Rapid pretreatment and detection of trace aflatoxin B1 in traditional soybean sauce

Rapid immunoassays for the detection of quinoxalines and their metabolites residues in animal-derived foods: A review

Quinoxalines are a class of veterinary drugs with antibacterial and growth-promoting functions. They are often widely used to treat and prevent animal diseases and are illegally used as animal growth promoters to increase economic benefits. Quinoxalines could be easily metabolized in animals to various residue markers and remain in animal-derived foods, which would pose a serious threat to human health. Consequently, it is necessary to detect the residues of quinoxalines and their metabolites. This article reviewed and evaluated immunoassays for quinoxalines and their metabolites in animal-derived foods, mainly including enzyme-linked immunosorbent assays, fluorescence immunosorbent assays, immunochromatography, and surface plasmon resonance biosensors. In addition, we deeply explored the design of haptens for quinoxalines and their metabolites and analyzed the effect of haptens on antibody performance. This paper aims to provide guidance and references for their accurate and sensitive detection, thereby ensuring food safety and human public health.

Mycotoxins in soybean-based foods fermented with filamentous fungi: Occurrence and preventive strategies

Fermented soybean products are widely consumed worldwide, and their popularity is increasing. Filamentous fungi, such as Actinomucor, Aspergillus, Monascus, Mucor, Penicillium, Rhizopus, and Zymomonas, play critical roles in the fermentation processes of many soybean foods. However, besides producing essential enzymes for food fermentation, filamentous fungi can release undesirable or even toxic metabolites into the food. Mycotoxins are toxic secondary metabolites produced by certain filamentous fungi and may be detected during the food production process. Without effective prevention strategies, mycotoxin contamination in fermented soybean products poses a risk to human health. This review focused on the changes in mycotoxigenic fungal abundance and mycotoxin contamination at different stages during the production of soybean-based fermented foods, as well as effective strategies for preventing mycotoxin contamination in such products. Data from relevant studies demonstrated a tendency of change in the genera of mycotoxigenic fungi and types of mycotoxins (aflatoxins, alternariol, alternariol monomethyl ether, deoxynivalenol, fumonisins, ochratoxin A, rhizoxins, T-2 toxin, and zearalenone) present in the raw materials and the middle and final products. The applicability of traditional chemical and physical mitigation strategies and novel eco-friendly biocontrol approaches to prevent mycotoxin contamination in soybean-based fermented foods were discussed. The present review highlights the risks of mycotoxin contamination during the production of fermented soybean products and recommends promising strategies for eliminating mycotoxin contamination risk in soybean-based fermented foods.

Advances in magnetic nanoparticles for the separation of foodborne pathogens: Recognition, separation strategy, and application

Foodborne pathogens contamination is one of the main sources of food safety problems. Although the existing detection methods have been developed for a long time, the complexity of food samples is still the main factor affecting the detection time and sensitivity, and the rapid separation and enrichment of pathogens is still an objective to be studied. Magnetic separation strategy based on magnetic nanoparticles (MNPs) is considered to be an effective tool for rapid separation and enrichment of foodborne pathogens in food. Therefore, this study comprehensively reviews the development of MNPs in the separation of foodborne pathogens over the past decade. First, various biorecognition reagents for identification of foodborne pathogens and their modifications on the surface of MNPs are introduced. Then, the factors affecting the separation of foodborne pathogens, including the size of MNPs, modification methods, separation strategies and separation forms are discussed. Finally, the application of MNPs in integrated detection methods is reviewed. Moreover, current challenges and prospects of MNPs for the analysis of foodborne pathogens are discussed. Further research should focus on the design of multifunctional MNPs, the processing of large-scale samples, the simultaneous analysis of multiple targets, and the development of all-in-one small analytical device with separation and detection.

A Rapid and Sensitive Fluorescent Microsphere-Based Lateral Flow Immunoassay for Determination of Aflatoxin B1 in Distillers' Grains

Aflatoxin B1 (AFB1) is a toxic compound naturally produced by the genera Aspergillus. Distillers' grains can be used as animal feed since they have high content of crude protein and other nutrients. However, they are easily contaminated by mycotoxins, and currently there are no rapid detection methods for AFB1 in distillers' grains. In this study, a lateral flow immunoassay (LFIA) based on red fluorescent microsphere (FM), is developed for quantitative detection of AFB1 in distillers' grains. The whole test can be completed within 15 min, with the cut-off value being 25.0 μg/kg, and the quantitative limit of detection (qLOD) being 3.4 μg/kg. This method represents satisfactory recoveries of 95.2-113.0%, and the coefficients of variation (CVs) are less than 7.0%. Furthermore, this technique is successfully used to analyze AFB1 in real samples, and the results indicates good consistency with that of high-performance liquid chromatography (HPLC). The correlation coefficient is found to be greater than 0.99. The proposed test strip facilitates on-site, cost-effective, and sensitive monitoring of AFB1 in distillers' grains.

Determination of 3-Methyl-quinoxaline-2-carboxylic Acid and Quinoxaline-2-carboxylic Acid in Pork Based on a Background Fluorescence Quenching Immunochromatographic Assay

A novel rapid method based on a background fluorescence quenching immunochromatographic assay (bFQICA) was established to achieve simultaneously the quantitative detection of 3-methyl-quinoxaline-2-carboxylic acid (MQCA) and quinoxaline-2-carboxylic acid (QCA), which were efficiently extracted and enriched 4 times using immunomagnetic beads from pork. The analysis of field pork samples by bFQICA was in accordance with that of LC-MS/MS; especially, the proposed bFQICA exhibited great advantages in convenience and efficiency, which only takes 30 min for the detection of MQCA and QCA.

Predominant Mycotoxins, Pathogenesis, Control Measures, and Detection Methods in Fermented Pastes

Fermented pastes are some of the most popular traditional products in China. Many studies reported a strong possibility that fermented pastes promote exposure to mycotoxins, including aflatoxins, ochratoxins, and cereulide, which were proven to be carcinogenic and neurotoxic to humans. The primary mechanism of pathogenicity is by inhibiting protein synthesis and inducing oxidative stress using cytochrome P450 (CYP) enzymes. The level of mycotoxin production is dependent on the pre-harvest or post-harvest stage. It is possible to implement methods to control mycotoxins by using appropriate antagonistic microorganisms, such as Aspergillus niger, Lactobacillus plantarum, and Saccharomyces cerevisiae isolated from ordinary foods. Also, drying products as soon as possible to avoid condensation or moisture absorption in order to reduce the water activity to lower than 0.82 during storage is also effective. Furthermore, organic acid treatment during the soaking process reduces toxins by more than 90%. Some novel detection technologies based on magnetic adsorption, aptamer probes, and molecular-based methods were applied to rapidly and accurately detect mycotoxins in fermented pastes.

An Automated and High-Throughput Immunoaffinity Magnetic Bead-Based Sample Clean-Up Platform for the Determination of Aflatoxins in Grains and Oils Using UPLC-FLD

Sample clean-up remains the most time-consuming and error-prone step in the whole analytical procedure for aflatoxins (AFTs) analysis. Herein, an automated and high-throughput sample clean-up platform was developed with a disposable, cost-effective immunoaffinity magnetic bead-based kit. Under optimized conditions, the automated method takes less than 30 min to simultaneously purify 20 samples without requiring any centrifugation or filtering steps. When coupled to ultra-high performance liquid chromatography with fluorescence detection, this new analysis method displays excellent accuracy and precision as well as outstanding efficiency. Furthermore, an interlaboratory study was performed in six laboratories to validate the novel protocol. Mean recovery, repeatability, reproducibility, and Horwitz ratio values were within 91.9%–107.4%, 2.5%–7.4%, 2.7%–10.6%, and 0.26%–0.90, respectively. Results demonstrate that the developed sample clean-up platform is a reliable alternative to most widely adopted clean-up procedures for AFTs in cereals and oils.

Toxins in Fermented Foods: Prevalence and Preventions-A Mini Review

Fermented foods (FF) are widely consumed around the world, and FF are one of the prime sources of toxins and pathogenic microbes that are associated with several foodborne outbreaks. Mycotoxins (aflatoxins, fumonisins, sterigmatocystin, nivalenol, deoxynivalenol, zearalenone, ochratoxin, and alternariol), bacterial toxins (shiga toxin and botulinum), biogenic amines, and cyanogenic glycosides are the common toxins found in FF in addition to the pathogenic microbes. Fermented milk products and meat sausages are extremely vulnerable to contamination. Cumulative updated information about a specific topic such as toxins in FF is essential for the improvement of safer preparation and consumption of fermented foods. Accordingly, the current manuscript summarizes the reported mycotoxins, bacterial toxins, and/or toxins from other sources; detection methods and prevention of toxins in FF (use of specific starter culture, optimized fermentation process, and pre- and post-processing treatments); and major clinical outbreaks. This literature survey was made in Scopus, Web of Science, NCBI-PubMed, and Google Scholar using the search terms "Toxins" and "Fermented Foods" as keywords. The appropriate scientific documents were screened for relevant information and they were selected without any chronological restrictions.

Design of Multifunctional Nanostructure for Ultrafast Extraction and Purification of Aflatoxins in Foodstuffs

Aflatoxins (AFs) are a class of carcinogens, associated with liver cancers, that exist in foodstuffs. There are extremely low maximum limits of AFs in foodstuffs (0.025-20 μg·kg^-1). Quick and sensitive detection of such low concentration of AFs in foodstuffs is dominated by the efficiency and selectivity of the AF enrichment process, which is extremely challenging although substantial efforts have been made in recent decades. Here we design and synthesize a multilayer nanoarchitecture composed of a broad-spectrum aflatoxin monoclonal antibody shell, chitosan middle layer, and magnetic bead core (denoted AF-mAb/CTS/Fe₃O₄). The efficiency of AF-mAb/CTS/Fe₃O₄ in extracting AFs has been found to be more than 60 times higher than both conventional immunoaffinity chromatography and solid-phase extraction. Furthermore, the nanocomposite displays excellent selectivity and good reusability as well as outstanding efficiency. When coupled to ultraperformance liquid chromatography-tandem quadrupole mass spectrometry, this new nanoarchitecture enables us to probe six AFs at concentrations as low as 0.003 μg·kg^-1 in foodstuffs with free matrix effects, which is nearly 10 times smaller than the regulated maximum tolerated does. It is believed that the new nanoarchitecture will provide an efficient and fast pathway to detect AFs in foodstuffs to protect human being from some critical liver cancers.

A sensitive and validated immunomagnetic-bead based enzyme-linked immunosorbent assay for analyzing total T-2 (free and modified) toxins in shrimp tissues

Accurate analyses of total T-2 (free and modified) in aquatic organisms including shrimp are important as the hazard caused by T-2 has been caught increasing attention. Therefore, acurate analysis of free T-2 especially of modified T-2 in shrimp tissues is important. A rapid, sensitive, and validated method for quantitative determination of free T-2 and modified T-2 toxin was developed using immunomagnetic-bead based enzyme-linked immunosorbent assay (IMB-ELISA). Super paramagnetic particles with a carboxyl group activated by an ester method coupled with envelope antigen 3- acetylneosolaniol- hemisuccinate - ovalbumin (3-Ac-NEOS-HS-OVA) was used to form immunomagnetic beads which could bind to T-2 skeletal structure antibodies. The conditions for magnetic bead coating of T-2 skeletal structure antibodies, and the concentrations of the polyclonal antibody and HRP-labeled goat anti-rabbit antibody were optimized. A good linear relationship with T-2 concentrations ranging from 5-75ng/mL (R² =0.9965) was observed. The detection limit of different shrimp tissues of the IMB-ELISA ranged from 2.53 to 3.20ng/mL. And the IC₅₀ was 63ng/mL. The recovery varied from 86% to 99% with a standard deviation of 2.8-5.8%. The application of this method to study the distribution in tissues showed that the total T-2 concentration in hepatopancreas was 26.7µg/kg > blood > head > muscle in the highest dose group of 12.2mg/kg. Our research showed a combination of ELISA and immunomagnetic bead technology provide a new, convenient approach to significantly improve the accuracy and sensitivity of total T-2 measurement in shrimp tissues.

Time-Resolved Fluorescent Immunochromatography of Aflatoxin B1 in Soybean Sauce: A Rapid and Sensitive Quantitative Analysis

Rapid and quantitative sensing of aflatoxin B1 with high sensitivity and specificity has drawn increased attention of studies investigating soybean sauce. A sensitive and rapid quantitative immunochromatographic sensing method was developed for the detection of aflatoxin B1 based on time-resolved fluorescence. It combines the advantages of time-resolved fluorescent sensing and immunochromatography. The dynamic range of a competitive and portable immunoassay was 0.3-10.0 µg·kg(-1), with a limit of detection (LOD) of 0.1 µg·kg(-1) and recoveries of 87.2%-114.3%, within 10 min. The results showed good correlation (R² > 0.99) between time-resolved fluorescent immunochromatographic strip test and high performance liquid chromatography (HPLC). Soybean sauce samples analyzed using time-resolved fluorescent immunochromatographic strip test revealed that 64.2% of samples contained aflatoxin B1 at levels ranging from 0.31 to 12.5 µg·kg(-1). The strip test is a rapid, sensitive, quantitative, and cost-effective on-site screening technique in food safety analysis.

Novel analytical procedure using a combination of hollow fiber supported liquid membrane and dispersive liquid-liquid microextraction for the determination of aflatoxins in soybean juice by high performance liquid chromatography - Fluorescence detector

This study describes a combination between hollow fiber membrane and dispersive liquid-liquid microextraction for determination of aflatoxins in soybean juice by HPLC. The main advantage of this approach is the use of non-chlorinated solvent and small amounts of organic solvents. The optimum extraction conditions were 1-octanol as immobilized solvent; toluene and acetone at 1:5 ratio as extraction and disperser solvents (100 μL), NaCl at 2% of the sample volume and extraction time of 60 min. The optimal condition for the liquid desorption was 150 μL acetonitrile:water (50:50 v/v) and desorption time of 20 min. The linear range varied from 0.03 to 21 μg L(-1), with R(2) coefficients ranging from 0.9940 to 0.9995. The limits of detection and quantification ranged from 0.01 μg L(-1) to 0.03 μg L(-1) and from 0.03 μg L(-1) to 0.1 μg L(-1), respectively. Recovery tests ranged from 72% to 117% and accuracy between 12% and 18%.

Quality evaluation of five commercial enzyme linked immunosorbent assay kits for detecting aflatoxin b1 in feedstuffs

The objective of this study was to evaluate the quality of five commercial enzyme linked immunosorbent assay (ELISA) kits (A, B, C, D, and E) from different suppliers for detecting aflatoxin B₁ (AFB₁). AFB₁-free corn samples supplemented with different levels of AFB₁ (5, 10, and 20 μg/kg) were used as positive controls and 6 replicates of each control sample were tested to evaluate the accuracy and precision of these kits. In addition, we also evaluated the performance of these ELISA kits for AFB₁ in 30 feed samples, including corn, distillers dried grains with soluble, wheat samples, soybean meal, and poultry feed, which were verified by high performance liquid chromatography. Results showed that the coefficients of variation ranged from 1.18% to 16.22% in intra-plate and 2.85% to 18.04% in inter-plate for the determination of AFB₁. The half maximal inhibitory concentration for five kits ranged from 3.72 to 7.22 μg/kg. The quantitation limits of AFB₁ were all under the legal limit in China but somewhat inconsistent with kit instructions. Although the recovery rate of four of the five kits were either less than 90% or more than 110%, all these values were acceptable in practice. Two kits had high false positive rates (C and E). In conclusion, our results revealed that the qualities of five tested ELISA kits were significantly different.

Recent mycotoxin survey data and advanced mycotoxin detection techniques reported from China: a review

Mycotoxin contamination in agro-food systems has been a serious concern over the last few decades in China, where the Ministry of Health has set maximum limits for mycotoxins in different agro-products. Overall survey data show that aflatoxin contamination in infant cereals, edible oils, raw milk, ginger and its related products are far below Chinese regulatory limits. The absence of aflatoxin M1 contamination in infant milk powders indicates a high standard of control. Aflatoxins in liquorice roots and lotus seeds have been reported for the first time. For deoxynivalenol, high levels were found in wheat grown in the Yangtze Delta region, which is more prone to rainfall, supporting Fusarium infection. The emerging mycotoxins beauvericins and enniatins have been reported in the medicinal herbs in China. Ochratoxin A in wine was below the European Union regulatory limits, but fumonisins in maize need to be monitored and future regulatory control considered. Overall from all the survey data analysed in this review, it can be concluded that 92% of the samples analysed had mycotoxin levels below the Chinese regulatory limits. In terms of detection techniques in recent years, immuno-based assays have been developed largely due to their excellent sensitivity and ease of use. Assays targeting multiple mycotoxins like aflatoxins, ochratoxin A, zearalenone and deoxynivalenol have been reported using microarrays and suspension arrays targeting in particular maize, rice and peanuts. Aptamer-based assays against ochratoxin A and aflatoxins B1 and B2 have been developed involving fluorescence detection; and surface plasmon resonance immunosensors have been developed targeting wine, maize, wheat, wild rye, hay and peanut oil with high sensitivity (> 0.025 ng l(-1)). Commercialisation of these technologies is much needed for wider usage in the coming years.

A review of biosensing techniques for detection of trace carcinogen contamination in food products

Carcinogen contaminations in the food chain, for example heavy metal ions, pesticides, acrylamide, and mycotoxins, have caused serious health problems. A major objective of food-safety research is the identification and prevention of exposure to these carcinogens, because of their impossible-to-reverse tumorigenic effects. However, carcinogen detection is difficult because of their trace-level presence in food. Thus, reliable and accurate separation and determination methods are essential to protect food safety and human health. This paper summarizes the state of the art in separation and determination methods for analyzing carcinogen contamination, especially the advances in biosensing methods. Furthermore, the application of promising technology including nanomaterials, imprinted polymers, and microdevices is detailed. Challenges and perspectives are also discussed.

Magnetic beads carrying poly(acrylic acid) brushes as “nanobody containers” for immunoaffinity purification of aflatoxin B1 from corn samples

Magnetic beads with poly(acrylic acid) brushes as “nanobody containers” for aflatoxin B₁ immunoaffinity purification.