SiO2球腔微电极阵列过氧化氢传感器制备及应用

将微过氧化物酶-11(MP-11)直接固定于二氧化硅球腔微电极阵列,制备一种新型电化学过氧化氢(H2O2)生物传感器。采用Langmuir-Blodgett技术在氧化铟锡(ITO)电极表面制备聚苯乙烯(PS)微球阵列,并以此阵列为模板采用溶胶-凝胶法在ITO电极上制备二氧化硅(SiO2)球腔阵列,最后将微过氧化物酶-11作为氧化还原模型蛋白直接吸附于球腔内,制得MP-11/SiO2球腔阵列/ITO电极。该电极对H2O2响应快速灵敏,可作为电流型H2O2电化学生物传感器,其线性范围为7.06×10-6～4.02×10-2mol/L,检出限为3.0×10-7mol/L,米氏常数为0.916mmol/L。将该法用于食品样品中的H2O2的检测,回收率在94%～97%之间,效果良好,可为食品中残存的H2O2检测提供一种方法。     

团聚状纳米AuPd修饰的H2O2生物传感器研究

采用微胶束法室温条件下制备团聚状的AuPd合金纳米粒子,使用紫外可见光谱(UV-vis),透射电镜(TEM),X-射线粉末衍射(XRD)和X-射线能量色散谱(EDS)表征团聚结构AuPd合金纳米粒子的形貌、尺寸、结构和组成。用制备的AuPd纳米粒子修饰辣根过氧化物酶玻碳电极,制备无电子媒介的过氧化氢生物传感器HRP/AuPd/GCE。使用循环伏安法和计时电流法表征了HRP/AuPd/GCE对H2O2的检测性能。实验结果表明:该传感器对H2O2具有良好的检测性能和稳定性,在H2O2浓度为1×10-7mol/L～5×10-3mol/L范围内检测电流与H2O2浓度有线性关系,线性相关系数R2=0.995 01,检出限为7.6×10-7mol/L。     

腌制食品中亚硝酸盐的电化学检测

目的:制备基于磷钨杂多酸盐(Na3PW12O40)的多层膜电化学传感器,实现其对腌制食品中亚硝酸盐含量的快速检测.方法:用层接层法(Layer-by-Layer)将Na3PW12O40和PAH交替沉积于以(PEI/PSS/PAH)为底层的ITO电极上,制得多层膜亚硝酸盐传感器,分析该传感器的电化学性质,并利用其在溶液中对亚硝酸根的安培传感,测定腌制食品中亚硝酸盐含量.结果:制备的传感器在亚硝酸盐浓度1.67×10-8～3.23×10-6mol/L范围呈现良好的线性关系,I(μA)=0.125+0.630c(μmol/L),R=0.9992(n=10),响应电流达到95%时所需时间小于3s.结论:用电化学方法检测操作简便,灵敏度高,检出限低,结果准确,可用于腌制食品中亚硝酸盐含量的检测.     

辣根过氧化物酶/聚乙烯醇缩丁醛/碳纳米管修饰玻碳电极检测过氧化氢

制备了辣根过氧化物酶/聚乙烯醇缩丁醛/碳纳米管修饰玻碳电极的过氧化氢生物传感器。以对苯二酚为电子媒介,采用循环伏安法和电流时间法考察了该传感器对H2O2的催化性能。讨论了媒介体浓度、工作电位、温度、pH对电极响应的影响。结果表明传感器对H2O2表现出良好的电催化性能。在pH=7.0,对苯二酚浓度4.2mmol/L,工作电位-250mV的实验条件下,H2O2浓度在1.67×10-7～1.29×10-5mol/L及1.58×10-5～1.17×10-3mol/L范围内与传感器的电流响应呈线性关系,检出限(S/N=3)为5.554×10-8mol/L。该传感器制备方法简单,成本低,稳定性好,对HO有快速灵敏的响应。     

磷酸盐—硅系纳米浆料助剂的分散稳定性

为研究纳米浆料助剂的稳定性对淀粉浆料性能的影响,分别以Na3PO4,Na4P2O7,(NaPO3)6和Na5P3O10为分散剂制备纳米SiO2浆料助剂,通过离心透光率、沉降积等指标表征该磷酸盐-硅系纳米浆料助剂的分散稳定性,研究其分散稳定性对淀粉浆液、浆膜及黏附性能的影响.实验表明:Na3PO4,Na4P2O7,(NAPO3)6和Na5P3O10的分散稳定能力依次增强,质量分数分别为0.5%,4%,8%和10%时分散效果最佳;这种助剂对淀粉浆液性能没有显著影响,对浆膜断裂强度及黏附性能的促进作用随着分散体系稳定性的提高而增强;以Na5P3O10为分散剂的纳米浆料助剂对淀粉浆料性能的促进作用最显著.     

ASSP工艺制备掺镧氧化铝膜研究

氧化铝膜作为典型的无机陶瓷膜材料,具有良好的热稳定性、化学稳定性和成膜性.用稀氨水正向滴定,通过控制沉淀反应速度(10 m L/m in～15 m L/m in)、反应终点(pH= 7),加入HAc作胶溶剂,于80 ℃恒温胶溶12 h,可制得稳定、透明的溶胶,用该溶胶可制得无开裂的La2O3-Al2O3 膜.采用XRD,SEM 等对膜的组成和形貌等物化性质的变化进行分析,结果表明,掺入6% 的La2O3 可以获得β-Al2O3 膜,膜的高温结构稳定性明显提高     

玉米秸秆纳米纤维素-淀粉膜的制备工艺优化及性能分析

本研究利用玉米秸秆纳米纤维素、玉米秸秆淀粉等作为成膜基材,通过共混流延法制备玉米秸秆纳米纤维素-淀粉膜。通过单因素实验和正交试验,对制备的纳米纤维素-淀粉膜的性能进行测定,考察各成膜基材对纳米纤维素-淀粉膜的机械性能、透湿系数、透光率、水溶性和透氧系数的影响,最终确定成膜液最佳配方组合:淀粉10.0%（W/V）、纳米纤维素5.0%（W/V）、羧甲基纤维素钠1.6%（W/V）、甘油2.3%（V/V）。在最优工艺条件下制备的纳米纤维素-淀粉膜综合效果最佳,并测得性能指标,膜厚（0.063±0.050）mm,抗拉强度14.92 MPa,断裂伸长率64.75%,透湿系数为2.19×10?12 g·m/m2·s·Pa,透光率87.60%,溶解时间97.00 s,透氧系数2.75×10?14 cm3·cm/cm2·s·Pa。     

氧化复合淀粉磷酸酯的干法制备

将双氧水(H2O2)对淀粉的氧化作用与三聚磷酸钠(STP)和淀粉的酯化反应相结合,采用干法工艺制备氧化复合淀粉磷酸酯。在H2O2用量2.0%,STP用量2.0%情况下可制得性能良好的肉制品品质改良剂———氧化复合淀粉磷酸酯。     

玉米醇溶蛋白肽-丁香酚纳米复合粒子稳定的皮克林乳液的制备及性质

采用胰蛋白酶对玉米醇溶蛋白进行水解,采用反溶剂法用制得的水相肽与丁香酚制备纳米复合粒子。考察油水比例、粒子质量浓度、离子强度、p H对纳米复合粒子制备乳液的性质影响。最终发现在油水体积比1∶5、粒子浓度0.06 7%、离子强度在0.3 mol/L、p H为7.5时,乳液的乳化活性为4.77×10~(-2) m~2/g、乳化稳定系数为1.368×10~(-2),离心分层系数为0.780。     

卡拉胶植物淀粉复合膜制备及其相关性能研究

采用木薯醋酸酯淀粉、玉米淀粉和卡拉胶复配制备复合膜材料。在分别研究三种单一成分的浓度-粘度-温度关系、溶解度、膨胀率等性能基础上,选择了成膜性较好的三种配比5∶3∶2,2∶6∶2和1∶7∶2(醋酸酯淀粉:玉米淀粉:卡拉胶),进一步分析了三种膜的透光率、水蒸气透过率和吸湿率等性能。结果表明1号膜(5∶3∶2)醋酸酯淀粉含量高,膜的抗拉强度和断裂伸展率最大,分别为5.13 MPa和6.0%,当卡拉胶比例一定的条件下醋酸酯淀粉对膜的水蒸气透过性和吸湿性影响显著,而对透光率影响不大,醋酸酯淀粉含量高的1号膜的吸湿增重、水蒸气透过系数和透光率分别为40.16%,0.49 g·mm/m~2·h·k Pa和44.5%(450 nm),而3号膜则分别为21.39%,0.34 g·mm/m~2·h·k Pa和34.80%(450 nm)。综上,醋酸酯淀粉和卡拉胶是影响膜各项性能的关键成分。     

喷气织机引纬筘槽内气流状态的影响因素

由于测量引纬筘槽内的气流速度可用于分析各工艺参数对引纬过程的影响,为此通过自行设计的测试装置,采用毕托管测试引纬筘槽内不同位置的气流速度,并研究喷向角和辅助喷嘴间距等工艺参数的适调范围。结果表明:引纬筘槽内不同位置具有不同的气流速度;供气压力在(2～4)×105 Pa范围内,辅助喷嘴喷射角不宜设置为5°,否则将导致引纬气流速度过低;辅助喷嘴间距缩短有利于提高引纬筘槽内的平均流速,当辅助喷嘴间距为65 mm时,引纬筘槽内的气流速度完全能够满足100 m/s的引纬要求。     

分散红60在超临界CO_2染色中的动力学及热力学

在自行研制的生产型超临界流体染色样机中,对分散红60染料在超临界CO2染色过程动力学进行研究。结果表明,染料在涤纶中的扩散系数随温度升高而增大,根据Arrhenius方程求得分散红60在超临界流体中染色涤纶的扩散活化能为22.22 kJ/mol,远小于在水介质中染色的扩散活化能163.84 kJ/mol。通过对分散红60染料在超临界CO2染色过程中的某些热力学参数研究表明,染料在超临界流体的上染量与染料用量成线性关系,上染过程是染料在纤维和流体之间的分配关系,分配系数和染色亲和力随温度升高而减小,染色热和染色熵均为负值,二者分别为-23.63 kJ/mol和-26.09 J/(mol·K)。     

Combined effects of mustard flour,acetic acid,and salt against Esherichia coil O157:H7 stored at 5 and 22 degrees C

The combined effects of acetic acid and mustard flour were investigated to ascertain their impact on Escherichia coli O157:H7 stored at 5 and 22 degrees C. Samples were prepared with various concentrations of acetic acid (0, 0.25, 0.5, 0.75, and 1% [vol/vol]) combined with 10% (wt/vol) Baltimore or Coleman mustard flour and 2% (fixed; wt/vol) sodium chloride. An acid-adapted mixture of three E. coli O157:H7 strains (10(6) to 10(7) CFU/ml) was inoculated into prepared mustard samples that were stored at 5 and 22 degrees C, and samples were assayed periodically for the survival of E. coli O157:H7. The numbers of E. coli O157:H7 were reduced much more rapidly at 22 degrees C than at 5 degrees C. E. coli O157:H7 was rapidly reduced to below the detection limit (<0.3 log10, CFU/ml) after 1 day at 22 degrees C, whereas it survived for up to 5 days at 5 degrees C. There was no synergistic or additive effect with regard to the killing of E. coli O157:H7 with the addition of small amounts of acetic acid to the mustard flour. When stored at 5 degrees C, mustard in combination with 0.25 (M-0.25), 0.5 (M-0.5), and 0.75% (M-0.75) acetic acid exerted less antimicrobial activity than the control (M-0). The order of lethality at 5 degrees C was generally M-0.25 = M-0.5 < M-0.75 = M-0 < M-1. The addition of small amounts of acetic acid (<0.75%) to mustard retards the reduction of E coli O157:H7. Statistical reduction in populations of E. coli O157:H7 (P < 0.05) was enhanced relative to that of the control (mustard alone) only with the addition of 1% acetic acid. This information may help mustard manufacturers to understand the antimicrobial activity associated with use of mustard flour in combination with acetic acid.     

In vitro antioxidant properties of indigenous underutilized fruits

In the present study, in vitro antioxidant and free radical scavenging capacity of methanol extracts from 10 underutilized fruits viz., Syzygium cumini, Murraya koenigii, Coccinia grandis, Opuntia dillenii, Carissa carandus, Kirganalia reticulata, Canthium parviflorum, Lantana camara, Alangium lamarckii, and Morus alba were evaluated using established in vitro models such as ferric reducing antioxidant power (FRAP), 2,2-diphenyl-1-picryl-hydrazyl (DPPH^•), 2,2′azinobis(3-ethylbenzothiozoline-6-sulfonic acid) diammonium salt (ABTS), hydroxyl radical (OH^•), nitric oxide radical (NO^•), super oxide radical (O₂^{• −}) scavenging, and metal chelating activities. All the fruit extracts contained substantial concentration of total phenolics, tannins, and flavonoids. The extracts of O. dillenii, M. koenigii, K. reticulata, L. camara, and M. alba registered higher activity in DPPH^•, ABTS^{• +}, and FRAP assays. Phenolic content of these fruits is significantly correlated with antioxidant capacity. Interestingly, all the extracts showed considerable nitric oxide, super oxide, and hydroxyl radical scavenging activities in a dose dependant manner when compared with the standard butylatedhydroxyl anisole (BHA). Our findings revealed that these underutilized fruits have potential as good sources of natural antioxidant/nutraceutical compounds.     

Effect of roasting on the radical scavenging activity of cocoa beans

The free-radical scavenging activity of cocoa samples subjected to different roasting treatments has been determined. The samples (raw, pre-roasted and roasted) were separated into four molecular weight fractions per sample (>30, 30–10, 10–5, and <5 kDa). The free-radical scavenging activity was determined with the DPPH^• (1,1-dipheny-2-picrylhydrazyl), and ABTS^•+ [2,2’-azinobis (3-ethylbenzothiazoline-6-sulfonic acid)] free-radical scavenging assays for all samples. Both tests were compared in terms of sensitivity and measurement precision, at different reaction times. Comparing the results from each test, the free-radical scavenging activity trends were similar for each fraction but with notable differences in the sensitivity of the assays. Analysis of the concentration of reducing substances, such as water soluble phenolics, melanoidins, carbohydrates, etc, in these fractions by the photometric Folin–Ciocalteu assay, showed a similar pattern to the free-radical scavenging activity trend. Moreover, this comparison showed that there were significantly (P < 0.05) more reducing substances and free-radical scavenging activity in the 10–5 kDa roasted cocoa bean fraction.     

Contamination of commercially available <Emphasis Type="SmallCaps"> L-</Emphasis>tryptophan by related substances

In 1989 a new autoimmune disease, the eosinophilia myalgia syndrome (EMS), was traced back to the intake of L-tryptophan (Trp) of a single manufacturer, Showa Denko (SD). In an epidemiological study, six minor contaminants (10-1,000 mg/kg Trp) were related to the occurrence of EMS. In this study the pattern of contaminants in pharmaceutical- and feed-grade Trp was investigated in a market survey of 21 lots of Trp raw materials of six different manufacturers, as well as one bioconversion broth, and four tablets. For total Trp-related impurities all UV_{220 nm} detectable substance peaks separated from Trp by RP-HPLC were calculated as N -acetyl-tryptophan. In all samples 4-,5-, 6-, and 7-OH-Trp, 1,2,3,4-tetrahydro-ß-carboline-3-carboxylic acid (THCC), 1-methyl-1,2,3,4-tetrahydro-ß-carboline-3-carboxylic acid (MTHCC) and 1-(3-indolylmethyl)-1,2,3,4-tetrahydro-ß-carboline-3-carboxylic acid (IMTHCC) as well as 2-[2,3-dihydroxy-1-(3-indolyl)-propyl]- L- tryptophan (dhPIT) were determined, since the last four are known to be major contaminants in biotechnologically manufactured Trp. Additionally, four EMS-related substances were been analysed: 3a-hydroxy-1,2,3,3a,8,8a-hexahydropyrroloindole-2-carboxylic acid (PIC), 2-(3-indolylmethyl)- L- tryptophan (IMT), 1,1'-ethylidenebis-( L- tryptophan) (EBT) and 3-(phenylamino)alanine (PAA). EBT was only detectable in a single SD-Trp sample known to be EMS associated. Low amounts of PAA (20 mg/kg) were detected in feed-grade Trp of one manufacturer as well as in SD-Trp. IMT was found in small amounts in recent pharmaceutical-grade Trp (10-25 mg/kg Trp), but in higher amounts in feed-grade Trp samples (120-1,400 mg/kg) as well as in pharmaceutical-grade Trp and Trp tablets manufactured prior to 1989 (70-660 mg/kg). PIC is a primary oxidation product of Trp; thus we detected 4-50 mg/kg of the earlier-eluting PIC diastereomer in recent pharmaceutical-grade Trp and up to 2,500 mg/kg in feed-grade Trp. Non-EMS correlated THCC, MTHCC, IMTHCC, and dhPIT proved to be the main contaminants in amounts of <10-13,500 mg/kg.     

Thermal inactivation of Escherichia coli O157:H7 and Escherichia coli isolated from morcilla as affected by composition of the product

Morcilla is a link sausage quite similar to black pudding, consisting of an inert casing stuffed with a mixture of beef blood, fat, and seasonings. Thirty samples of morcilla showed total microbial counts (6.3×10³–2.1×10⁸ Cfu/g ), molds and yeasts (8.9×10¹–6.3×10⁴ Cfu/g), sulfite-reducing microorganism (2.0×10¹–2.1×10²MPN/g); total coliforms (1.4×10¹–1.1×10³ MPN/g); fecal coliforms (7.0–1.5×10²MPN/g); Enterobactereaceae (1.6×10²–5.0×10⁵ Cfu/g). S. aureus and B. cereus were not detected. E. coli was detected in 76.6% of the samples analyzed. The thermal resistance (D and z-values) of Escherichia coli O157:H7 and E. coli isolated from morcilla were determined in nutrient broth and in a heating menstruun prepared with ground morcilla (discarding the casing) and added fat or starch. Higher fat and starch levels resulted in higher D-values (min) at 54, 58 and 62 °C for both strains. The z-values (°C) for isolated E. coli in nutrient broth (M1), ground morcilla (M2), M2+10% fat (M3), M2+20% fat (M4), M2+10% starch (M5), and M2+20% starch (M6) were 7.9, 7.8, 10.5, 10.4, 10.3, and 10.4, respectively, and for E. coli O157:H7 were 7.8, 7.4, 9.8, 10.2, 10.3, and 10.7. The composition of product affected heat lethality of the two strains of E. coli.     

Effect of different levels of beef bacterial microflora on the growth and survival of Escherichia coli O157:H7 on beef carcass tissue

The influence of various levels of endogenous beef bacterial microflora on the growth and survival of Escherichia coli O157:H7 on bovine carcass surface tissue was investigated. Bacterial beef microflora inoculum was prepared by enriching and harvesting bacteria from prerigor lean bovine carcass tissue (BCT) and was inoculated onto UV-irradiated prerigor BCT at initial levels of 10(5), 10(4), 10(3), and <10(3) CFU/cm2. Additional control BCT was inoculated with sterile H2O. E. coli O157:H7 was inoculated onto all tissues at an initial level of 10(2) CFU/cm2. Following a 48-h incubation at 4 degrees C, BCT was incubated up to 14 days at 4 or 12 degrees C, either aerobically or vacuum packaged. Regardless of the microflora level, there was no substantial growth of E. coli O157:H7 on BCT during storage at 4 degrees C under either aerobic or vacuum-packaged conditions. Instead, viable cell numbers at 4 degrees C remained constant, with no reduction in numbers associated with the different beef microflora levels. E. coli O157:H7 grew on all BCT stored at 12 degrees C, regardless of microflora inoculation treatment, reaching higher populations on aerobic samples than on vacuum-packaged samples in 10 days. However, the presence of the beef microflora did appear to delay the onset of growth or slow the growth of the pathogen, and E. coli O157:H7 counts on BCT without added microflora were generally higher following 7 to 10 days of 12 degrees C storage than those counts on BCT inoculated with beef microflora. These data demonstrate the importance of temperature control during meat handling and storage to prevent the outgrowth of this pathogen and indicate that proper sanitation and processing practices that prevent and reduce contamination of carcasses with E. coli O157:H7 are essential, regardless of background microflora levels.     

Survival ofEscherichia coliO157:H7,Listeria monocytogenesandSalmonella kentuckyin Norwegian fermented,dry sausage

Raw, newly produced sausages containing a mixed starter culture of lactobacilli and micrococci were each inoculated at separate locations (using a syringe) with low (10³–10⁴cfu) and high (10⁵–10⁷cfu) numbers of eitherEscherichia coliO157:H7, Listeria monocytogenes orSalmonella kentucky. Three identically prepared sausages were analysed at each sampling day during fermentation, maturation and storage at 4 and 20°C. In the low-inoculum samples, growth was observed initially (2 days) during fermentation forE. coliO157:H7 (3log₈increase in cfu) andL. monocytogenes(five-fold increase in cfu) but not forS. kentuckywhich decreased below the detection limit (150cfu sample^–1). None of the pathogens was detected after 5.5 months, neither at 4 nor 20°C. In the high-inoculum samples there was a decrease during fermentation and maturation for all the pathogens. After 5.5-months storage at 4°C, there was only about 90% reduction of the original inoculate ofL. monocytogenes, whereasE. coliO157:H7 survived at a low number (500cfu sample^–1) andS. kentuckydisappeared below the detection limit. After 5.5-months storage at 20°C, all the pathogens had disappeared below the detection limit. These results indicate that, from a safety point of view, it may be better to store these kinds of sausages at room temperature than in the cold, provided that the sensory qualities are retained and that similar results are obtained with other food pathogens.     

Effect of cooking procedures of kiymali pide,a traditional Turkish fast-food,on destruction of Escherichia coli O157:H7

The objective of the present study was to obtain data about cooking time and temperature of kiymali pide in the restaurants and to investigate thermal inactivation of E. coli O157:H7 during experimental kiymali pide making. A field study was conducted in randomly selected 23 of 87 pide restaurants. Processing parameters including oven temperature, cooking period and post-cooking temperature were determined. Kiymali pide samples were prepared using ground beef filling experimentally inoculated with E. coli O157:H7 (7.6 log₁₀ CFU/g). Pide samples were cooked at a conventional oven at 180 °C for 180, 240, 270, 300 and 330 s. Results of the current study suggest that cooking kiymali pide at 180 °C for at least 330 s (5.5 min) may provide sufficient food safety assurance (≥ 6 log₁₀ CFU/g) for E. coli O157:H7.