Mycotoxin contamination in corn smut (Ustilago maydis) galls in the field and in the commercial food products

Corn infected with Ustilago maydis, causal agent of common smut disease, produces galls that are used as food in certain cultures, but may be contaminated with mycotoxins. The objective of this study was to determine mycotoxin levels in common smut galls (CSGs) collected from the field at corn ear reproductive stages R1 through R5 and in commercial CSGs products. The study was conducted in 2012 and 2013. A simple extraction method for five mycotoxins was devised and the results showed the presence of these compounds in CSGs in corn during ear development at various physiological stages. Fumonisin was the major mycotoxin in CSG samples in both 2012 (63%, ≤150.7 μg g−1) and 2013 (46.9%, ≤20.9 μg g−1); followed by aflatoxin (2012: 2%, ≤14.7 ng g−1; 2013: 30.6%, ≤10.8 ng g−1) and zearalenone (2012: ≤41.70 ng g−1; 2013: ≤12.40 ng g−1). Deoxynivalenol (DON) was only detected in 2012 (≤1.6 μg g−1), and cyclopiazonic acid was only detected in 2013 (≤3.18 μg g−1). Commercial canned and fresh CSG samples also contained detectable amounts of mycotoxins including aflatoxin, fumonisin, CPA, and DON. Aspergillus flavus was isolated from selected 2013 CSG field samples at R2 or older (0–1.6 × 106 cfu/g), whereas Fusarium spp were isolated at R1 or older (0–7.5 × 107 cfu/g). These results indicate that CSGs can be infected with mycotoxigenic fungi and contaminated with mycotoxins. The incidence of mycotoxins in commercially available CSG products was highly variable and warrants further study.