表面增强拉曼光谱在食源性致病微生物检测中的应用研究

食源性致病微生物导致的食源性疾病已成为全球化的公共卫生问题。快速、有效地检测食源性致病微生物是实现食源性疾病预防与控制的关键环节，也是保障食品安全的技术关键。表面增强拉曼光谱(SERS)具有简单、快速、灵敏度高等优点，在食品安全、生物医学、环境监控等领域展现出良好的应用前景。介绍了近年来SERS在食源性致病微生物检测中的应用研究进展。对SERS技术概况、SERS增强理论及SERS增强基底进行了简要介绍，重点回顾了SERS在食源性致病微生物检测中的应用和发展现状。在食品安全分析方面，利用SERS与模式识别方法相结合对食品中常见食源性致病微生物能实现快速、有效鉴别，部分研究已应用于不同食品样品的分析，体现了SERS作为“指纹图谱”的分析优势；在医学诊断方面，SERS可对病理样品(如血液、尿液等)中食源性致病微生物进行快速检测，缩短了样本分析时间，使食源性疾病的快速诊断成为可能；随着微流控技术的发展，微流控平台结合SERS技术被称为“芯片实验室”应用于食源性致病微生物的检测，可提高分析的可控性，稳定性，特异性和灵敏度。通过对比分析，发现不同研究可采用不同分离方法、不同基底、不同目标捕获方式等实现了食源性致病微生物的检测，展示了不同方法间的差异性。已有研究表明了SERS在食源性致病微生物检测中应用可克服传统方法耗时等缺点，实现灵敏快速分析，为食品安全实时监控，食源性疾病即时诊断提供了有效的分析工具。同时，指出了SERS技术应用于食源性致病微生物分析依然面临很大挑战，(1)大多数研究并没有聚焦于实际样品，而标准培养液和实际样品的SERS检测存在较大差异，实际样品组分会对SERS响应产生干扰；(2)不同方法结果有较大差异，主要是由于纳米增强基底差异，吸附方式原理的差异，稳定性的差异等，因此需要更多深入研究进一步优化条件；(3)期望建立标准化的SERS方法替代传统技术，充分展示SERS作为新兴分析工具快速、灵敏、简捷的优势应用于食品安全，医学诊断等领域。将来，随着研究的深入及相关学科的发展，SERS作为极具潜力的快速分析工具，将在食品安全，生物医学等领域具有更广阔的应用前景。     

Tutorial review on validation of liquid chromatography–mass spectrometry methods: Part II

This is the part II of a tutorial review intending to give an overview of the state of the art of method validation in liquid chromatography mass spectrometry (LC–MS) and discuss specific issues that arise with MS (and MS–MS) detection in LC (as opposed to the “conventional” detectors). The Part II starts with briefly introducing the main quantitation methods and then addresses the performance related to quantification: linearity of signal, sensitivity, precision, trueness, accuracy, stability and measurement uncertainty. The last section is devoted to practical considerations in validation. With every performance characteristic its essence and terminology are addressed, the current status of treating it is reviewed and recommendations are given, how to handle it, specifically in the case of LC–MS methods.     

Complex dynamics in the Leslie–Gower type of the food chain system with multiple delays

In this paper, we present a Leslie–Gower type of food chain system composed of three species, which are resource, consumer, and predator, respectively. The digestion time delays corresponding to consumer-eat-resource and predator-eat-consumer are introduced for more realistic consideration. It is called the resource digestion delay (RDD) and consumer digestion delay (CDD) for simplicity. Analyzing the corresponding characteristic equation, the stabilities of the boundary and interior equilibrium points are studied. The food chain system exhibits the species coexistence for the small values of digestion delays. Large RDD/CDD may destabilize the species coexistence and induce the system dynamic into recurrent bloom or system collapse. Further, the present of multiple delays can control species population into the stable coexistence. To investigate the effect of time delays on the recurrent bloom of species population, the Hopf bifurcation and periodic solution are investigated in detail in terms of the central manifold reduction and normal form method. Finally, numerical simulations are performed to display some complex dynamics, which include multiple periodic solution and chaos motion for the different values of system parameters. The system dynamic behavior evolves into the chaos motion by employing the period-doubling bifurcation.     

Recent developments in food foams

The scientific literature from 2015 onwards with respect to foams and thin films in the context of foods has been reviewed. Proteins are the dominant foaming agents in foods, and investigations of the classic, meringue-forming egg white protein still dominate the literature because the unique properties of this system are still not properly understood. The current drive of many studies is to find suitable replacers of egg proteins, driven by consumer trends for more plant-based alternatives. This has led to investigations of the stabilizing properties of various protein aggregates, ‘nanoparticles’ and microgel particles as Pickering-type stabilizers of foams (Pickering foams). At the same time, other work has sought to manipulate the surface properties of biopolymer- and nonbiopolymer–based particles by chemical means, to make the particles adsorb more strongly. Few, truly novel foam stabilizers have emerged, but two include saponin aggregates and bacteria as particle-type stabilizers.     

Exhaled breath condensate: Determination of non-volatile compounds and their potential for clinical diagnosis and monitoring. A review

Exhaled breath condensate is a promising, non-invasive, diagnostic sample obtained by condensation of exhaled breath. Starting from a historical perspective of early attempts of breath testing towards the contemporary state-of-the-art breath analysis, this review article focuses mainly on the progress in determination of non-volatile compounds in exhaled breath condensate. The mechanisms by which the aerosols/droplets of non-volatile compounds are formed in the airways are discussed with methodological consequences for sampling. Dilution of respiratory droplets is a major problem for correct clinical interpretation of the measured data and there is an urgent need for standardization of EBC. This applies also for collection instrumentation and therefore various commercial and in-house built devices are described and compared with regard to their design, function and collection parameters. The analytical techniques and methods for determination of non-volatile compounds as potential markers of oxidative stress and lung inflammation are scrutinized with an emphasis on method suitability, sensitivity and appropriateness. The relevance of clinical findings for each group of possible non-volatile markers of selected pulmonary diseases and methodological recommendations with emphasis on interdisciplinary collaboration that is essential for future development into a fully validated clinical diagnostic tool are given.     

Determination of nitrofuran and chloramphenicol residues by high resolution mass spectrometry versus tandem quadrupole mass spectrometry

An ultra-high performance liquid chromatography based method, coupled to high resolution mass spectrometry (UHPLC–HRMS), was developed to permit the detection and quantification of various nitrofuran and chloramphenicol residues in a number of animal based food products. This method is based on the hydrolysis of covalently bound metabolites and derivatization with 2-nitrobenzaldehyde. Clean-up is achieved by a liquid/liquid and a reversed phase/solid phase extraction. Not only are the four conventional nitrofurans (nitrofurantoin, furazolidone, nitrofurazone and furaltadone) detected, but also nifursol, nitrovin and nifuroxazide. Furthermore, an underivatizable nitrofuran (nifurpirinol) and another banned drug (chloramphenicol) can be quantified as well. The compounds are detected in the form of their precursor ions, [M + H]⁺ and [M − H]⁻, respectively. The mass resolving power of 70,000 FWHM, and the applied mass window ensure sufficient selectivity and sensitivity. Confirmation is obtained by monitoring the HRMS resolved product ions which were derived from the unit-mass resolved precursor ions. The multiplexing capability of the utilized Orbitrap instrument provides not only highly selective, but also sensitive confirmatory signals. This method has been validated according to the CD 2002/657/EC for the following matrices: muscle, liver, kidney, fish, honey, eggs and milk.     

A novel amperometric biosensor based on a co-crosslinked l-lysine-α-oxidase/overoxidized polypyrrole bilayer for the highly selective determination of l-lysine

An amperometric biosensor for the determination of l-lysine based on l-lysine-α-oxidase immobilized by co-crosslinking on a platinum electrode previously modified by an overoxidized polypyrrole film is described. The optimization of experimental parameters, such as pH and flow rate, permitted to minimize significantly substrate interferences even using a low specific, commercial enzyme. The relevant biases introduced in the measurement of lysine were just about 1% for l-arginine, l-histidine and l-ornithine, roughly 4% for l-phenylalanine and l-tyrosine. The developed approach allowed linear lysine responses from 0.02 mM up to 2 mM with a sensitivity of 41 nA/(mM × mm²) and a detection limit of 4 μM (S/N = 3). No appreciable loss in lysine sensitivity was observed up to about 40 days. Allowing polypyrrole layer to remove interference from electroactive compounds, the present method revealed suitable to detect l-lysine in a pharmaceutical and cheese sample, showing a good agreement with the expected values.     

Response surface methodology (RSM) of chicken skin gelatin based composite films with rice starch and curcumin incorporation

This study aims to optimize the formulation of composite films based on chicken skin gelatin with incorporation of rice starch (10–20%, w/w) and curcumin (0.03–0.10%, w/v). The effect of their interaction on film's tensile strength (TS), elongation at break (EAB), water vapor permeability (WVP) and antioxidant properties (DPPH%) were investigated using a response surface methodology-central composite design (RSM-CCD). The optimized film formulation was further validated to indicate the validity of the prediction model. The optimum conditions of the film were selected with incorporation of rice starch at 20% (w/w) and curcumin at 0.03% (w/v). The optimized film formulation has revealed better mechanical properties with low WVP value and good antioxidant activity. The results showed that optimized composite films formulation based on chicken skin gelatin with the incorporation of rice starch and curcumin has proving good validation of model prediction and can be effectively utilized in food packaging industry.     

食品中7种常见的非食用色素检测研究进展

食用色素可以明显的改善食品外观,激发食欲,在食品行业有着广泛的应用,但一些不法分子为了牟取暴利向食品中添加非食用色素来代替食用色素,但是非食用色素对人体存在致癌风险。食品中常见的非食用色素有以下7种：碱性嫩黄O、碱性橙II、酸性橙II、苏丹红、罗丹明B、美术绿和孔雀石绿,而目前对这7种非食用色素的检测还未全部建立国家标准。本文综述了近3年来食品行业中针对这7种非食用色素的各种检验方法,以期为食品安全监督监督检测机构提供参考。     

应用ICP-MS和GFAAS测定藻类食品中铅、镉的方法研究及比较

建立微波消解-电感耦合等离子体-质谱法(ICP-MS)测定藻类食品中铅、镉含量的方法,并与国家标准方法石墨炉原子吸收光谱法(GFAAS)进行了比较.样品经过微波消解,分别使用ICP-MS和GFAAS测定藻类食品裙带菜和海带中铅、镉含量,各元素校正曲线的相关系数均大于0.9991,样品分析结果RSD均小于3.6%(n=6...