The present invention relates to a delivery system in the form of a dynamic mixture obtained by reacting together, in the presence of water, at least one hydrazine derivative with at least one perfuming, flavoring, insect repellent or attractant, bactericide or fungicide aldehyde or ketone. The inventive mixture is capable of releasing in a controlled and prolonged manner the aldehyde or ketone in the surrounding environment. Furthermore, the present invention concerns also the use of these dynamic mixtures as perfuming ingredients as well as the perfuming compositions or perfumed articles that include such mixtures.
