General Mills' US patent 6210741 issued 3rd April finetunes last year's patent 6010732 to disclose a faster production method for ready to eat (RTE) cereals. Extruders of higher revolution speeds (>700 RPM), short tapered screws (L/D<6), and short residence times (<5 seconds) are proposed.

Competitors in specific technology:
House Food Industrial
, Smith Kline Beecham, Wenger Manufacturing (tapered screw extruder) and Tate & Lyle.

Abstract:

    Disclosed are improved methods for preparing a grain based extrudate involving high screw speeds, short barrel length extruders and short residence times. Preferred methods of preparation reside in methods for preparing the present improved RTE cereal or snack products. The preferred methods contain the steps in sequence of feeding an at least partially ungelatinized grain based material to a cooker extruder having at least one rotating screw, said cooker extruder including a barrel preferably having a relatively short length to diameter ("L/D") ratio of substantially less than 12; working the grain based material by rotating the screw at a rotational speed of at least 700 rpm to mix and heat the cereal material and to compress the grain based material; and extruding the plasticized mass through at least one die orifice to form an extrudate. Its preferred product aspect provides RTE cereal or snack products in the form of a puffed grain based product piece having a density of about 10 to 100 g/l., a moisture content of 1.5% to 5%, and cell sizes expressed in cross sectional areas at the maximum diameter ranging from about 0.001 to 3 square millimeters with the majority of the cell sizes being substantially less than 1.0 square millimeters.

First of 4 Claims:

    A method of preparing an extruded grain based product comprising the steps of :

    A. feeding an at least partially ungelatinized grain based material to a cooker extruder having at least one rotating screw, said cooker extruder including a barrel having a length to diameter ("L/D") ratio, with the extruder barrel having an L/D of <=6 and wherein the grain based material includes greater than about 15% to about 40% of a nutritive carbohydrate sweetening ingredient and has a moisture content;
    B. working the grain based material by rotating the screw to impart sufficient amounts of Specific Mechanical Energy ("SME") to mix, heat and liquify the grain based material to a plasticized mass and to force the plasticized mass against a die plate at a pressure, wherein the screw rotational speed is at least 700 rpm and the residence time of the grain based material blend is <5 seconds; and
    C. forcing the plasticized mass through at least one die orifice in the die plate to obtain an extrudate.

By Navroz Havewala, just-food.com correspondent