A new validated HPLC-FLD method for detecting ochratoxin A in dry-cured meat and in blue cheese

Development and validation of a rapid and efficient method for simultaneous determination of mycotoxins in coix seed using one-step extraction and UHPLC-HRMS

Coix seed is an important food and traditional Chinese medicine in China and other Asian countries. Notably, coix seed is currently being used as a traditional medicine for the treatment of COVID-19 in China. However, coix seeds are generally contaminated by mycotoxins, and this risk cannot be ignored. In this paper, we developed a method that involves direct extraction and UHPLC-HRMS analysis for the simultaneous detection of 24 mycotoxins in coix seeds. UHPLC-HRMS instrument and data acquisition parameters, and the sample pretreatment were optimised. One-step extraction showed several advantages compared to the three commercial solid-phase extraction clean-up methods, including ease of use, reduced time of sample preparation, low cost, good recovery, and acceptable matrix effect. The method validation results indicate that all mycotoxins have good linearity and sensitivity. Recoveries were between 74.2-101.1%, and RSD ranged from 0.1-5.8%. The LOQs for 24 mycotoxins were in the range of 0.5-100 µg/kg. To survey the contamination levels of these mycotoxins in commercial coix seeds, more than 70 samples were collected from Chinese markets and were analysed using the newly developed method. Zearalenone (positive ratio: 98.7%, range:1.1-1562 µg/kg), deoxynivalenol (positive ratio: 87%, range: 8.4-382.5 µg/kg), nivalenol (positive ratio: 85.7%, range: 26.8-828.2 µg/kg), fumonisin B₁ (positive ratio: 84.4%, range:2.5-314.5 µg/kg), fumonisin B₂ (positive ratio: 75.3%, range:1.6-72.8 µg/kg), fumonisin B₃ (positive ratio: 48%, range:1.0-203.6 µg/kg), aflatoxin B₁ (positive ratio: 29.9%, range: 0.39-14.7 µg/kg), sterigmatocystin (positive ratio: 29.9%, range: 1.4-51.6 µg/kg), and tenuazonic acid (positive ratio: 19.5%, range 36.1-105.7 µg/kg) were the most frequent mycotoxin contaminants. These results highlight the importance of routine monitoring and control of mycotoxins in coix seeds.

The Occurrence and Dietary Exposure Assessment of Mycotoxins, Biogenic Amines, and Heavy Metals in Mould-Ripened Blue Cheeses

The occurrence and dietary exposure assessment of 16 mycotoxins, 6 biogenic amines (BAs), and 13 metallic elements in blue-veined cheeses (n = 46) is reported. Co-occurrence of mycophenolic acid (≤599 µg·kg-1) with roquefortine C (≤5454 µg·kg-1) was observed in 63% of the tested cheeses, while BAs were frequently present at concentrations between 0.2 and 717 mg kg-1. The concentrations of heavy metals in cheeses were very low. Chronic/acute exposure assessment based on consumption data from different European populations indicated that the levels of mycotoxins and heavy metals are safe to consumers, whereas, rather high hazard indexes (HI up to 0.77) were determined for BAs according to the worst-case scenario based on high consumption and 95th percentile occurrence. A more detailed acute dietary intake study indicated that histamine and tyramine were predominant among these BAs, reaching 27 and 41% of the acute oral intake reference doses.

Determination of Ochratoxin A in Wheat and Maize by Solid Bar Microextraction with Liquid Chromatography and Fluorescence Detection

Solid bar microextraction (SBME), followed by liquid chromatography with fluorescence detection (HPLC-FLD), for the quantification of ochratoxin A in wheat and maize was developed. Ground wheat and maize grains were extracted with acetonitrile-water-acetic acid (79:20:1, v/v/v), followed by defatting with cyclohexane, and subjected to SBME-LC-FLD analysis. SBME devices were constructed by packing 2 mg sorbent (C18) into porous polypropylene micro-tubes (2.5 cm length, 600 μm i.d., and 0.2 μm pore size). SBME devices were conditioned with methanol and placed into 5 mL stirred sample solutions for 70 min. After extraction, OTA was desorbed into 200 μL of methanol for 15 min, the solution was removed in vacuum, the residue was dissolved in 50 μL of methanol-water (1:1, v/v) and ochratoxin A content was determined by HPLC-FLD. Under optimized extraction conditions, the limit of detection of 0.9 μg·kg⁻¹ and 2.5 μg·kg⁻¹ and the precision of 3.4% and 5.0% over a concentration range of 1 to 100 μg·kg⁻¹ in wheat and maize flour, respectively, were obtained.

Detection and discrimination between ochratoxin producer and non-producer strains of Penicillium nordicum on a ham-based medium using an electronic nose

The aim of this work was to evaluate the potential use of qualitative volatile patterns produced by Penicillium nordicum to discriminate between ochratoxin A (OTA) producers and non-producer strains on a ham-based medium. Experiments were carried out on a 3% ham medium at two water activities (aw ; 0.995, 0.95) inoculated with P. nordicum spores and incubated at 25°C for up to 14 days. Growing colonies were sampled after 1, 2, 3, 7 and 14 days, placed in 30-ml vials, sealed and the head space analysed using a hybrid sensor electronic nose device. The effect of environmental conditions on growth and OTA production was evaluated based on the qualitative response. However, after 7 days, it was possible to discriminate between strains grown at 0.995 aw, and after 14 days, the OTA producer and non-producer strain and the controls could be discriminated at both aw levels. This study suggests that volatile patterns produced by P. nordicum strains may differ and be used to predict the presence of toxigenic contaminants in ham. This approach could be utilised in ham production as part of a quality assurance system for preventing OTA contamination.