GB2106367A

GB2106367A - The production of fat and meal from an animal raw material

Info

Publication number: GB2106367A
Application number: GB08227491A
Authority: GB
Inventors: Henrik Holst-Pedersen
Original assignee: Atlas AS
Current assignee: Atlas AS
Priority date: 1981-09-28
Filing date: 1982-09-27
Publication date: 1983-04-13
Also published as: DE3235831A1; GB2106367B; IE822336L; IE53502B1; DK428381A

Abstract

Animal raw material is comminuted, heated to 40 DEG to 60 DEG C and pressed to form a liquid phase and a solid cake. The fat is separated from the aqueous phase which is concentrated by evaporation, the concentrate optically being added to the press cake. The cake is subjected to drying and sterilization, at least at 110 DEG C (preferably at 120 DEG to 130 DEG C) for at least 10 minutes, before it leaves the dryer and is comminuted to feed meal.

Description

SPECIFICATION Process for the production of fat and meal from an animal raw material The invention relates to a process for the production of fat and feed meal from an animal raw material, in which process the previously comminuted raw material after heating to 40 to 600C is subjected to pressing to separate a liquid phase, mainly consisting of water and fat, from a solid press cake, which is comminuted and dried.

The animal raw material will mainly be slaughter-house waste, organs discarded by veterinary control, and self-dead animals. Raw materials of this kind often contain pathogenic microorganisms, and therefore the Veterinary Board requests a heat treatment in the processing to reduce the number of undesirable microorganisms to a harmless amount.

This is generally obtained by first subjecting the raw material to pressure cooking. Thus, according to the Danish Patent No.134,043 pressure cooking is carried out at a temperature of 1420C for 30 minutes, and there is further sterilized for another 30 minutes, after which evaporation of water is performed at ordinary pressure or in vacuum, for a period of 60 minutes. However, the energy consumption in this kind of working up is relatively high, and the fat content in the resulting feed meal is also often higher than desirable.

Tests carried out as a background for the present invention have shown that a good separation of fat from the proteinaceous material can be obtained without use of pressure cooking by a requisite comminution of the raw material.

Thus, according to the published specification of the Danish Patent Application No. 5433/80 a comminution of the raw material to pieces substantially not greater than 2 cm across, and heating to a temperature between 400C and 600C makes it possible by pressing in a screw press to remove a substantial part of the fat and water contained in the material, and to win a press cake with so low fat content that further removal of fat is unnecessary.

On this known background, the object of the invention is to provide a process in which a raw material as hereinbefore mentioned in an energyeconomic manner continuously and without pressure cooking can be worked up to technical fat and a feed meal in which the content of undesirable microorganisms and their spores is reduced to a harmless amount.

In the present process, the raw material is comminuted to a maximal size of about 2 cm, heated to a temperature between 50 and 600C, and pressed in a screw press with sieve walls, and the characteristic features of the process are that the liquid phase, after having passed a sludge separator from which the sludge is returned, is subjected to a separation of the fat from the aqueous phase, and that the aqueous phase is concentrated by evaporation and added to the press cake which is finally dried at least at 11 00C and sterilized by being kept at the drying temperature for at least 10 minutes, a mixing through stirring during the sterilization being controlled so as to ensure that steam from the sterilization material passes away countercurrently to said material.

Particularly in working up the liquid phase, the present process has features common to modern fishmeal processes, and with few modifications plants similar to those used in the fishmeal processes can also be used for the present process. This is a substantial advantage because the fishmeal apparatus functions well and has no unsolved working problems.

A substantial feature of the present process is the combination of the drying and subsequent sterilization of the press cake before the latter is comminuted to feed meal, because this combination gives a substantial profit as to energy, and the process is simplified and thus more reliable.

Deciding factors for ensuring the necessary sterilization is the temperature to which these must be heated, and the period during which the material is kept heated, because it must be ensured that not only the undesirable microorganisms, but also their more resistant spores are destroyed to a satisfactory degree.

Typical undesired microorganisms to be found in the raw materials for production of meat and bone-meal are salmonella bacteries, clostridiae, including Clostridium botulinum, as well as Bacillus antracis, and considerable investigations as to the heat resistances of the organisms have been carried out. Further, the raw materials sometimes contain Bacillus cereus, which is sporulating and when growing separates a toxin which can give rise to poisoning of humans and animals.

In investigations made in connection with the present process it has been found that the contents of fat and water in the feed meal is of substantial importance for the growth and heat resistance of the bacteriae.

in the investigations were used strains of Bacillus cereus and Clostridium sporogenes PA 3679, respectively, which according to investigations described in the literature is just as or more heat resistant than any of the pathogenic spore-forming microorganisms usually present in meat and bone-meal.

The investigations aimed at determining the heat resistance of the bacteriae spores under conditions, a.o. concerning contents of water and of fat, corresponding to those existing in drying meat and bone-meal by determining the number of surviving spores at temperature of 1000, 1100, 1200, 130" and 1400 after heating for 5, 10, 15, 20, 30 and 60 minutes.

Further, tests were made of heating naturally occurring microorganisms in the raw material.

These tests confirmed that the heat resistance of the latter was less than the heat resistance of the bacteriae spores used in the above investigations.

As a result of the investigations, it could be established that in order to obtain a necessary low content of spores in the present process, a material dried at least at 1100 should be kept at this temperature for at least 10 minutes.

To obtain further security of the meal being poor in spores, however, the meal is preferably dried at 1200 to 130"C and kept at this temperature for at least 10 minutes.

Because the material entering the drier has a very high content of bacteria, often 107 to 108 aerob germs per gram and often 106 to 107 clostridiae per gram, it is of the utmost importance that wholly or to a satisfying degree sterilized dried material is not contaminated with a material of high germ content. Such contamination could occur if, at the mixing normally carried out in the dryer to promote the drying process, non-sterile particles were admixed with the already sterilized material, or by the depositing in the sterile material of particles carried by the vapour from the evaporation.

This can be avoided by controlling the mixing during sterilization so that a minimal stay at sterilization temperature is secured for all of the material, and that the vapour from the sterilization material is led away countercurrently to said material. This ensures that no particles with a high germ content will be found in the sterilized material.

For the drying and sterilization can be used, for example, a modification of the drier known from the fishmeal industry, in which a horizontal drum enclosed by a heating jacket has a longitudinal hollow axle carrying circular discs with steam ducts connected to the hollow axle. By means of baffles, the interior of the drum can be divided into a drying zone and a delaying or keeping zone.

The latter has a mechanical forwarding system substantially preventing longitudinal mixing in the zone, but securing that all material get at least the residence time offered by the forwarding system.

In order to control the drying time and keeping time in the drum, the supply and removal of material can be by means of worm conveyors, the speed of rotation of which can be adjusted. The heating is preferably by pressurized steam.

Adjustments can also be made by changing the length of the keeping zone, by adjustment of the supply of steam or by a combination of the said methods.

Claims

1. A process for the production of fat and feed meal from an animal raw material, in which process the previously comminuted raw material after heating to between 40 and 600C is subjected to pressing to separate a liquid phase, mainly consisting of water and fat, from a solid press cake, which is comminuted and dried, characterised in that the liquid phase, after having passed a sludge separator from which the sludge is returned, is subjected to a separation of the fat from the aqueous phase, and that the aqueous phase is concentrated by evaporation and then added to the press cake, which is finally subjected to drying at least at 11000 and sterilized by being kept at the drying temperature for at least 10 minutes, a mixing through stirring during the sterilization being controlled as to ensure that steam from the sterilization material passes away countercurrently to said material.

2. A process for the production of fat and feed meal from an animal raw material, in which process the previously comminuted raw material after heating to between 400 and 600 is subjected to pressing to separate a liquid phase, mainly consisting of water and fat, from a solid press cake, which is comminuted and dried, characterised in that the press cake is dried at least at 11000 and sterilized by being kept at the drying temperature for at least 10 minutes, the material being mixed by stirring during sterilization in such a way as to ensure that steam from the sterilization process passes away countercurrently to said material.

3. A process for the production of fat and feed meal from an animal raw material according to claim 1 or claim 2 and substantially as hereinbefore described.