Development and in-house validation of a rapid and simple to use ELISA for the detection and measurement of the mycotoxin sterigmatocystin

Sterigmatocystin (STG) is a highly toxic secondary fungal metabolite structurally closely related to the well-known carcinogenic aflatoxins. Its presence has been reported in grains and grain-based products as well as in other foodstuffs like nuts, green coffee beans, spices, beer and cheese. Due to the lack of suitable data on the occurrence of STG, in 2013, the European Food Safety Authority (EFSA) could not characterise its risk for human health and recommended that more data on STG in food and feed needed to be collected. In order to provide a new tool for the specific detection of STG, a competitive enzyme-linked immunosorbent assay (ELISA) was developed, optimised and validated in this study based on a sensitive monoclonal antibody specific to STG with no cross-reactivity with aflatoxins. The sample preparation method for rice, wheat and maize was based on a modified QuEChERS (quick, easy, cheap, effective, rugged and safe) approach. The assay was validated for the detection of STG in rice, wheat and maize in accordance with the guidelines for validation of semi-quantitative screening methods included in Commission Regulation (EU) 519/2014. The screening target concentration (STC) was set at 1.5 μg/kg. The cutoffs for rice, wheat and maize were 1.2, 1.2 and 1.3 μg/kg and the false suspected rates were 0.34, 1.15 and 0.78%, respectively. Good correlation was found between the results obtained by the STG ELISA and LC-MS/MS method for naturally contaminated rice samples. This validated method can be applied as a sensitive and high-throughput screening for the presence of STG in a range of agricultural commodities.