Peanut Samples Research Articles

Isolation and Characterization Identification of Edophytic Nitrogen-Fixing Bacteria from Peanut Nodules.

This work was carried out to isolate and perform molecular identification and selection of endophytic nitrogen-fixing bacteria (ENFB) to be utilized as biofertilizer. In this research, nodulous samples of peanuts were collected from inside dyke areas, namely, Phuoc Hung of An Phu, An Giang, Vietnam. Ten colonies were isolated from nutrient agar plates containing YMA's medium. All isolates were rod shaped, Gram negative, and no spore creation. Biochemical tests indicated that they were obligate aerobes, catalase, oxidase, urea hydrolysis, well motile ability, and no nitrate reduction. The salt tolerance observed that most survived at 0.5% and 2% salinity (except Enterobacter cloacae subsp. dissolvens strain LMG 2683), while at 4%, only 3 isolates (Bacillus aryabhattai strain CM44, Enterobacter asburiae strain IIWM-JS-07L, and Bacillus songklensis strain KCa6) and at 5% only, 2 isolates survived, namely, Enterobacter asburiae strain IIWM-JS-07L and Bacillus songklensis strain KCa6. The result showed that most of ten ENFB strains could adapt to the range of 25°C and 45°C (except Enterobacter cloacae subsp. dissolvens strain LMG 2683 and Enterobacter mori strain cjy13 at 25°C). Out of ten isolates, three were finally selected for the next studies, which potentially have N-fixing ability and are utilized as biofertilizer in agricultural cultivation.

A DNA tetrahedral scaffolds-based electrochemical biosensor for simultaneous detection of AFB1 and OTA

Herein, a bifunctional electrochemical biosensor based on the DNA tetrahedral scaffolds (TDNs) was proposed, OTA@TDNs and AFB1@TDNs were adopted for electrochemical signal output in response to OTA and AFB1 concentration, simultaneously. In order to increase the conductivity of the biosensor, highly porous gold (HPG) was loaded on electrode surface by pulse electrodeposition. Under optimal conditions, the PFc displayed a linear range with AFB1 concentration between 0.05 ∼ 360 ng·mL−1 with the LOD of 3.5 pg·mL−1. And the PMB selective and sensitive responses to OTA are achieved with a linear range of 0.05 ∼ 420 ng·mL−1 and a LOD of 2.4 pg·mL−1. This biosensor has high sensitivity, selectivity and stability for OTA and AFB1 detection in peanut samples. The approach streamlines the experimental procedure, leading to significantly improve the detection efficiency of mycotoxins. Collectively, this method suggest a novel approach for the detection and monitoring of OTA and AFB1 in food sample.

Evaluation of the Level of Aflatoxins in Raw Peanuts and Reduction Levels of Aflatoxins in Peanuts through Nixtamalization (Lime Treatment) and Calcium Enrichment

Nixtamalization has been widely used as a method of reducing aflatoxin contamination in peanuts as well as in calcium enrichment. The aim of this study is to investigate the effects of nixtamalization on aflatoxin and nutrient content in peanuts among wholesalers and retailers at Nyamakima Market in Nairobi, Kenya. A representative sample was drawn from a population of 70 market vendors using a systematic random sampling technique, resulting in 35 raw peanut samples for analysis via ELISA to determine initial aflatoxin levels. These samples were then subjected to nixtamalization treatments of 4, 8, and 16 minutes. The findings revealed that the average concentration of total aflatoxins in peanuts initially exceeded the accepted safety limit, with 71% of the samples failing to meet the standards. However, nixtamalization led to a substantial reduction in aflatoxin levels by 49%, 48%, and 50% after treatment durations of 4, 8, and 16 minutes, respectively. Statistical analysis, including ANOVA and Two-sample T-tests, confirmed significant distinctions between initial and final mean aflatoxin levels post-treatment, as well as variations between treatments. The study also observed a significant variation in calcium levels between the different time treatments, supported by linear regression analysis, which demonstrated a robust correlation between time treatments and calcium levels (R2=0.83, P=0.011). Furthermore, the analysis revealed significant differences in mean moisture contents across various treatments (P=0.000), and a linear relationship between mean moisture content and exposure time (P=0.02). The results emphasize the positive impact of nixtamalization in reducing aflatoxin levels and enhancing calcium content in peanuts. However, it is crucial to note the negative effect on moisture content, which exceeded stipulated limits, potentially raising concerns about product safety and quality.

Sensory and Oxidative Stability of Roasted Peanuts Coated with Arabic Gum and A Synthetic Antioxidant During Storage

The impact of coating formulations containing Arabic gum (AG) and Arabic gum with 100 ppm BHT on the oxidative stability and sensory attributes of roasted peanuts during a 120-day storage period at room temperature (RT) was investigated and compared to roasted, uncoated peanuts (control). The oxidative stability of raw peanuts (P), roasted peanuts (RP), roasted and coated peanuts with Arabic gum (RCP-AG), and roasted and coated peanuts with Arabic gum and 100 ppm BHT (RCP-AG-BHT) was determined based on parameters such as free fatty acids percentage (FFA%), peroxide value (PV), p-Anisidine value (pAV), Totox value (TV), and sensory properties at intervals of 0, 30, 60, and 120 days.The estimated coating percentage (CP %) for all treatments is about 2.5% and the yield of oil from hydraulic pressed peanuts kernels and treatments were ranged from 35.6 to 47.1%. Nine fatty acids were identified from raw and roasted peanuts oil and characterized by large percentage of unsaturated fatty acids (USFAs) (82.1 %) with large proportion of oleic acid (49.45%) and linoleic acid (31.92%), while saturated fatty acids were 17.9%, with large proportion of palmitic acid (11.36%) followed by stearic acid (3.48%) in RP. The FFA (%) of extracted raw peanuts oil was 0.68%, this percentage was increased after roasting significantly (p< 0.05) in all treatments and control, but it didn't increase during storage period. An increase in PV values of roasted and treated samples were noticed throughout the storage time. After 4 months of storage, the maximum value of PV was (75.1 meq/kg) recorded by the roasted sample (RP), whereas the minimum value was (43.9 meq/kg) recorded by (RCP-AG- BHT). pAV increased significantly after roasting and during storage time in all peanuts samples. However, RP-AG-BHT showed no significant differences in pAV after one month of storage. An increase in TV values of roasted and treated samples were noticed throughout the storage time, while the TV for RP-AG and RP-AG-BHT where less when compared with the control (RP). There were no significant differences (P < 0.05) in the color, hardness and crunchiness between control and treatments after 2 months of storage. However, Glossiness, rancidity and off-flavor were significantly affected.

Analysis of roasted peanuts based on GC-MS combined with GC-IMS.

The present study used gas chromatography-mass spectrometry (GC-MS) and gas chromatography-ion mobility spectrometry (GC-IMS) to separate and identify the characteristic volatile flavor substances in 30 roasted peanut samples. GC-MS identified 59 volatile compounds, and GC-IMS detected 61 volatile flavor substances. The 30 peanut varieties were then divided into four groups on the basis of their volatile flavor substances using principal component analysis (PCA), and a fingerprint profile of the varieties' volatile characteristics was established from information peaks identified in the spectra. Descriptive sensory analysis (DSA) was performed to distinguish differences in flavor attributes between roasted peanut varieties. Partial least squares regression (PLSR) was performed with the volatile flavor content of roasted peanuts as the independent variable and the flavor attribute score as the dependent variable. These findings provide a basis for predicting the appeal of roasted peanuts based on their composition and demonstrate a potential avenue for improving food flavor quality.

A toluidine blue/porous organic polymer/2D MoSe2 nanocomposite as an electrochemical signaling platform for a sensitive label-free aflatoxin B1 bioassay in some crops

A label-free electrochemical immunosensor using a toluidine blue (TB)/porous organic polymer (POP)/two-dimensional molybdenum diselenide (2D MoSe2) nanocomposite is developed for highly sensitive detection of aflatoxin B1 (AFB1) in selected crops. A POP/2D MoSe2 composite material is employed to modify the surface of a screen-printed carbon electrode (SPCE). Subsequently, TB is adsorbed on the modified SPCE surface, and the resulting TB/POP/2D MoSe2 composite is then used to construct a biosensor. The new POP/2D MoSe2 nanocomposite offers a high surface-to-volume area and is a good electroactive and biocompatible adsorbent for loading TB probe and capture antibodies. Adsorbed TB onto the POP/2D MoSe2 nanocomposite is utilized as a redox probe for the signal amplification unit. This TB/POP/2D MoSe2 nanocomposite provides good electron transfer properties of TB redox probe, good electrical conductivity, good biocompatibility, and likable adsorption ability, thus obtaining a sufficient immobilization quantity of antibodies for the sensor construction. After immobilization of the anti-AFB1 antibody and blocking with BSA on the composite surface, the immunosensor is obtained for the detection of AFB1. Under optimum conditions, the sensor shows a linear logarithmic range of 2.5–40 ng mL−1 with a limit of detection (LOD) of 0.40 ng mL−1. The developed sensor provides several advantages in terms of simplicity, low cost, short analysis time, high selectivity, stability, and reproducibility. Additionally, the proposed immunosensor is successfully validated by the detection of AFB1 in rice, corn, and peanut samples. Utilizing the TB/POP/2D MoSe2 nanocomposite, this label-free electrochemical immunosensor demonstrates outstanding sensitivity and selectivity in detecting AFB1, making it a valuable tool for ensuring the safety of agricultural products and enhancing food security.

Micobiota de frutos secos provenientes de diferentes regiones de México

Background: Tree nuts and dried fruits are very profitable products, highly vulnerable to contamination and subsequent deterioration by molds such as Penicillium spp., Aspergillus spp. and Rhizopus spp. In Mexico, microbial contamination of nuts and dried fruits, particularly of the product sold for bulk consumption, which also has a lax regulation. Objectives: To study the fungal contamination status of peanuts, pecans, pumpkin seeds and walnuts from different regions of the country. Methods: The moisture content and water activity of 111 samples of peanuts (36), pecans (30), walnuts (12) and pumpkin seeds (33) were measured. Additionally, the different species of molds present in the samples were isolated and identified. Results and conclusions: Only some samples, mainly pumpkin seed, were found with mold and yeast contents above what is allowed by Mexican regulations. However, many samples were contaminated with toxigenic mold species, such as Aspergillus flavus, Penicillium spp. and Fusarium spp., as well as other deteriorating molds. Although contamination levels do not seem to be cause for alarm, the sale of nuts in bulk should be monitored and regulated, as there is a potential risk to the consumer if storage conditions are not adequate.

Quantification of Aflatoxin B1 by thin layer chromatography in present peanut samples contaminated by Aspergillus flavus commercialized in Brazil

The quantification of aflatoxin B1 was performed in (CCD) samples of peanut grains positive in culture media for Aspergillus flavus fungi from the city of São José dos Campos - SP; Brazil, comparing the results with the reference values of aflatoxin B1 allowed by ANVISA legislation. According to previous research, we obtained 4 positive samples in culture medium for Aspergillus flavus fungi, where these samples for this study were ground and then performed the following 4 steps of (Extraction, Extract Purification, Liquid Extraction and Thin Layer Chromatography) - Eluted with 5 ml of chloroform, polar substance capable of diluting the aflatoxin B1 being polar substances, after that they were revealed the silica plates in UV light - 366 nm where it was determined the values of Rf (Retention Factor) give each sample, then the results were applied in the formula of quantification of aflatoxin B1. We obtained positive results for 1 sample of the 4 with presence of A. flavus in the culture medium of peanut grains, but only in sample 11 we obtained the presence of aflatoxin B1 in high quantity with about 25.5 µg/kg, It concludes that the contaminated sample is above the ANVISA reference values, causing great pathological and neoplastic impact to the health of human beings, affirming that still there was limitrophic presence of aflatoxin B1 in sample 10, causing serious pathological and neoplastic problems, attributing that this present study and research stimulates and gives the basis of stimuli for unedited creation of anti-aflatoxin B1 serums.

A triple-signal strategy separated aptasensor for sensitive determination of aflatoxin B1 in peanut based on electrochemical and fluorescent dual-mode

It is necessary to develop accurate and sensitive AFB1 detection method due to its high toxicity of pathogenicity and carcinogenicity. The results of traditional single-mode AFB1 detection methods are easily affected by the test environment and human operation. Herein, an electrochemical and fluorescent dual-mode separated aptasensor was developed for detecting AFB1 with triple-signal readout. The AFB1 aptasensor was constructed by combining the Fc-labeled AFB1 aptamer with its complementary DNA (cDNA). Subsequently, the methylene blue (MB) was incorporated into dsDNA as another signal tag. In the presence of AFB1, the Fc tag approached to electrode surface, both of the cDNA and MB molecule released due to the interaction between AFB1 and its aptamer, resulting in “signal-on” and “signal-off” dual-signal strategy. There was a good linear relationship between the SWV electrochemical response signal and the logarithm of AFB1 concentration at 0.01–200 ng/mL (LOD 2.5 pg/mL, S/N = 3). Meanwhile, the released cDNA was designed to trigger hybridization chain reaction (HCR), and the HCR product was served as template for the formation of fluorescent copper nanoparticles (CuNPs). There was a good linear relationship between the fluorescent intensity of CuNPs and the logarithm of AFB1 concentration at 0.001–200 ng/mL (LOD 0.28 pg/mL, S/N = 3). The separated fluorescent method showed broadened linear range and lower LOD compared with SWV method, both up to 10-folds, which improved the detection sensitivity. The constructed dual-mode AFB1 aptasensor showed satisfactory selectivity, stability and reproducibility, and the good recoveries of real peanut samples indicated its practical application in food detection.

Target-Induced Electrochemical Sensor Based on Foldable Aptamer and MoS2@MWCNTs-PEI for Enhanced Detection of AFB1 in Peanuts.

Herein, a sensitive and selective electrochemical sensor based on aptamer folding was constructed to detect aflatoxin B1 (AFB1) in peanuts. Specifically, polyethylenimine-functionalized multiwalled carbon nanotubes modified with molybdenum disulfide (MoS2@MWCNTs-PEI) were used as the electrode matrix to enable a large specific surface area, which were characterized by the Randles-Sevcik equation. Additionally, AuNPs were used to immobilize the aptamer via the Au-S covalent bond and provide a favorable microenvironment for signal enhancement. Methylene blue (MB) was modified at the proximal 3' termini of the aptamer as the capture probe, while the signal transduction of the sensor was obtained through changes in conformation and position of MB induced by the binding between AFB1 and the probe. Changes in spatial conformation could be recorded by electrochemical methods more readily. This electrochemical aptasensor demonstrated remarkable sensitivity to AFB1 with an extensive detection range (1 pg/mL to 100 ng/mL) and a lower limit detection (1.0 × 10-3 ng/mL). Moreover, using the constructed aptasensor, AFB1 was identified successfully in peanut samples, with recoveries ranging from 95.83 to 107.53%, illustrating its potential use in determining AFB1 in food.

A novel ternary Y-DNA walker amplification strategy designed fluorescence aptasensor based on Au@SiO2@Fe3O4 nanomaterials for ochratoxin A detection.

Anovel ternary Y-DNA walker amplification strategy designed fluorescence aptasensor based on Au@SiO2@Fe3O4 nanomaterials for ultrasensitive and specific ochratoxin A detection in food samplesis presented. Au@SiO2@Fe3O4 nanomaterials provide the loading platform as well as separation and recovery properties for the ternary Y-DNA walker. The ternary Y-DNA walker is designed to be driven by Nb.BbvCI cleavinga large number of FAM probes to achieve signal amplification. SinceOchratoxin A (OTA) can bind to the constituent aptamer in the ternary Y-DNA walker, adding OTA will destroy the structure of the ternary Y-DNA walker, thereby inhibiting the driving process of the walker. After optimization of various parameters, a standard curve was obtained from 100 to 0.05ng·mL-1 of OTA with the limit of determination of0.027ng·mL-1. The spiked recovery of peanut samples by this method was 82.00-93.30%, and the aptasensorshowed excellent specificity and long-term stability. This simple, robust, and scalable oligonucleotide chain-based ternary Y-DNA walker can provide a general signal amplification strategy for trace analysis.

Profiling seventeen cultivars of roasted peanuts by descriptive sensory and flavor volatile analyses

The main objective of the study was to profile the aroma and flavor of 17 commercially available peanut cultivars through descriptive sensory analysis and instrumental measurements. Twelve runner (ten high-oleic varieties) cultivars, and five virginia (two high-oleic varieties) cultivars were studied. The peanut samples were roasted to medium roast levels before being subjected to proximate analysis, descriptive sensory analysis, gas chromatography-mass spectrometry (GC-MS) analysis, and fatty acid analysis. In general, the runners showed higher intensities of typical roasted flavors and related aroma volatiles compared to the virginia cultivars. TUFRunner™ ‘511′, TUFRunner™ ‘727′, FloRun™ ‘331′, and Florida-07 (high-oleic runner cultivars) were characterized by higher intensities of roasted flavors (descriptive) and aroma volatiles (pyrazines and aromatic aldehydes) compared to the rest of the runner and virginia cultivars. Two high-oleic virginia cultivars, Georgia 11 J and Bailey II were characterized darker roast-type descriptors and aroma volatiles. Although the principal components analysis (PCA) showed similar trends, it was evident that the relationship between roasted flavors (descriptive) and aroma volatiles (pyrazines and aromatic aldehydes) was not very strong. More in-depth studies are required to understand the roasted flavor generation in these commercial peanut cultivars under various roasting conditions.

A Sensitive and High Throughput LC-MS/MS Method for the Determination of Resveratrol in Peanut Matrix

A precise and very efficient tandem mass spectrometry method (LC-MS/MS) was developed to quantify the resveratrol in the peanut matrix. Two mobile phases made up of water and acetonitrile in a ratio of 98:2 (%v/v) with 0.1% formic acid and acetonitrile and water in a percentage of 98:2 %(v/v) with 0.1% formic acid were used in the LC-MS/MS analysis of resveratrol on a BEH C-18, 130A° (50mm 2.1mm, 1.7μm) analytical column with 0.3 mL/min of flow rate. A triple quadrupole mass spectrometer and a positive electrospray ionization system were used to quantify resveratrol in multiple reaction monitoring (MRM) modes. The technique was evaluated and was found capable of quantifying resveratrol in peanut samples starting at 10 ng/g in compliance with SANTE guidelines.

A high-performance method for quantitation of aflatoxins B1, B2, G1, G2: Full validation for raisin, peanut matrices, and survey of related products at Ho Chi Minh City.

Optimization and validation for simultaneous quantitation of four aflatoxins B1, B2, G1, and G2 in peanuts and raisins were performed on ultra-performance liquid chromatography in a combination of fluorescence detector, without derivatization. The advantages were short analysis time, simple sample handling, and reduced solvent consumption. Instrument detection limits of AFB1, AFB2, AFG1, and AFG2 were 0.07, 0.01, 0.1, and 0.008 μg/kg, respectively, lower than those obtained by LCMSMS and HPLC-FLD with derivatization. Two solvent mixtures were chosen for two different matrices whose matrix effect was not negligible (2.81%-8.04% for peanuts and 5.63%-11.43% for raisins). The linear ranges were from 0.2 to 20 μg/L for AFB1 and AFG1 and from 0.05 to 5 μg/L for AFB2 and AFG2. The limits of detection and quantification were 0.025-0.1 and 0.075-0.3 μg/kg for peanuts and raisins, respectively. Recoveries at three other concentrations from 0.75 to 125 μg/kg of total aflatoxins were obtained between 76.5% and 99.8% (with RSD < 6%) following the SANTE 11312/2021. Validation parameters complied with the requirements of ISO/IEC 17025:2017. The extracts and the sample could be stabilized at 4°C and 20°C for 24 h and at -20°C for up to 21 days, respectively. Thus, the study can be used as a standard method for the analysis of Aflatoxins (AFs) in peanut and raisin matrices. Investigation of 350 peanut samples collected at Markets in the central districts of HCM city showed that 28.6% were contaminated with AFB1 from 0.31 up to 554 μg/kg; 13.4% contained AFB2, and 5.7% of AFG1 in the range of 0.4-53 μg/kg and 0.4-9.57 μg/kg, respectively; AFG2 (about 0.6%) was detected from 0.45 to 0.75 μg/kg. Meanwhile, 12.8% exceeded the total aflatoxins limit, and 13.4% exceeded the AFB1 limit. AFs were almost not found in the 350 raisin samples.

Visual Measurement of Fumonisin B1 with Bipolar Electrodes Array-Based Electrochemiluminescence Biosensor

Fumonisin B1 (FB1) is a toxin produced by the metabolism of Fusarium oxysporum, which can cause serious effects on the nervous, respiratory, digestive, and reproductive systems of humans or animals; it is known as one of the highly toxic epidemic contaminants. Herein, we report the visual inspection of FB1 using bipolar electrodes (BPEs) with an array-based electrochemiluminescence (ECL) platform. The sensor consists of a PDMS cover and a glass substrate containing an array of 10 ITO electrodes. A specific sensing interface was constructed on the cathode of the BPE, which could modulate the ECL reactions that occurred at the anode of BPEs. To amplify the ECL signal, methylene blue (MB)-encapsulated Zr-MOFs (MB@Zr-MOFs) were synthesized and immobilized on the cathode of the BPE, which could amplify the ECL signal at the anode. By coupling the cyclic amplification effect of the DNA walker and nicking endonuclease (Nb.BbvCI), the biosensor can realize the visual measurement of FB1 in the range of 5 × 10−5~0.5 ng/mL. In addition, the developed biosensor was used to monitor the concentration of FB1 in maize and peanut samples. The recoveries were in the range of 99.2%~110.6%, which demonstrated the good accuracy of the designed BPE-ECL biosensor for FB1 assay in food samples.

Phosphonic acid in plant-based food and feed products – Where does it come from?

Salts of phosphonic acid (sodium or potassium phosphonate) or its ester fosetyl are highly effective systemic fungicides, which not only exhibit fungistatic activities, but also stimulate the natural defence systems of the plants against pathogens. Since EU legislation has approved potassium and sodium phosphonate as fungicides in 2013 and 2014, they are no longer permitted in organic agriculture. As a result, even minor contents of phosphonate in organic food samples are interpreted as an indication of a not permitted fungicide treatment. A maximum level of 0.01 mg/kg applies for food for infant nutrition. Here we present evidence from the scientific literature that phosphonate is also a natural compound, which occurs in significant amounts in the environment and is produced and consumed by microorganisms within the biogeochemical phosphorus cycle. Further potential sources for this chemical in the environment apart from agricultural fungicide applications are organophosphonates, as phosphonate occurs as a byproduct during their industrial production or during their microbial degradation in effluents from industry and households. An evaluation of Eurofins results from the analysis of phosphonate from 2017 to 2022 with methods achieving a limit of quantification (LOQ) of 0.01 mg/kg reveals that the compound was detected in 40.63% of all samples from organic and 43.42% from conventional agriculture, and in over 90% of organic samples of chickpeas, lentils, buckwheat, peanuts and wine. Furthermore, 97.3% of organic mushroom samples contain the compound and animal manure or compost used for cultivation is a potential source of the chemical. Consequently, other causes for phosphonate in food products than fungicide applications must be taken into account as well. Analysis of the ratio of the stable oxygen isotopes 18O and 16O was successfully applied to detect applications of mineral sulphur fertilizer in organic agriculture. Similarly, it might be also a promising tool to differentiate between phosphonate produced industrially and from natural sources.

A comparative study for evaluating the binding affinity of MARAS-selected aptamer and a patented aptamer towards aflatoxin B1 by electrochemical impedimetric aptasensing

Magnetic-assisted rapid aptamer selection (MARAS) is a technique that uses magnetic nanoparticles to efficiently separate aptamer-target complexes under an alternating magnetic field, thereby reducing the time and number of selection rounds required. This study investigated the applicability of MARAS in selecting aptamers against a small molecule, aflatoxin B1 (AFB1). Among the six MARAS-selected aptamers, DNA 1 demonstrated the highest binding affinity. Its Kd value, further estimated from aptasensing data, was 43.7 nM, which is comparable to the Kd value of the patented aptamer (55.6 nM). The DNA 1-immobilized aptasensor exhibited good repeatability (RSD < 7 %, N = 3), linearity (R2 = 0.9613 from 1 to 100 nM), and a calculated LOD of 0.42 nM. Specificity testing indicated that interferences from ochratoxin A, aflatoxin B2, aflatoxin G1, and aflatoxin G2 were all below 7 %. The developed aptasensor was also applied to detect AFB1 content in the peanut sample matrix, achieving a good recovery rate ranging from 94.3 % to 112.2 %. Overall, this study confirms the potential of MARAS as a promising technique for identifying aptamers with strong binding affinities towards low molecular weight compounds such as AFB1. Additionally, the DNA 1-immobilized aptasensor provided a simple, accurate, and cost-effective alternative for AFB1 monitoring.

Structure-switching aptasensors for sensitive detection of ochratoxin A.

Ochratoxin A (OTA) is a toxic metabolite commonly found in various foods and feedstuffs. Accurate and sensitive detection of OTA is needed for food safety and human health. Based on a common OTA-binding aptamer (OTABA), two structure-switching OTABAs, namely OTABA4 and OTABA3, were designed by configuring a split G-quadruplex and a split G-triplex, respectively, at the two ends of OTABA to construct aptasensors for the detection of OTA. The OTABA, G-quadruplex, and G-triplex all can capture the thioflavin T (ThT) probe, thereby enhancing the fluorescence intensity of ThT. Bonding with OTA could change the conformations of OTABA and G-quadruplex or G-triplex regions, resulting in the release of the captured ThT and diminution of its fluorescence intensity. Dual conformation changes in structure-switching OTABA synergistically amplified the fluorescence signal and improved the sensitivity of the aptasensor, especially for that with OTABA3. The detection limits of the OTABA4-ThT and OTABA3-ThT systems for OTA were 0.28 and 0.059 ng ml-1 , with a 1.4-fold and 6.7-fold higher sensitivity than that of the original OTABA-ThT system, respectively. They performed well in corn and peanut samples and met the requirements of the food safety inspections.

Quantitative analysis of aflatoxin B1 of peanut by optimized support vector machine models based on near-infrared spectral features

This study designs a chemometric framework for quantitatively evaluating aflatoxin B1 (AFB1) in peanuts based on near-infrared (NIR) spectroscopy technique. The NIR spectra of peanut samples exhibiting diverse fungal contamination levels were acquired using a portable NIR spectrometer. Subsequently, appropriate pre-processing techniques were employed for data refinement. To streamline the analysis, the iterative variable subset optimization (IVSO) technique was employed to conduct an initial screening of the pre-processed NIR spectra, eliminating numerous irrelevant variables. Building upon this screening process, the beluga whale optimization (BWO) algorithm was utilized to optimize the selected feature variables further. Subsequently, support vector machine (SVM) models were developed using the refined near-infrared spectral features to test AFB1 in peanuts quantitatively. The results indicate that the SVM model significantly improves detection performance and generalization proficiency, particularly after secondary optimization using BWO-IVSO. Among the different models considered, the SVM model established after BWO-IVSO optimization exhibited the most extraordinary level of generalization, with a root mean square error of prediction of 24.6322 μg∙kg−1, a correlation coefficient of 0.9761, and a relative percent deviation of 4.6999. Overall, this investigation highlights the effectiveness of the proposed NIR spectroscopy model based on BWO-IVSO-SVM for quantitatively analyzing AFB1 in peanuts. The study contributes valuable technical and methodological insights that can serve as a reference for rapidly determining mycotoxins in cereal crops.

CRISPR/Cas12a and G-quadruplex DNAzyme-driven multimodal biosensor for visual detection of Aflatoxin B1

Aflatoxin B1 (AFB1) contamination severely threatens human and animal health, it is thus critical to construct a strategy for its rapid, accurate, and visual detection. Herein, a multimodal biosensor was proposed based on CRISPR/Cas12a cleaved G-quadruplex (G4) for AFB1 detection. Briefly, specific binding of AFB1 to the aptamer occupied the binding site of the complementary DNA (cDNA), and cDNA then activated Cas12a to cleave G4 into fragments. Meanwhile, the intact G4-DNAzyme could catalyze 3, 3′, 5, 5′-tetramethylbenzidine (TMB) to form colourimetric/SERS/fluorescent signal-enhanced TMBox, and the yellow solution produced by TMBox under acidic conditions could be integrated with a smartphone application for visual detection. The colourimetric/SERS/fluorescent biosensor yielded detection limits of 0.85, 0.79, and 1.65 pg·mL−1, respectively, and was applied for detecting AFB1 in peanut, maize, and badam samples. The method is suitable for visual detection in naturally contaminated peanut samples and has prospective applications in the food industry.