Small grain cereals are frequently infected with mycotoxigenic Fusarium fungi. Oats have a particularly high risk of contamination with type A trichothecene mycotoxins; their glucoside conjugates have also been reported. Agronomy practices, cereal variety and weather conditions have been suggested to play a role in Fusarium infection in oats. The current study investigates concentrations of free and conjugated Fusarium mycotoxins in organic and conventional oats grown in Scotland. In 2019, 33 milling oat samples (12 organic, 21 conventional) were collected from farmers across Scotland, together with sample questionnaires. Samples were analysed for 12 mycotoxins (type A trichothecenes T-2-toxin, HT-2-toxin, diacetoxyscirpenol; type B trichothecenes deoxynivalenol, nivalenol; zearalenone and their respective glucosides) using LC-MS/MS. The prevalence of type A trichothecenes T-2/HT-2 was very high (100% of conventional oats, 83% of organic oats), whereas type B trichothecenes were less prevalent, and zearalenone was rarely found. T-2-glucoside and deoxynivalenol-glucoside were the most prevalent conjugated mycotoxins (36 and 33%), and co-occurrence between type A and B trichothecenes were frequently observed (66% of samples). Organic oats were contaminated at significantly lower average concentrations than conventional oats, whereas the effect of weather parameters were not statistically significant. Our results clearly indicate that free and conjugated T-2- and HT-2-toxins pose a major risk to Scottish oat production and that organic production and crop rotation offer potential mitigation strategies.

The presence of Fusarium mycotoxins is an intractable problem in cereal production, with T-2 and HT-2 posing a particular issue in oats. This study assesses the prevalence of Fusarium mycotoxins in unprocessed and de-hulled oats and oat food products and quantifies the bioaccessibility of T-2, HT-2 and HT-2-glucoside from oat porridge in vitro. Twenty unprocessed food oat samples were de-hulled and mycotoxins quantified in unprocessed grains, hulls and groats using LC-MS/MS. Seventy-seven oat food products (40 porridge samples, 10 granola and muesli samples, 11 oat biscuits, 11 oatcakes, 5 infant cereals) were analysed for mycotoxins. Two oat porridge samples were tested for bioaccessibility using Infogest 2.0 method followed by faecal microbiota incubations. T-2/HT-2 and their glucosides were the most prevalent mycotoxins in unprocessed food oats (85–100%). DON was also highly prevalent (70%) while DON-glucoside, NIV, ZEN and their glucoside were less frequently detected. Reduction of 89–100% was achieved by de-hulling oats for most mycotoxins except DON-glucoside (77% reduction). Oat food samples were also frequently contaminated with T-2+HT-2 (prevalence porridge 90%, granola and muesli 40%, oat biscuits 36%, oatcakes 73%) while no mycotoxins were detectable in infant cereal foods. Upon in vitro digestion, 73–82% of free and glucosylated T-2/HT-2 were readily bioaccessible, underlining their importance for human dietary exposure. The study highlights that T-2/HT-2 contamination is prevalent in oats and carry-over into food products cannot be completely avoided, potentially leading to mycotoxin exposure in oat food consumers.