菊粉酸降解动力学研究

通过考察温度、溶液pH值及水分含量对菊粉酸降解的影响,探索菊粉酸水解规律。结果表明:菊粉水溶液在pH 5.0～7.0、温度低于100℃时具有良好的稳定性;但当pH值低于4.0时,菊粉出现明显的水解反应。菊粉溶液在不同温度和pH值下的酸降解动力学表明,其水解反应遵循一级反应动力学方程。利用菊粉凝胶特性考察水分含量与菊粉酸降解的关系,发现相同pH值(pH=3)条件下,水分含量越高,菊粉降解速率越快,凝胶中菊粉降解速率低于菊粉水溶液降解速率。     

腌渍食品亚硝酸盐降解菌的分离、鉴定及其降解特性

从腌渍豆酱、香肠、腌渍萝卜中分离到5株乳酸菌,根据形态和生理生化特征等对分离到的菌株进行初步鉴定,并研究了分离菌株的生理学性质和降解特性.初步鉴定表明,L1,L3,L4和L5菌株为明串珠菌,L2菌株为链球菌.L2菌株最适生长温度为30 ℃,L1,L3,L4和L5菌株最适生长温度为25 ℃,5个菌株的最适生长pH值均为6.5,在4%～6% NaCl溶液中均能正常生长繁殖.L2菌株在30 ℃时对亚硝酸钠的降解率最高,其他菌株在25 ℃时最高;5个菌株均在pH=3.5时对亚硝酸钠的降解率最高.在适宜pH值和培养温度下,L3和L5菌株对亚硝酸钠的降解率超过93%,具有较大的应用价值.     

透明质酸降解工艺条件优化

以新鲜鸡冠为原料,采用乙醇法提取鸡冠中的透明质酸粗品,再用十六烷基三甲基溴化铵(CTAB)法对提出的粗品进行纯化。将纯化后的透明质酸用化学法进行降解,根据还原糖法测定降解后透明质酸的分子质量,进而确定降解程度。通过单因素试验和响应曲面法分析建立二次回归模型,对料液比、降解pH值、降解时间、过氧化氢浓度4个因素进行优化组合,确定降解鸡冠中透明质酸的佳工艺条件为:料液比(H2O2∶Vc,mol∶L)为4.13∶1、pH值为8.16、降解时间5 min、H2O2浓度为1.67 mol/L。经提取纯化得到的透明质酸的相对分子质量为22 671.88,经该工艺降解后得到的透明质酸的相对分子质量为1 764.67。     

pH值对透明质酸钠溶液溶血性测定的影响

目的 探讨pH值对透明质酸钠(HA)溶液溶血性的影响.方法 调整0.4%HA溶液的pH值,以1%羊血悬浮液检测溶血性.结果 0.4%HA溶液的pH<4时,溶血检测阳性;调整pH 5.5～8.0时,溶血阴性.结论 0.4%HA溶液在pH<4时,其溶血性检测结果为假阳性.检测时应将HA溶液的pH调至5.5～8.0.     

pH值对透明质酸钠溶液溶血性测定的影响

目的探讨pH值对透明质酸钠(HA)溶液溶血性的影响。方法调整0.4%HA溶液的pH值,以1%羊血悬浮液检测溶血性。结果0.4%HA溶液的pH<4时,溶血检测阳性;调整pH 5.5~8.0时,溶血阴性。结论0.4%HA溶液在pH<4时,其溶血性检测结果为假阳性。检测时应将HA溶液的pH调至5.5~8.0。     

黑米花色苷热降解动力学研究

黑米花色苷在酸性水溶液和10%乙醇溶液中的热降解性质。通过考察黑米花色苷含量在4℃、25℃、80℃和100℃下随时间的变化,通过计算得到黑米花色苷在两种溶液和不同温度条件下的降解速率k、半衰期t_(1/2)、温度系数Q_(10)、活化能Ea。结果表明:黑米花色苷在pH3去离子水和10%乙醇溶液中的热降解规律符合动力学一级反应规律,其热降解速率随温度升高而增大,黑米花色苷在pH 3去离子水溶液中的稳定性优于10%乙醇溶液。     

关于纺织品pH值检测中水萃取液的探讨

国标GB/T7573-2009《纺织品水萃取液pH值的测定》中没有明确选用三级水或0.1mol/L氯化钾溶液作为水萃取液,造成各实验室间数据的稳定性差、准确性低、重现性差等现象。通过对三种不同水萃取液(三级水、0.1mol/L氯化钾溶液、25℃时饱和氯化钾溶液)对不同pH值范围的纺织品水萃取液pH值测定比对试验,从重现性、稳定性、准确性等因素考虑,建议各实验室应选用0.1mol/L氯化钾溶液或25℃时饱和氯化钾溶液作为水萃取液。     

氧气对涡流空化降解壳聚糖的影响

研究了氧气在不同壳聚糖溶液初始质量浓度、pH值、温度、进口压力、空化时间等条件下,对壳聚糖涡流空化降解的影响。结果表明：壳聚糖溶液的初始质量浓度越低涡流空化降解效果越好,当溶液pH值为4.4、温度为70 ℃、进口压力为0.4 MPa、空化时间为3 h时,壳聚糖的特性黏度下降率最高;在不同涡流空化降解条件下,连续通入氧气均可显著促进壳聚糖降解产物特性黏度下降率的提高,在本实验中最大可提高35.36%;氧气对高质量浓度壳聚糖降解的促进作用更显著;氧气的通入减弱了pH值对壳聚糖降解的影响、在反应的初期大大加快了反应速率;降解后的壳聚糖主链结构及官能团基本没发生变化。     

pH值对透明质酸钠溶液溶血性测定的影响

目的探讨pH值对透明质酸钠（HA）溶液溶血性的影响。方法调整0．4％HA溶液的pH值,以1％羊血悬浮液检测溶血性。结果0．4％HA溶液的pH〈4时,溶血检测阳性;调整pH5．5—8．0时,溶血阴性。结论0．4％HA溶液在pH〈4时,其溶血性检测结果为假阳性。检测时应将HA溶液的pH调至5．5～8．0。     

纳米二氧化钛改性杨木的力学性能研究

采用水热-溶剂法合成纳米二氧化钛(TiO_2),并对速生杨木浸渍处理以改善其力学性能。通过改变纳米二氧化钛制备中溶液酸碱度与反应温度,对比不同工艺条件下改性材的力学性能,结果发现:溶液为中性(pH=7)时改性材抗弯强度与(MOR)弹性模量(MOE)最佳,溶液为碱性(pH=10)时改性材硬度值最大。在同一碱性溶液下,反应温度为80℃时改性材抗弯强度与弹性模量最佳,反应温度为90℃时改性材硬度值最大。     

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