Procedure for regulation of starch gelatinization and density of extruded food and animal feed.

THE INVENTION CONCERNS:

The invention concerns a procedure for regulation of the degree of gelatinization of starch and the density of the finished product of extruded food and animal feed.

By dividing and changing the proportions of the powdered mixture into a part (X), of which starch is gelatinized in an extruder cooking process, and an unheated part (Y), which is not gelatinized, and subsequently mixing the 2 formula parts, the degree of gelatinization and the density of the finished product can be regulated.

Compared to the extrusion process for feed and animal feed used today, this procedure makes regulation possible during operation with minimum expenditure of energy and wear parts.

The procedure consists of continuous feeding of a percentage (X) of the powdered mixture to an extruder cooker, in which the powder is extruder cooked in a cooking zone at high pressure until sufficient gelatinization and thermo-plastic condition are achieved.

Subsequently the extruded powder is cooled in a cooling zone. After cooling, a percentage (Y) of the powdered mixture is added continuously and is carried through a mixing zone, where the extruded percentage (X) and the unheated percentage (Y) are mixed.

After the mixing zone the mixture is pressed through a die, whereby the desired granulate size and shape are formed.

The finished granulate is dried and subsequently cooled to the desired moisture and temperature and is now a hard dust free granulate with a degree of gelatinization and density, which is specific proportionally to the powder shares (X) and (Y).

When the proportion between the percentages (X) and (Y) is changed, the degree of gelatinisation and the finished product density change accordingly.

STAGE OF TECHNOLOGY:

Extruded food and animal feed are produced in a continuous extruder cooker, gelatinizing the starch of a powdered mixture and thus enhancing the digestibility of the mixture and the cohesion to form granulate, pellets or other shapes, which remain dimensionally stable after drying and cooling.

Gelatinization of starch takes place at temperatures between 60 ⁰ C and 100 ⁰ C and pressure between 5 bar and 100 bar, at a moisture content between 15% and 40% and varying retention time. In an extruder screw a powder mixture is conveyed through an extruder head.

By changing the design of the extruder screw, it is possible to configure the shape to give the optimum process.

If it is desired to cook a meal mixture, it is done by creating a counter- pressure in the extruder to make the pressure rise, and higher pressure results in lower cooking temperature and less retention time.

The die, through which the extruded material is pressed to achieve the desired shape, gives a natural counter-pressure, and additional counter- pressure can be induced by giving the extruder screw a slight pitch at the end, or the extruder screw may be supplied with reverse pitch at the end. The extruder screw is built of screw segments to simplify the change of configuration, and it is also possible to configure an extruder screw to the right extruder cooking of a specific mixture.

The problem is that no specific mixture exists, because organic raw materials are being used, and the chemical content of these raw materials varies, i.e. even if the mixture contains the same physical constituents, the chemical contents of the mixture varies, e.g. moisture content, starch quantity, fat content and protein content vary.

Due to this circumstance the extruder must be reconfigured according to the chemical content of the mixture to achieve optimum extruder-cooking, and this can only be done, when the extruder is not in operation.

Various physical regulation devices have been made; so that a certain regulation of gelatinization and density can go on in the extruder during operation.

Various counter-pressure devices, such as valve-closing devices, all have the disadvantages that unnecessary steam is consumed, and turbulence is formed in the extruder screw resulting in quick wear of the extruder screw and the extruder head.

Common for the extruder-cooking processes with the simple counter- pressure devices, which are available today, is that water and steam are added to the whole mixture, and consequently water and heat from the whole mixture must be dried and cooled.

The Danish patent application No. PA 2005 00139 describes a procedure for production of feed premix encapsulated in digestible shells, in which the mixture to be extruder-cooked is divided into a starch part, which is extruder- cooked, and an unheated part, which is encapsulated and not extruder- cooked. The problem with this procedure is, that if the process is going to be used for a mixture with certain raw material content, and the raw materials containing the starch part are isolated, it is not possible to change the quantities, which are added as the starch part, and the quantities, which are added as the unheated part. Consequently there are no regulation options.

THE SPECIAL EFFECT GAINED COMPARED TO THE STAGE OF TECHNOLOGY:

It has been the goal of the invention to find an alternative extruder-cooking process for production of food and animal feed with the possibility of regulating the starch gelatinization and density.

Especially for extruded fish feed the density of the pellets is important, as the density determines the sinking speed in the fish water.

For pet food density is important, as the size of the parcel depends on the density of the pellets.

Fig. 1.0 shows a functional diagram with an example of a continuous extruder-cooking configuration, which meets the desired properties.

A percentage of the total food or animal feed mixture is fed to the first extruder head of the extruder-cooker (steam may be preheated); moisture or steam may also be added, if the moisture content of the mixture is not sufficient.

When moisture or steam is added, mixing must start immediately.

The extruder screw now conveys the mixture through a cooking zone; here the shell product is heated under high pressure and retention time to the temperature required to gelatinize and form a thermo-plastic condition.

The temperature rise is achieved by forming resistance during screw conveyance and by heating of the extruder heads, if required.

The mixture is now led on through a cooling zone, in which the mixture is cooled. The extruded mixture is carried on through an intake zone, in which a percentage of unheated mixture is added.

Upon addition of the unheated mixture, the two parts are carried through a mixing zone.

The mixture is pressed through a die, which determines the size and shape of granulates.

Hereafter the pellets are conveyed to drying and cooling, and the finished hard encapsulated pellets with a specific degree of gelatinization and density are ready to be stored.

THE MEANS USED TO ACHIEVE THE SPECIAL EFFECT OF THE INVENTION:

The special effect according to the invention is achieved by a procedure of the kind mentioned initially and characterized by the fact, that the mixture of food or animal feed to be extruder-cooked, is divided so that an optional percentage of the mixture (X) is extruder-cooked and mixed with an unheated percentage of the mixture (Y) thus regulating the degree of gelatinization and density of the extruded mixture.

With a small percentage (X) the total gelatinization of the starch of the mixture (X+ Y) is reduced, and the temperature is lowered, thereby achieving higher density.

With a large percentage (X) the gelatinization of the starch of the mixture (X ⁺ Y) is increased, and the temperature raised thereby achieving lower density.

MODE OF OPERATION OF THE PROCEDURE:

A percentage of a digestible starch or another powder mixture suitable for extruder-cooking is conveyed to an extruder-cooker, in which it is processed in a cooking zone, until sufficient gelatinization and thermo-plastic condition have been achieved.

The mixture is conveyed to a cooling zone, in which the extruded mixture is cooled as much as possible. After the cooling zone a percentage of the same mixture and the extruded and the unextruded mixtures are carried through a mixing zone for mixing of

(X ₊ Y).

After the mixing zone the mixture is pelleted through a die forming the desired size and shape of the pellets. When the mixture of the extruded and unextruded mixtures is dried and cooled, a hard product is formed, and it is possible to change the degree of gelatinization and density by changing the proportion between the extruded and unextruded mixtures.

COMMENT TO CLAIM 2:

In a special execution the cooling zone starts with a ventilating zone, in which the pressure is reduced to atmospheric pressure or lower thereby forcing cooling.

COMMENT TO CLAIM 3:

In a special execution the process is executed with separate machines for one or more process zones.

COMMENT TO CLAIM 4:

The mixture may contain any kind of food or feedstuff or mixtures hereof in any mixing proportion, liquid, paste-like as well as powdered.

COMMMENT TO CLAIM 5:

The mixture can contain any kind of flavour and aroma additives or mixtures thereof in any proportion.

Flavour and aroma additives can improve animal feed acceptance.

COMMENT TO CLAIM 6:

The mixture can contain any kind of vitamins, additives and minerals or mixtures thereof in any proportion.

COMMENT TO CLAIM 7: The mixture can contain any kind of functional matters of mixtures thereof in any proportion.

COMMENT TO CLAIM 8:

The mixture can contain any kind of pharmaceutical matter or mixtures thereof in any proportion.

COMMENT TO CLAIM 9:

The mixture can contain any kind of pH-lowering matters or mixtures thereof in any proportion. The purpose of pH-lowering matters is to conserve the feed.

COMMENT TO CLAIM 10:

The mixture can contain any form of matter which can form chemical reaction with the feed mixture or mixtures there of in any proportion.

COMMENT TO CLAIM 11 :

The mixture can contain hide or skin improving matters.

COMMENT TO CLAIM 12:

The mixture can contain anti-inflammatory enhancing matters.

COMMENT TO CLAIM 13: The mixture can contain antioxidant-enhancing matters.

COMMENT TO CLAIM 14:

The mixture can contain respiration-enhancing matters.

COMMENT TO CLAIM 15:

The mixture can contain immune defence enhancing matters.

COMMENT TO CLAIM 16:

The mixture can contain anti-parasite enhancing matters.

COMMENT TO CLAIM 17:

The mixture can contain pre-biotic or pro-biotic matters.

FIGURE INDEX: Fig. 1.0 shows the temperature and pressure progress in the extruder.

DETAILED EXPLANATION OF WHAT IS SHOWN IN THE DRAWING:

Fig. 1.0 shows a temperature and pressure diagram, which shows the principal temperature and pressure progress in relation to the position in the extruder-cooker.

An extruder-cooker consists of an extruder head, in which an extruder screw is rotating.

The extruder head and screw are often divided into a number of suitable segments, so that the head and screw can be configured to a specific job. At the intake zone (the rear end of the extruder) the percentage (X) of the mixture to be extruder-cooked is introduced.

The mixture can be added at room temperature or can be pre-heated and moistened by steam before addition.

If the mixture does not have sufficient moisture when fed into the intake zone

(A) water and/or steam must be added, and mixing will go on directly after the intake.

From the intake zone (A) the mixture is carried to the cooking zone (B), where a high pressure is built up by forming a back-pressure from the extruder screw and by heating the extruder head, if necessary, to promote the cooking process.

From the cooking zone (B) the mixture is carried to the cooling zone (C), which may have an outlet to open air, so that the pressure suddenly drops to atmospheric pressure, thereby creating quick evaporation and temperature drop.

From the cooling zone (C) the mixture is led through the intake zone (D), where the other percentage (Y) of the mixture is added unheated.

Upon addition of the unheated part (Y) to the mixture, the extruded part (X) and the unextruded part (Y) of the mixture is carried to a mixing zone (E), where they are mixed to a homogeneous mixture.

From the mixing zone (E) the mixture (X+ Y) is pressed through a die (F), in which the shape and size of the mixture are formed.