The capacity of several strains of yeasts to do the bioconversion of the methyl ricinoleate into γ-decalactone, was studied in a medium containing this methylic ester of fatty acid as sole carbon source. Amongst the strains which are able to do this bioconversion, two types of behaviour are observed: some of the strains produce γ-decalactone during all the incubation in bioconversion medium while others produce this aroma compound very quickly and then consume it fast too. The tested strains produce at the same time γ-decalactone and the corresponding acid form (4-hydroxy-decanoic acid), and this, in variable proportions.