Method and apparatus for extrusion of food products including back pressure valve/diverter

An extruder system comprising:

• an elongated tubular extruder barrel presenting an outlet end;
• an elongated, axially rotatable, flighted screw within said extruder barrel;
• a product treatment assembly located for receiving product after passage thereof through said extruder barrel,
• said treatment assembly comprising a product-guiding cowling open to atmospheric pressure and a sealed treatment housing having an inlet and an outlet, one end of said cowling disposed about said barrel segment outlet and the other end of the cowling located adjacent said treatment housing inlet,
• said treatment housing permitting superatmospheric pressure treatment of said product therein.

A method of processing a product comprising the steps of:

• providing an extruder including an elongated extruder barrel equipped with an elongated, axially rotatable, flighted screw therein, and an apertured die plate;
• passing product ingredients into and through said extruder and die plate to form an extrudate, and, during such passage, subjecting the ingredients to heat, pressure and shear in order to at least partially cook said ingredients;
• subdividing said extrudate;
• passing said subdivided extrudate through atmospheric pressure for a maximum period of up to about 1.5 seconds;
• directing said subdivided extrudate after said atmospheric passage into and through a sealed treatment housing;
• and
• subjecting the subdivided extrudate to a superatmospheric pressure treatment within said housing.