A dry substance which can be obtained by adjusting the pH value of butter serum or a liquid comprising reconstituted butter serum powder to 4.0 to 5.0, adding calcium chloride thereto to promote protein aggregation, removing the precipitate thus formed, ultrafiltering or microfiltering the supernatant, and then drying the liquid concentrate thus obtained and contains from 15 to 35% by weight of proteins and from 45 to 60% by weight of lipids wherein the content of complex lipids originating in milk amounts to 20% by weight or more in the dry product. Thus, it is possible to produce a powder being rich in milk-origin complex lipids which contains milk-origin phospholipids and milk-origin ganglioside at high concentrations and is usable as a starting material for producing a functional food, a substitute for maternal milk or a drug.