Food or edible material: processes – compositions – and products – Processes – Heating above ambient temperature
Patent
1995-03-29
1996-10-22
Yeung, George
Food or edible material: processes, compositions, and products
Processes
Heating above ambient temperature
99348, 366 87, 425197, 425199, 426448, 426516, A23L 100, A23P 100
Patent
active
055674631
DESCRIPTION:
BRIEF SUMMARY
SUMMARY OF THE INVENTION
The invention relates to a cooker-extruder with a feeding hopper as well as a single screw and a nozzle and according to an embodiment to a double screw extruder, for the production of thermally treated biopolymers.
Moreover, the invention relates to a process for cooking-extrusion of biopolymers for the production of thermally treated food granulates, snack products, cereals or similar products.
BACKGROUND OF THE INVENTION
Such cooker-extruders are known (see for eg. EP 0 221 918 B1).
General descriptions about cooker-extruders can be found, among others, in Judson M Harper "Extrusion of Foods" 1981 CRC Press, Inc. Boca Raton, Fla., USA, as well as Mercier, Linko, Harper "Extrusion-Cooking" 1989 American Association of Cereal Chemists, Inc. St. Paul, Minn., USA.
The requirements as to a cooker-extruder for biopolymers may be summarised as follows: determined by constant process conditions, good homogenising (mixing, defined temperature creation, good formability of the dough as well as low investment costs, low maintenance cost and flexible process design and finally good controllability at fast reaction times and simple handling, especially, during starting of operation, dismounting and cleaning.
As compared to double screw extruders, single screw extruders have significant advantages, as also presented here, since the former are complicated in construction, require significantly more wear parts and hence contribute to higher maintenance costs.
On the other hand one attributes lower flexibility to the single screw machines and especially one criticises the often nonreproducibility of the temperature conditions and bad mixing-effect/homogenising.
SUMMARY OF THE INVENTION
In cooker extruders of the type mentioned above, the invention is based on the problem to improve the behaviour of such a cooker extruder in a surprising manner in view of the homogenisation as well as in view of the texture of the end product, which should be more uniform, in view of sufficient and controllable expansion, as well as the controllability of the temperature using the relationship, of mass flow/screw speed. Also, the often negative influence of the fat and/or sugar in the raw material mix, on the texture of the product should be reduced.
According to the invention, this is achieved in a cooker extruder having a feeding hopper, at least one screw as well as a nozzle for the production of thermally treated biopolymers, by at least one spatula-pump arranged between the screw and the nozzle, each of which consist(s) of a matrix of holes and at least one associated spatula element (together defined as "spatula-pump").
In case of a single spatula-pump, the flight ends of the screw advantageously in a single screw extruder are formed in the shape of a wedge and use is made of the fact that the screw is allowed to rotate with a small gap with regard to a plate-with-holes. This configuration of the wedge shaped end of the extruder screw meets the above mentioned objective as per the invention, especially after being integrated with the plate-with-holes.
Preferably, at least two such spatula-pumps are positioned between the screw and the nozzle.
Surprisingly, not only is the above mentioned objective met but even the following achieved, thereby, that one supplements a conventional short single screw extruder, for example with a length to diameter ratio, L:D of say, 2:1, whose screw head is already formed in the shape of a spatula and which glides over a plate-with-holes, by one or more spatula-pumps of the type defined above, each of which consists of one or more spatula element(s) and one plate-with-holes:
The homogenising is improved and the texture of the end product becomes more uniform. The dough emerges more uniformly out of the nozzle. Inspite of the very small residence time (less than 8 seconds) significantly more fat and / or sugar can be processed while obtaining sufficient expansion (normally, the presence of fat and / or sugar leads to strongly reduced expansion). The controllability of the
REFERENCES:
patent: 4478516 (1984-10-01), Kessler
patent: 5055027 (1991-10-01), Sato
Dishong George W.
Schaaf Technologie GmbH
Yeung George
LandOfFree
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