Aflatoxins in acid-treated grain in Sweden and occurrence of aflatoxin M1 in milk

A survey of aflatoxins in acid-treated grain and milk from farms using such grain was conducted in Sweden during 1986. Aflatoxins occurred most frequently (40%) in grain treated with a new formula of diluted (700 g litre^?1) aqueous formic acid, but also in 31% of the samples of grain treated with 850 g litre^?1 aqueous formic acid. The lowest incidence was found in grain treated with propionic acid, where aflatoxins were found in only one sample (3%). Aspergillus flavus/A parasiticus occurred in the same manner, but were more frequent than the aflatoxins. When cultivated on aflatoxin-producing agar, positive reactions were more common (56%) among strains originating from grain treated with formic acid than among strains originating from grain treated with propionic acid (4%). Aflatoxin M¹ in concentrations over 50 ng kg^?1 was mainly found in milk from farms using formic acid, and in most of these cases aflatoxins were also detected in the grain samples. In some cases, milk from a single farm was contaminated enough to generate consumption milk from the dairy with aflatoxin M¹ concentrations above or close to 50 ng kg^?1. The risk of aflatoxin formation after inadequate treatment of grain with formic acid is very high and is considerably lower with propionic acid. Formic acid has now been prohibited for use as a preservative of high moisture grain in Sweden.