Method of wet peeling for brewer's spent grain

In a method of wet-peeling brewer's spent grain comprising supplying wet brewer's spent grain to a roll mill having at least one pair of rolls which separate the brewer's spent grain into component parts, including a protein-rich product and a husk, and recovering the separated protein-rich product, the improvement wherein each roll of the at least one pair of rolls has a cutting edge, with the cutting edges of respective rolls having a spacing therebetween, wherein the roll mill rotates the at least one pair of rolls at different rotational speeds and at a rotational speed ratio, and wherein the moisture content of the wet brewer's spent grain, the spacing between the rolls and the rotational speed ratio of the rolls are set so as to crush and peel a sufficient amount of an aleurone layer of the grain from the husk such that the protein-rich product contains at least 50% protein and comprises at least 30.3% by weight of the brewer's spent grain.