In vitro antifungal activity of residues from essential oil industry against Penicillium verrucosum, a common contaminant of ripening cheeses

• Essential oil industry residues as sources of bioactive compounds.
• Phenolic compounds as antifungal substances.
• Natural products for the development of cheese covers.
• Prevention and control of molds in cheeses.

Essential oil (EO) industry produces a considerable amount of solid residues during the distillation process, which results in pollution, management and economic problems worldwide. However, these wastes are especially rich in high added-value compounds that can be exploited as natural sources of bioactive compounds. In this connection, ethanolic extracts of solid agro-industrial residues from distillation of some Lamiaceae species were chemically and biologically characterized. The phenolic profile of the extracts was tentatively determined by LC-DAD-MS and the antifungal activity against Penicillium verrucosum was established in vitro by means of the broth microdilution M38-A method. As antifungal agents, the most active extracts were those from the solid residues of Hyssopus officinalis, yielding 50% inhibition of fungal development at a concentration around 92 μg mL−1, and Lavandula x intermedia var. Super (248 μg mL−1). The major phenolic compound present in Hyssopus officinalis residue was cyanidin 3-rutinoside, whilst 4-O-β-d-glucosyl-4-coumaric acid and ferulic acid O-glucoside were the most representatives in the Lavandula x intermedia residue. Solid residues from the industrial distillation of aromatic plants contain natural substances that may satisfactorily prevent fungal contamination on cheeses as well as providing a commercial and economical opportunity to agricultural by-products.