NO158546B - PROCEDURE FOR SEPARATING Grease FROM PROTEINOUS MATERIAL. - Google Patents

Description

The present invention relates to a process

method for the separation of fat from proteinaceous material and the recovery of one or more solid protein materials, such as meat milk and gelatin bones, from animal raw material, poultry and fish material, waste and other organic raw material.

Stabilized pure bone material suitable for the production of glue and gelatin can also be recovered when the raw material used includes a significant amount of raw bone material.

When processing animal melt material, roughly cut bones, animal waste and similar organic raw material containing fat and protein material to separate and recover fat and/or one or more solid protein materials according to the present commercial processes, the raw materials containing fat, meat tissue, bone and other protein material with a relatively high density has generally been processed in that the raw material's particle size has been significantly reduced and/or that all the raw material has been heated for a longer period of time while in contact with an aqueous medium in the form of steam and hot water or by the raw material has been heated in contact with liquid fat to pre-liquefy the fat in the raw material and reduce the moisture in the raw material to below approx. 10% by weight before the fat is separated from the material. When raw cut bone or other fat-containing crude protein material is heated while in contact with the hot aqueous medium, such as in a dry effecting process,

for a period of time long enough to cause liquefaction of the fat and significantly reduce the moisture content in the meat tissue, a significant part of the protein in the raw material is broken down and the quality of the fat is reduced. Also, when the bone is treated in a bath of liquid fat, the pores in the bone become saturated with fat and the surface of the bone material is covered with a layer of fat so that the appearance and quality of the bone for the production of high-quality gelatin and glue is reduced.

In order to avoid the reduction of the economic value and quality of the protein material associated with waste and raw bone material during the recovery of valuable fat and meat products, low-temperature deboning processes (deboning processes) have been developed to recover fat and meat tissue without heating to effect cooking and where the raw bone compressed in a press with a screw mounted in a perforated jacket so that soft non-bone parts comprising mainly fat, flesh tissue, bone marrow, blood, moisture and small bone fragments are forced through the perforations in the jacket wall and recovered as a paste while the pressed bone material and the like hard protein material together with a small amount of residual fat and meat tissue and similar soft protein material is removed separately from the end of the sheath. However, the paste produced by such deboning processes has only been used in livestock feed and other feed products, and the fat and/or meat values pressed from the organic raw material have not so far been separated and recovered as distinct products by a process in which the raw material is mechanically processed in an initial step in the process of separating and removing a major part of the fat and a large amount of the soft protein material without first finely dividing the whole raw material and/or without subjecting the whole raw material to heating while in contact with a hot aqueous medium or in a heated bath of liquid fat to effect drying.

An equally serious objection to previously known methods of separating and recovering fat and/or one or more solid protein products as distinct products from organic feedstock, such as decanting material, coarsely cut bones and waste, is the disproportionately large total amount of energy consumed in the previously known processes. With the previously known methods, a large amount of energy is thus required to reduce the raw bone material and other raw material to a size suitable for efficient heating in an aqueous fat bath so that the fat is pre-liquefied and easily separated from the meat tissue and so that the moisture is more easily separated. When the raw melting material containing a normal amount of fat with associated protein tissue and approx. 55% by weight of moisture is heated to effect liquefaction of the fat, the heat transfer efficiency drops from 303 kcal/hour to 75.6 kcal/hour as the moisture content reaches approx. 15% by weight. The boiling point of an aqueous liquid fat containing the amount of fat normally present in the raw melt material and approx. 55% by weight moisture with approx. 15% protein by weight, rises from 100° C to approx. 118° C after which the moisture content approaches 15% by weight moisture at atmospheric pressure. However, when a similar aqueous solution with a low fat content is heated to boiling to remove the moisture, the boiling point is at approx. 100° C at atmospheric pressure as the moisture content of the lean liquid approaches 15% by weight. Furthermore, when boiling the total crude melt mixture with its relatively high fat content, it is generally considered necessary to heat the mixture to a temperature between 127 and 149°C to effect maximum boiling to ensure a low fat content when heated.

heated mixture is pressed to remove the pre-liquefied fat.

A large amount of energy is also required to grind the hard dry cake from the press after separating the fat. Thus, it is obvious that heating a mixture with a low heat transfer efficiency to a temperature between 12 7

and 149° C before separating this requires the consumption of further large amounts of energy, degrades the quality of the products, increases the maintenance costs of the plant, especially due to frictional wear when the fat is separated from dry material in an oil press, and increases the costs of air- treatment in the facility to control bad odours.

It is therefore an aim of the invention to provide a more economical process for the separation and recovery of stabilized fat and/or solid protein material from organic raw material.

Other features of the invention will be apparent from the following detailed description and claims in connection with the accompanying drawings in which: fig. 1 shows a schematic block flow diagram of an embodiment of the invention; fig. 2A and 2B together show a schematic block flow diagram of a modified form of the method according to the invention, and FIG. 3A and 3B together show a schematic block flow diagram of a further modified form of the method according to the invention. The invention thus relates to a method for separating fat from proteinaceous material in animal, poultry and marine raw material containing fat, water and proteinaceous material, forming stabilized fat and stabilized protein material, by a mechanical low-energy melting process, which method is characterized by the combination of the following steps (1) the organic raw material, roughly divided, preferably with a piece size of 3 - 15 cm, is introduced into a screw press with a perforated wall section, (2) the organic raw material is passed without the addition of heat through the press by applying pressure to forcing through the perforated wall section a liquid mixture of (a) consisting mainly of an aqueous fluid, soft protein material of low density, a small amount of protein material of high density in the form of fine bone particles, and a major part of the fat, separating from a pressed low-fat solid material (b) containing a major portion of protein food high density aerial in the form of bone particles together with water and a smaller amount of low density soft protein material, (3) the mixture (a) is heated to the fat melting temperature of 52-86°C and ground, preferably to a maximum particle size of 10 mm, and the mixture is separated, preferably by centrifugation, into a liquid fat fraction (c) which also includes water containing dissolved protein material, and a low-fat protein fraction (d); (4) fat fraction (c) is heated and water and protein material are separated from the fat fraction to form a stabilized fat product; and (5) the low-fat protein fraction (d) and the pressed low-fat material (b) are combined and heated above 82°C to effect sterilization and drying to a maximum water content of 10% by weight, after which the dried mixture is screened to form a stabilized, low-fat, protein flour product.

More specifically, pure stabilized low-density proteinaceous solid material (ie, meat meal material) and stabilized high-quality fat can be separated and recovered as distinct products from raw material such as melt material, raw fish material, raw poultry material and deer material such as rough cut bones and waste, according to the embodiment of the invention shown in fig. 1 on the drawing when placing the raw material received from a slaughterhouse, a meat packing plant or a deboning plant etc. in a receiving container or shaft and continuous transport of the raw material with a screw conveyor or similar device from the receiving container past an electromagnet where foreign metal is removed and through a coarse size reducing apparatus where raw materials are reduced in size from their natural state to pieces preferably varying between 2.54 and 15.24 cm in length, suitable for insertion into a press. The bones leaving the coarse sorting equipment are in the form of a flowable mixture containing bone, bone marrow, fat, meat tissue and liquid including blood, other body fluids and moisture. The raw material, which may include bones with added fat and meat tissue, is passed under another electromagnet and introduced into a press, preferably a continuous screw type press with the screw mounted within a cage or casing with perforations or small openings in the wall thereof. The screw press preferably has a damper fitted at the outlet end or other device for regulating the pressure applied to the bones within the cage so that sufficient pressure can be applied to the raw bone in the press to force a significant amount of the fat and soft proteinaceous material together with fine bone and most of the liquid contained in the raw material through the small perforations or small openings in the wall of the cage, as the pressed hard bone materials with high density (together with residual fat and meat tissue) comprising approx. 4 7% by weight of the total raw material when roughly trimmed bone is torn off. The soft, low-density material removed as a slurry from the press generally comprises approx. 53% by weight of the raw material when tearing off rough cut bone. The material fed to the press is generally composed of crude fat, meat tissue, tendons, cartilage, bone marrow and fluids together with bone material. The composition of the slurry composed of soft material with low density and moisture will vary depending on the composition of the raw material fed to the press. A slurry obtained by pressing the roughly cut cube will generally contain approx. 30 wt% crude fat and 2 3 wt% wet, low-fat solid tissue, based on 100% of the roughly trimmed bone. After final drying of the wet, low-fat tissue, approx. 10% by weight dried solid tissue, again based on 100% rough cut bone. When the crude fat is dried, the yield of finished fat is approx. 18% by weight, based on 100% of the roughly cut bone material. A typical approximate composition of a slurry (paste) torn from the rough cut cube is 25% by weight crude fat, 35% by weight solids (ie soft tissue and fine bone), and 40% by weight moisture. Soft, low density material comprising the slurry scraped from cow offal and bones contained approximately 37.5% by weight fat, 51.5% by weight moisture with the balance being mainly solids. The slurry torn from sheep offal and bones typically has a composition of 27% fat by weight, 18% solids by weight and 55% moisture by weight. The high-density pressed material removed from the press after stripping generally comprises between 30 (i.e. when pressing sheep waste) and 48% by weight (i.e. when pressing the coarsely cut cube) of the raw material fed to the press, and generally has a fat content of approx. . 3% fat by weight, approx. 12% by weight of soft tissue and a moisture content of between 20 and 40% by weight. The composition of the high density pressed material remains essentially the same regardless of variations in the amount of fat, adipose tissue and moisture in the rough cut bone material fed to the press. As a specific example, pressed material with a high density from cow waste was found to contain approx. 40% by weight moisture, 2.16% by weight fat, 12% by weight soft tissue and where the balance was mainly high density proteinaceous material.

The soft material with mainly low density

in the slurry removed from the press containing a major part of the fat in the raw material and soft meat tissue together with fine bone material, is heated in a melting tank preferably to a minimum fat pre-liquefaction temperature of between 51.7 and 87.8° C, and preferably around 82.2° C. After passing over a permanent magnet to remove any remaining foreign metal, the heated slurry is pumped through a grater (ie, a wet hammer mill without a plate) where the slurry is sized to a maximum diameter of preferably 9.52 mm. The heated and size-regulated slurry is fed continuously to a fixed bowl centrifuge where the lighter fraction composed mainly of fatty material and a smaller amount of moisture with dissolved solids therein is drained into a crude fat storage tank, and the heavier fraction composed mainly of soft, wet, low-fat low-density protein tissue material containing between 2 and 5% fat by weight together with moisture and fine bone material is emptied into a storage funnel for low-fat tissue. The wet, soft, low-density, low-fat protein material or tissue is transported to a dryer where it is combined with hard bone or fibrous, high-density, low-fat protein material from the press. The preceding mixture of low-fat materials is sorted after drying to form a stable, light-coloured meat meal product.

The crude fat material drained from the centrifuge is preferably further processed in a waste heat evaporator to reduce the moisture content to approx. 15% moisture by weight, and is then heated in a final evaporator to reduce the moisture content of the fat to approx. 1/2% by weight which is then processed by sedimentation, centrifugation or filtration to remove the dried solid materials in the fat and give a clean light colored product. The fat product (i.e. tallow) that is recovered from the roughly cut cube has the following typical analysis values: between 0.50 and 3.50 F.F.A. (free fatty acids), a color value of between 5 and 7, approx. 0.46% moisture by weight, approx. 0.25% by weight unsaponifiables,, a Refined and Bleach

(R & B) value of approx. 0.2 r, and a titer of approx. 42° C.

The mixture of wet, low-fat, low-density protein material removed from the centrifuge and the wet, hard-pressed, high-density protein material removed directly from the press is fed continuously into a dryer in which the materials are heated to a temperature of about 93°C into any lean meat tissue adding to the pressed high-density protein material is brittle and the moisture content of the low-density, low-fat protein material and small bone particles is reduced to a maximum of 10% moisture by weight. The brittle, low-fat meat tissue is then easily removed from the bone particles completely by mechanical wear during the subsequent transport, screening and size sorting of the dry material. The drying step also sterilizes and stabilizes the low density proteinaceous solid material (ie meat meal material) and the bone particles (ie high density proteinaceous solid material). The dried material is sieved and sized by recycling through a reduction mill to form a stabilized low-fat meat meal material suitable for storage under dry ambient conditions. The meat meal material obtained, where hard cube material with high density has been separated as described here, generally comprises between 20 and 30% by weight of the raw material, and the meat meal material composition will generally be between approx. 6-10% fat by weight, approx.

33 - 63% by weight protein, approx. 25 - 48% by weight ash and between

3 and 10% moisture by weight, regardless of the type of raw material used. Higher levels of protein will be found in poultry meal (ie approx. 68% protein by weight) and in fish meal. The ash content in feather meal will be less than about 16% by weight, while the maximum ash content in the meat meal material is preferably around 3.7% by weight.

When the raw material fed to the press contains a large amount of proteinaceous material with a high dental value in the form of hard bone, such as in coarse-cut bone, marketed mixture of fat and bone or "deadstock" as opposed to conventional demelting material and waste, it is desirable to subject the dried mixture of dried high density lean protein material and low density lean protein material a dry separation treatment which removes from the mixture a significant amount of bone material (ie high density proteinaceous material) to reduce the ash content of the protein meal product. As meatloaf preferably has a maximum of approx. 35% ash by weight, it is important to be able to regulate the ash content in the meat meal in the manner indicated above and thereby avoid reducing the quality of the meat meal product.

The preferred dry separation treatment for removing bone material contained in the dry mixture of low-fat high-density and low-density proteinaceous material from the dryer is shown schematically in fig. 2A and 2B of the drawing (and also in Figs. 3A and 3B) and comprises subjecting the mixture of dry low-density protein material and high-density bone particles with crisp meat tissue attached thereto to a screening and sizing treatment which preferably separates from the dry mixture a fraction with a selected particle size range most applicable to the production of high quality gelatin. The selected particle size material from the sieve is preferably passed continuously through an air separator which removes much of the light bone particles and low-fat, low-density protein material that can be used in the meat meal product. The remainder of the selected particle size material composed mainly of high density clean bone material is placed on a gravity separator. The oversize material is recycled to the hammer mill and rescreened, and the undersize material is transported to a second screen and gravity separator for further processing.

The gravity separator is preferably an inclined vibrating air sieve table on which the higher density particles are collected at the upper end section while the low density particles remain at the lower end section of the air table. The dry separation treatment separates the high-density bone material from essentially all low-density, low-fat meat tissue and produces a clean, stabilized bone material that generally has a fat content of approx. 3% by weight and a moisture content of approx. 8% by weight, a protein content of approx. 30% by weight and an ash content of approx. 60% by weight. The high-density bone material meets the requirements for the highest quality gelatin bone product.

The undersized material from the first or primary screening can, after oven drying, be separated into a high density bone material with a small mean particle size (i.e. "rice bone") and a low-density protein material (i.e. fat flour material) with very fine bone particles therein, and the separation is preferably carried out by a second sieve and gravity separation apparatus similar to those previously described.

The low-density material removed by the air separator from the selected fraction in the primary screening apparatus, the low-density material removed from the lower end of the gravity separator, the low-density material removed from the recycled air stream in the gravity separator, the low-density material recovered from the fraction undersized in the second screening apparatus, and the low-density material recovered from the undersized fraction in the second gravity separator are all combined to form the meat meal material. A typical meatloaf produced as described above from the roughly cut cube has a composition of 49.62% protein, approx.

7.4% fat, approx. 34.78% ash and approx. 5.27% moisture.

The modified form of the invention shown in fig.

3A and 3B in the drawing is similar to that in fig. 2A and 2B with respect to the separation and recovery of meat meal material and bone material, but differ with respect to the method of obtaining pure stabilized fat from raw fat material and the processing

of the dissolved proteinaceous materials in the crude fat material.

In the processes shown in fig. 3A and 3B, the raw material from the crude fat storage tank is thus heated to a sterilization temperature of approx. 9 3.3° C and is fed into a split bowl strainer in which the fat is separated as a clean stabilized light-coloured fat containing approx. 1/2 wt% moisture. Water is added periodically to flush solid materials from the centrifuge when the bowl is split, and the rinse water and the solid materials are added to pressurized water from the centrifuge. The pressed water centrifuged from the crude fat and dissolved proteinaceous solid material is preferably pumped to a waste heat evaporator connected to the dryer where the dissolved proteinaceous solid material is concentrated from 15% by weight dry matter to 55% by weight dry matter by heating in vacuum at a temperature of preferably around 60°C. The concentrated solid material is then preferably fed into the dryer and finally forms part of the meat meal. By treating the press water in the previous way, additional protein (approx. 2% protein by weight) is recovered for meat milk, and it is unnecessary to throw material with a high BOD content into the plant's wastewater where treatment would be necessary.

Raw material

Any organic raw material containing fat and protein material can be used in one or more of the embodiments of the present invention, the preferred raw material used in the process is animal raw material containing fat and protein material and which includes any melting material used in the known wet- or dry-melting processes, waste from livestock, animals, poultry and fish, carcases from animals, poultry or fish, restaurant waste, market fat and bone mixture, rough-cut bone from boning plants and slaughterhouses, skin pieces and "dead stock". Although mixtures of any of the foregoing materials are used, raw material prior to processing is preferably separated into (1) hard bone material which has associated fat and flesh tissue or (2) soft waste material which generally consists of internal organs from the slaughtered mammals and which may contain feet and non-meat parts and which do not contain a large amount of hard bone material. The percentage of fat, tissue, bone and moisture in each of the raw materials can vary over a wide range. The hard bone raw material is preferably delivered in a feed hopper and the soft waste material is delivered in a separate hopper. Each of the feed hoppers is equipped with a screw conveyor that brings the raw material from the hopper past an electromagnet that removes foreign metal and - where the feed contains bone particles too large to be fed directly into a press - to a conventional coarse sorter that reduces the size of the raw material to pieces varying in size from between 2.54 x 2.54 cm and 2.54 x 15.24 cm. The raw material is then preferably transported to a vibrating hopper feeder to ensure a continuous supply of raw material for further continuous processing in a stripping apparatus when the raw material is delivered at intervals to the receiving container. The raw material has approx. 50% by weight total dry matter and an approximate composition on a weight basis of 30 - 40% by weight moisture, 20 - 30% by weight meat tissue, 15 - 20% fat and 18 - 22% bone which is useful for glue or gelatin, where additional bone goes into the meat meal material. The crushed raw material has a bulk density of approx. 897 kg/m . When slaughterhouse waste is the raw material, the moisture content can be as high as 6-8% by weight and the fat content can be as low as 8% fat by weight.

Røbene detractor

The conveyor device carries the raw material, preferably crushed in a coarse sorter and stored for a limited period of time in a vibrating hopper, over a second magnetic separator designed to remove any remaining foreign metal, and continuously feeds the crushed raw material in the preferred embodiment into a screw type press mounted within a sleeve preferably having adjustable lateral slits therein spaced apart by a distance less than the desired minimum size in the final product (ie about 0.24 cm when making legs for high quality gelatin) and preferably having a damper mounted axially therein at the outlet end of the sleeve intended to maintain a pressure on the raw material within the sleeve. A specific example of a satisfactory screw press is a 10 inch "Duke Pressor" manufactured by the Dupps Company of Germantown, Ohio. A 25.5 cm "Duke Pressor" has a capacity of approx. 9072 kg/h and uses an interrupted screw to prevent the formation of a mass of high density particles along the wall of the cylinder. When pressing rough cut bone with the "Duke Pressor" a damper pressure of preferably 21.1 kg/cm o is applied to the rough cut bone material using 75 - 80% power in a 200 horsepower electric motor to effectively separate the soft proteinaceous tissue with low density and fat from the high-density proteinaceous raw material. The pressed soft material is sheared from the raw bone remover as a viscous aqueous liquid slurry at a speed of approx. 408.2 kg/h and the pressed, hard, low-fat, high-density material is discharged from the stripping press at a rate of 362.8 kg/h. The hard proteinaceous material with high density is reduced

in the press into pieces with a maximum diameter of 3.81 cm where the size varies from 0.317 cm to 3.81 cm and generally between 0.635 and 3.175 cm. With regard to the composition of the raw material supplied to the press, the pressed hard material with high density that is drained from the screw press when it is operated as indicated above has a relatively uniform composition and will generally contain between 20 and 25% by weight of moisture, approx. 10 to 12 wt% meat tissue and between 3 and 6 wt% fat. The high-density material discharged from the decanter has a temperature of between 43.3 and 49°C entirely thanks to friction in the press. If a pressure is applied to the raw material in the press, the high density pressed hard material will have a smaller average particle diameter and contain an even smaller percentage of fat, meat tissue and moisture.

It is evident that a major part of the fat, together with a large amount of the soft proteinaceous tissue of low density associated with the raw material fed to the press, is separated from the hard proteinaceous material of high density by the stripping press, and that the press is a very effective means of remove fat and protein tissue from crushed crude protein material containing fat and protein tissue, without the need to bring the whole mass of raw material into contact with a heated aqueous solution or a heated bath of molten fat and without having to reduce the whole mass of the raw material to a small particle size.

Melting tank

The soft, low-density material containing fat and meat tissue which has been removed from the animal raw material is fed as a flowable aqueous liquid slurry into a melting tank which is preferably a jacketed stainless steel vessel adapted to be steam heated, and the slurry is preferably heated to a temperature above approx. . 52° C to effect melting of the fat. If desired, the slurry can be heated to a temperature not significantly above 82° C for a short time to kill microorganisms that induce hydrolysis of the fat, but the heating should not be so prolonged or so high that it denatures a significant amount of the protein in the slurry or darkens the color on the fat.

River

The slurry of stripped soft proteinaceous material of low density heated in the melting tank to a fat-liquefaction temperature preferably around 82°C is passed over a permanent magnet to remove foreign residual metal and is preferably pumped into a grater which may consist of a plateless wet hammer mill with a 0.952 cm's sieve through which the slurried solid materials are forced by the rotating hammers to tear fibers and free grease and moisture. The shredded slurry material is then pumped to a bowl centrifuge.

Bowl centrifuge

The shredded slurry at a temperature of up to 82° C is preferably fed to a solid bowl centrifuge adapted to separate the pre-liquefied fat fraction containing water and dissolved solid protein components from the wet, soft, low-density protein material comprising meat tissue, small bone material , hair, and solid foreign material, such as polyethylene and paper etc., and containing approx. 55% moisture by weight and generally only approx. 3% fat by weight. The pre-liquefied fat fraction is collected in a raw fat material storage tank and then processed to remove moisture and dissolved solids. The wet, soft, low-density, low-fat protein material is combined with the hard, high-density, low-fat protein material from the press, and the mixture is introduced into a dryer.

Waste heat evaporator

The crude fat material from the centrifuge is pumped to a primary evaporator which preferably utilizes exhaust steam from the dryer or hot steam recovered from other sources in the plant (i.e. waste heat) to heat the primary evaporator instead of steam from a steam boiler. A preferred type of waste heat evaporator is manufactured by Stord Bartz, A.S., Bergen, Norway, and is a vacuum type waste heat evaporator. The steam is supplied to the waste heat evaporator at a temperature of 93 - 100° C, and the boiling temperature in the waste heat vacuum for-

o

the steamer is 35 - 40 C. The moisture content of the crude fat material is reduced to approx. 15% by weight of moisture in the waste heat evaporator before the fat is fed to a final evaporator.

Fat end evaporator

The partially dried crude fat material containing approx. 15% by weight moisture and suspended proteinaceous materials are pumped to a final evaporator heated to at least 112.8°C by boiler steam to effect a reduction of the moisture content to approx. 1/2 wt% moisture. The dry fat containing suspended dry solids is preferably separated by sedimentation or filtration to remove dry suspended solids to form a stable light colored fat product.

Split bowl centrifuge

An optional procedure (as shown in Figs. 3A and 3B of the drawings for processing the crude fat material from the compact bowl centrifuge) involves heating the crude fat material and introducing the heated fat material (93.3 - 107° C) into a split bowl centrifuge adapted to separate stabilized light colored fat from pressed water comprising water with proteinaceous solid material (8 - 10% by weight) and fat. These solid residual materials are periodically flushed from the divided bowl with flushing water. The press water and the flushing water are preferably pumped to a waste heat evaporator in which the solid materials including proteinaceous material are concentrated at approx. 60° C to approx. 50% by weight dry matter and in concentrated dissolved solids are pumped to the dryer where they are mixed with low-fat wet proteinaceous solid material for processing into dry meat milk.

Drying

Although each of the wet low-fat proteinaceous materials can be dried separately, in a preferred embodiment of the invention the wet, low-density, low-fat proteinaceous material from the compact bowl trifle and the wet, hard, high-density, low-fat proteinaceous material from the press are combined and dried at the same time in a dryer to a moisture content below approx. 10% by weight moisture in a drying apparatus which is preferably a rotary disc dryer such as the Rotadisc dryer

manufactured by Stord Bartz, A.S., Bergen, Norway. The characteristic feature of the rotary disc dryer is the large heating surface provided by the hollow heated discs. The Rotacisc dryer is heated with steam normally at superatmospheric pressure up to approx. 5.9 7 kg/cm o, and the drying chamber can be adapted to vacuum operation if desired.

A dryer that has also been found to be suitable for drying the pressed hard lean protein crude and the wet lean soft crude protein is a continuously rotating vertical transfer trough dryer, such as the Wyssmont Turbo Dryer manufactured by the Wyssmont Company, Port Lee, New Jersey, in which the lean raw materials are continuously is moved through the dryer which has a plurality of vertically spaced troughs which continuously rotate about the vertical axis of the furnace and has stationary chambers which sweep away the pressed bone material from each trough onto a trough below, while continuously circulating heated gas around the troughs.

Other types of heaters can be used to dry the wet lean proteinaceous materials and embrittle the tissue that adds to the bone particles, such as a rotary steam tube dryer and a rotary drum dryer heated directly or indirectly with hot air, but precautions must be taken to avoid application of such elevated temperatures or extended residence times in a directly heated rotary drum which results in burning or scorching of the material, in particular when drying bone particles of approx. 1.2 7 cm in diameter or larger.

The low-density proteinaceous material and high-density proteinaceous material with added brittle tissue materials are removed from the dryer as a dried, low-fat mixture which is preferably air-cooled to ambient temperature after removal from the dryer and while being transported, preferably on a rotary conveyor. If desired, the conveyor may be enclosed in an air-cooled jacket to further increase the cooling and brittleness of the brittle pieces of tissue that add to the bone particles before the dried low-fat mixture is deposited on a screen separator and/or sizer.

Sight

The dried low-fat proteinaceous materials are conveyed to a screening and sorting apparatus which is preferably a floor type screen that vibrates back and forth in an inclined plane, such as a Rotex screen manufactured by Rotex, Inc., Cincinnati, Ohio. Overgrain material from the sieve is preferably recycled to a hammer mill to reduce the particle size so that the material will pass through the selected sieve size. Substantially all of the dry low-fat protein material passes through the selected sieve size, preferably an approx. 8 mesh sieve size, without requiring processing in the hammer mill so that only a small amount of energy is consumed during size processing, and the sorted material is taken to storage and comprises a stable meat meal or meat and bone meal product. The approximate analysis of the meat meal material contained in the above-described process of processing cow waste containing added slaughterhouse bone material is approx. 40 wt% protein, 7.5 wt% fat,

37.5 wt% ash and 9 wt% moisture.

When it is desired to reduce the percentage of bone material in the meat meal material or to produce pure stabilized bone for the production of high-quality gelatin from raw bone containing animal material, the dried, low-fat mixture is processed in an apparatus suitable for separating high-density bone material, preferably with a selected particle size of between 0.317 cm and 1.90 cm, from the dried, low-fat mixture. Such an apparatus is a vibrating two-deck gravity sieve separator adapted to remove particles of bone and organic tissue that are larger or smaller than desired in the final product, after which the material with the selected particle size is subjected to dry gravity separation to remove particles of organic tissue. A suitable screen separator or sorter for the production of high quality gelatin bones is a 34-4800 "Screenaire" vibrating screen separator manufactured by Forsbergs, Inc. of Thief River Fall, Minnesota, which has a capacity of approx. 54 31 kg/hour. In the production of high-quality gelatin legs, the upper of the two separate vibrating screens is preferably a 2-mesh screen that retains particles greater than 7.90 cm in diameter and the lower screen is a 6-mesh screen that retains particles larger than about. 0.317 cm so that the selected medium fraction recovered for further processing has a size range of 0.47 cm to 1.58 cm in diameter. The overgrain material is preferably recycled through a crushing mill. The sub-grain material with a particle size fraction below 0.47 cm is transported to a sieve sorter and a gravity separator which separates the sub-grain material into pure fine "rice bones" and meat meal.

The selected size material from the sieve separator is preferably passed through an air separator before the material is transferred to a gravity separator to recover the particles of very low density protein material to increase the efficiency of the gravity separation step and obtain a valuable meat meal material.

Gravity separator

The size selected material from the sieve is continuously transported to a dry gravity density separator adapted to recover very low density meat meal particles and provide a clean high density bone fraction which constitutes the desired low fat stabilized gelatin bone product with a particle size within the selected preferred range for the production of high-quality gelatin. The density separation is carried out by continuously delivering materials of selected size from a vibrating hopper by means of a vibratory feeder to a dry gravity separator table which in the preferred form comprises a reciprocating inclined air drill with a 10-mesh screening deck. A suitable gravity separator is manufactured by Forsbergs, Inc., which has a capacity of 1814 - 2268 kg/hr. The air pressure, the speed of the forward and backward movement as well as the slope of the screening deck on Forsberg's gravity separator can be varied to give the desired degree of density separation and final product. The particles of bone with a high density move upwards along the screen deck and are collected at the upper end of the screen deck separately from the low density particles of fat and meat tissue together with a small amount of light bone remaining at the lower end of the vibrating screen deck. The material with very low density that collects at the bottom of the inclined separator table consists mainly of brittle fat and meat tissue that can be used in meatloaf. Particles with intermediate density are preferably recycled through the gravity ion separator.

The high density bone material collected at the upper end section of the gravity separator is high quality, pure, stabilized bone material which is useful for making the highest quality gelatin (ie, photographic gelatin). Pure stabilized bone product which is obtained in the above-described manner from roughly cut cubed bone material has the following typical composition: 4.65% by weight moisture,

2.49 wt% fat, 1.98 wt% soluble ammonia, 29.05 wt% protein and 61.68 wt% ash.

Although the amount of each type of material separated and recovered from the raw material will depend on the amount of pressure applied to the raw material in the press, the manner in which the crusher, screen and gravity separator are operated, the yield of purified stabilized gelatin leg has the stated selected particle size range and the preceding analyzes are separated from low-fat proteinaceous material with low density and fat by the process described here has been as high as approx. 15.6% by weight, but the average is approx. 12% by weight based on 100% of the raw material consisting of rough-cut bone. The clean, stabilized fine bone material or "rice bone" obtained from the sub-grain material recovered from the screen separator varies between 12 and 8 wt.%, averaging 10 wt.% of the original rough cut bone raw material. "Rice bone" is of substantially the same quality as the high density stabilized gelatin bone product and with the selected particle size range.

The terms "stable", "stabilization" and "stabilized" as used in the description and/or the claims to characterize the products formed according to the invention, indicate a material which, when stored for a long time, does not develop a repulsive smell, does not discolor and is not attacked of bacteria, fungi or similar microorganisms. With bone material intended for use in the production of high-quality gelatin, the bone must be substantially free of appendage tissue and have a low fat content (ie a maximum fat content of 3% by weight) to facilitate the production of high-quality gelatin without the influence of fat, although bones can be stabilized with a higher fat content (ie up to 10% by weight).

The meat meal and bone material must also be heated during processing to effect stabilization, preferably by removal of moisture, to a temperature of 82°C to provide a "kill temperature" for any micro-organisms that may contaminate the raw bone while reducing the moisture content of the bone to a maximum content of 12% by weight and preferably less than 10% by weight so that the growth of microorganisms is not supported.

It should be understood that in the method according to the invention where the raw poultry material or raw fish material is used as raw material for the press instead of animal raw material, the low-protein, low-density product will be poultry meal material or fish meal material instead of meat meal material, and the description and requirements would have to be drawn up accordingly.

Claims (7)

1. Process for the separation of fat from proteinaceous material in animal, poultry and marine raw material containing fat, water and proteinaceous material, during the formation of stabilized fat and stabilized proteinaceous material, by a mechanical low-energy melting process, characterized by the combination of the following steps (1 ) the organic raw material, coarsely divided, preferably with a piece size of 3 - 15 cm, is introduced into a screw press with a perforated wall section, (2) the organic raw material is passed without the addition of heat through the press by applying pressure to force through the perforated wall section a liquid mixture of (a) consisting mainly of an aqueous fluid, soft protein material of low density, a small amount of protein material of high density in the form of fine bone particles, and a major part of the fat, as it is separated from a pressed low-fat solid material ( b) containing a major part of high-density protein material in the form of bone particles together one with water and a smaller amount of soft protein material of low density, (3) the mixture (a) is heated to the fat melting temperature of 52-86°C and comminuted, preferably to a maximum particle size of 10 mm, and the mixture is separated, preferably by centrifugation, to a liquid fat fraction (c) which also includes water containing dissolved protein material, and a fat-poor protein fraction (d); (4) fat fraction (c) is heated and water and protein material are separated from the fat fraction to form a stabilized fat product; and (5) the low-fat protein fraction (d) and the pressed low-fat material (b) are combined and heated above 82°C to effect sterilization and drying to a maximum water content of 10% by weight, after which the dried mixture is screened to form a stabilized, low-fat protein flour product. 2. Method according to claim 1, characterized in that the mixture in step (5) is heated sufficiently to cause brittleness of low-fat meat tissue on the bone particles, and that the brittle, low-fat meat tissue is separated from the bone material by mechanical rubbing during the subsequent treatment of the dried mixture . 3. Method according to claim 1 or 2, characterized in that the dried mixture in step (5) is separated, preferably by sorting and gravity separation, forming a stabilized, low-fat protein flour product and at least one further product comprising low-fat bone material. 4. Method according to claim 3, characterized in that the dried mixture in step (5) is sieved and sorted to separate a material with a particle size between 3.17 mm and 19.05 mm while under-sized material is collected separately, and that the sieved material is then further separated to form stabilized low-fat protein flour product and low-fat bone material with a size between 4.76 mm and 15.87 mm of a quality suitable for the production of high-quality gelatin. 5. Method according to claim 1, characterized in that the liquid fat fraction (c) in step (4) is heated in a vacuum waste heat evaporator to reduce the moisture content to 15% by weight, and then dried at min. 112°C to a maximum moisture content of 0.5% by weight in a final evaporator to the fat sterilization temperature. 6. Method according to claim 1, characterized in that the liquid fat fraction (c) in step (4) is heated to dry solid protein material suspended in the liquid fat, after which the dried, solid protein material is separated from liquid fat by sedimentation or filtration. 7. Method according to claim 1, characterized in that the liquid fat fraction (c) in step (4) is heated and centrifuged to separate indicated water containing dissolved protein material from the liquid fat, forming a stabilized fat product with a moisture content of 0.5 by weight, the separated water containing dissolved protein material is heated to reduce the water content, and the concentrated protein material is combined and dried in step (5) with fraction (d) and the pressed fatty material (b).