Procedure for preparing a fraction F of sunflower flour containing at least 50% by weight with respect to the total dry weight of the protein fraction and 10% by weight with respect to the total dry weight of the fraction or less of fibers raw, which comprises the following steps: a) preparation of a starting material by deagglomeration of a sunflower meal containing at least 30% by weight with respect to the total dry weight of the protein flour and having a content of humidity less than 12% in particles smaller than 5 mm； b) successive screening of the starting material obtained to obtain at least the following fractions: the fraction F-b1, in which the particle size is from d1 to d2； the fraction F-b2, in which the particle size is from d3 to d1； and the fraction F-b3, in which the particle size is smaller than d3； c) deagglomeration and successive screening of the F-b1 fraction to obtain at least the following fractions: - the F-c1 fraction, in which the particle size is from d4 to d5； and - the fraction F-c2, in which the particle size is smaller than d4； d) air current screening of fractions F-b2 and F-c1 to obtain at least the following fractions: - fraction F-d1, in which the particle size is greater than d6； - the fraction F-d2, in which the particle size is from d7 to d6； and - the fraction F-d3, in which the particle size is smaller than d7； e) deagglomeration and successive screening of - the F-d1 fraction to obtain an F-e1 fraction, in which the particle size is smaller than d8； and / or - the F-d2 fraction to obtain an F-e2 fraction, in which the particle size is smaller than d9； and / or - the F-d3 fraction to obtain an F-e3 fraction, in which the particle size is smaller than d10； f) and mixing of fractions F-b3, F-c2, F-e1 and / or F-e2 and / or F-e3 to obtain fraction F； wherein - d1 is 600 μm to 1600 μm； - d2 is from 2000 μm to 5000 μm； - d3 is 150 μm to 500 μm； - d4 is 150 μm to 500 μm； - d5 is 600 μm to 1600 μm； - d6 is 800 μm to 1000 μm； - d7 i
