Showing papers in "Food Analytical Methods in 2017"

Electronic Nose as a Tool for Monitoring the Authenticity of Food. A Review

Abstract: Counterfeiting of food is recently one of the risks relevant for producers, distributors, retailers, consumers, and national governments from economic (price), health (allergens), and religious reasons. Flavour of several food products is one of the key attributes of their quality and authenticity. In the case of some foods, the aroma of a product is specific enough to discriminate an original product from its fraud or adulterated counterpart. Electronic nose (e-nose) is a rapid and powerful technique, which requires no special sample preparation to determine the aroma of a product. In the present review, the applications of different e-noses and chemometrics for determination of food authenticity including adulteration and confirmation of origin are discussed. E-noses of various configurations are a very promising tool for testing the authenticity of food products.

Classification of Honey from Its Bee Origin via Chemical Profiles and Mineral Content

Abstract: Raw honeys from four different bee species, namely the honey bees and stingless bees, were classified based on its chemical profiles, mineral contents and heavy metals. Chemical profiles including proximate composition, predominant sugars, hydroxymethylfurfural content, and diastase activity were determined following official methods while mineral and heavy metals contents were obtained from atomic adsorption spectrometry (AAS) and inductively coupled plasma-mass spectrometry (ICP-MS) measurements, respectively. Both hierarchical cluster analysis and principal component analysis show high possibility of distinguishing honey by its bee species of honey bees (Apis spp.) and stingless bees (Heterotrigona itama) based on distinctive differences in chemical compositions and mineral contents. Potassium and sodium were the major elements in raw honey samples at average of 904.9 and 617.6 mg/kg, respectively. Honey from stingless bee contained more protein, 0.85 g/100 g and less total sugar of fructose and glucose at 24.99 g/100 g. The information of bee speciation origin of honey bees and stingless bees enhances the identity of honey on the product labelling.

Application of Ultrasonic Assisted-Dispersive Solid Phase Extraction Based on Ion-Imprinted Polymer Nanoparticles for Preconcentration and Trace Determination of Lead Ions in Food and Water Samples

Abstract: In this paper, we describe ultrasonic assisted-dispersive solid phase extraction based on ion-imprinted polymer (UA-DSPE-IIP) nanoparticles for the selective extraction of lead ions. Ultrasound is a good and robust method to facilitate the extraction of the target ions in the sorption step and elution of the target ions in the desorption step. The ion-imprinted polymer nanoparticles used in the UA-DSPE-IIP were prepared by precipitation polymerization technique. The ion-imprinted polymer nanoparticles was synthesized using 2-vinylpyridine as a functional monomer, ethylene glycol dimethacrylate as the cross-linker, 2,2′- azobisisobutyronitrile as the initiator, 1,3,4-thiadiazole-2,5-dithiol as the ligand, methanol/dimethyl sulfoxide as the solvent, and lead as the template ion, through precipitation polymerization technique. The IIP nanoparticles were characterized by Fourier transformed infra-red spectroscopy (FTIR), thermogravimetric and differential thermal analysis (TGA/DTA), and scanning electron microscopy (SEM). Box-Behnken design (BBD) was used for optimization of sorption and desorption steps in UA-DSPE-IIP. In the sorption step: pH of solution, IIP amount (mg), sonication time (min) for sorption and in the desorption step: concentration of eluent (mol L−1), volume of eluent (mL), and sonication time (s) for desorption was investigated and optimized by the Box-Behnken design. The optimum conditions for the method were pH of solution: 7.5, sonication time for sorption 7.5 min, IIP amount 24 mg, type and concentration of eluent HCl 1.4 mol L−1, volume of eluent 2.1 mL, and sonication time for desorption 135 s. Under the optimized conditions, the limit of detection and relative standard deviation for the detection of lead ions by UA-DSPE-IIP was found to be 0.7 μg L−1 and <4%, respectively.

Optimization of Extraction Parameters of Total Phenolics from Annona crassiflora Mart. (Araticum) Fruits Using Response Surface Methodology

Abstract: In this study, response surface methodology was used to optimize the extraction temperature (25–75 °C) and ethanol concentration (0–70 %, ethanol/water, v/v) to maximize the extraction of total phenolic compounds (TPC) from araticum pulp. The efficiency of the extraction process was monitored over time, and equilibrium conditions were reached between 60–90 min. A second-order polynomial model was adequately fit to the experimental data with an adjusted R 2 of 0.9793 (p < 0.0001) showing that the model could efficiently predict the TPC content. Optimum extraction conditions were ethanol concentration of 46 % (v/v), extraction temperature of 75 °C and extraction time of 90 min. Under the optimum conditions, the araticum pulp showed high TPC content (4.67 g GAE/100 g dw) and also high antioxidant activity in the different assays used (46.56 μg/mL, 683.65 μmol TE/g and 1593.72 μmol TE/g for DPPH IC50, TEAC and T-ORACFL, respectively). From our extraction procedure, we successfully recovered a significantly higher amount of TPC compared to other studies in the literature to date (1.5–22-fold higher). Furthermore, TPC and antioxidant activity were present in the fruit in levels that are difficult to find in other common fruits. These results expose a potential approach for improving human health through consumption of araticum fruit.

Comparative Study of the Antioxidant Capacity of Four Stilbenes Using ORAC, ABTS+, and FRAP Techniques

Abstract: Researchers use several different analytical techniques, such as ORAC, ABTS·+, or FRAP, for measuring the antioxidant capacity of bioactive compounds. However, many authors do not take into account that these three techniques have different objectives. This contribution reports on the use of two types of tests to evaluate the antioxidant activity of four stilbene tests based first on the hydrogen atom transfer reaction (ORAC method) and the second on the single electron transfer reaction (ABTS·+ and FRAP assays). For the ORAC assay, the greatest antioxidant activity was shown by resveratrol, followed by oxyresveratrol, pterostilbene, and pinosylvin, while in the ABTS.+ assay, the highest antioxidant capacity was presented by oxyresveratrol, followed by resveratrol, pinosylvin, and finally pterostilbene. In the FRAP assay, the reducing activity shown by all the stilbenes was below that obtained for trolox. The role of phenolic hydroxyl groups was studied. The technique used should be selected taking into account the objectives and the conditions of the medium.

Optimization of Extraction Parameters of Protein Isolate from Tomato Seed Using Response Surface Methodology

Abstract: Response surface methodology (RSM) and a central composite rotatable design (CCRD) were used to optimize the extraction conditions of protein isolate from the defatted tomato seed meal, which is a by-product of tomato processing. Water to raw material ratio, extraction time, and mixing time were the most significant (p < 0.01) factors affecting the protein yield. Optimum extraction was obtained with 82.81/1 (v/w) water to raw material ratio, 49.76 h extraction time, and 24.56 min mixing time. Confirmatory studies revealed that the protein yield under these conditions was 80.37 %, which is well in close agreement with the value predicted by the model (81.22 %). The results of optimized defatted tomato seed protein isolate (DTSPI) molecular weight distribution showed that two protein fractions and three major groups of polypeptides were identified by gel electrophoresis. DTSPI had also most of the essential amino acids and hence could be considered as bioactive peptides. DTSPI showed also a higher antioxidant capacity with an IC50 value of about 40.89 and 18.45 μg/mL, respectively, with DPPH free radical scavenging activity and ABTS•+ radical scavenger methods. The results obtained suggest that DTSPI with good functional properties could be useful in the health food/nutraceutical/pharmaceutical industry for various applications.

Microwave-Assisted Digestion Using Diluted Nitric Acid for Multi-element Determination in Rice by ICP OES and ICP-MS

Abstract: In this work, microwave-assisted digestion using the diluted nitric acid procedure for trace elements determination in rice samples by inductively coupled plasma optical emission spectrometry (ICP OES) and inductively coupled plasma mass spectrometry (ICP-MS) was investigated in a multivariate way. The response surface methodology (RSM), based on the Box–Behnken design, was employed to obtain the optimum conditions of the significant parameters. The optimal conditions, for 250 mg of sample, could be obtained at a temperature of 200 °C, digestion time of 20 min, and 4.5 mol L−1 for nitric acid concentration. The accuracy of the optimized method was evaluated by analysis of the rice flour certified reference materials (NIST SRM 1568a) and spike recoveries. The results showed good agreement with the reference values of the CRM samples. The analytical method was applied to the determination of Al, As, Ca, Cd, Cu, Fe, K, Mg, Mn, Mo, Se, and Zn in rice samples. Considering some critical parameters such as cost, green chemistry, and analyst safety, the proposed method has advantages compared to classical microwave-assisted digestion procedures based on concentrated acids.

Screening the Multi-Element Content of Pleurotus Mushroom Species Using inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES)

Abstract: Considering the worldwide popularity of cultivated Pleurotus mushrooms as food, analyses of their chemical composition are required to ensure product safety. The aim of this study was to compare the content of 62 elements in fruit bodies of six cultivated species of the genus Pleurotus (five strains of Pleurotus ostreatus, Pleurotus eryngii, Pleurotus djamor, Pleurotus citrinopileatus, Pleurotus florida, and Pleurotus pulmonarius), collected from their producers between 2009 and 2015. Only 31 elements (Al, As, B, Ca, Cd, Cr, Cu, Er, Fe, In, K, Lu, Mg, Mn, Na, Nd, P, Pb, Pt, Re, Rh, Sc, Se, Sr, Te, Th, Ti, Tm, U, Zn, and Zr) were detectable in the tested Pleurotus species in each year of their collection. The obtained results revealed three significantly diverse groups with similar abilities to accumulate 31 elements within 7 years of mushroom production. The species and strains were grouped as follows: P. florida and P. pulmonarius (first group); P. ostreatus HK35, P. ostreatus 930, P. eryngii, and P. djamor (second group); and P. ostreatus 80, P. ostreatus H195, P. ostreatus K22, and P. citrinopileatus (third group). In spite of differences between the tested Pleurotus species and strains, presented in the form of graphical Heatmaps, the intake of these mushrooms was not related with any health risk for consumers.

Novel Spectroscopic Method for Determination and Quantification of Saffron Adulteration

Abstract: In this study, a spectroscopic method was developed for the determination and quantification of saffron adulteration with some plant adulterants (safflower, marigold, and turmeric). For this purpose, three spectroscopic techniques, namely, attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, Raman spectroscopy, and laser-induced breakdown spectroscopy (LIBS), were applied, and the superiority of the techniques was investigated by using principal component analysis (PCA). All spectral data were compared, and the best discrimination among saffron and plant adulterants was obtained with LIBS according to PCA results. Following this analysis, partial least squares (PLS) method was carried out using LIBS data to reveal the level of plant adulteration in saffron samples. A good linearity was obtained with a coefficient of determination (R 2) values of 0.999 for calibration and cross-validation in the range of 10–50% with a limit of detection (LOD) and quantification (LOQ) of 1.86 and 9.32%, respectively. Taking the results into consideration, it was seen that the LIBS technique combined with PLS provides a sensitive determination of plant adulterants in saffron under 10%, which is difficult to detect using the reference UV-Vis spectroscopic method.

Determination of Pesticide Residues in Whole Wheat Flour Using Modified QuEChERS and LC–MS/MS

Abstract: Pesticides in food are a major issue due to their intensive use in agriculture. Thus, an appropriate control of their residues in food samples should be done. In this study, a multiresidue method for the quantification of 37 pesticides in whole wheat flour was developed and validated. The modified QuEChERS (without cleanup) procedure followed by ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC–MS/MS) was used for analysis. The method was validated according to the European Union SANCO/12,571/ 2013 guidelines and Brazilian Manual of Analytical Quality Assurance. The following parameters were evaluated on the method validation: linearity, limit of detention, limit of quantification, matrix effect, precision, accuracy evaluating the percentage of recovery at three different spike levels, and robustness. Acceptable values were obtained. The linear range used was 1–200 μg kg−1, resulting to r 2 of >0.99. The recovery was satisfactory with 70 and 120 % and RSD of <20 % for most compounds. Assessing the samples collected in the south Brazil region, some pesticide residues were detected in whole wheat flour (carbendazim, chlorpyrifos, deltamethrin, imidacloprid, malathion, pendimethalin, pirimiphos-methyl, triamedifom, and triadimenol). The applicability of this analytical approach was confirmed by successful determination of pesticides in whole wheat flour, a complex matrix.

Chromatographic Fingerprinting with Multivariate Data Analysis for Detection and Quantification of Apricot Kernel in Almond Powder

Abstract: Adulteration of almond powder samples with apricot kernel was solved by gas chromatographic fatty acid fingerprinting combined with multivariate data analysis methods (principal component analysis (PCA), PCA-linear discriminant analysis (PCA-LDA), partial least squares (PLS), and LS support vector machine (LS-SVM). Different almond and apricot kernel samples were mixed at concentrations ranging from 10 to 90% w/w. PCA and PCA-LDA methods were applied for the classification of almonds, apricot kernels, and mixtures. PLS and LS-SVM were used for the quantification of adulteration ratios of almond. Models were developed using a training data set and evaluated using a validation data set. The root mean square error of prediction (RMSEP) and coefficient of determination (R 2) of validation data set obtained for PLS and LS-SVM were 5.01, 0.964 and 2.29, 0.995, respectively. The results showed that the methods can be applied as an effective and feasible method for testing almond adulteration.

Establishment of an Aqueous PEG 200-Based Deep Eutectic Solvent Extraction and Enrichment Method for Pumpkin (Cucurbita moschata) Seed Protein

Abstract: A novel approach for ultrasound–microwave synergistic extraction (UMSE) of pumpkin seed protein was developed using aqueous poly (ethylene glycol) (PEG 200)-based deep eutectic solvent (DES) as a green extraction medium. Key factors controlling the extraction and optimal operating conditions were optimized by combining the one variable at a time and response surface methodology. Results showed that the PEG 200 as a hydrogen bond donor combined with choline chloride as a typical hydrogen bond acceptor had a highest extraction efficiency among different solvents. The optimal extraction parameters were optimized as follows: PEG 200-based DES concentration, 28% w/w; solid to liquid ratio, 28 g mL−1; microwave power, 140 W; and extraction temperature, 43 °C. Under the optimal parameters, the actual extraction yield was 93.95 ± 0.23% (n = 3). The precipitation rate of pumpkin seed protein was 97.97% with a precipitation time of only 4 min by using an isoelectric point-ethanol-PEG 200 DES ternary co-precipitation method. Overall, this integrated method of PEG 200-based DES and UMSE exhibits a powerful tool for the rapid and efficient extraction of pumpkin seed protein.

The Mesoporous Porphyrinic Zirconium Metal-Organic Framework for Pipette-Tip Solid-Phase Extraction of Mercury from Fish Samples Followed by Cold Vapor Atomic Absorption Spectrometric Determination

Abstract: In this study, the highly stable mesoporous porphyrinic zirconium metal-organic framework, namely PCN-222/MOF-545 (Zr-MOF), was prepared and used for pipette-tip solid-phase extraction of Hg(II). As a high-capacity sorbent, 4 mg of the Zr-MOF was placed into a conventional pipette tip and used, for the first time, for the fast extraction and preconcentration of mercury ions. For desorption, 50 μL of 10% HCl was used by 15 repeated aspirating/dispensing cycles, and Hg ions in elusion were measured by a cold vapor atomic absorption spectrometer. Affecting parameters on extraction efficiency were studied, and optimum conditions were established as amount of sorbent 2 mg, pH was adjusted to 5.0, the eluting volume was 15 μL, and extraction was performed on 1.8 mL of the sample. The optimal number of aspirating/dispensing cycles for extraction and desorption of analytes was found to be 10 and 15 cycles, respectively. The limit of detection of the method was found to be 20 ng L−1 with a relative standard deviation of ≤3.1% (for seven replicate analyses of 20 μg L−1 of mercury). Adsorption capacity and enrichment factor were 35.5 mg g−1 and 120-fold, respectively. The proposed method was successfully applied for the determination of Hg(II) ions in fish samples.

Recombinase Polymerase Amplification-Based Assay for Rapid Detection of Listeria monocytogenes in Food Samples

Abstract: Listeria monocytogenes (L. monocytogenes) is a Gram-positive microbe and is reported to be potentially pathogenic for both humans and animals, exhibiting a high mortality rate of up to 30%. The invention of a fast and sensitive method of point-of-care testing (POCT) is of great significance for the field of food safety of the rapid detection of harmful microbes and prevention of food contaminated by such microbes from reaching the markets. A novel isothermal molecular amplification technique, recombinase polymerase amplification (RPA), has been used to detect L. monocytogenes in food combined with a highly sensitive end determining method, lateral flow dipstick (LFD) technology. RPA-LFD was implemented at 37 °C, and amplification only took 20 min. By optimizing the primers and probes, the system had no cross-reaction with seven other pathogens, and it was proven to have a 100 times higher sensitivity (1360 cfu/mL) than a real-time PCR for L. monocytogenes testing. Also, RPA-LFD was applied without complex or expensive equipment, only a thermostatic heater such as the Thermomixer Comfort was required. Thus, RPA-LFD was found to be a solution for POCT for L. monocytogenes, especially for low-resource locations with little available laboratory equipment.

Simultaneous Determination of Quercetin, Rutin, Naringin, and Naringenin in Different Fruits by Capillary Zone Electrophoresis

Abstract: A fast and reliable capillary zone electrophoretic (CZE) method has been developed for the simultaneous determination of four fruit flavonoids using photodiode array (PDA) detector. The effects of CE parameters including concentration and pH of the running buffer, voltage, and injection time were optimized. Under the optimized conditions, all flavonoids were well determined in a 10 mM borate buffer of pH 8.5 within 10 min at an applied voltage of 25 kV. Naringin, naringenin, and quercetin were found to have linear response in the range of 3.12–200 μg/mL whereas rutin’s response was linear from 6.25 to 200 μg/mL. LOD was found to be 0.406, 0.314, 0.582, and 0.333 μg/mL and LOQ 1.355, 1.046, 1.941, and 1.11, respectively. Relative standard deviations (RSD) were found to be less than 3 % for both migration time and peak height which shows long-term stability and good reproducibility of the developed method. The method was successfully applied for the simultaneous determination of flavonoids from various fruit juice samples.

Enhancing Visible and Near-Infrared Hyperspectral Imaging Prediction of TVB-N Level for Fish Fillet Freshness Evaluation by Filtering Optimal Variables

Abstract: Total volatile basic nitrogen (TVB-N) is one of the most important indicators for evaluation of fish protein degradation and freshness loss. A novel algorithm of Physarum network (PN) combined with genetic algorithm (GA) was developed to select optimal wavelengths from hyperspectral images for enhancing the TVB-N level prediction in grass carp fish fillet. Partial least squares regression (PLSR) and least squares support vector machines (LS-SVM) calibration models were built using six optimal wavelengths selected by the PN-GA method and the PN-GA-PLSR model showed better performance for predicting the TVB-N value with determination coefficient in prediction (R 2 P ) of 0.956 and root mean square errors in prediction (RMSEP) of 1.737 mg N/100 g. The PN-GA-PLSR model established using the optimal wavelengths and image texture variables extracted by gray-level gradient co-occurrence matrix (GLGCM) algorithm showed higher R 2 P of 0.981 and lower RMSEP of 1.435 mg N/100 g. The results indicated that the PN-GA method was a good technique for selecting optimal wavelengths for enhancing prediction ability of hyperspectral imaging, which also demonstrated the efficiency and usefulness of this method for monitoring the freshness degree during fish cold storage.

Geographical Origin Discrimination of Oolong Tea (TieGuanYin, Camellia sinensis (L.) O. Kuntze) Using Proton Nuclear Magnetic Resonance Spectroscopy and Near-Infrared Spectroscopy

Abstract: A total of 90 oolong tea samples were collected from three different growing places in the Fujian province of China. Both proton nuclear magnetic resonance (1H NMR) and near-infrared spectroscopy (NIR) were used to analyze the collected tea samples. With the aid of chemometric methods, differential components in 1H NMR data and characteristic wavenumbers from NIR spectra were identified. Since NMR and NIR provide complementary information for tea samples, data fusion was carried out by combining 1H NMR and NIR spectra of the collected tea sample. Experimental results showed that a better discrimination accuracy of geographical origins of oolong tea could be achieved by combining NMR and NIR data (86.2–95.8%), as compared to using NMR data (68.2–78.7%) or NIR data (80.0–89.3%) alone. The current data suggested that a combination of NMR and NIR methods could serve as an efficient way for geographical origin discrimination and qualitative control of oolong tea.

Non-Destructive Prediction of Moisture Content and Freezable Water Content of Purple-Fleshed Sweet Potato Slices during Drying Process Using Hyperspectral Imaging Technique

Abstract: The aim of this study was to investigate the feasibility of hyperspectral imaging in measuring moisture content and freezable water content during drying process. Hyperspectral images were acquired for purple-fleshed sweet potato (PFSP) slices during contact ultrasound assisted hot drying (CUHAD) process, and the corresponding mean reflectance spectra from regions of interest in visible and near infrared (371–1023 nm) regions were extracted. Moving average, Savitzky-Golay smoothing filter (S_G filter) and multiplicative scatter correction (MSC) were investigated to preprocess the raw spectra and partial least square regression (PLSR) calibration model was established to analyze the relationship between the extracted spectral data and measured quality attributes. Comparing the performance of model based on different preprocessing methods, the PLSR model with MSC pre-treatment presented better results with coefficients of determination for prediction ( $$ {R}_P^2 $$ ) of 0.9837 and 0.9323 for moisture content and freezable water content, respectively. Instead of selecting full range spectra data, optimal wavelengths were identified based on the regression coefficients (RC) method. Then two linear calibration algorithms named PLSR and multiple linear regression (MLR), and a non-linear calibration algorithm named backpropagation (BP) neural network were used to establish models to predict quality attributes of samples simultaneously. The results showed that the RC-MLR with $$ {R}_P^2 $$ of 0.9359 and 0.8592 was considered as the best for determining moisture content and freezable water content of PFSP slices. Therefore, the study demonstrates the potential of using hyperspectral imaging in tandem with chemometrics analysis as an objective, fast and non-destructive method for predicting the moisture content and freezable water content at different dehydrated times.

One-Step QuEChERS-Based Approach to Extraction and Cleanup in Multiresidue Analysis of Sulfonylurea Herbicides in Cereals by Liquid Chromatography–Tandem Mass Spectrometry

Abstract: A one-step quick, easy, cheap, effective, rugged, and safe (QuEChERS)-based approach to extraction and cleanup in multiresidue pesticide analysis is presented for the first time. The experiment was designed to detect 23 sulfonylurea herbicides in a complex cereal matrix. The challenge was to choose the optimal conditions of one-step extraction and cleanup. Chitin, diatomaceous earth, and octadecyl were investigated as cleanup sorbents. Chitin, citrate buffer, and 1 % formic acid in acetonitrile yielded the best results. The effectiveness of sulfonylureas extraction was evaluated at three different spiking levels (0.005, 0.05, and 0.5 mg kg−1) in wheat, rye, and oat using liquid chromatography–tandem mass spectrometry. The one-step QuEChERS provided recoveries in the 70–120 % range for 23 sulfonylureas in all cereal matrices. Matrix effects were evaluated and were not significant for all herbicides, showing suppression or enhancement (between −19 and 13 %). Precision, calculated as relative standard deviation (RSD), was below 20 %. A linear dependence was observed in the range of 0.005–2.0 mg kg−1, and the correlation coefficient was R 2 > 0.999. Expanded measurement uncertainty was estimated to be between 9 and 24 %, on average. The validated method was employed in analysis of 89 real grain samples.

Screening of over 600 pesticides, veterinary drugs, food-packaging contaminants, mycotoxins, and other chemicals in food by ultra-high performance liquid chromatography quadrupole time-of-flight mass spectrometry (UHPLC-QTOFMS)

Abstract: In this article, an accurate mass multiresidue screening method has been developed for the determination of over 630 multiclass food contaminants in different matrices using ultra-high performance liquid chromatography/(quadrupole)-time-of-flight mass spectrometry. The compounds included in the study were 426 pesticides, 117 veterinary drugs, 42 food-packaging contaminants, 21 mycotoxins, 10 perfluorinated compounds, 9 nitrosamines, and 5 sweeteners. The separation was carried out by liquid chromatography using a C18 column (50 mm × 2.1 mm, 1.8 μm particle size). The identification of the targeted species was accomplished using accurate masses of the targeted ions (protonated or deprotonated molecule) along with retention time data and characteristic fragment ion for reliable identification, using specific software for automated data mining and exploitation. The performance of the screening method was validated in terms of linearity, matrix effect, and limits of quantification for three representative food matrices (tomato, orange, and baby food) using a generic sample treatment based on liquid partitioning with acetonitrile (QuEChERS). The overall method performance was satisfactory with limits of quantification lower than 10 μg kg −1 for the 44 % of studied compounds. In some cases (ca. 10–15 % of the pesticides depending on the matrix tested, maximum residue levels were not fulfilled). In orange, 15 % of the compounds displayed LOQs above the maximum residue levels (MRLs) set for the studied pesticides, which can be partially attributed to matrix effects. Moderate signal suppression was observed in the three matrices tested in most cases, being orange the matrix which produced the highest matrix effect and baby food the lowest one.

Development of an icELISA and Immunochromatographic Assay for Methyl-3-Quinoxaline-2-Carboxylic Acid Residues in Fish

Abstract: To evaluate residues of olaquindox (OLA) and its marker compound methyl-3-quinoxaline-2-carboxylic acid (MQCA) in aquatic products in the field, five types of hapten and corresponding antigens with exposure of different antigenic determinants were designed and synthesized. The optimal immunogen-coating combinations were obtained by antiserum detection and heterologous coating screening, successfully achieving a highly specific monoclonal antibody (mAb) against MQCA. Based on the highly specific mAb 1A11 showing no cross-reactivity with other analogs, an indirect competitive ELISA and an immunochromatographic strip for MQCA detection in fish were developed using the MQCA derivative MQCA-(NH2)4 coupled to KLH as the immunogen and MQCA-NH2 coupled to OVA as the heterologous coating antigen. The IC50 value of the indirect competitive enzyme-linked immunosorbent assay (icELISA) was 3.17 ng/mL, and the linear range was 0.58–17.29 ng/mL for MQCA under optimized concentrations of coating antigen and antibody of 0.03 and 0.3 μg/mL, respectively. The recoveries of MQCA by the developed icELISA in fish samples ranged from 81.6 to 90.7%. The cutoff value of the strip was 5 ng/mL, and the limit of detection was 0.25 ng/mL under optimal working conditions of 4 μL 0.1 M K2CO3 and 50 μL 0.2 mg/mL per 1 mL colloidal gold solution. The developed icELISA and immunochromatographic strip will be very useful tools for the primary screening of MQCA in fish.

Liquid Chromatography–Tandem Mass Spectrometry Multiclass Method for 46 Antibiotics Residues in Milk and Meat: Development and Validation

Abstract: A screening method for analysis of 46 antibiotics residues, belonging to different classes, such as tetracyclines, sulfonamides, fluoroquinolones, β-lactams, cephalosporins, macrolides and other minority groups was developed and validated for application in bovine milk and bovine, swine, poultry, equine, fish and shrimp meat samples. Sample preparation consists in solvent extraction followed by clean up with C18 bulk and low temperature purification. Instrumental analysis was performed using liquid chromatography coupled to tandem mass spectrometry system. Chromatographic separation was achieved using a C18 column. Mobile phase was composed by methanol and water. The method was validated according to Commission Decision 2002/657/EC criteria. Validation parameters such as specificity and detection capability (CCβ) were determined and considered suitable to the established criteria. Values of CCβ ranged from 1.0 to 50.0 μg L−1 or μg Kg−1, depending on the compound and the matrix. The proposed method has been applied into Brazilian National Residue Control Plan since 2013 for the determination of antibiotic residues. A total of 3833 samples were analyzed until the current date and 13 samples showed positive results with concentrations above the permitted. The method is fast, easy and adequate for high throughput analysis in routine laboratories.

Application of High-Performance Liquid Chromatography with Diode Array Detector for Simultaneous Determination of 11 Synthetic Dyes in Selected Beverages and Foodstuffs

Abstract: A simple, inexpensive and robust high-performance liquid chromatography diode array detector (HPC-DAD) procedures are proposed to analyse food dyes in beverages, hard candy and fish roe samples. An ether-linked phenyl stationary phase provides sufficient selectivity and chromatographic performance for separation of 11 sulfonated azo dyes. Beverage samples were only diluted (and degassed when needed) before analysis. Solid-phase extraction (SPE) or matrix solid-phase dispersion (MSPD) procedures are proposed for efficient extraction of the analytes from candies or fish roe samples, respectively. Limits of detection (LODs) were from 0.005 to 0.013 μg mL−1 and limits of quantification (LOQs) between 0.014 and 0.038 μg mL−1. HPLC-DAD method was validated in terms of intra- and inter-day accuracy and precision at three concentration levels 2, 1, and 0.1 μg mL−1. Validation was also performed for SPE and MSPD extraction procedures including intra- and inter-day accuracy (Recovery %) and precision (RSD%), as well as intra-laboratory reproducibility. Application to analysis of beverages and food samples available to consumers proved that described methods are suitable for the routine analysis of dyes in food products.

Dispersive Liquid-Liquid Microextraction Method for HPLC Determination of Phenolic Compounds in Wine

Abstract: A fast and efficient dispersive liquid-liquid microextraction (DLLME) method was developed for extraction of phenolic compounds from red, rose, or white wine followed by HPLC determination in this study. After different extraction solvents and conditions were evaluated, the fastest and highest efficiency extraction of 12 phenolic compounds including gallic acid, protocatechuic acid, chlorogenic acid, catechin, vanillic acid, caffeic acid, syringic acid, epicatechin, p-coumaric acid, trans-ferulic acid, quercetin, and kaempferol was achieved by using 1000 μL of ethyl acetate as an extraction solvent and 500 μL of acetonitrile as a dispersive solvent. The mixtures of solvents were mixed with 1000 μL of wine sample for 10 s of extraction time. The extractions were carried out two times. Under the optimal condition, the extraction recoveries of 12 phenolic compounds were in a range from 76.56 to 137.74%. Meanwhile, the linearity, sensitivity, and precision of an optimized HPLC analysis method were evaluated. The results showed that each phenolic compound had a good regression coefficient (R 2). The limits of detections and quantifications for all the 12 compounds were at 0.001 to 0.133 and 0.004 to 0.433 mg/L, respectively. The relative standard deviations of intra- and inter-day determinations of the 12 compounds were below 6.58 and 4.11%, respectively. The results showed that the red wines had the highest concentration of total phenolic compounds (48.74–196.07 mg/L), followed by the rose wine (31.11 mg/L) and white wine (11.18–30.39 mg/L). Catechin was the dominant phenolic in all the wines (exception of wine sample W8) and ranged from 3.02 to 72.89 mg/L. In general, the developed dispersive liquid-liquid microextraction with HPLC analysis is a fast and efficient method to determine the phenolic compounds in wine.

Determination of squalene in organic extra virgin olive oils (EVOOs) by UPLC/PDA using a single-step SPE sample preparation.

Abstract: In this paper, a simple extraction and fast detection procedure was used to determine squalene (SQ) in extra virgin olive oils (EVOOs). SQ was purified from EVOOs by an efficient single-step solid phase extraction (SPE), and its content was determined using an UPLC-PDA instrument. The adopted technique was evaluated for accuracy, linearity, sensitivity, and repeatability. The precision of the SPE extraction was satisfactory and the mean recoveries were 91.9 ± 0.4 and 96.3 ± 0.3 % for 25 and 50 mg L−1 level of addition, respectively. The selected chromatographic conditions allowed a very fast SQ determination; in fact, it was well separated in ∼0.54 min with good resolution. The UPLC method showed a good linearity in the range 50–500 mg L−1 (R 2 = 0.9998). Method sensitivity was evaluated by measuring the limits of detection (LOD) that was 0.3 mg L−1. The method was utilized for SQ determination in 33 different organic EVOO samples, coming from different countries (Turkey, Tunisia, Spain, Portugal, Greece, USA, Slovenia, Albania, Israel, Italy) and the data were statistically evaluated.

Food Analysis by Microextraction Methods Based on the Use of Magnetic Nanoparticles as Supports: Recent Advances

Abstract: In the last years, nanotechnology progress has impact several fields of food science. In food analysis, new nanomaterials have been developed in order to extract minority food components. Recently, magnetic nanoparticles (MNPs) have been used as sorbents in methodologies based on dispersive solid-phase microextraction. The main advantage of MNPs as sorbent is their magnetic behavior, which it allows to separate from the food matrix minor components with the aid of a magnet. This MNP property avoids tedious centrifugation and filtration steps, and in turn decreasing sample preparation times and source of errors. The MNPs as sorbent do not need to package in a column, and the separation process is quickly. Other advantages of MNPs in the microextraction of food components are low cost, high concentration factors, and low detection limits; this has allowed the diversification of its applications. Several methods and compounds have been used in the design and functionalization of MNPs, this review focuses in the description of these, especially for the analysis of contaminants (for example, pesticides, heavy metals, drugs, compounds produced during food processing, adulterants, among others).

Quantification of Fatty Acids in Human, Cow, Buffalo, Goat, Yak, and Camel Milk Using an Improved One-Step GC-FID Method

Abstract: An efficient gas chromatographic method for the accurate analysis of fatty acid composition in milk was validated. This method provides an excellent resolution of almost 60 fatty acids from odd branched chain fatty acids (OBCFA), trans-monoenoic fatty acid to polyunsaturated fatty acids (PUFA) simultaneously. The quantitation limit was as low as 0.33~1.80 mg/100 g milk with a good intra-day (RSD 0.53~9.6%) and inter-day (RSD 1.25~9.1%) repeatability with an average recovery of 97.3%. This method was applied to determine the fatty acid composition in human, cow, buffalo, goat, yak, and camel milk. Human milk had the lowest amount of saturated fatty acids and highest amount of polyunsaturated fatty acids (31.7 ± 0.31 g/100 g total fatty acids). Yak milk contained the highest amount of C18:1 trans-11 (3.06 ± 0.03 g/100 g total fatty acids). Furthermore, the high proportion of butyric acid (12.2 ± 0.09 g/100 g total fatty acids), OBCFA (2.16 ± 0.02 g/100 g total fatty acids), α-linolenic acid (2.12 ± 0.02 g/100 g total fatty acids), and arachidonic acid (1.35 ± 0.02 g/100 g total fatty acids) were found in the milk from two-humped camel.

A Simple and Rapid Extraction Method to Evaluate the Fatty Acid Composition and Nutritional Value of Goji Berry Lipid

Abstract: In this paper, the results of a study on lipid fraction from goji berries are reported. A rapid and simple method based on magnetic stirring with chloroform/methanol mixture and final clean-up with deionized water was developed, which avoided the presence of polar substances in the final extract. The proposed method was compared with conventional (Folch and Soxhlet methods) and unconventional (hexane/2-propanol or methyl-tert-butyl ether extraction) procedures. Sixteen commercial goji samples have been extracted by the developed method; then, the fatty acid composition was determined by high-resolution gas chromatography-flame ionization detector (HRGC-FID) analysis of derivatized samples. Generally, the results obtained underlined the important role of goji berry as a natural source of unsaturated fatty acids (78.0–86.0 %) with a high content of n-6 polyunsaturated fatty acids (PUFA, 48.2–60.2 %), a satisfactory n-6/n-3 PUFA ratio, and a good PUFA/saturated fatty acid ratio.

Simultaneous Determination of Amaranth and Nitrite in Foodstuffs via Electrochemical Sensor Based on Carbon Paste Electrode Modified with CuO/SWCNTs and Room Temperature Ionic Liquid

Abstract: A carbon paste electrode modified with 1-methyl-3-butylimidazolium bromide and CuO decorated single-wall carbon nanotubes (1-M-3-BIBr/CuO/SWCNTs/CPE) was utilized for nanomolar determination of amaranth in the presence of nitrite using square wave voltammetric (SWV) method. The structure of CuO/SWCNTs was investigated by SEM method. 1-M-3-BIBr/CuO/SWCNTs/CPE exhibited an enhancement in electro-oxidation current and active surface area. Also, 1-M-3-BIBr/CuO/SWCNTs/CPE exhibited indicated high catalytic activity toward the electro-oxidation of amaranth and simultaneous determination of it in the presence of nitrite. The 1-M-3-BIBr/CuO/SWCNTs/CPE achieved dynamic ranges 0.004–750 μM and 1.0–10,000 μM between the oxidation currents and the concentration of amaranth and nitrite, respectively. We obtained the detection limit of 1.0 nM and 0.5 μM for amaranth and nitrite, respectively. The 1-M-3-BIBr/CuO/SWCNTs/CPE was successfully applied to analysis of amaranth and nitrite in foodstuffs.

Development of a Nanobody-Based Competitive Dot ELISA for Visual Screening of Ochratoxin A in Cereals

Abstract: A polyvinylidene fluoride membrane-based dot immunoassay using nanobody (Nb) for rapid, qualitative, and visual detection of ochratoxin A (OTA) in cereals was developed. On the basis of optimal assay conditions, the cut-off level of this method assessed visually was 5 μg/kg for OTA, and the final results were obtained within 20 min. This method was simple with no time-consuming cleanup procedure. Good accuracy and reproducibility were obtained in recovery experiments. Results of the Nb-based dot ELISA are in agreement with the ELISA kit, except for samples that were negative for OTA presence assessed through Nb-based dot ELISA but found positive through the ELISA kit. These results indicated that the developed method could be a useful on-site screening tool for rapid detection of OTA in cereals without special instrument.