谷在储藏时的品质,收获后的稻谷通常需要干燥到一定水分后储藏,研究稻谷干燥过程的热湿传递规律具有重要意义。目前稻谷干燥过程中热湿传递的分析大多基于连续介质假说和局部热湿平衡原理而进行的,这种方法的局限性在于很难获得粮堆干燥过程中粮粒内部的热湿迁移规律。本文基于稻谷粮堆孔隙尺度和粮粒尺度,采用局部非平衡热湿传递模型,模拟分析了在对流干燥条件下稻谷单颗粒以及颗粒群的热湿传递规律。研究结果表明,本研究模拟值与文献中干燥实验数据相对误差(RE)小于6.50 %,平均相对偏差(MRD)小于4.00 %,得出该模型具有一定的准确性;与基于局部热湿平衡多孔介质热湿耦合研究方法所得的稻谷颗粒群温度和水分传递结果进行对比,本研究所建立的模型更能准确体现出谷物颗粒在通风干燥时内部的热湿迁移规律。本研究所开发的模型能预测不同尺度下稻谷颗粒的温度和水分分布。     

基于数值预测的稻谷横向降温保水通风最佳湿度研究

本实验基于多孔介质热湿传递原理和粮粒吸湿/解吸湿理论,建立了通风过程中粮堆内部热湿耦合传递方程,采用数值预测的方法,研究了吨粮通风量不变、粮堆初始温度与通风空气温度差8℃情况下,粮堆初始平衡湿度与通风空气湿度差分别为-5%、0%和5%时,粮堆内部温度和水分随时间的变化规律。探究了通风湿度对稻谷横向保水降温通风过程中粮堆温度和水分的影响,分析了一定初始粮温和水分时通风空气温湿度对降温保水的效果,得到了稻谷横向降温保水通风的最佳湿度。研究结果可以丰富和完善横向降温保水通风工艺,同时也为横向降温保水通风的操作提供依据。     

基于多物理场分析稻谷保质储藏的研究（网络首发、推荐阅读）

基于稻谷粮堆内部流动和热湿耦合传递的数学模型,结合稻谷黄变动力学模型,采用数值模拟的方法对比研究了全年自然储藏与分阶段自然储藏工况下,浅圆仓内部稻谷温度和水分分布的演化规律以及稻谷黄变规律。在温湿度基础上,进一步考虑黄变对稻谷大跨度周期储藏的保质研究,结果表明：储藏365 d结束时,有通风条件的分阶段自然储藏的平均温度比全年自然储藏低约18 ℃,平均水分低约0.5%,平均黄度值低约0.8;低温空气通入高温粮仓既可以降低温度,又可以降低粮食水分,缓解稻谷黄变的进程,分阶段自然储藏更有利于稻谷的长期保质储藏;仓壁附近的稻谷极易受外界环境温度的影响,可在仓壁外侧刷涂层,降低太阳辐射的影响。     

不同通风温度下储粮仓横向降温保水通风数值模拟研究（网络首发、推荐阅读）

为保证长期储藏的稻谷品质,对相同湿度不同通风温度条件下储粮横向降温保水通风模拟分析研究具有重要意义。基于吸湿性多孔介质的传热传质理论,结合应用已有的粮堆热湿传递的数学模型,并以数值模拟的方法分析相同湿度时不同进风温度对储粮仓温度与水分变化规律。结果表明：当粮堆初始温度为25 ℃、进风温度为17 ℃时,粮堆的降温速率最快,粮粒的吸湿与解吸湿过程也最先达到平衡,粮堆内部的保水效果最佳;其中距离进风口处0.4 m粮层与不同温度的进风空气进行热湿耦合传递时,粮层温度、水分下降趋势一致,该粮层进风温度越高,水分丢失现象越明显;进风温度越低,粮堆温度的下降幅度越大。随着与进风口距离的增加,粮层的降温效果变差,在通风温度为19 ℃时,距离风口处26.2 m粮层温度几乎保持粮仓初始温度不变,达不到降温效果。     

仓储粮堆内部自然对流和热湿传递的数学分析及验证

本文基于仓储粮堆内部自然对流、热湿耦合传递的数学模型,采用数学分析的方法对模型中各个方程中的各项的物理意义和数量级大小进行了分析,探讨了仓储粮堆内部自然对流、热量传递和水分迁移过程的相互关系。提出了判断粮堆内部自然对流强弱的瑞利数及其影响因素,分析了仓型结构、粮种及仓外大气温度对粮堆内部自然对流、热量传递和水分迁移的影响,并通过数值模拟对数学分析结果进行了验证。结果表明,数学分析方法是分析仓储粮堆内部自然对流、热量传递和水分迁移过程的一种有效途径,数学分析的结果可以为仓型设计、储粮生态系统的模拟、仓储技术管理提供借鉴。     

密闭储存粮堆内部自然对流和热量传递分析

基于多孔介质流动和传热传质理论,建立了仓储粮堆内部自然对流、热湿耦合传递的数学模型。采用近似分析原理和数值模拟方法研究了仓储粮堆内的传热和自然对流过程及其影响因素。结果表明对于颗粒较小的谷物如小麦,储存过程中的温度主要受热传导的影响,但是对于颗粒较大的谷物如玉米,自然对流的影响会更大。通过理论分析和数值模拟证明了粮仓中低速的水分迁移对储粮温度变化影响很小。在"瘦高"型的圆筒仓中,自然对流的影响作用较强,自然对流作用会使粮仓内温度混合更加均匀。     

双扩散传热传质模型及在横向谷冷通风中应用

首先建立了单颗粒小麦内部水分迁移模型,基于有限元的方法数值模拟了颗粒内部水分变化规律,通过回归数值模拟数据,得到了颗粒平均水分模型和平均水分变化的干燥(或吸湿)速率模型。在此基础上推导出了谷物颗粒堆积床双扩散传热传质模型,并采用有限元的方法数值模拟分析了就仓横向(水平)谷冷通风时仓储粮堆内部热湿耦合传递规律。通过比较数值模拟和试验测定数据,验证了所建立的模型的合理性。分析了横向谷冷通风时粮粒温度和水分以及粮粒周围空气温度的变化规律,探讨了横向谷冷通风时粮堆内部降温效果。     

双扩散传热传质模型及在横向谷冷通风中应用

本文首先建立了单颗粒小麦内部水分迁移模型,基于有限元的方法数值模拟了颗粒内部水分变化规律,通过回归数值模拟数据,得到了颗粒平均水分模型和平均水分变化的干燥(或吸湿)速率模型。在此基础上推导出了谷物颗粒堆积床双扩散传热传质模型,并采用有限元的方法数值模拟分析了就仓横向(水平)谷冷通风时仓储粮堆内部热湿耦合传递规律。通过比较数值模拟和实验测定数据,验证了所建立的模型的合理性。分析了横向谷冷通风时粮粒温度和水分以及粮粒周围空气温度的变化规律,探讨了横向谷冷通风时粮堆内部降温效果。     

基于Fortran程序对储粮通风温度水分和害虫演替的模拟研究

世界各国因储粮害虫对粮食造成的损失非常严重,为了降低粮食在储藏期间的损耗,所以研究储粮通风过程中害虫增长量的变化至为重要。文章基于多孔介质热湿耦合理论,建立了浅圆仓的粮堆内部热湿传递和流动的数学模型以及害虫和熏蒸经验模型,并基于Fortran语言编程,模拟分析了通风状态下粮堆温度、水分含量、储粮害虫增长量以及杀虫剂浓度衰减的变化。结果表明：通风对粮堆内部温度和水分以及害虫生长影响明显。粮堆的水分含量近似对称分布,而受太阳辐射的影响,粮仓不同方向壁面的温度分布并不对称。储粮害虫在粮仓内的数量分布与温度、水分等因素有关,在壁面附近害虫分布较多,且在筒仓中心区域出现分层现象。杀虫剂浓度衰减也受温度的影响,温度高会影响杀虫剂的降解,导致杀虫剂浓度较低     

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