Preliminary in vitro Results on the Use of the Culinary-Medicinal Mushroom Pleurotus eryngii var. eryngii as Potential Secondary Starter in the Cheese Aging Process.

During cheese ripening, filamentous fungi play a key role in the development of cheese organoleptic properties, contributing through their metabolic activity to the enhancement of aroma, texture, and color. Uncontrolled, spontaneous fungal colonization may lead to the colonization of species capable of producing secondary metabolites that can have adverse effects on human and animal health. To guide the ripening process, improve cheese quality, and reduce potential safety risks, selected secondary starters have been used. Typically, the filamentous fungi utilized for this purpose are from the genus Penicillium (like P. roqueforti), whereas the feasible application of basidiomycetes in cheese ripening remains is still not extensively explored. Four fungal strains of Pleurotus eryngii var. eryngii, isolated from Sicily and Apulia (Italy), were evaluated as potential secondary starter cultures for cheese ripening. Preliminary in vitro assay highlighted the ability of all strains to grow under culture conditions simulating a cheese-like environment. Furthermore, co-inoculation experiments were conducted with Aspergillus westerdijkiae, an ochratoxin A (OTA)-producing species frequently associated with cheeses ripened in natural environments, such as caves, in the presence of Debaryomyces hansenii, a yeast with known pro-technological role, and the four selected P. eryngii strains. Based on these preliminary strain-dependent results, coinoculation of D. hansenii with P. eryngii strains is associated with a strong decrease in OTA production by A. westerdijkiae, as well as a reduction in fungal growth, compared to control (A. westerdijkiae alone) OTA levels were frequently below the detection or quantification limits, while growth reduction ranged from 10.1% (BAF 27) to 28.3% (ITEM13731). These preliminary findings represented a promising application of selected P. eryngii var. eryngii strains, in combination with D. Hansenii, as innovative secondary starter cultures for cheese ripening, with possible benefits for both product quality and food safety, although the specific contribution of each microorganism is still unclear. Therefore, further studies will be additionally conducted to determine the roles of the involved strains and to investigate their pro-technological characteristics in cheese, in terms of proteolytic and lipolytic activity, as well as their characteristic VOC emissions, which are also key factors (for quality) in the aging process.