A process for producing a composition which is particularly rich in D-mannitol, the latter being present in the form of crystals having a volume average diameter greater than 20 μm, wherein the
crystals correspond to a very large extent to the δ polymorph. This process makes use of the evaporative crystallization technique, in which the seeding and then the controlled growth of the
crystals is carried out at different evaporation rates. Finally, very pure δ crystals are advantageously obtained, which have a better compressibility than the α and β homologues thereof and
which, by virtue of the sizes thereof, result in a powder which is not subject to caking