Native yeasts of dry-cured ham as biological control agents against Penicillium nordicum.

Dry-cured hams during the ripening stages are commonly covered by moulds and yeasts whose type and extension depends on ecological conditions in the maturing rooms. The microbial community is important as it determines the characteristics of final products, like flavour and aroma. Nevertheless, some microorganisms can produce undesirable metabolites, as P. nordicum, a fungus able to synthesise ochratoxin A (OTA), a nephrotoxin with negative effects on human and animal health . Different approaches can be applied to reduce fungal growth, but the application of biological control agents (BACs), never taken in consideration to reduce mould contamination on proteinaceous food, could represent a suitable opportunity. The aim of this work was to evaluate in vitro the ability of selected authochtonous yeasts (Debaryomyces spp., Candida zeylanoides and Hyphopichia burtonii), isolated from the ham surface, to compete with P. nordicum in the perspective of being used as starter inoculum to prevent or minimize OTA contamination. P. nordicum growth was drastically reduced in co-presence of all yeasts, with C. zeylanoides and D. hansenii as the most and the least efficient, respectively. The efficacy of yeasts in reducing P. nordicum growth decreased with increasing fungal inoculum concentration. OTA production was also considerably influenced by yeasts and sodium chloride in the media; all species tested reduced significantly OTA production, irrespective of the concentration of fungal inoculum. This approach gave promising results and the application of natural yeasts microflora as starter inoculum can be of interest to inhibit P. nordicum contamination of dry-cured hams. Further studies are ongoing to define and check the application method in vivo.