Processed meat products frequently suffer from fungal and mycotoxin contamination, mostly ochratoxin A (OTA). Penicillium nordicum is considered responsible for this contamination, but Aspergillus westerdijkiae has recently been associated with high levels of OTA in meat products. Several biocontrol agents have been tested against P. nordicum growth and OTA production in meat products, but A. westerdijkiae has not been considered. The aim of this work was to evaluate in vitro the effect of a commercial starter culture used in sausage fermentation and of sausage-native yeasts on OTA production by A. westerdijkiae, as compared with the highly studied P. nordicum, in meat-based culture media. Four representative yeasts isolated from dry-cured sausage and a commercial starter culture were coinoculated with both fungi in different meat-based media, under varying conditions. Fungal growth was determined by measuring colony diameter, and OTA production was quantified by HPLC-FLD. A. westerdijkiae was significantly stimulated to produce OTA under all tested conditions, and, in ham, OTA production by P. nordicum was stimulated by co-culture with the starter culture. In conclusion, endogenous or added microorganisms enrolled in fermentation or in biocontrol in meat products seem to exert varying responses on different ochratoxigenic fungi, thus leading to unforeseen safety problems.

Processed meat products are of worldwide importance, but they are highly prone to fungal and ochratoxin A (OTA) contamination. In previous studies, several Lactic Acid Bacteria (LAB) and yeasts have been tested as biocontrol agents against P. nordicum growth and OTA production in meat products, with promising results. However, A. westerdijkiae has been poorly studied for this matrix.The aim of this work was to evaluate in vitro the mechanisms underlying the effects of a commercial starter culture and of a meat-native Candida zeylanoides strain on the growth and OTA production of P. nordicum and A. westerdijkiae, by co-culture in ham and sausage-based media under different conditions.In ham medium, C. zeylanoides live cells, cell broth and diffused compounds significantly inhibited OTA production by P. nordicum, but live cells of the starter culture significantly increased it. For A. westerdijkiae strong and significant stimulation was observed by direct contact in both media.In conclusion, ochratoxigenic fungi do not all respond to antagonistic microorganisms in the same way. This study sheds some light on the mechanisms behind the different effects of microorganisms.