A Miniaturized and Highly Sensitive "Windmill" Three-Channel Fluorescence Detector for Simultaneous Detection of Various Mycotoxins

A novel "windmill" three-channel light-emitting diode induced fluorescence detector (LED-IF) was proposed to maximize the excitation efficiency and fluorescence collection efficiency. Compared with the typical collinear arrangement, the fluorescence intensity of the three channels was increased by 7.85, 3.88, and 2.94 times, respectively. The compact shaping optical path was designed to obtain higher excitation efficiency and a lower background stray light effect caused by high divergence angle high-power ultraviolet (UV)-LEDs simultaneously, which increased the sensitivity of three channels by 4.6 to 5.7 times. It was found that using a photodiode (PD) with a flat window and a larger photosensitive surface can collect the Lambertian emission fluorescence in the flow cell more efficiently, increasing the signal-to-noise ratio of each channel 1.3 to 1.8 times. The limits of detection (LODs, 3 times peak-peak noise) of aflatoxin B2 (AFB2), ochratoxin (OTA), and zearalenone (ZEN) were 0.33, 1.80, and 28.2 ng/L, respectively. Finally, six mycotoxins were analyzed simultaneously by the detector coupling with HPLC. The results showed that the sensitivity of the detector was at the best level to date, which was better than that of the top commercial fluorescence detectors (FLDs). The developed detector has the advantages of having small volume, low cost, and long lifetime and being robust, which has wide application and market prospects.

Screening of mycoflora and ochratoxin A on common culinary herbs and spices in Kenya

The study aimed to screen fungal diversity and ochratoxin A levels on culinary spice and herb samples sold in open-air markets and supermarkets in Nairobi County, Kenya. All herbs were grown in Kenya, while locally-produced and imported spices were purchased from both types of retail outlet. The results showed a high frequency of Aspergillus and Penicillium species contaminating the samples. The isolated species included Aspergillus ochraceous, Aspergillus nomiae, Aspergillus niger, Aspergillus flavus, Aspergillus ustus, Aspergillus terrus, Aspergillus nidulans, Aspergillus clavutus, Penicillium crustosum, Penicillium expansum, Penicillium brevicompactum, Penicillium glabrum, Penicillium thomii, Penicillium citrinum, Penicillium polonicum, and Cladosporium cladosporioides. Total fungal count on spice and herb samples collected from various sources varied between 6 and 7 CFU/mL. Of imported spices, garlic had the highest fungal diversity, while cardamom had the least. For spices from both open market and supermarket outlets, cloves had the highest fungal diversity, while white pepper had the least. For the herbs sampled from the open markets, basil was the most contaminated, while sage was the least. In supermarket samples, parsley, sage, and mint had the highest fungal diversity, and bay had the least. The results indicate the contamination of spices and herbs with OTA at high concentrations. The calibration curve was saturated at 40 µg/kg; with samples of garlic, cinnamon, red chili, basil, thyme, mint, sage, and parsley having levels above this. Of the spices, imported ginger had the highest OTA levels (28.7 µg/kg), while turmeric from the open market had the least, 2.14 µg/kg. For herb samples, parsley from the open market had the highest OTA levels at 29.4 µg/kg, while marjoram from the open market had the lowest at 6.35 µg/kg. The results demonstrate the presence of mycotoxigenic fungi and OTA contamination of marketed culinary herbs and spices beyond acceptable limits. Hence, there is a need for informed and sustainable mitigation strategies aimed at reducing human exposure in Kenya to OTA mycotoxicosis through dietary intake of spices and herbs.

Recent advances in nanomaterial-based optical biosensors for food safety applications: Ochratoxin-A detection, as case study

Global population growth tremendously impacts the global food industry, endangering food safety and quality. Mycotoxins, particularly Ochratoxin-A (OTA), emerge as a food chain production threat, since it is produced by fungus that contaminates different food species and products. Beyond this, OTA exhibits a possible human toxicological risk that can lead to carcinogenic and neurological diseases. A selective, sensitive, and reliable OTA biodetection approach is essential to ensure food safety. Current detection approaches rely on accurate and time-consuming laboratory techniques performed at the end of the food production process, or lateral-flow technologies that are rapid and on-site, but do not provide quantitative and precise OTA concentration measurements. Nanoengineered optical biosensors arise as an avant-garde solution, providing high sensing performance, and a fast and accurate OTA biodetection screening, which is attractive for the industrial market. This review core presents and discusses the recent advancements in optical OTA biosensing, considering engineered nanomaterials, optical transduction principle and biorecognition methodologies. Finally, the major challenges and future trends are discussed, and current patented OTA optical biosensors are emphasized for a particular promising detection method.

Aflatoxin M1 Analysis in Urine of Mill Workers in Bangladesh: A Pilot Study

Presence of aflatoxin B1 (AFB1) in food and feed is a serious problem, especially in developing countries. Human exposure to this carcinogenic mycotoxin can occur through dietary intake, but also through inhalation or dermal contact when handling and processing AFB1-contaminated crops. A suitable biomarker of AFB1 exposure by all routes is the occurrence of its hydroxylated metabolite aflatoxin M1 (AFM1) in urine. To assess mycotoxin exposure in mill workers in Bangladesh, we analyzed AFM1 levels in urine samples of this population group who may encounter both dietary and occupational AFB1 exposure. In this pilot study, a total of 76 participants (51 mill workers and 25 controls) were enrolled from the Sylhet region of Bangladesh. Urine samples were collected from people who worked in rice, wheat, maize and spice mills and from controls with no occupational contact to these materials. A questionnaire was used to collect information on basic characteristics and normal food habits of all participants. Levels of AFM1 in the urine samples were determined by a competitive enzyme linked immunosorbent assay. AFM1 was detected in 96.1% of mill workers' urine samples with a range of LOD (40) of 217.7 pg/mL and also in 92% of control subject's urine samples with a range of LOD of 307.0 pg/mL). The mean level of AFM1 in mill workers' urine (106.5 ± 35.0 pg/mL) was slightly lower than that of the control group (123.3 ± 52.4 pg/mL), whilst the mean AFM1 urinary level adjusted for creatinine was higher in mill workers (142.1 ± 126.1 pg/mg crea) than in the control group (98.5 ± 71.2 pg/mg crea). Yet, these differences in biomarker levels were not statistically significant. Slightly different mean urinary AFM1 levels were observed between maize mill, spice mill, rice mill, and wheat mill workers, yet biomarker values are based on a small number of individuals in these subgroups. No significant correlations were found between the study subjects' urine AFM1 levels and their consumption of some staple food items, except for a significant correlation observed between urinary biomarker levels and consumption of groundnuts. In conclusion, this pilot study revealed the frequent presence of AFM1 in the urine of mill workers in Bangladesh and those of concurrent controls with dietary AFB1 exposure only. The absence of a statistical difference in mean biomarker levels for workers and controls suggests that in the specific setting, no extra occupational exposure occurred. Yet, the high prevalence of non-negligible AFM1 levels in the collected urines encourage further studies in Bangladesh regarding aflatoxin exposure.

Evaluating aflatoxins and Sudan dyes contamination in red chili and turmeric and its health impacts on consumer safety of Lahore, Pakistan

Spices are contaminated with aflatoxins (AFs) and Sudan dyes which are classified as class Group 1 and Group 3 human carcinogens by the International Agency for Research on Cancer (IARC) respectively and their prolonged exposure may raise a human health concern. A total of 474 samples of red chili and turmeric were collected from Lahore city and were subjected to quantitative and qualitative AFs and Sudan dyes analysis by thin layer chromatography (TLC) respectively. The number of red chili and turmeric samples with ≥10 μg/kg of total AFs (European Union standard limit) were 70% and 33% respectively and considered unfit for human consumption. The presence of Sudan dyes in red chili and turmeric samples was 67% and 27% respectively. The mean estimated daily intake (EDI) among females and males was 0.0019 μg/kg bw/day, 0.0012 μg/kg bw/day for red chili, and 0.0008 μg/kg bw/day, 0.0006 μg/kg bw/day for turmeric respectively. The mean value of margin of exposure (MOE) among females and males for ingestion of AFs-contaminated red chili and turmeric was 210.25, 332.13, 501.02, and 699.31 respectively. Therefore, the current study demands a continuous monitoring plan and the implementation of novel techniques to enhance the product's quality and protect public health.

Detection of ochratoxin A using a "turn-on" fluorescence assay based on guanine quenching of the aptamer

Ochratoxin A (OTA) is a common mycotoxin with high carcinogenicity; therefore, it is crucial to establish a simple, rapid, and sensitive method for its detection. In this study, we developed a "turn-on" fluorescence assay for detecting OTA based on guanine quenching of the aptamer. The method uses fluorescein (FAM) fluorophore to label the complementary strand of the OTA aptamer, Fc-DNA. In the absence of OTA, the Fc-DNA hybridizes with the aptamer to form a double strand. Due to the occurrence of photo-induced electron transfer (PET), the FAM fluorescence signal is quenched as the FAM on the Fc-DNA approaches the guanine of the aptamer at the 5' end. When OTA is present, the aptamer binds to it and thus, is unable to hybridize with Fc-DNA to form a double strand; the FAM fluorescence signal is restored as FAM moves away from the guanine of the aptamer. The assay achieved OTA detection at a detection limit of 28.4 nM. The application of the original guanine of the aptamer as the quenching agent helps avoid the complex designing and labeling of the aptamer, which ensures the high affinity of the aptamer for OTA. Meanwhile, this "turn-on" detection mode helps avoid potential false-positive results as in the "turn-off" mode and improves the assay's sensitivity. Additionally, the method has good selectivity and can be used to detect OTA in traditional Chinese medicine. This method provides a simple, low-cost, and rapid method for OTA detection.

Determination of Mycotoxin Contamination Levels in Rice and Dietary Exposure Assessment

The contamination by aflatoxins, ochratoxin A, and zearalenone of samples of paddy and polished rice stored in silos located in Chiriquí, Panama, was evaluated. A total of 23 samples were extracted using immunoaffinity columns and analyzed by high-performance liquid chromatography (HPLC) with a fluorescence detector (FLD) and post-column photochemical derivatization. For the method used, the detection limits were lower than 0.25 μg/Kg for aflatoxins (AFB₁, AFB₂, AFG₁, AFG₂) and ochratoxin A and 9.35 μg/Kg for zearalenone; the limits of quantification were between 0.25 and 18.75 μg/Kg, respectively. Of the samples analyzed, all of the paddy rice samples were positive for at least one of the mycotoxins studied, zearalenone being the one found with the highest incidence (90.91%); for the polished rice samples, the mycotoxin with the highest incidence was zearalenone (50%), although in concentrations lower than those established in European legislation (100 μg/Kg). The estimate of the daily zearalenone intake according to the concentrations found was always less than 0.07 μg/Kg/bw. This is the first report on the determination of 6 mycotoxins in rice grains from Panama by the HPLC-FLD methodology. Considering the high incidence of mycotoxins in the analyzed rice samples, regular control in the production process is recommended to improve quality and ascertain its safety.

Dietary Exposure and Risk Assessment of Mycotoxins in Thyme and Thyme-Based Products Marketed in Lebanon

This study aimed at evaluating the incidence of aflatoxin B1 (AFB1) and ochratoxin A (OTA) in thyme and thyme-based products, related dietary exposure, and cancer risk for regular and high consumption. A total of 160 samples were collected, and 32 composite samples were analyzed. AFB1 and OTA were respectively found in 84% (27/32) and 38% (12/32) of the samples. AFB1 exceeded the limits in 41% (13/32) and 25% (8/32) of the samples according to the Lebanese and European standards, respectively. OTA was unacceptable in only 6% (2/32) and 3% (1/32) of the samples according to the Lebanese and European standards, respectively. AFB1 and OTA daily exposure was shown to be 4.270 and 1.345 ng/kg bw/day, respectively. AFB1 was shown to be associated with 0.41 and 0.35 additional cancer cases per 100,000 persons per year for regular consumption, respectively; while for high consumption, an increase of 0.911 and 0.639 cancer cases per 100,000 person per year was noted, respectively. The margin of exposure (MOE) for OTA was >10,000 for the non-neoplastic effect and >200 for the neoplastic effect, representing no toxicological concerns for consumers.

Aflatoxin B1 in imported cinnamon consumed in the Yazd province of Iran

Aflatoxins are toxic secondary metabolites produced mainly by Aspergillus flavus and A. parasiticus, which are fungal contaminants found in several foodstuffs, including spices. In this study 40 cinnamon samples were collected in November and December 2020 in the Iranian province of Yazd and analysed for the presence of aflatoxin B₁ (AFB₁) by high performance liquid chromatography. Seven out of 40 (17.5%) samples were contaminated with AFB₁ at levels ranging from 0.59 to 5.8 μg/kg. In addition, 2.5% of cinnamon samples contained AFB₁ concentrations above the maximum level of 5 μg/kg, as established by the Iranian national standard. Due to the harmful effects of aflatoxins, even at low amounts, these can cause serious chronic health problems. Therefore, continuous control to avoid AFB₁ contamination in foodstuffs is required.

Natural Occurrence of Ochratoxin A in Spices Marketed in the Czech Republic during 2019-2020

Spices are a popular ingredient in cuisine worldwide but can pose a health risk as they are prone to fungal infestation and mycotoxin contamination. The purpose of this study was to evaluate ochratoxin A (OTA) in 54 single-kind traditional and less traditional spices, each of which was purchased in six samples of different batches (324 samples in total) at the Czech market during 2019-2020. The HPLC-FLD method with pre-treatment by immunoaffinity columns was employed to determine OTA. The limits of detection and quantification were 0.03 ng g^-1 and 0.10 ng g^-1, respectively. A total of 101 (31%) samples of 19 spice kinds were positive at concentrations ranging from 0.11-38.46 ng g^-1. Only turmeric was contaminated with an OTA level exceeding the European Union limits. However, most spices have no regulation, thus further extensive monitoring of various mycotoxins in various kinds of spices is necessary. Chilli and black pepper are the most studied spices for OTA contamination, however, many other kinds of spice can also be highly contaminated, but studies on them are less common, rare, or have not yet been performed. The uniqueness of this study lies in the wide range of spice types studied for the presence of OTA on the Czech market.

Electrochemiluminescence Immunosensor Based on Nanobody and Au/CaCO3 Synthesized Using Waste Eggshells for Ultrasensitive Detection of Ochratoxin A

A novel ultrasensitive electrochemiluminescence (ECL) immunoassay based on Au/CaCO₃ was proposed for detecting ochratoxin A (OTA) in coffee. Au/CaCO₃ nanocomposites synthesized using waste eggshells as the template with a large surface area and excellent electrochemical properties were applied for immobilizing a large amount of Ru(bpy)₃ ²⁺ and conjugating a high-affinity nanobody (prepared by the phage display technique). Coupling of the Au/CaCO₃ nanocomposites and nanobody technologies provided an ultrasensitive and highly selective ECL immunosensor for OTA detection in the range of 10 pg/mL-100 ng/mL with a low detection limit of 5.7 pg/mL. Moreover, the as-prepared ECL immunosensor showed excellent performance and high stability. Finally, the proposed ECL sensor was applied to analyze OTA in coffee samples, confirming the desirable accuracy and practical applicability potential. Overall, this work presents a new nanomaterial for fabricating the sensing interface of immunosensors by harnessing natural waste as the source and a method for detecting toxic OTA in foods.

Evaluation of fungal contamination and ochratoxin A detection in different types of coffee by HPLC-based method

Background

Mycotoxins are secondary fungal metabolites that are produced by some toxigenic fungi on foodstuffs which are poisoning and potentiate for human's health hazards. In coffee samples, ochratoxin A and fungal contamination were examined.

Methods

Immunoaffinity columns were used for treating of all 50 samples from four types of coffee, after that high‐performance liquid chromatography was used for determining the amount of ochratoxin. For the identification of fungi, all coffee samples were cultured in appropriated media.

Results

The results showed that all samples were contaminated by ochratoxin A but only up to 50% of them had toxins higher than acceptable level as detected in black beans (47%), green beans (33.3%), torch (33.3%), and espresso (25%). Black coffee had a higher mean concentration of ochratoxin A than green coffee.

Conclusion

Predominant fungi isolated from coffee samples were Aspergillus species. Finally, careful monitoring of mycotoxins in coffee samples is essential to improve the quality of this favorable beverage in future.

Survey of aflatoxins and ochratoxin A contamination in spices by HPLC-based method in Shiraz, Southern of Iran

Among food and agricultural products, spices play important roles in the diets of millions of people worldwide. These products may be colonized by fungi genus and subsequently mycotoxin production. Due to the large demand and supply of spice for cooking, preservative effects, or medicine purpose, it is essential that further investigation is designed to examine mycotoxins in spice. In the present study, the possible contamination of spices by aflatoxins (AFTs) and ochratoxin A (OTA) were analyzed. A total of 80 spice samples (curry, sumac, ginger, and saffron) were purchased and cultured on appropriate medium. Simultaneously mycotoxins from spices were extracted with immunoaffinity columns (IAC), and the occurrence of AFTs (B1 + B2 + G1 + G2) and OTA was then determined using high-performance liquid chromatography (HPLC) with a fluorescence detector (FD). The results depicted that 62 (77.5%) and 58 (72.5%) spice samples were contaminated with AFTs and OTA, respectively. Out of the 80 analyzed spices samples, the mean concentration of AFTs and OTA was higher in the curry samples. Among spices that contaminated with mycotoxins, 5 (6.25%) and 2 (10%) of the samples were above the acceptable limit of AFTs (≥ 10 μg/kg) and OTA (≥ 15 μg/kg), respectively. Aspergillus species were the predominant species isolated, followed by Penicillium, and finally Mucor species.Among the examined samples, only few curry samples were contaminated with mycotoxins above acceptable limit. Despite this low level of contamination, this spice is used daily in the cuisine of this region of the world, and consequently, even the small amount of these heat stable toxins for a long time may cause many adverse effects. Hence, it is recommended to monitor the toxicogenous fungi contamination and level of mycotoxins in the spices.

Molecular and HPLC-based approaches for detection of aflatoxin B1 and ochratoxin A released from toxigenic Aspergillus species in processed meat

BACKGROUND

Meat-products are considered an enriched media for mycotoxins. This study aimed to investigate the prevalence of toxigenic Aspergillus species in processed meat samples, HPLC-quantitative measurement of aflatoxin B1 and ochratoxin A residues, and molecular sequencing of aflR1 and pks genes. One hundred and twenty processed beef meat specimens (basterma, sausage, and minced meat; n = 40 for each) were collected from Ismailia Province, Egypt. Samples were prepared for total mold count, isolation, and identification of Aspergillus species. All samples were analyzed for the production of both Aflatoxin B1 and Ochratoxin A mycotoxins by HPLC. Molecular identification of Aspergillus flavus and Aspergillus ochraceus was performed using PCR amplification of the internal transcribed spacer (ITS) region; furthermore, the aflR1 and pks genes were sequenced.

RESULTS

The total mold count obtained from sausage samples was the highest one, followed by minced meat samples. The prevalence of A. flavus was (15%), (7.5%), and (10%), while the prevalence of A. ochraceus was (2.5%), (10%), and (0%) in the examined basterma, sausage, and minced meat samples, respectively. Using PCR, the ITS region was successfully amplified in all the tested A. flavus and A. ochraceus strains. Aflatoxin B1 was detected in six basterma samples (15%). Moreover, the ochratoxin A was detected only in four sausage samples (10%). The aflR1 and pks genes were amplified and sequenced successfully and deposited in the GenBank with accession numbers MF694264 and MF694264, respectively.

CONCLUSIONS

To the best of our knowledge, this is the first report concerning the HPLC-Molecular-based approaches for the detection of aflatoxin B1 and ochratoxin A in processed beef meat in Egypt. The production of aflatoxin B1 and ochratoxin A in processed meat constitutes a public health threat. Aflatoxin B1 is commonly associated with basterma samples. Moreover, ochratoxin A was detected frequently in sausage samples. The routine inspection of mycotoxins in processed meat products is essential to protect human consumers.