A Bowman Birk Inhibitor (BBI) concentrate including at least 50% soy protein by weight of dry matter; and a chymotrypsin inhibitor activity level of at least 200 milligrams of chymotrypsin inhibited per gram of dry matter of product. A method of making a BBI concentrate including the steps of providing acid extracted solubles from a defatted soybean material; mixing acetone with the acid extracted solubles to form a precipitate mixture; separating the precipitate from the mixture of acetone and acid extracted solubles; diluting the separated precipitate with water to form an aqueous solution; ultrafiltering the aqueous solution to obtain a retentate. The defatted soybean material may be defatted soybean flakes or flour. The step of providing acid extracted solubles includes slurrying the defatted soybean flakes with water to form slurry, adjusting the pH of the slurry to 4.0 to 6.5 using hydrochloric acid and separating the solubles from the slurry.