魔芋薄层变温热风干燥特性实验研究

在风速0.75 m/s、厚度5、6及7 mm条件下,对魔芋进行温度50→70℃和70→50℃的薄层变温热风干燥实验,分析了变温温度(50→70℃和70→50℃)及芋片厚度(5、6和7 mm)对魔芋干燥速率的影响,用9个数学模型对魔芋变温实验数据进行拟合,计算魔芋的有效水分扩散系数,并将魔芋薄层变温干燥与恒温干燥进行对比。结果表明:变温条件相同时,魔芋的干燥时间随着芋片厚度的增加而增加;最适合魔芋薄层变温干燥特性的模型是Two-term模型;魔芋的有效水分扩散系数D_(eff)随着芋片厚度的增加而增大;在风速及厚度条件相同时,薄层变温干燥的最大干燥速率比恒温干燥的最大速率更高,且由低温后高温(50→70℃)的变温方式效果更好。     

红肉苹果片穿流式热风薄层干燥特性及数学模型

以新疆红肉苹果为试材,研究不同切片厚度、热风温度及热风速率下苹果切片的干燥特性,通过Origin8.0软件对试验数据进行数学模型拟合,得到红肉苹果片的热风薄层干燥模型。结果表明,热风温度、切片厚度和热风风速对红肉苹果片的干燥特性均有一定影响,热风温度对其影响程度最为显著。热风温度越高,切片厚度越小,风速越大,红肉苹果片的干燥速率越大。综合而言,在热风温度80℃、切片厚度2 mm、热风速度1.5m/s时,红肉苹果片干燥速率最大。所选6个数学模型均可以较好地阐述红肉苹果片在热风薄层干燥过程中的水分变化规律,其中Page模型具有最高的R~2值、最低均方根误差RMSE及卡方值χ~2,更适于评估红肉苹果片干燥过程中的水分脱除规律。     

柠檬热风干燥特性及数学模型

以新鲜柠檬为原料,研究其热风干燥特性及数学模型。以柠檬片厚度、热风温度、热风风速为因素,分析其对柠檬热风干燥特性的影响,建立柠檬热风干燥的干燥特性曲线、干燥速率曲线,并利用SAS8.0软件对试验数据进行拟合,构建柠檬热风干燥数学模型。结果表明:热风温度、柠檬片厚度对柠檬热风干燥的速率有较大影响,而热风风速对干燥速率的影响较小;柠檬热风干燥符合Page模型。     

花椒真空干燥特性分析及动力学模型研究

为了探求花椒真空干燥特征,提高干燥速率,实现花椒真空规模化干燥。选取干燥温度为50、60、70℃,真空度为-0.06、-0.04、-0.02 MPa,装载量为30、40、50 g进行全面试验,考察3个因素对花椒干燥总时间和干燥速率的影响。利用7种经典干燥数学模型对9组实验数据进行非线性拟合,利用决定系数R2、残差平方和(SSE)、卡方χ2三个指标对拟合结果进行评价,选取其最优模型与建立的BP神经网络模型进行对比检验。结果表明,三次多项式模型的拟合R2值都达到0.999、SSE值最低达到了7.0E-4,χ2值最低达到3.08E-5是7种经典模型中描述花椒真空干燥动力学特性的最优模型。但三次多项式模型拟合检验的平均相对误差值为1.98%高于BP神经网络模型的平均相对误差值(1.13%),因此BP神经网络是更适合描述花椒干燥动力学特性的数学模型。     

糜子籽粒双向通风干燥特性及数学模型研究

以糜子籽粒为原料,运用双向通风谷物干燥实验台对糜子籽粒进行干燥试验,研究糜子籽粒在不同热风温度、热风风速和物料厚度条件下含水率的变化过程,分析各因素对糜子籽粒干燥速率的影响,探究干燥特性与各因素之间的变化关系,建立糜子籽粒双向通风干燥的数学模型。结果表明:热风温度对糜子籽粒干燥速率影响较大,热风风速次之。当热风温度60℃、热风风速4 m/s、物料厚度20 mm时,糜子籽粒双向通风干燥速率最快,建立的基于Page方程的糜子籽粒双向通风干燥数学模型拟合效果较好。     

白萝卜薄层热风干燥特性及其数学模型

以新鲜白萝卜为原料,研究在不同的热风温度、热风风速和切片厚度条件下,白萝卜的热风干燥特性。通过试验数据拟合,比较7种数学模型在白萝卜热风干燥过程中的适用性。结果表明:白萝卜热风干燥以降速过程为主,无明显的恒速阶段。干燥温度、切片厚度对白萝卜的干燥速率影响较大,风速影响较小。干燥温度越高、切片厚度越薄、风速越快,干燥用时越短。通过比较各模型的相关系数(R~2)、卡方值(χ~2)和均方根误差(RMSE),结果显示Page模型的拟合效果最好,该模型的R~2为0.997 6、χ~2为2.615×10~(-4)、RMSE为0.014 6。且用模型外的试验数据进行验证,也表现出较好的拟合度。白萝卜的有效水分扩散系数(Deff)为7.560×10~(-10)~2.130×10~(-9),随着干燥温度、风速和切片厚度的增加而增大。白萝卜的干燥活化能为26.34kJ/mol。此外,还对白萝卜片干燥前后的色差进行了测定和分析,结果表明:在50~80℃时,随着温度的增加,干燥成品的L~*值逐渐降低,而b~*、a~*以及总色差ΔE~*值呈升高的趋势。     

竹笋热风薄层干燥特性及动力学分析

干燥是竹笋加工中最为常见的一种方式,为了解竹笋在热风薄层干燥条件下的干燥特性,本实验以大叶麻竹笋为试验原料,竹笋片干基含水率和干燥速率为试验测试指标,研究了不同干燥温度、风速和笋片厚度等因素对干燥速率的影响,并建立竹笋热风薄层干燥的动力学模型。结果表明:热风薄层干燥温度、风速和笋片厚度均对竹笋的干燥特性影响较大。随着干燥温度和风速的升高,干燥速率增加;随着笋片厚度的增加,干燥速率降低。不同条件下的干燥均可分为加速、恒速和降速干燥3个阶段。竹笋的适宜热风薄层干燥条件为干燥温度80℃、风速2.0 m/s、笋片厚度1.0 cm。竹笋热风薄层干燥的动力学满足Page模型,Page模型适合对竹笋热风薄层干燥过程进行描述和预测。所得研究结果将为竹笋干的热风薄层干燥可控制工业化生产提供参考。     

魔芋热泵干燥特性及数学模型的研究

为解决魔芋干燥过程中褐变问题,采用热泵低温干燥技术结合护色剂处理,对魔芋进行了干燥研究。考察了干燥温度、风速、切片厚度等因素,对魔芋热泵干燥特性的影响,得到了魔芋干燥特性曲线。并通过origin软件对实验数据进行拟合,建立了魔芋热泵干燥数学模型。研究结果表明:温度越高、风速越大、切片厚度越薄,干燥速率快,干燥时间短。干燥温度对魔芋热泵干燥速率影响较大,风速对干燥速率的影响较小,魔芋热泵干燥过程符合Page干燥模型,其R2值最大,平均RMSE和SEE值最小,分别为0.99971、0.00559和0.00104。热泵干燥的魔芋色泽呈乳白色,感官品质良好。     

人造米热风干燥特性及干基含水率预测模型

为研究人造米热风干燥特性,对人造米在热风不同干燥温度(60～80 ℃)、风速(1～2 m/s)以及料层厚度(2～6 cm)进行干燥试验。根据试验所得数据,计算出不同干燥条件下人造米的有效水分扩散系数,探究不同干燥温度、风速与料层厚度对人造米有效水分扩散系数的影响关系。进一步建立干燥动力学模型,并与试验数据拟合得出模型拟合程度。结果表明,人造米在热风干燥前期为升速干燥阶段,而后进入降速干燥阶段,无明显的匀速干燥阶段。与干燥温度与风速相比,料层厚度对人造米有效水分扩散系数影响最大。通过计算模型决定系数高于0.983,均方根误差小于0.007,模型拟合度较好。该模型能够准确预测人造米热风干燥过程中的含水率变化过程。     

魔芋片热风对流干燥速率影响因素

研究魔芋片在热风对流干燥过程中芋片干燥速率变化,以及温度和干燥介质流量对其的影响.研究结果表明:魔芋片的对流干燥过程可分为预热期、恒速干燥期和降速干燥期3个阶段;升高干燥温度和增大干燥介质流量,会使干燥速率增大,恒速干燥期缩短,降速期干燥速率下降加快,110℃是魔芋片对流干燥的最佳温度.     

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