Extrusion enables preparation of dual-textured cookies, described as “crisp on the outside, soft in the middle.” The processing method co-extrudes two different doughs, one inside the other. While the choice of sweetener creates the gradient in texture, the equipment encrusts one dough around another. The method also suits filled cookies.

First developed in Japan by Rheon (with US offices at Rheon USA, Irvine, CA), encrusting machines have found wide application in many parts of the world for production of specialty products containing various types of fillings. The inventor of this technology sought a way to make traditional filled buns, a product disappearing from the Japanese culture because its manual preparation was difficult and costly.

The encrusting process starts by pumping the two doughs from their separate hoppers into a compound nozzle so that the interior dough is surrounded by the exterior dough. The resulting rope passes into a ring-style sealing assembly that resembles a camera’s shutter mechanism. The ring pinches the outside dough to seal it to itself and completely enfold the filling or interior dough. The rope advances, and a second pinch rounds the dough into a sphere. Optional forming equipment can be added that will create different shapes such as twists with two fillings, four-color cookies, swirls and crease patterns, as well as leaving the top of the cookie open expose the filling or different color cookie dough.

Rheon recently improved its extruding process so that when handling chocolate chip dough, “the chocolate chips will not be crushed or misshaped,” according to the company. A color touch-screen panel controls the action of the pumps and the encrusting ring. Depending on piece size, these systems output 10 to 90 pieces per minute per lane. The standard system handles pieces weighing 10 to 300 g (0.35 to 10.6 oz) each.

Multiple-dough extrusion systems are now also available from DFE Meincke and Reiser.