Abstract: A method and apparatus for incorporating one or more additives throughout an expanded food product. An expandable mixture of moistened farinaceous and/or proteinaceous materials is extruded at elevated temperatures and pressures through the die orifice of an expander-cooker into the cylindrical bore of a tubular extrusion die which is secured to the external face of the extruder die plate. The cylindrical bore of the tubular die has the same cross-sectional area and shaped as the die orifice of the extruder, so that as the mixture passes longitudinally through the tubular die it is still radially confined and is maintained at the same high pressure and temperature as when extruded through the die orifice. One or more liquid additives are injected under pressure into the body of the farinaceous and/or proteinaceous mixture as it is passed through the tubular die, through a nozzle mounted concentrically within the cylindrical bore of the tubular die.

Abstract: The method of producing a dry expanded pet food by extrusion cooking of a blended mixture of proteinaceous material slurry and dry farinaceous material. The proteinaceous material slurry is adjusted to have a fat content of at least 25%, is elevated to a temperature in the range of 150.degree. to 175.degree. F, and then homogenized to reduce particle size and distribute the fat content uniformly through the mixture. Farinaceous materials constituting an appropriate dried ground mix of cereals, vitamins, minerals, and preservatives are added to the proteinaceous slurry. Following the extrusion cooking step, which results in the expansion of the cooked material, the cooked material is dried to a water content of from 7% to 15%, resulting in a microbiologically stable, appetizing animal food.