The present invention relates to a method of fractioning natural raw materials and separating nutritive substances from the formed fractions, in which method the raw material is dried at a temperature of -40-50 °C and ground lightly so that the seeds of the raw material separate from the fruit flesh and skin portion without breaking, after which the seeds are separated from the dried and ground raw material and a second light grinding is carried out on the formed seedless fruit flesh and skin fraction so that the nutritive substances therein are not damaged, whereby a powder is provided, which is screened or classified, whereby the nutrient-rich skin powder fraction can be separated from the other fractions. The invention also relates to the skin fraction formed from the berry raw material.