The present invention is directed a process for the manufacture of a powder comprising vegetation water rich in water-soluble polyphenols, especially rich in hydroxytyrosol, as well as to the powders themselves and dietary supplements, especially in form of tablets, food, feed and cosmetic preparations containing such powders. The process comprises the following steps: A) providing vegetation water (concentrate) containing water-soluble polyphenols; B) (optionally) modifying the water content of the vegetation water (concentrate); C) optionally centrifuging the vegetation water (concentrate) and separating the water-soluble part; D) spray-drying or granulating the (water-soluble part of the) vegetation water (concentrate), preferably in presence of an adjuvant; E) optionally washing the thus obtained powder comprising vegetation water rich in water-soluble polyphenols with an organic solvent.