Showing papers in "Food Analytical Methods in 2014"

Evaluation of Aluminium Complexation Reaction for Flavonoid Content Assay

Abstract: Two widely applied spectrophotometric assays based on aluminium complex formation used for determination of total flavonoid content in food or medicinal plant samples were examined for several compounds from different classes of flavonoid family. The method which involves the measurement at 410–430 nm after addition of AlCl3 solution is selective only for flavonols and flavones luteolin. The procedure in the presence of NaNO2 in alkaline medium seems to be specific for rutin, luteolin and catechins, but also phenolic acids exhibit considerable absorbance at 510 nm. Application of both procedures to natural samples gave different order in terms of their flavonoid content. Thus, the expression “total flavonoid” content is not adequate as the results of both methods are dependent on the structure of the individual flavonoids present.

Multiplex PCR in Species Authentication: Probability and Prospects—A Review

Abstract: Food forgery is one of the most articulated socio-economic concerns which contributed to increase people’s awareness on what they eat and how and where it is produced. Consumers are anxious about the consequences of food falsification on their choices, religious rituals, health, and hard-earned fortunes. The recent scandals of horse and rat meats in Europe and China have given us a brainstorming apprehension on the detection, differentiation, and identification of meat products. To restore consumers’ trust and protect wildlife in natural habitats, researchers and policy-making and policy-implementing authorities have massively monitored all steps in the production of foods and food materials. Analytical approaches based on lipids, proteins, and DNA have been proposed for the authentication of meat species under pure and complex matrices. However, protein and lipid-based methods are less effective since the target biomarkers could be modified throughout the processing treatments. On the other hand, DNA-based species identification schemes have gained wider acceptance and reliability because of the superior stability and universality of DNA in all tissues and cells. We systematically presented here major species detection schemes with special emphasis on multiplex polymerase chain reaction (PCR) of both end-point and real-time platforms. We believe this short but comprehensive review would serve as a reference guide for the developers and users of multiplex PCR and others DNA-based techniques.

Loop-Mediated Isothermal Amplification (LAMP) for the Detection of Salmonella in Food

Abstract: Salmonella infection represents a considerable global burden, with significant health and economic impacts. Salmonellosis is most often attributed to the consumption of contaminated foods such as poultry, beef, pork, eggs, milk, seafood, nut products, and fresh produce. Increased public awareness related to food-borne contamination resulted in greater efforts to develop more sensitive, rapid, and inexpensive methods of pathogens detection. Loop-mediated isothermal amplification (LAMP) constitutes a promising solution for rapid diagnosis of food-borne pathogens and is increasingly been applied for the specific diagnosis of different pathogens, Salmonella included. We have reviewed the application of LAMP for the specific detection of Salmonella in food matrices, compared with conventional culture techniques, and in terms of applicability, food matrices, type of assays, target genes, assay temperature, time and equipment, specificity, sensitivity, and robustness. The pros and cons of Salmonella LAMP assays are presented. The potential of LAMP for the development of new on-site diagnostics for the food and agricultural industries and its use as a routine Salmonella screening tool are discussed. Salmonella-specific LAMP assays are expected to provide a very robust, innovative, and powerful molecular diagnostic method for food safety testing services and public health authorities.

Development of a Novel Methodology for the Analysis of Ergosterol in Mushrooms

Abstract: Sterols are important molecules in the unsaponifiable fraction of several matrices. Ergosterol, which is an important vitamin D2 precursor, is clearly the main sterol in mushrooms. Herein, an analytical method for ergosterol determination in cultivated and wild mushrooms was developed using high-performance liquid chromatography coupled to ultraviolet detection. The chromatographic separation was achieved in an Inertsil 100A ODS-3 reversed-phase column using an isocratic elution with acetonitrile/methanol (70:30, v/v) at a flow rate of 1 mL/min. Different extraction methodologies were tested, using n-hexane, methanol/dichloromethane (75:25, v/v) or chloroform/methanol (20:10, v/v). The method was optimised using Fistulina hepatica and proved to be reproductive and accurate. Ergosterol was the most abundant sterol by a greater extent in all mushrooms. In general, the cultivated species showed higher contents, mainly Agaricus bisporus and Lentinus edodes. Among wild species, Boletus edulis was the mushroom with the highest content in ergosterol. Results were expressed in fat content, dry weight and fresh weight bases. The assessment of ergosterol amounts might be very useful due to the bioactive potential that has been attributed to this molecule and its derivatives.

Development of a Broad Specific Monoclonal Antibody for Fluoroquinolone Analysis

Abstract: Fast and sensitive screening of antibiotics is a great need in food quality assurance A monoclonal antibody specific to fluoroquinolones (FQ) was obtained using ciprofloxacin (CPF) derivant as hapten The antibody was characterized with broad recognition to CPF (100 %), enrofloxacin (ENF, 7389 %), norfloxacin (7357 %), nadifloxacin (6728 %), danofloxacin (5309 %), pefloxacin (5026 %), lomefloxacin (3566 %), enoxacin (1240 %), and sarafloxacin (323 %) Then, an enzyme linked immunosorbent assay (ELISA) was established The optimized concentrations of coating antigen and antibody were 01 and 05 μg/ml, respectively Various parameters including pH values, ionic strength and the concentration of antibody and antigen were optimized for this assay The ELISA was found to have the best sensitivity in assay buffer of pH 6 and sodium chloride content 16 % (m/v) using CPF as tested compound Fortified milk samples with CPF and ENF (50 and 250 μg/l) and fortified chicken samples (10 and 50 μg/kg) were analyzed with the proposed measure The ELISA was examined with recovery range of 94–104 % for milk detection and 93–108 % for chicken detection The coefficient variation data for intra-assay and inter-assay ranged from 424 % to 1216 % All results indicate the potential extensive application prospects of this ELISA in FQ monitoring for food safety

Variable Selection in Visible and Near-Infrared Spectral Analysis for Noninvasive Determination of Soluble Solids Content of ‘Ya’ Pear

Abstract: Informative variable selection or wavelength selection plays an important role in the quantitative analysis of near-infrared (NIR) spectra because the modern spectroscopy instrumentations usually have a high resolution and the obtained spectral data sets may have thousands of variables and hundreds or thousands of samples. In this study, a new combination of Monte Carlo–uninformative variable elimination (MC-UVE) and successive projections algorithm (SPA; MC-UVE-SPA) was proposed to select the most effective variables. MC-UVE was firstly used to eliminate the uninformative variables in the raw spectra data. Then, SPA was applied to determine the variables with the least collinearity. A case study was done based on the NIR spectroscopy for the non-destructive determination of soluble solids content (SSC) in ‘Ya’ pear. A total of 160 samples were prepared for the calibration (n = 120) and prediction (n = 40) sets. Three calibration algorithms including linear regressions of partial least square regression (PLS) and multiple linear regression (MLR), and nonlinear regression of least-square support vector machine (LS-SVM) were used for model establishment by using the selected variables by SPA, UVE, MC-UVE, UVE-SPA, and MC-UVE-SPA, respectively. The results indicated that linear models such as PLS and MLR were more effective than nonlinear model such as LS-SVM in the prediction of SSC of ‘Ya’ pear. In terms of linear models, different variable selection methods can obtain a similar result with the RMSEP values range from 0.2437 to 0.2830. However, combination of MC-UVE and SPA was helpful for obtaining a more parsimonious and efficient model for predicting the SSC values in ‘Ya’ pear. Twenty-two effective variables selected by MC-UVE-SPA achieved the optimal linear MC-UVE-SPA-MLR model compared with other all developed models by balancing between model accuracy and model complexity. The coefficients of determination (r 2), root mean square error of prediction, and residual predictive deviation by MC-UVE-SPA-MLR were 0.9271, 0.2522, and 3.7037, respectively.

Effects of Temperature, Time, and pH on the Stability of Anthocyanin Extracts: Prediction of Total Anthocyanin Content Using Nonlinear Models

Abstract: In this study, different anthocyanin sources including grape skin, black carrot, and red cabbage were used to determine the effect of thermal treatment, different acidity levels, and time on the anthocyanin content and degradation. The total anthocyanin contents were modeled by neuro fuzzy inference system (ANFIS) and artificial neural network (ANN) models. The red cabbage anthocyanin stabilities were higher than others. The anthocyanins degraded more rapidly at higher temperatures. The anthocyanin contents of samples decreased with the increase of pH from 3 to 7. Comparison of the models showed that the ANFIS model performed better than the ANN model for the estimation of total anthocyanin content in all samples. The lowest root mean square error (0.0457) and highest R2 (0.9942) values were obtained for red cabbage and grape skin in the validation period with the ANFIS model, respectively. This study showed that both models can be utilized efficiently for the prediction of total anthocyanin content affected by temperature, time, and pH.

Multi-mycotoxins Analysis in Dried Fruit by LC/MS/MS and a Modified QuEChERS Procedure

Abstract: A sensitive and reliable multi-mycotoxin method was developed for the simultaneous determination of 16 toxicological important mycotoxins, such as aflatoxins B1, B2, G1, and G2; enniatins A, A1, B, and B1; beauvericin; ochratoxin A; fumonisin B1, B2, and B3; diacetoxyscirprenol; HT-2; and T-2 toxin in dried fruits using liquid chromatography combined with electrospray ionization-triple quadrupole tandem-mass spectrometry. Mycotoxins have been extracted from the samples using a modified quick, easy, cheap, effective, rugged, and safe procedure. The method was based on a single extraction with acidified acetonitrile, followed by partitioning with salts, avoiding any further clean-up step. Limits of detections ranged from 0.08 to 15 μg kg−1 and limits of quantification ranged from 0.2 to 45 μg kg−1, which were below the legal limit set by the European Union for the legislated mycotoxines. The recoveries in spiked samples ranged from 60 to 135 % except for beauvericin using matrix-matched calibration curves for quantification, with good inter- and intraday repeatability (respective relative standard deviation ≤20 and 9 %). The developed method was applied to 15 commercial dried fruits: raisins, figs, apricots, plums, and dates purchased in local markets from Spain. Among the mycotoxins studied, enniantins and aflatoxins were the most predominant mycotoxins.

Identification of Acacia Honey Adulteration with Rape Honey Using Liquid Chromatography–Electrochemical Detection and Chemometrics

Abstract: The adulteration of honey is generally a concern of consumers and management departments of safety and quality. Adding low-price honey to high-price honey is often seen in the market. In this study, a reliable and simple method of liquid chromatography–electrochemical detection (LC-ECD) was presented to detect the adulteration of acacia honey which was added with rape honey at different levels (5–50 %, w/w). Chromatographic separation was carried out with a reversed phase column, and the mobile phase was methanol/2 % (v/v) aqueous acetic acid. Fingerprints of authentic honeys showed that the contents of chlorogenic acid were higher in acacia honey (1.738 mg kg−1), while those of ellagic acid were much lower (0.274 mg kg−1) in rape honey, so the chlorogenic acid and ellagic acid could be considered as possible markers of acacia and rape honeys, respectively. Samples were classified by cluster analysis and principal component analysis (PCA) according to the contents of phenolic acids. The results of PCA showed that chlorogenic acid and ellagic acid were the major variables, and no adulterated sample was identified as authentic honey. The results of cluster analysis (CA) indicated that the samples were appropriately divided into three main clusters, and adulterated samples were identified. Therefore, acacia honey adulteration with rape honey could be undoubtedly detected by LC-ECD combined with chemometric methods down to the level of 5 %.

Simultaneous Classification of Teas According to Their Varieties and Geographical Origins by Using NIR Spectroscopy and SPA-LDA

Abstract: Due to the human health benefits already scientifically proven, tea (Camellia sinensis) has been widely studied in the literature. Several studies report the classification of the variety or geographical origin of teas, separately. Thus, this paper has proposed a methodology for simultaneous classification of tea samples according to their varieties (green or black) and geographical origins (Brazil, Argentina, or Sri Lanka). For this purpose, near-infrared (NIR) spectroscopy and three differing supervised pattern recognition techniques, namely SIMCA (soft independent modeling of class analogy), PLS-DA (partial least squares-discriminant analysis), and SPA-LDA (successive projections algorithm associated with linear discriminant analysis) have been used. Despite having good results, both full-spectrum PLS-DA and SIMCA were not able to achieve 100 % classification accuracy, regardless of the significance level for the F test in the case of the SIMCA model. On the other hand, the resulting SPA-LDA model successfully classified all studied samples into five differing tea classes (Argentinean green tea; Brazilian green tea; Argentinean black tea; Brazilian black tea; and Sri Lankan black tea) using 12 wave numbers alone.

A Preconcentration Procedure for Determination of Ultra-Trace Mercury (II) in Environmental Samples Employing Continuous-Flow Cold Vapor Atomic Absorption Spectrometry

Abstract: New functionalized magnetic nanoparticles as solid-phase sorbent were prepared and investigated for extraction of ultra-trace amounts of mercury from environmental samples. The Fe3O4 magnetic nanoparticles functionalized with dithizone were characterized by Fourier transform infrared spectrometer. X-ray diffraction and scanning electron microscopy confirmed the size of nanoparticles. Effects of several factors on the extraction procedure were investigated. The optimized conditions were established to be 80 mg of polymer, 8.5 for solution pH, 5 min for adsorption time, 5 min for desorption time, 2 mL for HCl (0.1 mol L−1)/ thiourea 0.05 % as the eluent, 500 mL for breakthrough volume, and without addition of salt. Under the optimal conditions, the limit of detection, maximum capacity, and preconcentration factor were 0.05 ng mL−1, 0.557 mmol g−1, and 250, respectively. Limit of quantification was in the range of 0.2–2 ng mL−1 for various matrices. Accuracy and precision of the method were about ±2.0 and below 11.1 %, respectively. Finally, the present method has been successfully applied to mercury determination in table salt, green tea, vegetables, toothpaste, and water samples. The mercury content found in the real samples was from 0.6 to 15.74 ng mL−1 without addition of mercury.

An Improved Ultrasound Clevenger for Extraction of Essential Oils

Abstract: A new process employing ultrasound technology to improve hydrodistillation extraction was designed and developed. The extraction process (sono-Clevenger) was performed under simultaneous sonication using an ultrasonic horn in situ to provide rapid and complete recovery of analytes from the matrix. The extraction of essential oil from orange peels with conventional Clevenger extraction was compared with the sono-Clevenger process using physicochemical characterization and gravimetric analysis. The new procedure provided a substantial reduction in the extraction time when compared to conventional process without interfering on composition of target compounds.

A Modified QuEChERS Sample Preparation Method for the Analysis of 70 Pesticide Residues in Tea Using Gas Chromatography-Tandem Mass Spectrometry

Abstract: A modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) method for the simultaneous determination of 70 pesticides in tea was developed using gas chromatography-tandem mass spectrometry. Prior to acetonitrile extraction of the target compounds from tea matrix, samples were soaked in distilled water to improve the extraction efficiency. A mixture of adsorbents containing primary–secondary amine, octadecylsilane, graphite carbon black, and multiwalled carbon nanotubes was applied for the cleanup. Additional steps of concentration and solvent exchange were performed to reduce the amount of co-extracts and to decrease the limit of detection of the method. For all pesticides, good linear calibrations with coefficients (R 2) ≥0.99 were obtained at the concentration levels of 10, or 50 to 1,000 μg ml−1. The limits of quantifications (LOQs) were 5–25 μg ml−1, respectively. The recovery rates of samples spiked with 20, 100, and 200 μg kg−1 of analytes ranged from 71 % to 105 %. In addition, the relative standard deviations were lower than 20 %. A total of 331 tea samples were analyzed using this method, and the levels of five pesticide residues in nine tea samples exceeded the strictest maximum residual limits (MRLs).

Evaluation and Optimization of the Analysis of Fatty Acid Types in Edible Oils by 1H-NMR

Abstract: In recent years, new different methods for the determination of fatty acid types (FAT) by nuclear magnetic resonance (NMR) have been developed. Although in general good results have been obtained, these methods employ long acquisition times and a wide variety of approaches and NMR parameters to resolve the FAT. For this reason, we have developed a NMR analysis optimization. This new method was used to evaluate the different 1H-NMR methodologies against gas chromatography–flame ionization detection (GC-FID), considered as the reference method. We have applied our easy and quick methodology to the analysis of three different composition oils: sunflower, olive, and linseed oil. Using our optimized NMR methodology, it was possible to obtain in <1 min the FAT with the same accuracy and better reproducibility than by GC-FID. Furthermore, a complete 1H-NMR spectrum assignation and evaluation of minor components allows obtaining extra information about the composition, quality, and conservation of the analyzed edible oils.

Development of an Electrochemical Sensor for the Determination of Amaranth: a Synthetic Dye in Soft Drinks

Abstract: The voltammetric behaviour of synthetic food colourant, amaranth, was studied using a multiwalled carbon nanotube (MWCNT) thin film-modified gold electrode in 0.1 M acetate buffer solution of pH 5.0. A well-defined oxidation peak was obtained for amaranth at 0.792 V with the modified electrode. The diffusion controlled oxidation of amaranth at the modified electrode can be attributed to the electrocatalytic nature of MWCNT, since the bare electrode has not produced an electrochemical signal under the same experimental conditions. The operational parameters such as supporting electrolyte, pH of the solution and amount of MWCNT–Nafion suspension were optimised. Under optimum conditions, the oxidation peak current varies linearly with concentration in the range from 1.0 × 10−5 M to 1.0 × 10−6 M with a limit of detection at 6.8 × 10−8 M. The developed sensor has good sensitivity and selectivity towards oxidation of amaranth. The sensor was successfully employed for the determination of amaranth in three different samples of soft drinks, and the results were in good agreement with the standard spectrophotometric method.

Application of Polypropylene Amine Dendrimers (POPAM)-Grafted MWCNTs Hybrid Materials as a New Sorbent for Solid-Phase Extraction and Trace Determination of Gold(III) and Palladium(II) in Food and Environmental Samples

Abstract: A new method which utilizes a polypropylene amine dendrimers (POPAM)-grafted multi-walled carbon nanotubes (MWCNTs) hybrid materials as an effective sorbent in solid-phase extraction has been developed for separation and preconcentration of Au(III) and Pd(II) trace levels in food, water and soil samples. The optimum experimental conditions such as pH, flow rates, type, concentration, and volume of the eluent for elution of gold and palladium ions, breakthrough volume, and effect of potentially interfering ions on separation and determination of these noble metals were investigated. The extraction recoveries for the mentioned noble metals were greater than 98 % and the limits of detection were 0.08 and 0.12 ng mL−1 for gold and palladium, respectively. The relative standard deviations of the method were less than 4 % for eight separate column experiments for determination of 5.0 μg of gold and palladium ions. The adsorption capacity of the modified MWCNT was 92 mg g−1 for gold and 74 mg g−1 for palladium on POPAM-grafted MWCNTs. Validation of the suggested method was performed by analyzing certified reference materials. Finally, the proposed method was applied for determination of gold(III) and palladium(II) in real samples, including fish, shrimp, water, and soil.

Magnetic Chitosan Nanocomposite Used as Cleanup Material to Detect Chloramphenicol in Milk by GC-MS

Abstract: A novel method for determination of chloramphenicol in milk samples was introduced. Magnetic Fe3O4@chitosan nanocomposites were synthesized by adding chitosan to the surface of magnetic Fe3O4 using glutaraldehyde as cross-linker. Extraction with ethyl acetate, the study used the magnetic Fe3O4@CS as cleanup materials, without an additional cleanup step, to detect chloramphenicol in milk samples. To obtain maximal cleanup efficiency, several parameters were investigated including amount of magnetic materials, pH of the solution, purification time, and temperature. Under the optimal conditions (the amount of 100 mg/g of magnetic materials, pH = 5, 10 min, and 20 °C), the sensitivity of the proposed method had improved about tenfold than that of without magnetic materials. Moreover, the decision limits and detection capability were 0.05 and 0.11 μg/kg, respectively, which were comparable to those measured by most methods. The rapid, simple, solvent-saving, and efficient method was proved to be robust in monitoring [d(−)-theo-2-dichloroacetamido-1-p-nitrophenyl-1,3-propanediol] in milk samples.

Determination of Sulfonamides in Chicken Meat by Magnetic Molecularly Imprinted Polymer Coupled to HPLC-UV

Abstract: In this work, Fe3O4 magnetic nanoparticles were synthesized and modified by a molecularly imprinted polymer for easy and selective extraction and determination of sulfonamides in chicken meat samples. Imprinted polymer magnetic nanoparticles were characterized by Fourier transform infrared spectroscopy, X-ray diffraction pattern, thermal analysis, and scanning electron microscope micrograph. The template was removed by methanol elution. The effective parameters on extraction and determination of sulfonamides on the sorbent such as eluent type, extraction solvent, and adsorption and desorption times were optimized. Sulfonamide separation and determination were performed by high-performance liquid chromatography–UV. The linear ranges for sulfonamides were 0.5–150 μg/L and the limits of detection were 0.1–0.5 μg/L. Relative standard deviations were within 4.3–5.4 %. The method showed good selectivity for extraction of sulfonamides in real samples.

Differentiation of Romanian Wines on Geographical Origin and Wine Variety by Elemental Composition and Phenolic Components

Abstract: Several wines were analyzed by high-performance liquid chromatography (HPLC-PDA), inductively coupled plasma mass spectrometry (ICP-MS), and flame atomic absorption spectroscopy (FAAS) in order to associate the concentration levels of the chemical parameters with the geographical origin of wines and wine varieties. Thus, the concentrations of 22 elements (Li, Be, Co, Ni, Cs, U, Pb, V, As, Ba, Cr, Cu, Zn, Al, Mn, Rb, Sr, Fe, Ca, Mg, Na, and K) and seven phenolic compounds (gallic acid, (+)-catechin, (−)-epicatechin, p-coumaric acid, ferulic acid, trans-cinnamic acid, and resveratrol) were analyzed in 22 wines from two different wine-producing areas of Romania. Among the phenolic compounds, (+)-catechin, (−)-epicatechin, p-coumaric acid, ferulic acid, and resveratrol concentrations were the most useful markers for wine differentiation by geographical origin and wine variety, whereas Ba, Be, Cr, Cs, Li, Mg, Na, Ni, Sr, U, and Zn were the main inorganic parameters selected. To explore the distribution pattern of the samples, aimed at differentiating the wine samples by geographical region and wine variety, principal component analysis (PCA) was applied to the obtained data.

An Electrochemical Nanosensor for Simultaneous Voltammetric Determination of Ascorbic Acid and Sudan I in Food Samples

Abstract: In this work, we describe application of a high-sensitive electrochemical sensor for determination of ascorbic acid (AA) in the presence of high concentration of Sudan I in food samples. In the first step, we study synthesis and characterization of NiO/NPs with X-ray diffraction (XRD) method. In the second step, application of NiO/NPs describe in the preparation of carbon-paste electrode modified with (9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboximido)-4-ethylbenzene-1,2-diol (DEDED) as a high-sensitive and selective voltammetric sensor for determination of AA and Sudan I. The electrocatalytic oxidation of AA at the modified electrode was investigated by cyclic voltammetry, chronoamperometry and square wave voltammetry (SWV). For the mixture containing AA and Sudan I, the peaks potential was well separated from each other. Their square wave voltammetrics peaks current increased linearly with their concentration at the ranges of 0.01–600 and 0.5–1,000 μM, with the detection limits of 0.006 and 0.2 μM, respectively. Finally, the proposed method was also examined as a selective, simple, and precise electrochemical sensor for the determination of AA and Sudan I in real samples such as fruit juices, fresh vegetable juice, chilli sauce and tomato sauce.

Analysis of Antioxidant Activity, Chlorogenic Acid, and Rutin Content of Camellia sinensis Infusions Using Response Surface Methodology Optimization

Abstract: Optimization of the extraction process of green tea using response surface methodology (RSM) was performed The optimized conditions were 1491 min and 9415 °C (2,2-diphenyl-1-picrylhydrazyl (DPPH) assay) The experimental values were close with the predicted values The procedure was used to measure antioxidant activity using DPPH free radical and phenolic compounds of all types of Camellia sinensis and Tabebuia impetiginosa infusions The antioxidant activity of infusions was in the order (mean for analyzed types) of pure green tea > white tea > green tea with additives > black tea = Pu-erh tea > semifermented tea > Red Lapacho After the fermentation process, the content of rutin is lowered and the amount of gallic acid in infusions is increased A negative correlation between total phenolic acids and organic acids was also observed (R 2 = 06437) Red Lapacho infusion contains phenolic acids such as caffeic, protocatechuic, p-coumaric, ferulic, and syringic No rutin and quercetin were found in this beverage

Application of Vis/NIR Spectroscopy for Chinese Liquor Discrimination

Abstract: As one of the most widely consumed alcoholic beverages, Chinese liquor varies greatly in price, flavor, and quality This diversity calls for effective and reliable discrimination methods In an attempt to find the best liquor discrimination method, this study used different methods to analyze and identify 730 Chinese liquor samples including 22 kinds, ten brands, and six flavors These samples, covering most of the famous liquors in China, were analyzed by visible and near-infrared (Vis/NIR) spectroscopy and modeled by three classification methods including supporting vector machine, soft independent modeling of class analogy, and linear discriminate analysis based on principal component analysis (PCA-LDA) Pretreatments and parameters for each model were optimized, and models discrimination ability was compared The research finds that PCA-LDA was the best model with an average prediction rate of 9894 % in the training set and 9570 % in the test set The correct rates for brands, flavor styles, ages, and alcohol degrees were all higher than 95 % It shows that Vis/NIR is a reliable, inexpensive, and effective tool for Chinese liquors discrimination

Determination of Triazole Fungicides in Vegetable Samples by Magnetic Solid-Phase Extraction with Graphene-Coated Magnetic Nanocomposite as Adsorbent Followed by Gas Chromatography–Mass Spectrometry Detection

Abstract: A graphene-based magnetic nanocomposites (G-Fe3O4 MNPs) was synthesized and used as the adsorbent for the extraction of some triazole fungicides (triadimefon, paclobutrazol, hexaconazole, myclobutanil, diniconazole, propiconazole, and tebuconazole) in cucumber, cabbage, and tomato samples prior to gas chromatography–mass spectrometry detection. Various experimental parameters affecting the extraction efficiencies, such as the amount of G-Fe3O4 MNPs, extraction time, pH and salt concentration of the sample solution, and desorption conditions were investigated. Under the optimized experimental conditions, the enrichment factors of the method for the analytes were in the range from 461 to 697. The signal response was linear in the range of 0.5–35.0 ng g−1 for all the analytes with the correlation coefficients ranging from 0.9810 to 0.9986. The limits of detection (S/N = 3) of the method for the analytes were between 0.01 and 0.10 ng g−1. The recoveries of the method for the seven triazoles were in the range from 84.4 to 108.2 % with RSDs between 3.4 and 10.6 %.

Determination of Chlorpyrifos in Rice Based on Magnetic Molecularly Imprinted Polymers Coupled with High-Performance Liquid Chromatography

Abstract: The magnetic molecularly imprinted polymers (MMIPs) were prepared and used for the selective separation of chlorpyrifos from rice samples. The MMIPs were synthesized by surface-imprinted polymerization, using functionalized Fe3O4 particles as magnetic cores, chlorpyrifos as template, methacrylic acid as functional monomer, and trimethylolpropane trimethacrylate as cross-linker. Magnetic particles were characterized by scanning electron microscopy, Fourier-transform infrared spectrometry, physical property measurement system, and thermogravimetric analyzer. Adsorption studies were carried out to investigate the specific binding capacity, kinetics, and recognition specificity. The kinetic property of MMIPs was well fitted to the pseudo-second-order equation. The selective recognition experiment demonstrated that MMIPs had high selectivity towards chlorpyrifos over reference compound. Chlorpyrifos extracted from the rice samples was purified with MMIPs and detected by high-performance liquid chromatography. Under the optimal conditions, the detection limit of chlorpyrifos was 0.0072 μg g−1. The relative standard deviations of intra- and interday ranging from 2.4 to 4.6 % and from 3.5 % to 7.3 % were obtained, respectively. The recoveries of chlorpyrifos at three different fortified concentrations (0.025, 2.5, and 5 μg g−1) were in the range of 81.2–92.1 %.

Preparation and Evaluation of Histamine Imprinted Polymer as a Selective Sorbent in Molecularly Imprinted Solid-Phase Extraction Coupled with High Performance Liquid Chromatography Analysis in Canned Fish

Abstract: A series of molecularly imprinted polymers (MIPs) were prepared against histamine. Different template/monomer ratios were applied to optimize the imprinting condition. Methacrylic acid (MAA) as a functional monomer and Chloroform as a solvent were applied in polymerization process. The binding properties of MIPs were studied in comparison with a blank non-imprinted polymer. The optimized polymer, with a histamine/MAA ratio of 1/4, was selected as a sorbent in molecularly imprinted solid-phase extraction (MISPE) of histamine from canned fish. Scatchard analysis of MIP-histamine interactions revealed two types of binding sites for MIP: high affinity (KD = 11.11 μM) and low affinity (KD = 333.3 μM). The MISPE procedure was calibrated and a recovery of 76.5–97.6 % was obtained. The intra-and inter-day precision values were less than 5.70 % and 10.1 %, respectively. The selectivity of MISPE for histamine was also studied in comparison with some other structurally similar amines, which could be simultaneously present in canned fish. The performance of the imprinted polymer was examined and the results indicated that its good selectivity and affinity for histamine was very promising. Therefore, the proposed calibrated method could be applied in selective extraction and analysis of histamine in canned fish.

Canine-Specific PCR Assay Targeting Cytochrome b Gene for the Detection of Dog Meat Adulteration in Commercial Frankfurters

Abstract: This report described a cytochrome b (cytb)-based polymerase chain reaction (PCR) assay for the detection of canine tissues in commercial frankfurters. Discriminating detection of canine derivatives in processed food products has important application in halal authentication as well as in health, religions, and fare trades. The assay based on a pair of canine-specific primers that targeted a 100 bp region of canine mithochondrial-cytb gene which is present in multiple copies and highly conserved within the same species. The specificity of the assay was tested against dog and eight most common animal meat species as well as five plant species commonly found in frankfurter formulation. The stability and specificity of the assay were verified under different thermal processing conditions under pure and complex matrices. Three commercial brands of chicken and beef frankfurters were tested in triplicate, and specific PCR products were obtained only from deliberately contaminated formulations. The detection limit of the assay was 0.1 % (0.02 ng DNA) of canine meat spiked with other meats in a typical frankfurter formulation. Shorter amplicon length, superior stability, and higher sensitivity of the assay suggested its potential application in the screening of canine-origin biomaterials in processed food products.

Highly Sensitive Detection of Organophosphorus Pesticides Represented by Methamidophos via Inner Filter Effect of Au Nanoparticles on the Fluorescence of CdTe Quantum Dots

Abstract: A sensitive fluorescence detection method of organophosphate pesticides (OPs) represented by methamidophos was developed using the inner filter effect (IFE) of Au nanoparticles (AuNPs) on CdTe quantum dots (QDs). The fluorescence of CdTe QDs was remarkably quenched with the presence of AuNPs via IFE. Acetylcholinesterase (AChE) catalyzed the hydrolysis of acetylthiocholine into thiocholine, which could induce the aggregation of AuNPs and decrease their characteristic absorption, making IFE-decreased fluorescence of CdTe QDs recovered. OPs can inhibit the activity of AChE, thus preventing the aggregation of AuNPs and the fluorescence recovery of CdTe QDs. Therefore, the IFE of fluorescence between AuNPs and CdTe QDs could convert the absorption signal to fluorescence signal, which improved the detection sensitivity of OPs in vegetables. Under the optimum conditions, the response was linearly proportional to the concentration of methamidophos in the range of 0.06∼0.78 mg/kg with a detection limit of 2 μg/kg (3σ) which was superior to the method of GB/T 5009.199-2003. The proposed assay exhibited good reproducibility and accuracy, providing a simple and rapid method for the screening of OPs.

A Fast and Accurate UPLC Method for Analysis of Proteinogenic Amino Acids

Abstract: A reliable and inexpensive method for the measurement of proteinogenic amino acids was developed. It allows the screening of large sample volumes that is important for current food and feed applications, but also for future biobased applications. The method is based on acid hydrolysis and automated pre-column derivatision in the injection needle of the autosampler using o-phthalaldehyde/ethanethiol reagent in combination with 9-fluorenylmethyl chloroformate. The calculated mean limit of detection and limit of quantification of pure amino acids were 2.3 and 4.6 μM, respectively. With this method, it was possible to accurately analyse the amino acid composition of bovine serum albumin, soy meal, Jatropha press cake, and cyanophycin. Mean reproducibility of all amino acids from bovine serum albumin was 6.8 %, with a mean recovery of 95 %. The sample run time is 16 min with a total cycle time from injection to injection of an acid hydrolyzed sample of 22 min, resulting in a greener method due to a reduction in solvent consumption.

Classification of Green and Black Teas by PCA and SVM Analysis of Cyclic Voltammetric Signals from Metallic Oxide-Modified Electrode

Abstract: Forty-three samples of green and black teas were analyzed by an electronic tongue technique. A class of metallic oxide-modified nickel foam electrodes (SnO2, ZnO, TiO2, Bi2O3) was compared in their sensitivity in this system. The signals obtained by cyclic voltammetry were submitted to multivariate data analysis. In the explorative analysis based on principal component analysis (PCA), the score plots showed that two of these sensors were able to distinguish varieties of teas. The resulting PCA scores were modeled with a support vector machine (SVM) that accomplished final prediction with the qualitative classification of teas. The optimal SVM model was achieved after grid search optimization of some parameters and the conduction of the three commonly used kernel functions. With a comparison of classification accuracies, Bi2O3-modified nickel foam electrode performed the best among the four electrodes and SVM model using the polynomial kernel attained the highest within the three used kernels. This work demonstrated that cyclic voltammetry combined with the SVM pattern recognition method could be successfully applied in the classification of green and black teas.

Characterization of Volatile Organic Compounds of Vinegars with Novel Electronic Nose System Combined with Multivariate Analysis

Abstract: A novel electronic nose system (also called artificial olfaction system) based on colorimetric sensor array was developed for characterization and identification of the volatile organic compounds (VOCs) of vinegars fermented from different raw materials. Fifteen chemo-responsive dyes including nine metalloporphyrins and six pH indicators were selected according to their sensitivity to volatile compounds from vinegar samples. The colorimetric sensor array was made by printing selected chemo-responsive dyes on a silica gel plate. A color change profile for each sample was obtained by differentiating the images of the colorimetric sensor array before and after exposure to the odorant of vinegar sample. The digital data (i.e., red, green, and blue components of the image) representing the color change profiles for the vinegar samples were analyzed. Genetic algorithm partial least squares was employed to select sensitive image digital variable to build a calibration model. Several methods (i.e., linear discrimination analysis, LDA; partial least square discrimination analysis; artificial neural network) were also used comparatively for classification, the result was evaluated by the % correct identification of samples. The optimal model was achieved by LDA model with 14 image digital variables used, and all the vinegar samples were correctly identified both in training and testing sets. This research suggests that the system shows significant potential in vinegar VOCs characterization and discrimination.