Effect of commercial starter cultures and native yeasts on Ochratoxin A production in meat products
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abstract
Ochratoxin A (OTA) is one of the most important mycotoxins in animal and human food chains, and its distribution is universal. Increased oxidative stress, inhibition of protein synthesis, and DNA damage are some of OTA’s mechanisms of action. It is nephrotoxic, teratogenic, immunotoxigenic and carcinogenic.
OTA is produced by several strains of Penicillium and Aspergillus species. In dry-cured and fermented meat products, it is strongly associated with Penicillium nordicum, but Aspergillus westerdijkiae, a strong OTA producer usually associated with contamination of coffee beans, has also been found to be responsible for high OTA levels in cured meat products.
Because of its harmful effects, many efforts have been put on the development of strategies able to reduce the accumulation of OTA in food products, either by inhibition of fungal growth, inhibition of OTA production or OTA degradation.
This work aimed to evaluate the role of yeasts, previously isolated from meat products, and of a commercial starter culture, on the growth of OTA-producing fungi as well as on OTA production, by using meat-based culture media as model systems.
A commercial starter culture and 2 yeasts (Candida zeylanoides and Rhodotorula mucilaginosa) isolated from pork sausage were co-inoculated with P. nordicum and A. westerdijkiae separately in three meat-based culture media - ham, traditional sausage and industrial sausage - at different conditions: 15 °C and 20 °C; water activity 0.99, 0.98 and 0.96, for 15 days. Fungal growth was determined by measuring colony diameter and OTA was quantified by HPLC-FLD after extraction with methanol.
Results showed that P. nordicum was only able to produce OTA in ham-based medium, with significant reduction of OTA production caused by all co-cultures, being C. zeylenoides the most effective. On the other hand, all co-cultures of A. westerdijkiae lead to a significant stimulation of OTA production, when compared with the control (A. westerdijkiae only).
This is the first study evaluating the effects of either native or commercial starter cultures on the OTA-producing fungus A. westerdijkiae in meat products, and it highlights the need to account for all mycotoxigenic fungi potentially present in food products.
Studies are currently being developed to try to understand the mechanism behind these unexpected results.
