Magnetic molecularly imprinted polymer extraction of chloramphenicol from honey

A rapid and selective method was successfully developed using magnetic molecularly imprinted polymer (MMIP) as sorbent for the extraction of chloramphenicol from honey samples. The extraction process was carried out in a single step by blending and stirring the sample, extraction solvent and polymers. When the extraction was completed, the MMIPs adsorbing the analyte were separated from the sample matrix by an external magnet. The analyte eluted from the MMIPs by methanol under ultrasound assisted was analysed by liquid chromatography–tandem mass spectrometry. Various parameters affecting the extraction efficiency were evaluated for achieving optimal recovery and reducing non-specific interactions. Under optimal conditions, the detection limit of CAP was 0.047 ng g⁻¹. The relative standard deviations of intra- and inter-day ranging from 4.1% to 5.3% and from 2.9% to 7.1% were obtained, respectively. The method was applied to determine CAP in six honey samples. The recoveries of CAP in these samples from 84.3% to 90.9% were obtained.     

Determination of chloramphenicol in shrimp by liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS-MS)

A liquid chromatographic method with electrospray ionization tandem mass spectrometric (LC-ESI-MS-MS) detection and identification is described for the determination of chloramphenicol (CAP) in shrimp tissue. Homogenized shrimp samples were extracted by liquid–liquid extraction using ethyl acetate. d₅-Chloramphenicol (5D-CAP) was used as the internal standard. Data acquisition was in negative-ion multiple reaction monitoring (NMRM) mode using three transition reactions for CAP (m/z 321?→?152, m/z 321?→?257 and m/z 321?→?194) and two for d₅-chloramphenicol (m/z 326?→?262 and m/z 326?→?157). Method validation was carried out according to European Commission decision 2002/657/EC. The calibration curve was linear in the range 0.10–2.00 µg l^?1, with typical r ²?>?0.99. The decision limit (CCα) and detection capability (CCβ) were 0.06 and 0.10 µg kg^?1, respectively. There was no influence of the matrix on the determination of chloramphenicol.     

Detection of Salmonella Enteriditis from Egg Components Using Different Immunomagnetic Beads and Time-resolved Fluorescence

The types of chemical linkage used to bind antibodies to magnetic beads to form immunomagnetic beads (IMB) were compared in the capture and detection of Salmonella Enteriditis from egg white, egg yolk, and whole egg. Egg components were inoculated with outbreak strains of S. Enteriditis. After incubation under different conditions, IMBs derived from linking antibodies to core magnetic beads via biotin–streptavidin interactions, Schiff-base bonds and unspecified proprietary chemistry were used to capture S. Enteriditis. Europium-labeled anti-Salmonella antibodies completed the sandwich, and time-resolved fluorescence served as the means of detection. For the Salmonella isolated in stationary phase and cultured from universal pre-enrichment broth (UPB), the detection signal intensity was affected by the chemistry utilized to link the antibodies to IMB, with results varying among the three test strains. When S. Enteriditis was cultured in egg yolk alone, plating data were similar to those of the growth of S. Enteriditis in UPB. Egg white by itself did not support the growth of S. Enteriditis. The addition of UPB to egg white restored the growth of Salmonella and yielded stronger detection signals than from cultures obtained from UPB with egg yolk. The detection signals obtained from the immunoassay were less intense for cultures grown in egg yolk + UPB than from cultures grown in UPB alone. The lower detection signals elicited by all IMBs suggest the availability of the antigenic groups recognized by the antibodies on IMBs was reduced in the presence of egg yolk.     

基于核酸适配体和G-四链体免标记荧光分析法检测氯霉素

目的 基于核酸适配体和G-四链体(G-quadruplex,G4)结构建立一种免标记荧光分析法检测氯霉素(chloramphenicol, CAP)含量,应用于化学分析、环境检测、食品安全等领域。方法 G4探针和适配体(aptamer,AP)在Tris-HCl缓冲液中合成,由于G4探针与适配体的结合抑制了G4的形成,N-甲基卟啉二丙酸IX(N-methylmesoporphyrin IX, NMM)染料无法被G4结构增强,荧光强度较弱,加入CAP竞争结合适配体,使得G4探针结构改变,通过荧光强度产生的变化分析样品中的CAP含量。围绕G4检测探针进行系列优化,包括探针序列、Tris-HCl缓冲液体系中钾离子和镁离子浓度、G4探针浓度与AP浓度比例。结果 当CAP质量浓度在1～10ng/mL时,体系的荧光强度增长值(Y)与CAP质量浓度(X)呈线性关系,线性方程为Y=59.091X+1.733(r2=0.9939)。根据3倍相对标准偏差(3σ/K,n=11)计算该方法 检出限,为0.518ng/mL。本方法 对卡那霉素、链霉素和庆大霉素无荧光响应,具有良好选择性和特异性。结论 本方法 重复...     

Analysis and monitoring of chloramphenicol residues in food of animal origin in Slovenia from 1991 to 2000

To prevent the illegal use of chloramphenicol (CAP), regulatory control of its residues in food of animal origin is essential. In Slovenia, the monitoring of CAP residues for statutory purpose started in 1991. The results of a 10-year period are presented. CAP residues were determined by capillary gas chromatography (GC) with electron capture detection (ECD) using meta-CAP as an internal standard (ISTD). Before chromatographic determination, analytes were derivatized by silylation. Overall, CAP recovery, adjusted for ISTD, was for bovine muscle tissue and raw cow's milk (in the region of 2-10 μg kg^-1) 89 and 102%, respectively, and for whole eggs, 87% (in the region of 1-10 μg kg^-1). The use of meta-CAP improved significantly the precision of the method. The detection limit for CAP was 1 μg kg^-1, which was sufficiently sensitive for routine use. A total of 1308 random samples of Slovenian origin were analysed from 1991 to 2000, covering all parts of the country. CAP was found only in one milk sample in 1997 at a concentration of 4.6 μg kg^-1.     

高效液相色谱法测定牛奶中氯霉素残留量的研究

为了快速、简便、灵敏地测定牛奶中的氯霉素残留，建立了高效液相色谱分析法，牛奶样品先用含1％高氯酸的乙酸乙酯沉淀蛋白质和提取氯霉素，提取液浓缩干后用0.5mol/L高氯酸溶液溶解，以正己烷去除脂溶性杂质，在波长278nm处用高效液相色谱仪测定氯霉素，本方法最低检出浓度为1．1μg/kg，氯霉素浓度在20μg/kg－100μg/kg范围内，方法平均回收率为88．0％－97．7％，RSD为5．3％－6．4％，本方法适于牛奶中氯霉素残留的监测。     

Supercritical fluid extraction in situ derivatization for simultaneous determination of chloramphenicol,florfenicol and thiamphenicol in shrimp

The applicability of supercritical fluid extraction in situ derivatization was investigated for determination of trace amounts of amphenicols (chloramphenicol, florfenicol and thiamphenicol) in shrimp. Quantification was performed by using electron-capture negative chemical ionisation-gas chromatography/mass spectrometry (NCI–GC/MS). The parameters of supercritical fluid extraction (addition of modifier, temperature, pressure, extraction time and extraction mode) and in situ derivatization (collection solvent and derivatization reagent) were varied with control. The optimum extractions were obtained using 600 μL ethyl acetate as a modifier for supercritical carbon dioxide with static extraction for 5 min, then dynamic extraction for 10 min at 25 MPa and 60 °C. The conditions for in situ derivatization were 200 μL N,O-bis(trimethylsilyl) trifluoroacetamide containing 1% trimethylchlorosilane in 20 mL ethyl acetate as collection solvent. The new method of supercritical fluid extraction in situ derivatization was found to be linear over the concentration range of 20–5000 pg/g, with detection limits ranging from 8.7 to 17.4 pg/g (using the selective ion monitoring mode), with a R.S.D. (relative standard deviation) less than 15.3% (n = 5). Analysis of spiked shrimp samples revealed that matrix had little effect on extraction. The results presented here indicate that supercritical fluid extraction in situ derivatization is for the trace analysis of amphenicol bacteriostats in shrimp samples.     

Characterization of glucoamylase immobilized on magnetic nanoparticles

Magnetic support was prepared by precipitation from an alkaline solution of divalent and trivalent iron ions and subsequently was modified with 3‐aminopropyltriethoxysilane. FTIR analysis showed existence of a new Si–O–Fe bond in obtained particles. Scanning electronic microscopy images shows that the nanoparticles of all samples have particle size below 30 nm. Glucoamylase AMG 300L was immobilized onto the modified magnetic support using glutaraldehyde as a coupling agent. Obtained preparations had specific activity of 148 U/g of the support when measured at 55°C using maltose as substrate. The immobilized enzyme exhibited mass transfer limitation as reflected by a higher apparent K_m value and a lower energy of activation. The immobilization was almost completely terminated after 30 min of the reaction at 30°C. The highest immobilization yield of the enzyme was achieved at glutaraldehyde concentration of 10 mM. The immobilization did not influence considerably on optimum pH and temperature of substrate hydrolysis catalyzed by investigated enzyme (55°C, pH 4.5). Moreover, immobilized glucoamylase was easily separated from the reaction medium by an external magnetic field and retained about 60% of initial activity after nine repeated cycles of enzyme reaction followed by magnetic separation.     

东南亚天然香辛原料精油在泰式酸辣虾粉中风格呈味的探讨

以东南亚香辛原料提炼出的精油作为主要风味剂,结合海鲜提取物—虾提取物,经科学调配,开发出风味独特、深受市场欢迎的东南亚特色风味调味料—泰式酸辣虾粉,并对其风格形成进行探讨。     

纤维材料降噪结构体的研究进展

为有效提高纤维材料降噪结构体的降噪性能,简述了近年来国内外纤维材料降噪结构体研究进展,依据纤维集合体的降噪机制,将纤维材料降噪结构体划分为多孔吸声复合降噪、多孔与共振复合降噪、多孔与阻尼复合降噪等类型。阐述了各种种纤维材料降噪结构体所用的纤维种类,介绍了各种类型纤维材料降噪结构体的构建方法,考察了各种类型纤维材料降噪结构体的结构组成,探讨了各种类型纤维材料降噪结构体的降噪效果,分析了不同类型纤维材料降噪结合体的作用机制,并对纤维材料在未来降噪领域的发展前景进行了展望,指出轻薄化、绿色化与多功能化是降噪功能纤维集合体的发展方向,为将来纤维材料在降噪领域的应用与发展提供了参考。     

Antioxidative and antimicrobial effects of low molecular weight shrimp chitosan and its derivatives on seasoned-dried Pangasius fillets

This study was performed to evaluate the efficacy and applicability of low molecular weight shrimp chitosan (LMWC) and its derivatives (chitosan nanoparticles, CN; chitosan hydrochloride salt, CHS) as a preservative against lipid oxidation and microbial growth in seasoned-dried Pangasius hypophthalmus fillets during storage. All chitosans exhibited antioxidant activity in vitro (2,2-diphenyl-1-picrylhydrazyl radical scavenging activity, total reducing power ability and lipid peroxidation inhibition activity). The lipid oxidation in dried pangasius fillets that were seasoned by immersing in a solution containing 1.5% chitosan was suppressed during the 8-week storage; such effect was more effective than immersing in a solution containing 0.05% vitamin C. Likewise, LMWC and its derivatives were more effective in inhibiting microbial growth (lower total viable count and yeast/mould counts) than the control. These results clearly show that LMWC and its derivatives could be a potent antioxidant and antimicrobial preservative in seasoned-dried pangasius fillets during 8-week storage at 20 °C.     

Impact of pulsed electric field pretreatment on yield and quality of lipid extracted from cephalothorax of Pacific white shrimp (Litopenaeus vannamei) by ultrasound-assisted process

Pacific white shrimp cephalothorax was subjected to pulsed electric field (PEF) pretreatment at different electric field strengths (4, 8, 12 and 16 kV cm⁻¹) and pulse numbers (120, 160, 200 and 240) to enhance the extraction yield of lipids. PEF-treated samples were subsequently subjected to lipid extraction using ultrasound-assisted extraction (UAE) process at ultrasound amplitude of 80% for 25 min in continuous mode. PEF-pretreated samples subjected to UAE rendered the highest lipid yield (30.34 g 100 g⁻¹ solids). PEF pretreatment resulted in reduced lipid oxidation as evidenced by the decreases in peroxide value (PV) and thiobarbituric acid reactive substances (TBARS). Lipids from PEF-pretreated samples extracted using UAE had higher content of PUFAs and carotenoids, including astaxanthin, astaxanthin monoester, astaxanthin diester, canthaxanthin and β-carotene. Overall, PEF pretreatment helped in enhancing the extraction yield of lipids and carotenoids from shrimp cephalothorax and reduce lipid oxidation to some extent.     

Salt reduction: Moving from consumer awareness to action

Globally, the average daily dietary salt intake is more than double the recommended level. Given the major role that salt plays in the development of cardiovascular disease, it is important to reduce total salt intake. Key sources of salt in the diet include commercially prepared or manufactured food products and discretionary salt added by consumers during cooking and consumption. Therefore a significant lowering in the current salt intake requires a shift in both commercial foods and consumer behaviour. In terms of commercial foods, the challenge is to achieve further reductions in the salt content while maintaining good taste, stability and texture to ensure consumers will like (or even prefer) these reformulated products. However, a change in consumer behaviour is also required to ensure that lower salt products are accepted and that consumers do not add salt back during cooking. Consumer behaviour change in this area remains complex and has received relatively little attention so far. It is hard for consumers to estimate their salt intake and, while most campaigns focus on raising awareness of reducing salt, this awareness may not always lead to action. The development of scalable and effective salt-reduction behaviour change interventions requires a more in-depth understanding of the relevant consumer behaviours and their determinants, as well as the development of practical behaviour change techniques and facilitators (e.g., provision of appealing lower salt products). Moreover, to speed up the salt reduction progress from ‘awareness’ to ‘action’, key stakeholders need to take responsibility and agree on actions for executing product reformulation and creating consumer behaviour change programmes. This review is intended to inform and support the ongoing development of effective action-oriented global strategies for salt reduction.     

刺葡萄花色苷色素稳定性研究

刺葡萄皮富含色素,具有良好的开发前景。研究了不同浓度的双氧水、抗坏血酸、亚硫酸钠、山梨酸钾和苯甲酸钠溶液对刺葡萄色素的影响,结果表明:双氧水能与刺葡萄色素发生强烈的氧化作用;抗坏血酸、亚硫酸钠对色素没有辅色作用,反而会加速色素液的褪色,且随浓度的增大,褪色速度加快;低浓度(≤0.05g/mL)的山梨酸钾和苯甲酸钠溶液对色素的影响较小。     

蜜柚叶黄酮的提取及其抗氧化与降尿酸活性研究

研究蜜柚叶总黄酮的提取工艺、抗氧化活性及其对黄嘌呤氧化酶的抑制活性。采用正交实验对蜜柚叶黄酮的提取工艺进行优化,探究蜜柚叶黄酮的最佳提取工艺条件。并通过DPPH自由基、羟自由基及超氧阴离子清除实验探究蜜柚叶黄酮对自由基离子的清除活性;通过黄嘌呤氧化酶活性抑制实验初步判断其降尿酸功效。结果表明:蜜柚叶黄酮的最佳提取条件为料液比1:30（g/mL）、乙醇浓度80%、浸提时间6 h、浸提温度80℃,黄酮得率为12.41 mg/g。蜜柚叶黄酮对DPPH自由基、羟自由基及超氧阴离子均表现出较强的清除活性,IC50值分别为:1.47、1.04、1.49 mg/mL。同时,蜜柚叶黄酮对黄嘌呤氧化酶抑制活性的IC₅₀值为4.8 mg/mL。      

Compositions and yield of lipids extracted from hepatopancreas of Pacific white shrimp (Litopenaeus vannamei) as affected by prior autolysis

Compositions and yield of lipids extracted from hepatopancreas of Pacific white shrimp (Litopenaeus vannamei) subjected to autolysis at 60 °C for different times (0, 30, 60, 90 120 and 150 min) were investigated. Extraction yield increased from 7.4% to 8.8% as autolysis time increased from 0 to 150 min. Coincidental increase in total carotenoid content was obtained with increasing autolysis time (p < 0.05). The increases in thiobarbituric acid-reactive substances (TBARS) and p-anisidine value (AV) of lipids were noticeable when autolysis time increased (p < 0.05). However, no changes in free fatty acid (FFA) content were observed within the first 60 min of autolysis (p > 0.05), but subsequently increased up to 150 min. (p < 0.05). No differences in fatty acid profiles of lipids extracted from hepatopancreas without and with 60 min prior autolysis were observed. Lipids extracted contained docosahexaenoic acid (DHA; C22:6(n − 3)) as the most abundant fatty acid, followed by eicosapentaenoic acid (EPA; C20:5(n − 3)). Therefore, prior autolysis at 60 °C for 60 min increased the extraction yield without negative effect on lipid quality.     

油炸马铃薯片中丙烯酰胺形成的协同阻断研究

目的研究油炸温度、油炸时间对马铃薯片中丙烯酰胺生成的影响,进而探讨半胱氨酸(Cys)和热烫处理对丙烯酰胺生成的协同阻断作用。方法将试样马铃薯片分别在不同浓度的Cys(0~5 g/L)溶液中,进行热烫(25~85℃)前处理,在不同温度(140~220℃)以及油炸时间(0~35 min)条件下,油炸处理,利用衍生化气相色谱-质谱联用(GC-MS)法测定样品中的丙烯酰胺含量。结果无预处理下,油炸马铃薯片中丙烯酰胺的生成量,随油炸时间或油炸温度的增加,呈先升高后降低的变化趋势,油炸温度为180℃的条件下,油炸3 min时,达到最大值5.16 mg/kg;油炸时间为5 min的条件下,油炸温度为200℃时,达到最大值4.85 mg/kg。热烫前处理对丙烯酰胺生成具有显著抑制效果,抑制率随热烫温度的升高而增大,室温条件下Cys溶液浸泡对丙烯酰胺生成具有抑制效果,抑制率随Cys浓度增加未见明显变化,然而温度升高后,出现协同阻断效应,Cys浓度为5 g/L和热烫温度为85℃的条件下,丙烯酰胺抑制率达100%。结论 Cys和热烫处理对抑制丙烯酰胺的生成存在协同阻断效应,协同作用下的抑制率与两者单独作用相比显著增加。     

基于相容关系下的知识粗糙熵的属性约简

依据相容关系下知识粗糙熵的概念,通过对不完备信息系统中知识与粗糙熵之间的关系以及基于粗糙熵的属性重要性的分析,提出了基于相容关系的知识粗糙熵的启发式约简算法.实例分析表明,作为一种有效的数据挖掘工具,该算法是有效的,具有推广价值.     

Rapid colorimetric detection of proteins and bacteria using silver reduction/precipitation catalyzed by gold nanoparticles

A colorimetric immunoassay has been developed based on the reduction and precipitation of silver ions catalyzed by colloidal gold. This method was evaluated for a noncompetitive heterogeneous immunoassay to detect ovalbumin as a model protein and Escherichia coli as model bacterium. The influence of relevant experimental variables, including the reaction time of antigen with antibody, the dilution ratio of the colloidal gold-labeled protein, time allowed for silver reduction/precipitation reaction and other parameters were examined and optimized. This colorimetric method of detection is convenient, easy to use and economic. The presence of the target molecules or antigens can be visually inferred based on the color change that occurs in a short time without using major instrumentation. This method is widely amenable for detection of proteins, viruses and bacteria.     

阻燃聚酯纤维织物的碱减量处理研究

探讨了阻燃聚酯织物碱减量处理的影响因素,并与普通聚酯织物进行了比较.实验结果表明,碱用量、处理时间、促进剂的用量对阻燃聚酯织物减量率的影响较普通聚酯织物大得多,在实际加工过程中为了获得稳定的产品质量,不宜采用普通季铵盐阳离子表面活性剂作促进剂,必须更为严格地控制工艺条件.