Disclosed is a method of producing a food product having a fat and/or protein content, the method comprising: combining under a temperature of above about 100 Deg. C, an elevated pressure of between about 5 to about 280 bar (0.5 to 28 MPa) and at a pH of 5 at least about 6.2, a grain or grain-containing material and dissolved air floatation (DAF) sludge to form a mixture； wherein the pH of the mixture is increased to a pH of at least about 6.2 by the addition of an alkali. The food product may be used as pet food or animal food.
