基于介电频谱的灵武长枣品质参数的预测模型

为寻找预测灵武长枣品质的最优模型,以长枣的介电损耗因子?"和介电常数?’频谱进行内部品质参数(可溶性固形物、可滴定酸含量和含水率)的建模研究。通过遗传算法(genetic algorithm,GA)和相关系数(correlation coefficients,CC)法提取了介电谱的有效信息;采用偏最小二乘(partial least squares,PLS)、主成分回归(principal components regression,PCR)和支持向量机(support vector machine,SVM)法建立了品质参数的预测模型;以决定系数(R~2)、校正标准偏差和预测标准偏差等模型评价方法确定了品质参数的最优预测模型。结果表明:基于介电损耗因子?"建立的可溶性固形物含量、可滴定酸含量和含水率的最佳预测模型分别为GA-PCR、GA-PLS和GA-PLS,且R~2均达到0.9以上;基于介电常数?’建立的可溶性固形物含量、可滴定酸含量和含水率的最佳预测模型分别为CC-PLS、GA-SVM和GA-PLS,R~2达到0.8以上,且验证效果较好。本研究为利用介电频谱快速预测长枣品质提供了可靠的方法。     

梨生长发育后期介电特性、生理特性和内部品质的关系

为了了解生长发育后期梨的介电特性与生理特性和内部品质的关系,采用同轴探头技术测量了生长发育后期2个月内梨在20~4500 MHz间的介电参数(相对介电常数ε'和介质损耗因子ε"),同时测量了梨的生理参数(乙烯释放量和呼吸强度)以及内部品质参数(可溶性固形物含量SSC、硬度和含水率)。结果表明:在所测频率范围内,ε'随频率的增加而减小,ε"在25 MHz附近存在极大值,在1300 MHz附近存在极小值。ε'和ε"随时间的推移先减小后增大。糖度和硬度随时间的推移呈下降趋势。呼吸高峰出现于乙烯释放高峰之前,且乙烯释放高峰的出现时间与介电参数由减小到增大的转折点相同。介电参数与SSC和硬度之间没有明显的线性关系。研究说明,梨的介电特性是生理特性的反映,可以根据介电参数值判断梨的成熟情况,但是单一频率下的介电参数值很难用于评价梨的内部品质。     

低温低压静电场处理结合微孔PE膜包装对不同成熟度灵武长枣贮藏品质的影响

以不同成熟度(半红期、2/3红期和全红期)的灵武长枣为研究对象,采用低温低压静电场结合PE保鲜膜袋对其进行贮藏保鲜,分析不同成熟度的灵武长枣在贮藏期间抗坏血酸(VC)、总酸(TA)、可溶性固形物(TSS)、硬度和失重率等理化指标的变化,并进行感官评价。结果表明:全红期和半红期的灵武长枣保鲜期较短,软化、酒化速度快,营养成分损失快,而2/3红期的灵武长枣的保鲜效果最佳,果实水分损失最小;保持了较高的果实硬度和VC含量;减缓了可溶性固形物和可滴定酸的损耗,保持较好的口感。说明在(0.0±0.5)℃,200mV的低压静电场结合微孔PE保鲜膜袋的处理下,2/3红期的灵武长枣的在贮藏70d后,仍然保持了良好的食用品质。     

灵武长枣的成熟度与其电学特性关系研究

为了解灵武长枣的成熟度与其电学特性的关系,以5种不同成熟度的灵武长枣为对象,利用LCR测试仪测试了长枣的电学参数。研究了长枣成熟度与其电学参数之间的关系,寻求能够反映长枣成熟度的敏感电学参数。结果显示:复阻抗Z、串联等效电容Cs、电抗X、串联等效电感Ls、相对介电常数ε’在特定的频率,具有一定的区分长枣成熟度能力。在3.16~316.2 k Hz及3.16~1.58 MHz内,可分别利用Z值和Cs值区分十成熟枣果。在251.2~1.26 MHz频率内,可利用Cs值区分十成熟、九成熟及六成熟枣果。10~63 k Hz内可用Ls值、X值区分出十成熟果以及六成熟果。在3.16~1 MHz的频率范围内,可用ε’值区分十成熟长枣。而在10~31.6 k Hz频段范围内,随成熟度的提高灵武长枣的介电损耗因素ε’’呈单调下降的变化规律,不同成熟度枣果的介电损耗因素ε’’值两两之间的差异均达到显著水平(P0.05),可以以介电损耗因素ε’’评价辨别灵武长枣的成熟度。     

基于介电频谱的枣果品种鉴别模型的建立

利用LCR测试仪在1~1 000 kHz的频率范围内,选取55个频率点,测定灵武长枣、冬枣和团枣的介电损耗因子ε"频谱和相对介电常数ε’频谱,通过主成分分析(principal component analysis,PCA)法和遗传算(genetic algorithm,GA)法提取介电频谱的有效信息,并选取偏最小二乘判别分析(partial least squares discriminant analysis,PLS-DA)、线性判别分析(linear discriminant analysis,LDA)和支持向量机(support vector machine,SVM)3种方法进行枣果品种的鉴别模型研究。结果表明,频率和品种对枣果的介电参数均有显著性影响;用PCA与GA方法提取频谱有效信息的建模效果要优于原始频谱的建模效果;SVM法的建模效果要优于PLS-DA与LDA法的建模效果;以介电损耗因子ε"建立的PCA-SVM模型优于介电常数ε’的GA-SVM模型,其预测集的鉴别准确率为100%。因此,基于介电损耗因子ε"频谱的PCA-SVM模型为枣果品种鉴别的最优模型。     

甲基托布津和氯化钙等药剂处理对新疆阿拉尔地区骏枣贮藏特性的影响

以新疆阿拉尔地区骏枣为试验材料,用不同浓度的甲基托布津溶液及甲基托布津与氯化钙的混合溶液处理骏枣,在温度(0~4)℃、相对湿度90%~95%的冷库中贮藏,每隔14 d测定骏枣的生理指标,以研究甲基托布津和钙处理对骏枣贮藏特性的影响。结果表明:骏枣在冷藏期间,其腐烂率和失重率逐渐增大,硬度和Vc含量逐渐降低、呼吸强度先降低再升高,可溶性固形物含量先上升、再下降、再上升,而总酸含量则先降低再升高;甲基托布津和钙处理可以降低骏枣的腐烂率和失重率、减缓果实硬度的下降、使总酸含量升高,加大可溶性固形物含量的波动幅度,但对其呼吸强度、可溶性固形物含量、Vc含量的影响并不明显。贮藏至70 d时,0.05%甲基托布津+1%CaCl_2处理有最小的失重率和呼吸强度、最高的可溶性固形物含量、最低的总酸含量、次低的腐烂率、次高的硬度及较高的Vc含量。综合考虑各因素,以0.05%甲基托布津+1%CaCl_2处理为宜。     

蜂胶涂膜对圆脆鲜枣贮藏保鲜效应

采用蜂胶涂膜剂对圆脆鲜枣进行保鲜处理,通过测定贮藏期鲜枣的腐烂指数、失重率、硬度、可溶性固形物含量、可滴定酸含量、Vc含量及呼吸强度的变化,评价其对圆脆鲜枣的保鲜效果。结果表明,蜂胶涂膜保鲜处理可以显著地降低圆脆鲜枣的失重率和腐烂指数,维持圆脆鲜枣的硬度,抑制可溶性固形物含量、可滴定酸含量和Vc含量的下降及呼吸强度增大,能明显延缓圆脆鲜枣采后的衰老,有效延长圆脆鲜枣的贮藏保鲜期,1.5%蜂胶涂膜处理保鲜效果最佳。     

薄膜袋包装对新疆阿拉尔地区圆脆枣贮藏特性的影响

以新疆阿拉尔地区圆脆鲜枣为试材,研究不同薄膜袋包装对低温冷藏条件下圆脆鲜枣贮藏特性的影响。结果表明,低温(0℃~4℃)贮藏时,不包装的圆脆枣果实皱缩严重,易失去鲜食品质,包装处理较好地保存了枣果的外观品质、降低了果实失重率、减缓了果实硬度的下降、保持了较高的可溶性固形物含量,但增加了枣果的腐烂率;在枣专用保鲜袋、保鲜袋和普通袋3种包装处理中,用专用保鲜袋装枣有利于减少果实腐烂、保持其可溶性固形物和VC含量,但在降低失重率、保持果实硬度和可滴定酸含量等方面优势并不明显;综合考虑,贮藏圆脆枣时以枣专用保鲜袋包装为佳。     

温度波动对灵武长枣贮藏品质的影响

为研究温度波动对灵武长枣采后贮藏品质的影响,将灵武长枣进行自发气调包装,然后在(0±0.1)、(0±0.5)、(0±1)℃下贮藏。通过测定灵武长枣贮藏期间感官品质、丙二醛、V_C、可滴定酸、可溶性固形物和电导率等来比较不同贮藏温度的保鲜效果。试验结果表明:(0±0.1)℃下贮藏的灵武长枣保鲜效果最好,有效维持灵武长枣的感官品质,减缓了V_C的降解,同时有效抑制可滴定酸和可溶性固形物含量的降低以及丙二醛的增长。     

基于介电特性的枣果品质识别试验研究

为了寻求灵武长枣外在品质更稳定的快速无损识别方法,利用LCR测试仪测定了不同大小等级、不同颜色、不同形状及损伤与否的长枣介电特性参数,筛选出差异明显的敏感电学参数;在选定频段内对其变化规律曲线进行拟合和相关性分析;用t检验法对拟合曲线的相关系数进行统计学分析。在3.55 kHz~0.10 MHz频率段的并联等效电容Cp和在3.98 kHz~0.10 MHz频率段的并联等效电感Lp进行枣果大小等级的准确识别;在199.53 kHz~2.51 MHz频率段内的Z值可进行颜色识别;在0.01~1.00 MHz频率段内可以以电导G值进行枣果形状的准确识别;在5.01kHz~0.10 MHz频率段的串联等效电感Ls和3.16 kHz~0.10 MHz频率段内的电抗X值可以准确识别枣果的损伤与否。各组数据差异极显著(P0.01),拟合曲线均平行,所以基于介电特性的枣果品质识别是可行的。     

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