Natural control of bacteria affecting meat quality by a neem (Azadirachta indica A. Juss) cake extract

The antibacterial activity of an ethylacetate neem cake extract (NCE) against bacteria that affect meat quality, namely Campylobacter jejuni, Carnobacterium spp., Lactobacillus curvatus, Lactobacillus sakei and Leuconostoc sp., is reported. The antibacterial activity was detected using standardised disc diffusion and macrodilution methods. The bacterial growth inhibition zone ranged from 11.33 ± 0.58 to 22.67 ± 0.58 mm (100 μL NCE). There is significant difference between the growth inhibition zone of NCE and the control (ciprofloxacin 100 μg). The percent of bacterial growth reduction range was 79.75 ± 1.53 to 90.73 ± 1.53 (100 μg NCE) as compared with control (without NCE). NCE in different amounts counteracted the growth of all tested bacteria.     

高效液相色谱-串联质谱法测定加工肉制品中莱克多巴胺及克伦特罗的含量

建立了高效液相色谱串联质谱测定加工肉制品中莱克多巴胺和克伦特罗的方法。采用阳离子交换色谱柱(SCX)分离目标化合物,改进了前处理方法,采用PXC固相萃取柱净化,并对洗脱溶液和高效液相色谱串联质谱的各参数进行优化。高效液相色谱流动相流速为0.4 mL/min,进样量为10μL,柱温为40℃。样品均质后加入30μLβ-盐酸葡萄糖醛苷酶-芳基硫酸酯酶,并经0.02 mol/L乙酸铵溶液(pH 5.2)提取,离心,过固相萃取柱净化。两种目标化合物在0.1～100μg/L范围内线性关系良好,检出限和定量下限分别不超过0.04μg/kg和0.15μg/kg。样品平均加标回收率为72%～98%,RSD低于8.5%。结果表明,此方法适于加工肉制品中莱克多巴胺和克伦特罗的测定。     

Radiation decontamination of meat lyophylized products

There is an increasing demand for a powder soups and sauces composed with lyophylizated meat. Technology of lyophylization is not always accompanied by thermal treatment of raw materials. That is the reason the meat lyophylization process does not ensure as good microbiological quality as is required. Degree of microbiological decontamination and organoleptic properties of lyophilized meat were investigated after radiation treatment.     

Validation of a liquid chromatography–tandem mass spectrometry method for the identification and quantification of 5-nitroimidazole drugs and their corresponding hydroxy metabolites in lyophilised pork meat

A liquid chromatography–electrospray ionisation tandem mass spectrometry method for the simultaneous detection and quantitation of 5-nitroimidazole veterinary drugs in lyophilised pork meat, the chosen format of a candidate certified reference material, has been developed and validated. Six analytes have been included in the scope of validation, i.e. dimetridazole (DMZ), metronidazole (MNZ), ronidazole (RNZ), hydroxymetronidazole (MNZOH), hydroxyipronidazole (IPZOH), and 2-hydroxymethyl-1-methyl-5-nitroimidazole (HMMNI). The analytes were extracted from the sample with ethyl acetate, chromatographically separated on a C₁₈ column, and finally identified and quantified by tandem mass spectrometry in the multiple reaction monitoring mode (MRM) using matrix-matched calibration and ²H₃-labelled analogues of the analytes (except for MNZOH, where [²H₃]MNZ was used). The method was validated in accordance with Commission Decision 2002/657/EC, by determining selectivity, linearity, matrix effect, apparent recovery, repeatability and intermediate precision, decision limits and detection capabilities, robustness of sample preparation method, and stability of extracts. Recovery at 1 μg/kg level was at 100% (estimates in the range of 101–107%) for all analytes, repeatabilities and intermediate precisions at this level were in the range of 4–12% and 2–9%, respectively. Linearity of calibration curves in the working range 0.5–10 μg/kg was confirmed, with r values typically >0.99. Decision limits (CCα) and detection capabilities (CCβ) according to ISO 11843-2 (calibration curve approach) were 0.29–0.44 and 0.36–0.54 μg/kg, respectively. The method reliably identifies and quantifies the selected nitroimidazoles in the reconstituted pork meat in the low and sub-μg/kg range and will be applied in an interlaboratory comparison for determining the mass fraction of the selected nitroimidazoles in the candidate reference material currently developed at IRMM.     

辐照肉制品中2-十二烷基环丁酮的测定

采用GB/T 21926-2008《辐照含脂食品中2-十二烷基环丁酮测定气相色谱/质谱法》对辐照肉制品中的2-十二烷基环丁酮进行测定,鉴别辐照肉制品。样品用索氏抽提,经冷冻离心和弗罗里硅土层析净化,用气相色谱质谱联用法测定。2-十二烷基环丁酮的浓度在0.01~0.5 mg/L与色谱峰面积呈良好的线性关系,r=0.999 6。对未经辐照的样品进行加标回收试验,加标回收率为83.1%~94.0%,测定结果的相对标准偏差小于6%(n=6)。     

Simultaneous determination of multiveterinary drug residues in pork meat by liquid chromatography‐tandem mass spectrometry combined with solid phase extraction

An LC‐MS/MS method developed for simultaneous analysis of 54 veterinary drug residues of six families in pork meat samples, including sulfanilamide, nitroimidazoles, quinolones, macrolide antibiotics, lincosamides, and praziquantel. The pork meat sample was prepared by extraction with ACN, and clean‐up on a C₁₈ SPE cartridge. The sample was separated on a C₈ column and eluted with ACN, methanol, and formic acid. The MS/MS detector is operated in the multiple reaction monitoring mode, acquiring two specific precursor‐product ion transitions per target compound. The method showed excellent linearity (R² ≥ 0.99) and high precision (relative SD, RSD ≤ 19.8%) for all compounds. The method quantification limits of 54 veterinary drug residues were in the range of 0.3–3.0 μg/kg. Recoveries for most analytes based on matrix‐matched calibration in matrices were 20.9–121.0%. This method has been successfully applied for analysis of more than 100 pork meat samples from the local market; five of the 54 drugs were detected.     

Highly sensitive multianalyte immunochromatographic test strip for rapid chemiluminescent detection of ractopamine and salbutamol

A novel immunochromatographic assay (ICA) was proposed for rapid and multiple assay of β₂-agonists, by utilizing ractopamine (RAC) and salbutamol (SAL) as the models. Owing to the introduction of chemiluminescent (CL) approach, the proposed protocol shows much higher sensitivity. In this work, the described ICA was based on a competitive format, and horseradish peroxidase-tagged antibodies were used as highly sensitive CL probes. Quantitative analysis of β₂-agonists was achieved by recording the CL signals of the probes captured on the two test zones of the nitrocellulose membrane. Under the optimum conditions, RAC and SAL could be detected within the linear ranges of 0.50–40 and 0.10–50 ng mL⁻¹, with the detection limits of 0.20 and 0.040 ng mL⁻¹ (S/N = 3), respectively. The whole process for multianalyte immunoassay of RAC and SAL can be completed within 20 min. Furthermore, the test strip was validated with spiked swine urine samples and the results showed that this method was reliable in measuring β₂-agonists in swine urine. This CL-based multianalyte test strip shows a series of advantages such as high sensitivity, ideal selectivity, simple manipulation, high assay efficiency and low cost. Thus, it opens up new pathway for rapid screening and field analysis, and shows a promising prospect in food safety.     

支持向量回归-同步荧光光谱法预测鸭肉中克百威残留

为了满足鸭肉中克百威残留分析及快速检测的要求,基于克百威水解物在巯基乙醇存在的条件下能与邻苯二甲醛反应产生具有强荧光性衍生物的方法,建立了应用同步荧光光谱法测定鸭肉中克百威残留量的预测模型。对含有克百威鸭肉样品的三维同步荧光光谱进行分析,确定其最佳波长差Δλ为120 nm;利用遗传算法(GA)结合交互验证均方根误差(RMSECV)从240～450 nm光谱中筛选出19个波长作为定量分析模型的输入特征变量;对SVR、PCR、PLS 3种回归模型的性能进行比较,实验发现SVR模型的预测结果最好,其预测集的决定系数(r2)和预测均方根误差(RMSEP)分别为0.999 4和0.878 7。研究结果表明,采用同步荧光光谱法结合支持向量回归算法测定鸭肉中克百威的残留量,具有快速、预测精度高等特点,可为检测鸭肉中的克百威残留量提供一种可行的方法。     

Preparation of porous magnetic molecularly imprinted polymers for fast and specifically extracting trace norfloxacin residue in pork liver

Here, magnetic molecularly imprinted polymers were designed for norfloxacin via oil‐in‐water emulsifier‐free emulsion method. It was prepared by simply mixing norfloxacin, methacrylic acid‐co‐ethylene glycol dimethacrylate copolymer, and Fe₃O₄ together at room temperature. Characterized by multiple analytical tools, the particle size, pore size, pore volume, specific surface area, and saturation magnetization of the product were about 30 µm, 10–500 nm, 2.92 mL/g, 105.84 m²/g, and 3.052 emu/g, respectively. And the adsorption capacity was high at 27.04 mg/g towards norfloxacin. Combined with ultra high performance liquid chromatography, it was used to determine norfloxacin in real samples. Average recoveries were above 77.44% with relative standard deviations between 1.21 and 6.85% at three spiked levels (n = 3) for lake water and pork liver. The determination was achieved for the most complex biosample pork liver spiked with norfloxacin low to 30 ng/g, about 100 times less than the maximum residue limit regulated by Commission of the European Communities. All evidences demonstrated that the magnetic molecularly imprinted polymers can be used in practice for monitoring norfloxacin either in environmental water or meat product with high accuracy and reliability.     

干柱法测定肉制品中脂肪含量

建立了干柱法测定肉制品中脂肪含量的最佳条件.使用7.5cm×27mmi.d 玻璃层析柱;以Celite 545/CaHPO_4·2H_2O(9+1)为非脂成分捕集物,再装入样品、无水机Na_2SO_4、Celite545混合物制备干柱.用50mL CH_2Cl_2/CH_3OH(9+1)进行洗脱,可在1h内洗脱完毕.测定了5种肉制品的脂肪含量,并做了脂肪酸分析.与传统的氯仿/甲醇法做了对比,结果一致;统计检验表明,两方法间不存在显著性差异,但干柱法更加快速、简便.