Applications In Food Analysis Research Articles

Gold Nanoparticle Sensor for the Visual Detection of Pork Adulteration in Meatball Formulation

We visually identify pork adulteration in beef and chicken meatball preparations using 20 nm gold nanoparticles (GNPs) as colorimetric sensors. Meatball is a popular food in certain Asian and European countries. Verification of pork adulteration in meatball is necessary to meet the Halal and Kosher food standards. Twenty nm GNPs change color from pinkish-red to gray-purple, and their absorption peak at 525 nm is red-shifted by 30–50 nm in 3 mM phosphate buffer saline (PBS). Adsorption of single-stranded DNA protects the particles against salt-induced aggregation. Mixing and annealing of a 25-nucleotide (nt) single-stranded (ss) DNA probe with denatured DNA of different meatballs differentiated well between perfectly matched and mismatch hybridization at a critical annealing temperature. The probes become available in nonpork DNA containing vials due to mismatches and interact with GNPs to protect them from salt-induced aggregation. Whereas, all the pork containing vials, either in pure and mixed forms, consumed the probes totally by perfect hybridization and turned into grey, indicating aggregation. This is clearly reflected by a well-defined red-shift of the absorption peak and significantly increased absorbance in 550–800 nm regimes. This label-free low-cost assay should find applications in food analysis, genetic screening, and homology studies.

Development of a molecularly imprinted polymer for patulin in apple juice

The design of imprinted polymers selective towards patulin (PAT) and their application in food analysis are reported for the first time. Different templates, functional monomers and molar ratios were evaluated related to binding capacity and specificity. Besides the toxin itself, the implementation of structural analogues (2-hydroxynicotinic acid, 5-indanol and 3-hydroxyphtalic anhydride) as templates was evaluated. A molecularly imprinted solid-phase extraction (MISPE) procedure was optimised for the selective clean-up of apple juice samples. Depending on the spiked concentration, recoveries after MISPE and non-imprinted solid-phase extraction varied respectively from 60% to 66% and from 40% to 41%. Limit of detection and limit of quantification were 10.0 µg/kg and 33.3 µg/kg, respectively. Equilibrium experiments and Scatchard analysis disclosed the presence of two classes of binding sites in the imprinted polymer. The dissociation constant (KD) of the higher affinity binding sites was 3.3 µmol/l, while the KD of the lower affinity binding sites was 260.7 µmol/l. The performance of the molecularly imprinted polymer throughout the clean-up was compared to liquid-liquid extraction and a C18 sorbent. Cross-reactivity experiments demonstrated that MISPE was substantially more selective than C18 clean-up. Moreover chromatograms, with less interfering peaks, were observed with MISPE resulting in a sensitive and reliable quantification of PAT.

Design of an imprinted clean-up method for mycophenolic acid in maize

In the present work, the development of imprinted polymers selective towards mycophenolic acid and their application in food analysis are reported for the first time. To synthesize the molecularly imprinted polymer (MIP) 4-vinylpyridine and ethyleneglycol dimethacrylate were applied as functional monomer and cross-linker, respectively. Besides the toxin itself, the implementation of structural analogues as templates was evaluated. A molecularly imprinted solid-phase extraction (MISPE) procedure was designed for the selective clean-up of maize extracts. Binding experiments and Scatchard analysis indicated the presence of specific binding sites in the imprinted polymers. The imprinting effect varied along with the selected template. The dissociation constant ( K D) of the higher affinity binding sites ranged from 0.8 μmol/l to 15.6 μmol/l, while the K D of the lower affinity binding sites was in the range of 138.5–519.3 μmol/l. The performance of the MIPs throughout the clean-up of spiked maize sample extracts was evaluated and compared with the results obtained when applying a non-imprinted polymer. Depending on the polymers and the spiked concentration, recoveries after MISPE and non-imprinted solid-phase extraction varied respectively from 49% to 84% and from 28% to 31%. The imprinted polymers were superior regarding matrix effect, limit of detection (LOD) and limit of quantification (LOQ). LOD ranged from 0.17 μg/kg to 0.25 μg/kg and LOQ varied from 0.57 μg/kg to 0.82 μg/kg. Analysis of 15 maize samples by liquid chromatography tandem mass spectrometry revealed that the MIPs could be excellent sorbents for clean-up of contaminated food samples.

Synthesis and application of a T-2 toxin imprinted polymer

The synthesis of a T-2 toxin imprinted polymer and its application in food analysis are reported for the first time. A molecularly imprinted polymer (MIP) for the selective recognition of T-2 toxin (T-2) was synthesized by bulk polymerization. Methacrylamide and ethyleneglycol dimethacrylate were applied as functional monomer and cross-linker, respectively. Molecularly imprinted solid-phase extraction (MISPE) procedures were optimized for further application in the analysis of T-2. Scatchard plot analysis revealed that two classes of imprinted binding sites were formed in the imprinted polymer. The dissociation constant ( K D) of the higher affinity binding sites was 7.0 μmol/l, while the K D of the lower affinity binding sites was 54.7 μmol/l. The performance of the MIP throughout the clean-up of spiked maize, barley and oat sample extracts was compared with the results obtained when using non-imprinted polymer, OASIS HLB ® and immunoaffinity columns (IAC). Depending on the food matrix and the spiked concentration, recoveries after MISPE and non-imprinted solid-phase extraction varied respectively from 60% to 73% and from 21% to 57%. Recoveries obtained after clean-up using OASIS HLB ® and IAC were in the range of 74–104% and 60–85%, respectively. Although highest recoveries were obtained with OASIS HLB ® sorbents, the designed MIP and the IAC were superior regarding selectivity, cross-reactivity, matrix effect, limits of detection (LOD) and limits of quantification (LOQ). Depending on the matrix, LOD after MISPE ranged from 0.4 μg/kg to 0.6 μg/kg and LOQ from 1.4 μg/kg to 1.9 μg/kg. LOD and LOQ after OASIS HLB ® clean-up varied from 0.9 μg/kg to 3.5 μg/kg and from 3.1 μg/kg to 11.7 μg/kg, respectively. The LOD and LOQ values obtained with IAC were in the range of 0.3–2.3 μg/kg and 1.0–7.7 μg/kg, respectively. Analysis of 39 naturally contaminated samples (maize, barley and oat) by liquid chromatography tandem mass spectrometry revealed that the MIP could be an excellent alternative for clean-up of contaminated food samples.

The immobilization of Cytochrome c on MWNT–PAMAM–Chit nanocomposite incorporated with DNA biocomposite film modified glassy carbon electrode for the determination of nitrite

A novel and sensitive biosensor was developed for the determination of nitrite. Firstly, multi-walled carbon nanotubes–poly(amidoamine)–chitosan (MWNT–PAMAM–Chit) nanocomposite along with the incorporation of DNA was used to modify the glassy carbon electrode. Then the immobilization of Cyt c was accomplished using electrochemical deposition method by consecutive cyclic voltammetry (CV) scanning in a neutral Cyt c solution. CV behaviors of the modified electrodes showed that the MWNT–PAMAM–Chit nanocomposite is a good platform for the immobilization of DNA and Cyt c in order, at the same time, an excellent promoter for the electron transfer between Cyt c and the electrode. At high potential, the immobilized Cyt c could be further oxidized into highly reactive Cyt c π-cation by two-step electrochemical oxidation, which could oxidize NO2 − into NO3 − in the solution. Therefore, a nitrite biosensor based on the biocatalytic oxidation of the immobilized Cyt c was fabricated, which showed a fast response to nitrite (less than 5 s). The linear range of 0.2–80 μM and a detection limit of 0.03 μM was obtained. Finally, the application in food analysis using sausage as testing samples was also investigated.

Molecularly imprinted solid-phase extraction of fumonisin B analogues in bell pepper, rice and corn flakes

A molecularly imprinted polymer (MIP) for the recognition of fumonisin B analogues (FB) using 2-(diethylamino) ethyl methacrylate (DEAEM) as functional monomer and trimethylolpropane trimethacrylate (TRIM) as cross-linker was prepared by bulk polymerization in acetonitrile. Fumonisin B1 (FB1) was used as a template molecule. A molecularly imprinted solid-phase extraction (MISPE) procedure was developed for further application in the analysis of FB. The performance of the MIP throughout the clean-up of spiked bell pepper, rice and corn flake sample extracts was compared with the results obtained when using non-imprinted polymer, C18, strong anion exchange and immunoaffinity sorbents. Extracts were analysed for FB with liquid chromatography-tandem mass spectrometry (LC-MS/MS) after clean-up. Depending on the food matrix and the concentration range of the fumonisins, recoveries after MISPE varied from 62 to 86%, from 62 to 83%, and from 67 to 81% for fumonisin B1 (FB1), fumonisin B2 (FB2) and fumonisin B3 (FB3), respectively. The selectivity of the synthesized MIP for mycotoxins belonging to the group of FB was confirmed by evaluating cross-reactivity from analogue structures and other mycotoxins. Analysis of 39 naturally contaminated samples (corn flakes) by liquid chromatography tandem mass spectrometry indicated that the synthesized MIP could be an excellent alternative for clean-up and pre-concentration of FB in food samples. Pearson correlations between immunoaffinity clean-up and MISPE were calculated and amounted to 0.923 for FB1, 0.808 for FB2, and 0.759 for FB3. It was shown that the developed MIP could be reused more than 50 times. The synthesis of an FB1 imprinted polymer and its application in food analysis is reported for the first time.

Comparison of tandem-in-space and tandem-in-time mass spectrometry in gas chromatography determination of pesticides: Application to simple and complex food samples

Gas chromatography coupled to tandem mass spectrometry (GC–MS/MS) is one of the most powerful techniques in pesticide residue analysis. MS/MS can be conceived in two ways: tandem in space (e.g. triple quadrupole, QqQ) or in time (e.g. ion trap, IT). QqQ and IT are commonly interfaced to GC; however, there has not been any direct comparison between them in pesticide residue analysis so far. In the present work, the performance of GC coupled to these two analyzers (GC–QqQ–MS/MS and GC–IT–MS/MS) was studied and compared for pesticide residue analysis as well as its application in food analysis. The large volume injection (LVI) technique together with programmed-temperature vaporization (PTV) was applied. For this purpose, 19 pesticides, including organochlorine and organophophorus pesticides and pyrethroids, were analyzed in both systems. Mass spectrometric data, performance characteristics (linearity, intra-day and inter-day precision) and the influence of the matrix nature on the analysis of low concentrations were compared. The target compounds were analyzed in solvent and in two representative food matrices such as cucumber (high water content) and egg (high fat content). MS data and intra-day precision were similar in QqQ and IT, whereas inter-day precision was significantly worse in QqQ. Linearity (expressed as determination coefficient, R 2) in the range 10–150 μg L −1 was adequate in both systems; however, better R 2 values were obtained with the QqQ analyzer in high and low concentration ranges (1–50 and 1–750 μg L −1, respectively). The influence of the matrix nature on the analysis of low concentrations of each analyzer was also evaluated. The QqQ and IT performance was similar in cucumber and solvent. However, QqQ provided better sensitivity in egg working in selected reaction monitoring (SRM).

An electropolymerized Nile Blue sensing film-based nitrite sensor and application in food analysis

This paper reports a poly-Nile Blue (PNB) sensing film based electrochemical sensor and the application in food analysis as a possible alternative for electrochemical detection of nitrite. The PNB-modified electrode in the sensor was prepared by in situ electropolymerization of Nile Blue at a prepolarized glassy carbon (GC) electrode and then characterized by cyclic voltammetry (CV) and pulse voltammetry in phosphate buffer (pH 7.1). Several key operational parameters affecting the electrochemical response of PNB sensing film were examined and optimized, such as polarization time, PNB film thickness and electrolyte pH values. As the electroactive PNB sensing film provides plenty of active sites for anodic oxidation of nitrite, the nitrite sensor exhibited high performance including high sensitivity, low detection limit, simple operation and good stability at the optimized conditions. The nitrite sensor revealed good linear behavior in the concentration range from 5.0 × 10 −7 mol L −1 to 1.0 × 10 −4 mol L −1 for the quantitative analysis of nitrite anion with a limit of detection of 1.0 × 10 −7 mol L −1. Finally, the application in food analysis using sausage as testing samples was investigated and the results were consistent with those obtained by standard spectrophotometric method.

The contribution of planar chromatography to food analysis

Food generally enjoys public confidence; food analysis, however, is a growing and challenging sector. Analytical methods must keep pace with the continuously changing attitudes and preferences of consumers to ensure product quality. Planar chromatography, a very flexible technique for rapidly changing issues, can assist food analysts. But few users of planar chromatography (approx. 10%) use high-performance thin-layer chromatography (HPTLC). Use of appropriate instrumentation will improve the precision of the method. There is therefore, much potential to increase the efficacy and attraction of planar chromatographic applications in food analysis. Validated HPTLC methods fulfill the requirements for reliable food analysis in many fields. Planar chromatography can support food analysis by simultaneous determination of analytes with different detection principles, for example point of care analysis by digital imaging and effect-directed assays via bioactivity-based detection. Parallel analyses under identica...

Catalytic activity of iron hexacyanoosmate(II) towards hydrogen peroxide and nicotinamide adenine dinucleotide and its use in amperometric biosensors

Hydrogen peroxide and nicotinamide adenine dinucleotide (NADH) may be determined amperometrically using screen-printed electrodes chemically modified with iron(III) hexacyanoosmate(II) (Osmium purple) in flow injection analysis (FIA). The determination is based on the exploitation of catalytic currents resulting from the oxidation/reduction of the modifier. The performance of the sensor was characterized and optimized by controlling several operational parameters (applied potential, pH and flow rate of the phosphate buffer). Comparison has been made with analogous complexes of ruthenium (Ruthenium purple) and iron (Prussian blue). Taking into account the sensitivity and stability of corresponding sensors, the best results were obtained with the use of Osmium purple. The sensor exhibited a linear increase of the amperometric signal with the concentration of hydrogen peroxide in the range of 0.1–100 mg L −1 with a detection limit (evaluated as 3 σ) of 0.024 mg L −1 with a R.S.D. 1.5% for 10 mg L −1 H 2O 2 under optimized flow rate of 0.4 mL min −1 in 0.1 M phosphate buffer carrier (pH 6) and a working potential of +0.15 V versus Ag/AgCl. Afterwards, a biological recognition element – either glucose oxidase or ethanol dehydrogenase – was incorporated to achieve a sensor facilitating the determination of glucose or ethanol, respectively. The glucose sensor gave linearity between current and concentration in the range from 1 to 250 mg L −1 with a R.S.D. 2.4% for 100 mg L −1 glucose, detection limit 0.02 mg L −1 (3 σ) and retained its original activity after 3 weeks when stored at 6 °C. Optimal parameters in the determination of ethanol were selected as: applied potential +0.45 V versus Ag/AgCl, flow rate 0.2 mL min −1 in 0.1 M phosphate buffer carrier (pH 7). Different structural designs of the ethanol sensor were tested and linearity obtained was up to 1000 mg L −1 with a maximum R.S.D. of 5.1%. Applications in food analysis were also examined.

A Novel Nitrite Amperometric Sensor and Its Application in Food Analysis

AbstractBrilliant cresyl blue (BCB), one of the phenoxazine dyes, was electropolymerized on the glassy carbon (GC) electrode. The resulting electroactive polymer film could provide more active sites for anodic oxidation of nitrite, based on which a novel nitrite sensor was developed. The optimized fabrication and sensing conditions were investigated. This sensor exhibited high sensitivity, low detection limit and simple operation toward the electrochemical oxidation of nitrite. It was successfully applied to the determination of nitrite in some food samples and the results were consistent with those obtained with the standard spectrophotometric procedure.

Enzymatic methods in food analysis: determination of ascorbic acid

The feasibility and expediency of enzymatic methods application in food analysis is demonstrated by the example of ascorbic acid (AsA) determination in foods. Enzymatic determination of ascorbic acid is based on its action as a second substrate of horseradish (HRP) and peanut (PNP) peroxidases in the reactions of o-dianisidine (OD) and 3,3’,5,5’-tetramethylbenzidine (TMB) oxidation with hydrogen peroxide. The rates of the reactions are monitored spectrophotometrically by measuring the duration of the induction period on kinetic curves plotted in coordinates absorption-time. The proposed procedures are sensitive ( c L = 0.1 μM), simple, and rapid. The procedure using horseradish peroxidase and the reaction of TMB oxidation was used to determine ascorbic acid in fruit juices, milk and sour-milk products for babies’ nutrition.

A procedure to assess linearity by ordinary least squares method

A detailed procedure for testing linearity of calibration curves in method validation by the ordinary least squares method (OLSM), including experimental design, estimation of the parameters, outlier treatment and evaluation of the assumptions, was proposed. The theoretical background was discussed and the assumptions considered were: (i) normality, homoscedasticity and independency of residuals and (ii) adjustment to the correct model. The procedure involved precise statistical techniques that were easily carried out by any commercial spreadsheet software. The suitability of the procedure for assessing linearity was demonstrated by the application in food analysis.

Determination of Hydrogen Peroxide, Glucose and Hypoxanthine using (Bio)Sensors Based on Ruthenium Dioxide‐Modified Screen‐Printed Electrodes

Screen‐printed electrodes modified with ruthenium dioxide were investigated as amperometric sensors for the determination of hydrogen peroxide using flow injection analysis (FIA). With additions of enzymes (glucose oxidase or xanthine oxidase) immobilized onto the electrode surface via Nafion films, corresponding biosensors for the quantification of glucose or hypoxanthine were developed. Factors influencing their amperometric responses (operational potential, flow rate, pH of the phosphate buffer carrier) were studied in detail. Applications in food analysis were also examined. Supported by the Ministry of Education, Youth, and Sport of the Czech Republic (project MSM0021627502) and from the Grant Agency of the Czech Republic (No. 203/05/2106). Partial support of the CEEPUS program (project PL‐110) is also gratefully acknowledged.

Surface plamon resonance imaging of DNA based biosensors for potential applications in food analysis

The adsorption processes of oligonucleotides immobilised onto suitable photolithographic patterned gold substrates have been investigated in aqueous buffer solution by using a home made surface plasmon resonance (SPR) imaging equipment. A rapid self-assembled method for the construction of DNA chips to be used in SPR imaging experiments have been followed. The immobilised DNA molecules (probes) adopted in our SPR experiments anchored to a gold surface via thiol group were 5'thiol-modified containing a (CH(2))(15) tail. The hybridisation processes taking place with its complementary sequence have been observed and characterized by monitoring phenomena by a SPR imaging system. The two analysed oligonucleotides (probes and target) are of interest in plant gene biotechnological application and differing for the presence at the 5'-end of a poly T16 spacer. Dynamic investigation of smallest changes in SPR imaging pictures performed in liquid phase in the presence of DNA complementary probes have been performed. Quantitative information in terms of threshold of sensitivity has been extracted by using a specific images treatment.

Capillary electrophoresis-mass spectrometry of basic proteins using a new physically adsorbed polymer coating. Some applications in food analysis.

A new physically adsorbed capillary coating for capillary electrophoresis-mass spectrometry (CE-MS) of basic proteins is presented, which is easily obtained by flushing the capillary with a polymer aqueous solution for two min. This coating significantly reduces the electrostatic adsorption of a group of basic proteins (i.e., cytochrome c, lysozyme, and ribonuclease A) onto the capillary wall allowing their analysis by CE-MS. The coating protocol is compatible with electrospray inonization (ESI)-MS via the reproducible separation of the standard basic proteins (%RSD values (n = 5) < 1% for analysis time reproducibility and < 5% for peak heights, measured from the total ion electropherograms (TIEs) within the same day). The LODs determined using cytochrome c with total ion current and extracted ion current defection were 24.5 and 2.9 fmol, respectively. Using this new coating lysozymes from chicken and turkey egg white could be easily distinguished by CE-MS, demonstrating the usefulness of this method to differentiate animal species. Even after sterilization at 120 degrees C for 30 min, lysozyme could be detected, as well as in wines at concentrations much lower than the limit marked by the EC Commission Regulation. Adulteration of minced meat with 5% of egg-white could also be analysed by our CE-MS protocol.

Application of gas chromatography in food analysis

Gas chromatography (GC) is used widely in applications involving food analysis. Typical applications pertain to the quantitative and/or qualitative analysis of food composition, natural products, food additives, flavor and aroma components, a variety of transformation products, and contaminants, such as pesticides, fumigants, environmental pollutants, natural toxins, veterinary drugs, and packaging materials. The aim of this article is to give a brief overview of the many uses of GC in food analysis in comparison to high-performance liquid chromatography (HPLC) and to mention state-of-the-art GC techniques used in the major applications. Past and current trends are assessed, and anticipated future trends in GC for food applications are predicted. Among the several new techniques being developed, the authors believe that, in food analysis applications, fast-GC/mass spectrometry (MS) will have the most impact in the next decade. Three approaches to fast-GC/MS include low-pressure GC/MS, GC/time-of-flight (TOF)-MS and GC/supersonic molecular beam (SMB)-MS, which are briefly discussed, and their features are compared.

Analysis of the murine intercellular adhesion molecule-1 promoter in H441 cells exposed to TNF-alpha: [formula omitted] and Bei Wu. Baylor College of Medicine, Houston, TX

The feasibility and expediency of enzymatic methods application in food analysis is demonstrated by the example of ascorbic acid (AsA) determination in foods. Enzymatic determination of ascorbic acid is based on its action as a second substrate of horseradish (HRP) and peanut (PNP) peroxidases in the reactions of o-dianisidine (OD) and 3,3’,5,5’-tetramethylbenzidine (TMB) oxidation with hydrogen peroxide. The rates of the reactions are monitored spectrophotometrically by measuring the duration of the induction period on kinetic curves plotted in coordinates absorption-time. The proposed procedures are sensitive (cL = 0.1 μM), simple, and rapid. The procedure using horseradish peroxidase and the reaction of TMB oxidation was used to determine ascorbic acid in fruit juices, milk and sour-milk products for babies’ nutrition.

Non-destructive spectroscopic techniques for the measurement of food quality

Since the 19th century, many regions of electromagnetic energy, beginning with the visible region of the electromagnetic spectrum, have been exploited to provide analytical instrumentation. Many of these techniques, especially those that are non-destructive, are already being used, or could be used, for the analysis of food characteristics and components. In this review article, the advantages of spectroscopic analysis are noted, and 12 forms of spectroscopy are described in terms of their basic principles and what information they can provide; in addition, examples of their applications in food analysis are provided. The use of several spectroscopic techniques for imaging purposes is also described. Discussion also notes the importance of the techniques and their potential for inclusion among the methods that are approved by international standards organizations. Finally, a list of publications is provided, from which further details of the techniques and instrumentation can be found.

Multidimensional detection methods for separations and their application in food analysis

The use of the multidimensional detection systems, mass spectrometry and NMR, with separation techniques is discussed with a consideration of their actual or potential application in food analysis. The features of the most commonly used interfaces for coupling liquid chromatography (LC) and mass spectrometry (MS) are briefly examined and examples from the literature on the use of LC-MS in the analysis of natural components in foodstuffs are reported. The potential capabilities for food analysis of LC-NMR, supercritical fluid chromatography (SFC)-MS and capillary electrophoresis (CE)-MS are highlighted.