Current analytical methods for trichothecene mycotoxins in cereals

Application of luminescent Photobacterium Phosphoreum T3 for the detection of zearalenone and estimating the efficiency of their enzymatic degradation

Zearalenone (ZEN), a nonsteroidal estrogenic mycotoxin, causes enormous economic losses in the food and feed industries. Simple, rapid, low-cost, and quantitative analysis of ZEN is particularly urgent in the fields of food safety and animal husbandry. Using the bioluminescent bacterium Photobacterium phosphoreum T3, we propose a bioluminescence inhibition assay to evaluate ZEN levels quickly. The limit of detection (LOD), limit of quantification (LOQ), and quantitative working range of this bioluminescence inhibition assay were 0.1 µg/mL, 5 µg/mL, and 5-100 µg/mL, respectively. The concentration-response curve of the bioluminescence inhibition rate and ZEN concentration was plotted within the range 5 to 100 μg/mL, as follows: y = 0.0069x2 - 0.0190x + 7.9907 (R2 = 0.9943, y is luminescence inhibition rate, x is ZEN concentration). First, we used the bioluminescence inhibition assay to detect the remaining ZEN in samples treated with purified lactonohydrolase ZHD101. The bioluminescence inhibition assay results showed a strong correlation with the HPLC analysis. Furthermore, we successfully evaluated the overall toxicity of samples treated with purified peroxidase Prx and H2O2 using the P. phosphoreum T3 bioluminescence inhibition assay. The results indicate that the degradation products of ZEN created by purified peroxidase Prx and H2O2 showed little toxicity to P. phosphoreum T3. In this study, a simple, rapid, and low-cost assay method of zearalenone by bioluminescent P. phosphoreum T3 was developed. The bioluminescence inhibition assay could be used to estimate the efficiency of enzymatic degradation of ZEN.

Simultaneous determination of 17 regulated and non-regulated Fusarium mycotoxins co-occurring in foodstuffs by UPLC-MS/MS with solid-phase extraction

Fusarium species produce numerous mycotoxins known to co-occur in food. While some of these mycotoxins (e.g., deoxynivalenol, fumonisins) are regulated in several countries, others are non-regulated (e.g., nivalenol, beauvericin). In this study, UPLC-MS/MS with solid-phase extraction cleanup was used to determine 17 Fusarium mycotoxins (FTs) simultaneously. The method showed excellent performance in terms of linearity (R2 > 0.99), LOD (<1.2 μg/kg), LOQ (<3.6 μg/kg), accuracy (70.0-116.3 %), repeatability (<15.7 %), reproducibility (<25.3 %), and expanded uncertainty (<41.7 %). The validated method was successfully applied to 198 marketed food samples collected in South Korea. Of the tested samples, 79 % were contaminated with at least one FT. Job's tears showed the highest prevalence of 14 FTs, and sorghum had the highest total FTs level (3.03 mg/kg). The results suggest that this method can be used for the simultaneous analysis of 17 FTs in food samples, which would serve as crucial information for risk management.

Potential Toxicity and Mechanisms of T-2 and HT-2 Individually or in Combination on the Intestinal Barrier Function of Porcine Small Intestinal Epithelial Cells

Under natural conditions, T-2 toxin can be easily metabolized to HT-2 toxin by deacetylation, and T-2 and HT-2 are usually co-contaminated in grain and feed at a high detected rate. Our previous information indicated that T-2 toxin could injure the function of the intestinal barrier, but the combined toxicity and mechanism of T-2 and HT-2 on the intestinal cells of porcines are still unknown. Therefore, we aimed to explore T-2 and HT-2 individually and combined on cellular viability, cell membrane integrity, the expression of tight junction-related proteins, and the generation of inflammatory factors in porcine intestinal epithelial cells (IPEC-J2). The results showed that T-2 and HT-2, individually or in combination, could induce a decrease in cell viability, an increase in LDH release and IL-1, IL-6, and TNF-α generation, and a decrease in the anti-inflammatory factor IL-10. Based on the analysis of immunofluorescence staining, real-time PCR, and western blotting, the tight junction protein expressions of Claudin-1, Occludin, and ZO-1 were significantly decreased in the T-2 and HT-2 individual or combination treated groups compared with the control. Furthermore, all the parameter changes in the T-2 + HT-2 combination group were much more serious than those in the individual dose groups. These results suggest that T-2 and HT-2, individually and in combination, could induce an intestinal function injury related to an inflammatory response and damage to the intestinal barrier function in porcine intestinal epithelial cells. Additionally, T-2 and HT-2 in combination showed a synergistic toxic effect, which will provide a theoretical basis to assess the risk of T-2 + HT-2 co-contamination in porcine feed.

Investigation of Spectroscopic Peculiarities of Ergot-Infected Winter Wheat Grains

Wheat has played an important role in human agriculture since ancient times. Increasing rates of processed wheat product fabrication require more and more laboratory studies of product quality. This, in turn, requires the use, in production and in field conditions, of sufficiently accurate, fast and relatively low-cost quality control methods, including the detection of fungal diseases. One of the most widespread fungal diseases of wheat in the world is ergot caused by the fungi genus Claviceps. Optical methods are promising for this disease identification due to the relative ease of implementation and the possibility of performing fast analyses in large volumes. However, for application in practice, it is necessary to identify and substantiate characteristic spectral markers that make it possible to judge the sample contamination. In this regard, within the framework of this study, the methods of IR absorption spectroscopy in the MIR region and reflection spectroscopy in the UV-vis-NIR ranges, as well as luminescence spectroscopy, were used to study ergot-infected grains of winter wheat of the "Moskovskaya 56" cultivar. To justify the choice of the most specific spectral ranges, the methods of chemometric analysis with supervised classification, namely PCA-LDA and PCA-SVM, were applied. The possibility of separating infected grains according to the IR absorption, reflection spectra in the UV-vis-NIR ranges and visible luminescence spectra was tested.

Electronic Nose for the Rapid Detection of Deoxynivalenol in Wheat Using Classification and Regression Trees

Mycotoxin represents a significant concern for the safety of food and feed products, and wheat represents one of the most susceptible crops. To manage this issue, fast, reliable, and low-cost test methods are needed for regulated mycotoxins. This study aimed to assess the potential use of the electronic nose for the early identification of wheat samples contaminated with deoxynivalenol (DON) above a fixed threshold. A total of 214 wheat samples were collected from commercial fields in northern Italy during the periods 2014−2015 and 2017−2018 and analyzed for DON contamination with a conventional method (GC-MS) and using a portable e-nose “AIR PEN 3” (Airsense Analytics GmbH, Schwerin, Germany), equipped with 10 metal oxide sensors for different categories of volatile substances. The Machine Learning approach “Classification and regression trees” (CART) was used to categorize samples according to four DON contamination thresholds (1750, 1250, 750, and 500 μg/kg). Overall, this process yielded an accuracy of >83% (correct prediction of DON levels in wheat samples). These findings suggest that the e-nose combined with CART can be an effective quick method to distinguish between compliant and DON-contaminated wheat lots. Further validation including more samples above the legal limits is desirable before concluding the validity of the method.

A versatile Y shaped DNA nanostructure for simple, rapid and one-step detection of mycotoxins

A versatile Y shaped DNA nanostructure has been developed for simple, rapid and one-step simultaneous detection aflatoxin B1 (AFB1) and ochratoxin A (OTA). Y shaped duplex DNA arms was formed with two DNA tweezer at the ends. The aptamer sequence at the third end can bind to its target mycotoxins with strong affinity and then release the two DNA fragments. The released DNA fragments can open the DNA tweezers at the ends of Y shaped DNA arm. The amounts of AFB1 and OTA can be quantitative detection through the recovery of the fluorescent intensities. This strategy is simple and rapid with self-powered DNA hybridization reaction to control the "open" of Y shaped DNA tweezers. Furthermore, it can be finished in 60 min with only one-step of operation. The linear range of AFB1 was from 0.5 to 200 ng/mL (R² = 0.995) and linear relationship of OTA was obtained from 4 to 300 ng/mL (R² = 0.990). It also has been successfully applied for mycotoxins detection in real food samples. Importantly, the target mycotoxins can be extended to others by simply replacing the corresponding aptamer sequences.

Phage Display Selection of an Anti-Idiotype-Antibody with Broad-Specificity to Deoxynivalenol Mycotoxins

The use of synthetic antibody libraries and phage displays provides an efficient and robust method for the generation of antibodies against a wide range of targets with highly specific binding properties. As the in vitro selection conditions can be easily controlled, these methods enable the rapid generation of binders against difficult targets such as toxins and haptens. In this study, we used deoxynivalenol mycotoxin as a target to generate anti-idiotype-antibodies with unique binding properties from synthetic antibody libraries. The binding of the selected anti-idiotype antibodies can be efficiently inhibited with the addition of free isoforms of deoxynivalenol. The antibody was consecutively used to develop deoxynivalenol-specific ELISA and TRF-immunoassays, which can detect deoxynivalenol and two of the most common metabolic isoforms in the range of 78-115 ng/mL.

Determination of deoxynivalenol and its major conjugates in cereals using an organic solvent-free extraction and IAC clean-up coupled in-line with HPLC-PCD-FLD

A method for the determination of deoxynivalenol (DON) and its major conjugates in cereals was developed including an immunoaffinity column (IAC) clean-up coupled in-line with high-performance liquid chromatography, post-column derivatisation and fluorescence detection. An IAC for DON with cross-reactivity to 15-AcDON, 3-AcDON and DON-3-G enabled this approach. The isolated analytes were introduced into the chromatographic system without aliquotation employing the hot water elution technique, resulting in the desired low LOQ values for monitoring these analytes in cereals. The absence of any organic solvent during sample preparation in combination with an in-line IAC clean-up renders the method simple, fast, and environmentally friendly. Special attention was paid to inherent IACs properties such as cross-reactivity, analytes' competition and capacity. The method was applied to determine DON and its major conjugates in barley, wheat and maize in the range of 10-1000 µg kg^-1 of DON, 10-300 µg kg^-1 of DON-3-G and 15-AcDON and 10-100 µg kg^-1 of 3-AcDON. The apparent recoveries varied from 87% to 110% (average of 98%) and the intermediate precision was below 13.5% RSD (except for DON-3-G in wheat). Fifteen maize, wheat and barley samples were analysed revealing levels of DON conjugates that accounted from 9% to 60% of the "total DON" content (m/m). In general, the frequency and the measured mass fractions decreased in the following order: DON>DON-3-G>15-AcDON>3-AcDON.

Fourier transform near-infrared and mid-infrared spectroscopy as efficient tools for rapid screening of deoxynivalenol contamination in wheat bran

BACKGROUND

Deoxynivalenol (DON) is the most common Fusarium mycotoxin occurring in wheat and wheat-derived products, with several adverse and toxic effects in animals and humans. Although bran fractions produced by milling wheat have numerous health benefits, cereal bran is the part of the grain with the highest concentration of DON, thus representing a risk for consumers. Increased efforts have been made to develop analytical methods suitable for rapid DON screening.

RESULTS

The applicability of Fourier transform near-infrared (FTNIR), or mid-infrared (FTMIR) spectroscopy, and their combination for rapid analysis of DON in wheat bran, was investigated for the classification of samples into compliant and non-compliant groups regarding the EU legal limit of 750 µg kg^-1 . Partial least squares-discriminant analysis (PLS-DA) and principal component-linear discriminant analysis (PC-LDA) were employed as classification techniques using a cutoff value of 400 µg kg^-1 DON to distinguish the two classes. Depending on the classification model, overall discrimination rates were from 87% to 91% for FTNIR and from 86% to 87% for the FTMIR spectral range. The FTNIR spectroscopy gave the highest overall classification rate of wheat bran samples, with no false compliant samples and 18% false noncompliant samples when the PC-LDA classification model was applied. The combination of the two spectral ranges did not provide a substantial improvement in classification results in comparison with FTNIR.

CONCLUSIONS

Fourier transform near-infrared spectroscopy in combination with classification models was an efficient tool to screen many DON-contaminated wheat bran samples and assess their compliance with EU regulations. © 2018 Society of Chemical Industry.

Rapid and sensitive double-label based immunochromatographic assay for zearalenone detection in cereals

A double-label immunochromatographic based assay (DL-ICA) was developed to monitor zearalenone (ZEN) levels in cereals, based on Eu³⁺ nanoparticles (EuNP). The DL-ICA exhibited excellent sensitivity, reliability and selectivity in real samples. It showed low limits of detection (0.21-0.25 μg/kg) and broad analytical ranges (up to 120 μg/kg). The total analytical time, including sample preparation and DL-ICA execution, was reduced by 15 min compared with HPLC. The recovery rates ranged from 95.0-118.4%, with relative standard deviations (RSD) <11.6%. Inter- and intra-day validations were assessed, recovery rates of 89.3-106.9% and RSD of 2.3-9.7% were obtained, suggesting considerable stability and reliability for the assay. An excellent correlation was observed between DL-ICA and a reference HPLC method (R² = 0.9899). Compared to current immunoassays, the current DL-ICA is inexpensive, highly sensitive, and rapid. Therefore, DL-ICA constitutes a novel tool for monitoring mycotoxins in food and feed to ensure safety.

Rapid prediction of deoxynivalenol contamination in wheat bran by MOS-based electronic nose and characterization of the relevant pattern of volatile compounds

BACKGROUND

Deoxynivalenol (DON) is a mycotoxin, mainly produced by Fusarium sp., most frequently occurring in cereals and cereal-based products. Wheat bran refers to the outer layers of the kernel, which has a high risk of damage due to chemical hazards, including mycotoxins. Rapid methods for DON detection in wheat bran are required.

RESULTS

A rapid screening method using an electronic nose (e-nose), based on metal oxide semiconductor sensors, has been developed to distinguish wheat bran samples with different levels of DON contamination. A total of 470 naturally contaminated wheat bran samples were analyzed by e-nose analysis. Wheat bran samples were divided in two contamination classes: class A ([DON] ≤ 400 µg kg^-1 , 225 samples) and class B ([DON] > 400 µg kg^-1 , 245 samples). Discriminant function analysis (DFA) classified wheat bran samples with good mean recognizability in terms of both calibration (92%) and validation (89%). A pattern of 17 volatile compounds of wheat bran samples that were associated (positively or negatively) with DON content was also characterized by HS-SPME/GC-MS.

CONCLUSIONS

These results indicate that the e-nose method could be a useful tool for high-throughput screening of DON-contaminated wheat bran samples for their classification as acceptable / rejectable at contamination levels close to the EU maximum limit for DON, reducing the number of samples to be analyzed with a confirmatory method. © 2018 Society of Chemical Industry.

Risk to human and animal health related to the presence of 4,15-diacetoxyscirpenol in food and feed

4,15‐Diacetoxyscirpenol (DAS) is a mycotoxin primarily produced by Fusarium fungi and occurring predominantly in cereal grains. As requested by the European Commission, the EFSA Panel on Contaminants in the Food Chain (CONTAM) assessed the risk of DAS to human and animal health related to its presence in food and feed. Very limited information was available on toxicity and on toxicokinetics in experimental and farm animals. Due to the limitations in the available data set, human acute and chronic health‐based guidance values (HBGV) were established based on data obtained in clinical trials of DAS as an anticancer agent (anguidine) after intravenous administration to cancer patients. The CONTAM Panel considered these data as informative for the hazard characterisation of DAS after oral exposure. The main adverse effects after acute and repeated exposure were emesis, with a no‐observed‐adverse‐effect level (NOAEL) of 32 μg DAS/kg body weight (bw), and haematotoxicity, with a NOAEL of 65 μg DAS/kg bw, respectively. An acute reference dose (ARfD) of 3.2 μg DAS/kg bw and a tolerable daily intake (TDI) of 0.65 μg DAS/kg bw were established. Based on over 15,000 occurrence data, the highest acute and chronic dietary exposures were estimated to be 0.8 and 0.49 μg DAS/kg bw per day, respectively, and were not of health concern for humans. The limited information for poultry, pigs and dogs indicated a low risk for these animals at the estimated DAS exposure levels under current feeding practices, with the possible exception of fattening chicken. Assuming similar or lower sensitivity than for poultry, the risk was considered overall low for other farm and companion animal species for which no toxicity data were available. In consideration of the similarities of several trichothecenes and the likelihood of co‐exposure via food and feed, it could be appropriate to perform a cumulative risk assessment for this group of substances.

A Review of Current Methods for Analysis of Mycotoxins in Herbal Medicines

The presence of mycotoxins in herbal medicines is an established problem throughout the entire world. The sensitive and accurate analysis of mycotoxin in complicated matrices (e.g., herbs) typically involves challenging sample pretreatment procedures and an efficient detection instrument. However, although numerous reviews have been published regarding the occurrence of mycotoxins in herbal medicines, few of them provided a detailed summary of related analytical methods for mycotoxin determination. This review focuses on analytical techniques including sampling, extraction, cleanup, and detection for mycotoxin determination in herbal medicines established within the past ten years. Dedicated sections of this article address the significant developments in sample preparation, and highlight the importance of this procedure in the analytical technology. This review also summarizes conventional chromatographic techniques for mycotoxin qualification or quantitation, as well as recent studies regarding the development and application of screening assays such as enzyme-linked immunosorbent assays, lateral flow immunoassays, aptamer-based lateral flow assays, and cytometric bead arrays. The present work provides a good insight regarding the advanced research that has been done and closes with an indication of future demand for the emerging technologies.

Updated Overview of Infrared Spectroscopy Methods for Detecting Mycotoxins on Cereals (Corn, Wheat, and Barley)

Each year, mycotoxins cause economic losses of several billion US dollars worldwide. Consequently, methods must be developed, for producers and cereal manufacturers, to detect these toxins and to comply with regulations. Chromatographic reference methods are time consuming and costly. Thus, alternative methods such as infrared spectroscopy are being increasingly developed to provide simple, rapid, and nondestructive methods to detect mycotoxins. This article reviews research conducted over the last eight years into the use of near-infrared and mid-infrared spectroscopy to monitor mycotoxins in corn, wheat, and barley. More specifically, we focus on the Fusarium species and on the main fusariotoxins of deoxynivalenol, zearalenone, and fumonisin B1 and B2. Quantification models are insufficiently precise to satisfy the legal requirements. Sorting models with cutoff levels are the most promising applications.

Effect of primary processing on the distribution of free and modified Fusarium mycotoxins in naturally contaminated oats

Oat (Avena sativa L.) ranks seventh in the world cereal production and is considered to be an important source for many valuable components of nutritional and biological importance, i.e. proteins, fats, carbohydrates, fibre, minerals and vitamins. Because of these properties the amount of oat used for human consumption has increased progressively during the last years. Unfortunately, the quality of this grain crop is often compromised by mycotoxin contamination, which is relatively ubiquitous despite efforts to control the problem. Therefore, it is important to investigate the distribution pattern of mycotoxins and their conjugated derivatives in contaminated oat grains. For this purpose we have developed a state-of-the-art multi-mycotoxin high-resolution mass spectrometry method and analysed oat samples for their content of the most important mycotoxins commonly occurring in Norwegian cereal grain. Quantitative mapping of selected Fusarium free and modified mycotoxins was performed in fractions collected during processing trials consisting of dehulling and sequential pearling. Both the derivative free mycotoxins and their metabolites were mainly present in the hulls compared to the oat kernel, thus dehulling resulted in a significant reduction of the total mycotoxin load, followed by some further reduction by pearling. Furthermore, free and modified mycotoxins were unevenly distributed in relation to each other throughout the grain fractions, showing a shift towards glucosidated forms, such as deoxynivalenol-3-glucoside and HT-2-3-glucoside in the oat kernel, which highlights potential food safety concerns associated with in planta modified mycotoxins.

Determination of T-2 and HT-2 Toxins in Oats and Oat-Based Breakfast Cereals by Liquid-Chromatography Tandem Mass Spectrometry

This protocol specifies an accurate and sensitive method for the determination of T-2 and HT-2 toxins content in oats and oat-based foods using liquid chromatography with tandem mass spectrometry detection. T-2 and HT-2 toxins are extracted from the test material with a mixture of acetonitrile and water. The filtered extract is dried, reconstituted with a mixture of methanol and water, then purified on a polymeric solid-phase extraction cartridge. Toxins are finally eluted from the column with methanol and quantified by reversed phase high performance liquid chromatography with tandem mass spectrometry detection.

Determination of type A trichothecenes in coix seed by magnetic solid-phase extraction based on magnetic multi-walled carbon nanotubes coupled with ultra-high performance liquid chromatography-tandem mass spectrometry

Magnetic solid-phase extraction (m-SPE) is a promising sample preparation approach due to its convenience, speed, and simplicity. For the first time, a rapid and reliable m-SPE approach using magnetic multi-walled carbon nanotubes (m-MWCNTs) as the adsorbent was proposed for purification of type A trichothecenes including T-2 toxins (T2), HT-2 toxins (HT-2), diacetoxyscirpenol (DAS), and neosolaniol (NEO) in coix seed. The m-MWCNTs were synthesized by assembling the magnetic nanoparticles (Fe3O4) with MWCNTs by sonication through an aggregation wrap mechanism, and characterized by transmission electron microscope. Several key parameters affecting the performance of the procedure were extensively investigated including extraction solutions, desorption solvents, and m-MWCNT amounts. Under the optimal sample preparation conditions followed by analysis with ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS), high sensitivity (limit of quantification in the range of 0.3-1.5 μg kg(-1)), good linearity (R (2) > 0.99), satisfactory recovery (73.6-90.6 %), and acceptable precision (≤2.5 %) were obtained. The analytical performance of the developed method has also been successfully evaluated in real coix seed samples. Graphical Abstract Flow chart of determination of type A trichothecenes in coix seed by magnetic solid-phase extraction coupled with ultra-high performance liquid chromatography-tandem mass spectrometry.

Critical evaluation of indirect methods for the determination of deoxynivalenol and its conjugated forms in cereals

A critical assessment of three previously published indirect methods based on acidic hydrolysis using superacids for the determination of “free” and “total” deoxynivalenol (DON) was carried out. The modified mycotoxins DON-3-glucoside (D3G), 3-acetyl-DON (3ADON), and 15-acetyl-DON (15ADON) were chosen as model analytes. The initial experiments focused on the stability/degradation of DON under hydrolytic conditions and the ability to release DON from the modified forms. Acidic conditions that were capable of cleaving D3G, 3ADON, and 15ADON to DON were not found, raising doubts over the efficacy of previously published indirect methods for total DON determination. Validation of these indirect methods for wheat, maize, and barley using UHPLC-MS/MS was performed in order to test the accuracy of the generated results. Validation data for DON, D3G, 3ADON, and 15ADON in nonhydrolyzed and hydrolyzed matrices were obtained. Under the tested conditions, DON was not released from D3G, 3ADON, or 15ADON after hydrolysis and thus none of the published methods were able to cleave the modified forms of DON. In addition to acids, alkaline hydrolysis with KOH for an extended time and at elevated temperatures was also tested. 3ADON and 15ADON were cleaved under the alkaline pH caused by the addition of KOH or aqueous K₂CO₃ to “neutralize” the acidic sample extracts in the published studies. The published additional DON increase after hydrolysis may have been caused by huge differences in matrix effects and the recovery of DON in nonhydrolyzed and hydrolyzed matrices as well as by the alkaline cleavage of 3ADON or 15ADON after the neutralization of hydrolyzed extracts.

Molecular imprinting science and technology: a survey of the literature for the years 2004-2011

Herein, we present a survey of the literature covering the development of molecular imprinting science and technology over the years 2004-2011. In total, 3779 references to the original papers, reviews, edited volumes and monographs from this period are included, along with recently identified uncited materials from prior to 2004, which were omitted in the first instalment of this series covering the years 1930-2003. In the presentation of the assembled references, a section presenting reviews and monographs covering the area is followed by sections describing fundamental aspects of molecular imprinting including the development of novel polymer formats. Thereafter, literature describing efforts to apply these polymeric materials to a range of application areas is presented. Current trends and areas of rapid development are discussed.

Rapid analysis of deoxynivalenol in durum wheat by FT-NIR spectroscopy

Fourier-transform-near infrared (FT-NIR) spectroscopy has been used to develop quantitative and classification models for the prediction of deoxynivalenol (DON) levels in durum wheat samples. Partial least-squares (PLS) regression analysis was used to determine DON in wheat samples in the range of <50–16,000 µg/kg DON. The model displayed a large root mean square error of prediction value (1,977 µg/kg) as compared to the EU maximum limit for DON in unprocessed durum wheat (i.e., 1,750 µg/kg), thus making the PLS approach unsuitable for quantitative prediction of DON in durum wheat. Linear discriminant analysis (LDA) was successfully used to differentiate wheat samples based on their DON content. A first approach used LDA to group wheat samples into three classes: A (DON ≤ 1,000 µg/kg), B (1,000 < DON ≤ 2,500 µg/kg), and C (DON > 2,500 µg/kg) (LDA I). A second approach was used to discriminate highly contaminated wheat samples based on three different cut-off limits, namely 1,000 (LDA II), 1,200 (LDA III) and 1,400 µg/kg DON (LDA IV). The overall classification and false compliant rates for the three models were 75%–90% and 3%–7%, respectively, with model LDA IV using a cut-off of 1,400 µg/kg fulfilling the requirement of the European official guidelines for screening methods. These findings confirmed the suitability of FT-NIR to screen a large number of wheat samples for DON contamination and to verify the compliance with EU regulation.

Cross-reactivity of antibodies with phenolic compounds in pistachios during quantification of ochratoxin A by commercial enzyme-linked immunosorbent assay kits

Ochratoxin A (OTA), a nephrotoxic mycotoxin, naturally occurs in wide range of agricultural commodities. Typical screening of OTA involves various enzyme-linked immunosorbent assay (ELISA) methods. Pistachio (Pistacia vera L.) is a rich source of phenolic compounds that may result in a false positive due to structural similarities to OTA. The present study investigated the cross-reactivity profiles of phenolic compounds using two commercial ELISA test kits. High-performance liquid chromatography was used to confirm the concentration of OTA in the pistachio samples and compared with the results obtained from ELISA. When the degree of interaction and 50 % inhibitory concentration of phenolic compounds were determined, the cross-reactivity showed a pattern similar to that observed with the commercial ELSIA kits, although quantitatively different. In addition, the degree of interaction increased with the increasing concentration of phenolic compounds. The ELISA value had stronger correlations with the content of total phenolic compound, gallic acid, and catechin (R(2) = 0.757, 0.732, and 0.729, respectively) compared with epicatechin (R(2) = 0.590). These results suggest that phenolic compounds in pistachio skins may cross-react with the OTA antibody and lead to a false positive or to an overestimation of OTA concentration in ELISA-based tests.

Determination of nivalenol in food and feed: an update

Based on the recent scientific opinion published by the EFSA CONTAM panel on the risks to human and animal health related to the presence of nivalenol in food and feed, this article provides an update on the determination of this Fusarium mycotoxin. After a brief introduction into the chemistry of nivalenol, chromatographic methods as well as other approaches are being discussed. Methods for the determination of nivalenol are well established and can be applied for the analysis of cereals, food, feed and biological samples. Accurate quantification of nivalenol is mostly carried out by liquid chromatography coupled with (multi-stage) mass spectrometry (MS) often within a multi-analyte approach. Some novel techniques, such as direct analysis in real time (DART) MS and electrochemical methods, have shown potential to determine nivalenol, but applications for routine measurements are not yet available. None of the currently available analytical methods has been formally validated in interlaboratory validation studies. While a certified calibrant for nivalenol is available, no matrix reference materials have been developed. Due to the scarcity of appropriate antibodies also no rapid immunochemical methods specific for nivalenol have become available.

Performance criteria for rapid screening methods to detect mycotoxins

The paper describes the validation of screening methods that are used for official control to classify samples into negative and suspect positive samples. The concept is based on the principle that negative samples are considered as compliant, whereas suspect positive samples need to be re-analysed with confirmatory methods. An important performance criterion often used is a maximum value of 5% for the probability of false negative results obtained on samples that contain the analyte at the legal limit. Since the result of analysis is a binary decision, specific validation schemes need to be applied. The paper places emphasis on practical aspects of the calculation of the method performance characteristics, which are required to check whether the methods fulfil the performance criterion. The paper shows that screening methods based on a visual inspection, e.g. a dipstick, require special data treatment. In contrast there are many methods where the classification into negative and suspect positive samples is based on the comparison of a measured response against a cut-off value. This type of methods can be validated with quantitative statistics. The paper also elaborates on the calculation of the rate of false positive results of compliant samples. In addition the impact on the economical aspect of the use of the screening method is estimated, taking into account external factors such as the cost ratio between the screening and the confirmatory method and the occurrence of non-compliant samples in the entire population of the samples.

Using commercial immunoassay kits for mycotoxins: ‘joys and sorrows’?

Rapid test methods are widely used for measuring mycotoxins in a variety of matrices. This review presents an overview of the current commercially available immunoassay rapid test formats. Enzyme linked immune-sorbent assay (ELISA), lateral flow tests, flow through immunoassay, fluorescent polarisation immunoassay, and immunoaffinity columns coupled with fluorometric assay are common formats in the current market. The two existing evaluation programs for commercial testing kits by United State Department of Agricultural Grain Inspection, Packers & Stockyards Administration (USDA-GIPSA) and AOAC Research Institute are introduced. The strengths and weaknesses of these test kits are discussed with regard to the application scope, variance, specificity and cross reactivity, accuracy and precision, and measurement range. Generally speaking, the current commercially available testing kits meet research and industrial needs as ‘fit-for-purpose’. Furthermore, quality assurance concerns and future perspectives are elaborated for broader application of commercial test kits in research, industry and regulatory applications. It is expected that new commercial kits based on advanced technologies such as electrochemical affinity biosensors, molecularly imprinted polymers, surface plasmon resonance, fluorescence resonance energy transfer, aptamer-based biosensors and dynamic light scattering might be available to users in the future. Meanwhile, harmonisation of testing kit evaluation, incorporation of more quality assurance into the testing kit utilisation scheme, and a larger variety of kits available at lower cost will expand the usage of testing kits for food safety testing worldwide.

Cross-reactivity of rapid immunochemical methods for mycotoxins detection towards metabolites and masked mycotoxins: the current state of knowledge

The cross-reactivity of antibodies employed within immunochemistry-based analytical methods may lead to overestimation of the results. Under certain conditions, specifically when controlling mycotoxin maximum limits serious problems can be encountered. Not only the structurally related mycotoxins, such as their masked (conjugated) forms, but also the unidentified matrix components are responsible for concentration overestimation of respective target analytes. The cross-reactivity phenomenon may also pose a risk of miss-interpretation of the proficiency tests results, when the assigned value becomes influenced by over-estimated results reported by users of immunochemical tests. In this paper, the current state of the knowledge on trueness problems associated with the rapid screening immunochemical methods have been reviewed. Special attention is focused on discussion of cross-reactivity in the ELISA tests, because this rapid test dominates the routine screening practice. However, the cross-reactions reported in lateral flow test strips, fluorescence polarisation immunoassay, or immunosensors have also been addressed.

Experimental design for in-house validation of a screening immunoassay kit. The case of a multiplex dipstick for Fusarium mycotoxins in cereals

The benefits of using rapid qualitative methods to verify compliance of food and feed with legislation requirements include user-friendly format, the possibility of detection without expensive instrumentation, rapid response and affordable price. Prior to their use, however, the methods have to pass validation experiments, in order to assess their performance profile. An experimental protocol for in-house validation of a screening immunoassay has been designed and applied to evaluate performance characteristics of a multiplex dipstick kit for the determination of major Fusarium toxins, namely zearalenone, T-2 and HT-2 toxins, deoxynivalenol and fumonisins in wheat and maize. The test is intended for screening of cereals on the presence/absence of these mycotoxins at maximum permitted levels established by European legislation or target levels. The response of the measurement is determined with a reader device. Samples classified as negative are considered as compliant, whereas positive samples need to be re-analysed with confirmatory methods. The in-house validation design consisted of three steps, namely (1) estimating the precision of the method including "between day" effects and influences from different varieties of the matrices, (2) establishing robust cutoff values for the dipstick response at target mycotoxin levels assuming an acceptable rate of false negative results of 5% and (3) assessment of the rate of false positive results of blank samples and samples containing the target analytes below the legal limits. The total precision expressed as relative standard deviation and determined individually for each analyte/concentration/matrix combination varied from 9 to 30% and was considered as acceptable. In 17 out of 28 cases, the repeatability standard deviation was the most important factor. The predominance of the repeatability compared to the other factors (matrix, days) was an indicator for the ruggedness of the assay. The validation study demonstrated that the test was able to differentiate blank samples from samples contaminated at target mycotoxin levels with a false positive rate lower than 6%. Considering realistic mycotoxin occurrence in European samples, significant economical benefits can be expected when using the test under real-world conditions.