The present invention relates to the field of flavor or perfumery. More particularly, it concerns a composition of matter comprising : i) at least one compound of formula (I) in the form of any of its stereoisomers; and wherein R1 represents a phenyl group optionally substituted by one or two C1-3 alkyl or alkoxy groups or by one or two halides group; R2 and R3 represent, independently from each other, a heterocyclic group comprising from 1 to 3 heteroatoms selected from nitrogen, oxygen and sulfur, optionally substituted by one or two C1-3 alkyl groups; and ii) at least a C1-6 linear or branched alkyl lactate. The use of said composition of matter in a flavor or perfumery composition is also part of the invention. Therefore, following what is mentioned herein, the present invention comprises the invention's composition of matter as part of a flavoring or perfuming composition or of a flavoring or perfuming consumer product. The process to prepare the invention's composition of matter and the polymorph of compound of formula (I), in particular of N-(1H-pyrazol-3-yl)-N-(thiophen-2-ylmethyl)-2-(ptolyloxy)acetamide, are also an object of the invention.