CA1314256C - Continuous digest process for the manufacture of concentrated protein products from animal materials - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A method for the production of concentrated protein products from raw animal materials is disclosed.
Raw animal material is reduced to a compact mass, combined with enzymes in a mixing vessel, and heated to form a pre-digestion mixture. The pre-digestion mixture is transferred to a series of individual digester units arranged in uninterrupted succession. After digestion, the protein product is deboned. A portion of the deboned protein product is recycled to the mixing vessel. The non-recycled portion of the deboned protein product is pasteurized and evaporated to obtain a concentrated protein product.

Description

CONTINUOUS DIGEST PROCESS FOR THE MANUFACTURE OF
CONCENTRATED PROTEIN PRODUCTS FROM ANIMAL MATERIALS

This invention relates to a process for the digestion of animal materials and the resulting production of concentrated protein products.
The by-products resulting from animal (e.g., fish) processing operations often contain substantial amounts of protein. It is economically desirable to recover this protein for various uses, including livestock feed supplements and food flavor enhancers. Many attempts have been made to recover protein from animal waste products. For example, U.S. Pat. Nos. 4,361,586 to Meinke; 4,293/571 to Olofsson, et al.; 4,176,199 to Vollmer, et al. 3,970,520 to Feldman, et al.; 3,928,630 to Perini; 3,796,811 to Huth, et al.; and Russian Patent No. 441,915 disclose methods in which animal by-products are enzymatically hydrolyzed to produce concentrated protein materials. However, the methods disclosed in these patents have particular disadvantages. Many of the methods require long reaction times and are not adaptable to large scale operations. For example, U.S. Pat. Nos.
4,361,568 and 3,928,630 require up to 24 hours ~or digestion. U.S. Pat. No. 4,176,199 requires 4 to 6 hours for digestion. In addition, the above-cited systems do not disclose specific means to monitor and control clogging as the materials are being processed. These systems may only accommodate raw materials having a relatively low percentage of nondigestible solids.
An object of the present invention is to provide 3Q a process whereby animal materials may be digested to form a concentrated protein product.

1 3 1 ~256 Another object of the present invention is to provide a process for digesting animal materials which requires minimal digestion time.
A further object of the present invention is to provide a process for digesting animal materials in which the potential for clogging of the materials being digested is minimized.
A still further object of the present invention is to provide a process for digesting animal materials which is capable o~ continuous, economical, large-scale operation.
These and other objects of the invention will become apparent from the ensuing drawings and detailed description.
In accordance with an illustrated embodiment of the present invention, fish by-products are ground, combined with enzymes in a mixing vessel, and heated to form a pre-digestion enzyme/tissue mixture. The invention is also usable with other animal materialsl including but not limited to poultry, beef, or lamb. The pre-digestion mixture is then digested in an uninterrupted series of individual digester units to produce a protein product.
Each digester unit contains an agitator to mix the materials and enhance digestion. The uninterrupted series of individual digester units, in comparison with large "batch" systems, provides the following advantages: 1) decreased digestion time, due to increased agitation; 2) uniform digestion time, resulting from the continuous flow of materials; and 3) greater control over the degree of protein hydrolysis, resulting from precise control of digestion time.

After digestion, the nondigestibles (consisting largely of fish bones) are removed from the protein product. A portion of the deboned protein product is recycled to the initial mixing vessel. Recycling provides heat and additional enzymes to the pre-digestion mixture for enhanced digestion. Also, recycling increases the ratio of liquids to solids, reducing the possibility of system clogging. The non-recycled, deboned protein product is pasteurized and concentrated to produce a high density protein product.
Fig. 1 is a general schematic representation of the process disclosed herein.
Fig. 2 is a detailed schematic representation of a preferred embodiment of the process disclosed herein.
The present invention is generally described in the schematic representation of Fig. 1. Raw animal material 10 is added to a grinder 12 and passed into a mixing vessel 14. The animal material 10 may consist of mammals, poultry, or fish, or their by-products. Enzymes 16 are added to the mixing vessel 14 and combined with the raw material 10. The mixture is then passed through a heat exchanger 18. After heating, the mixture is digested in a series of digesters arranged in uninterrupted succession. Fig. l shows two digesters 20a, 20b having agitators 22a, 22b, respectively. The sequential arrangement of digesters 20a, 20b provides enchanced agitation in comparison with conventional "batch"
systems. The enhanced agitation results in decreased digestion time. From the digesters 20a, 20b, the material is deboned (if necessary) in a deboner unit 24~ A portion of the deboned product is recycled to the mixing vessel 14 through line 25. Recycling provides additional heat and 1 ~14256 enzymes to the raw materia~ 10 in the mixing vessel 14.
In addition, recycling dilutes the raw material 10, reducing the possibility of clogging in the system. The non-recycled portion of the deboned product is heated in a pasteurizer 26, evaporated in a concentrator 28, and isolated.
For purposes of further illustration and explanation, the invention will be des~ribed with reference to the processing of raw fish material with particular reference to Fig. 2. Raw fish material 30 containing approximately 25% solids is added to a grinder unit 32 (Autio Co. Model 801, 15 H.P. fitted with an RMF
Co. 3/8" slanted hole end-plate) at a rate of 2,000 lb/hr. The raw material 30 may constitute whole fish or waste scraps, including "fillet frames" (remains from filleted fish). Also, the raw material 30 may be pre-ground before entering the grinder 32 to facilitate its passage through the end-plate of the grinder 32.
~fter passing through the grinder 32, the raw material 30 is added to a mixing vessel 34 (Autio Co. 500 lb. cap. bin with 2.5" vane pump) where enzymes 36 are added. The mixing vessel 34 is fitted with a screw conveyor/transfer pump unit 37 which blends the materials. Addition of the enzymes 36 may not be necessary if autolytic enzymes endogenous to the raw materials bein~ diqested are present in sufficient quantities. However, the use of additional enzymes provides more predictable and controllable digestion. The added enzymes 36 may include tuna visceral extracts, papain, or other proteolytic enzymes. Papain (Rohm Tech, Corolase 100), the preferred enzyme, is added in quantities of approximately 500 ml/1000 lb. of whole fish, or 200 ml/1000 lb. of scrap fish. In addition, acids, e.g. phosphoric, or acetic, may be optionally added to the raw material for enhanced enzyme activity. The type of acid and quantity used will depend on the enzymes involved.
After passing through the mixing vessel 34, the raw material 30 and enzymes 36 (at a temperature [Tl] of approximately 40 F) move through line 38 to an optional in-line disintegrator 40. (It should be noted that all lines shown in the embodiment of Fig. 2 are approximately 2" in diameter, except where otherwise indieated.) The optional in-line disintegrator 40 may not be necessary if finely-ground raw materials are used. The optional in-line disintegrator 40 reduces the flesh portions of the raw material 30 to a slurry. The bones and other solids are reduced to individual fragments 1/4" to 3/8" in diameter.
The mixture is passed through line 42 into a heat exchanger 44 (DeLaval Co., Contherm, model 6x4 4 ft2 tubular scraped surface heat exchanger). The heat exchanger 44 consists of an inner cylinder (not shown) jacketed by a second cylinder through which steam [Sl]
at 200 lb/hr (30-75 psig) passes. Inside the inner cylinder is a conventional ~craper/agitator unit driven by a motor 46 to increase heat transfer and prevent blockage of the cylinder. The raw material 30 and enzymes 36 pass through the inner cylinder and are heated by the steam passing through the second cylinder. Steam condensate produced in the heat exchanger 44 is collected in a trap 48 and released from the system. The heated mixture leaves the exchanger 44 at an approximate temperature [T2] of 140 F.

131425h After release from the heat exchanger 44 and passage through line 50, the mixture enters the digester units 52a, 52b (350 lb. capacity cylinders, with 12"
diameter and 60" length) connected by line 54 in uninterrupted succession. The heated materials pass continuously through the digesters 52a, 52b, where the materials are agitated by stirring units 56a, 56b.
Passa~e through the digesters 52a, 52b occurs in approximately 21 minutes. During this time, the mixture is converted to a liquid protein product. The arrangement of continuous digesters 5~a, 52b provides decreased digestion time in comparison with single-vessel "batch"
systems. 5pecifically, the smaller, individual digesters 52a, 52b permit substantially increased a~itation of the raw material 30 and enzymes 36. Increased agitation results in decreased digestion time. ~lso, the use of small digesters permits digested products immediately to pass through the system, avoiding the delays inherent in single vessel "batch" systems.
The liquid protein product leaves the digesters 52a, 52b, and proceeds through line 58 into an open-air collection funnel 59. From the open-air funnel 59, the materials enter a bone separator 60. Should excess solids block the mouth of the bone separator 60, fluid flow through the funnel 59 will cease, permitting the system operator immediately to recognize and rectify the problem. The bone separator 60 is a centrifugal decanter (DeLaval Co. NX207 - 7 1/2 H.P.~, although a vibrating filtration screen may be used. The centrifugal decanter, as shown in Fig. 2, is operated at approximately 3600 rpm, substantially less than normal operating speed. Reduced decantation speeds are necessary to minimize protein i 3 1 4256 losses inherent at high speeds. Bone and other undesired materials 61 are removed by the bone separator 60 at a rate of 240 lb/hr.
The deboned protein product then passes through line 62, with a portion of the product entering line 64 and regulator valve 66. The material in line 64 (at an approximate temperature [T3] of 125 F) contains 20~
solids. It is recycled at 200 lb/hr to the mixing vessel 34. At the mixing vessel 34, the deboned protein product is added to the initial mixture of enzymes 36 and raw material 30. Recycling the deboned protein product provides added heat and enzymes to the initial mixture for enhanced digestion. In addition, the recycled product dilutes the waste material 30, resulting in diminished viscosity and the reduced possibility of system clogging.
Dilution also facilitates the use of raw materials with a high percentage of nondigestible solids, including crab and shrimp waste.
The non-recycled portion of the deboned protein product passes through line 68 and check valve 70 to a pasteurizer unit 720 Pasteurization is necessary to inactivate enzymes and destroy pathogenic microorganisms in the product. The pasteurizer unit 72 consists of a direct steam injection heater (Cherry Burrell 3/8" UHT
steam injection heater), in which steam is injected into the deboned protein product. The product then flows into line 76. The deboned protein product and steam are held in line 76 for approximately 3 seconds at a temperature between 240-260 F [T4]. A steam source [S2] provides the steam at a rate of 300 lbs/hr, 75 psig. At 240-260 ~, undesired bacteria are destroyed and enzymes are inactivated. The maintenance of [T4] is possible 1 3 1 ~256 through the action of a throttling valve 78 to which line 76 is connected. Valve 78 maintains the pressure in pasteurizer 72 and line 76 at 40 psig. At this pressure, the temperataure in pasteurizer 72 and line 76 can be as high as 285 F, the saturation temperature of steam at 40 psig. The length of line 76 is such that the product passage time therethrough will be approximately 3 seconds. As the protein product flows through throttling valve 78, the pre.ssure is reduced ~o 3.7 psia t22.5" Hg vacuum) and a portion of the water in the product flashes to steam. This reduces the product temperature to approximately 150 F as the pasteurized protein product (a liquid/vapor combination) enters a cyclonic separator 80.
The liquid portion of the protein product enters the lower region 81 of separator 80, while vapor remains in the upper portion 82. The temperature [T5] of the liquid in lower region 81 of separator 80 is approximately lS0 F.
The liquid passes from the separator 80 through system line 83 to a centrifugal pump 85 (2hp, 3600 rpm).
Antioxidant (Ethoxyquin) is pumped into line 83 by metering pump 84 at a rate of 20 grams/hr to inhibit oxidation of oils in the product. The antioxidant and protein product are mixed as they pass through pump 85.
From centrifugal pump 85, the liquid product enters line 88, and passes into a plate type heat ~xchanger 90 at a rate of approximately 40 gpm. The liquid is placed in heat exchange relationship with steam fro~ a source S3 (delivered at 440 lb/hr, 2 psig). The liquid product is further evaporated by heat in exchanger 90. The condensed steam from heat exchanger 90 enters a trap 92, and is eliminated.

_~_ 131~256 After ~urther evaporation, the concentrated liquid product leaves the exchanger 90, enters the lower region 81 of the separator 80, and repeats the process described above. The vapors leaving the exchanger 90 enter the upper region 82 of the separator 80, combining with previously produced vapors. The vapors pass from the upper region 82 of the separator 80 into line 96 (4"
diameter) at a rate of 440 lb/hr. From line 96, the vapors enter a water cooled heat exchanger 98 (20 ft2 shell and tube type). The vapors are condensed in the heat exchanger 98, passed into vacuum pump 100 (3 h.p.
SIHI, model LPH 3404), and removed.
The concentrated liquid protein product not entering the heat exchanger 90 from the concentrator 80 is passed into line 102 (at a rate of 1320 lb/hr), through a pump 104 (1 hp, Waukesha, model 15 Universal), and through valves 106 (check-type) and 108 (2 way plug type). After entering valve 108, a portion of the concentrated liquid protein product passes into line 110, through another valve 112, and into a refrigerated storage tank 114 t2000 gallon capacity) at a rate of 660 lb/hr. The material in the tank 114 is continuously agitated by an agitator unit 116 to avoid separation of oils in the material and to facilitate cooling.
The storage tank 114 has two purposes. First, it retains materials ready for spray drying. ~s explained below, materials are subjected to spray drying at a rate of 660 lb/hr. However, materials leave the separator 80 at approx. 1320 lb/hr. To account for the differences in flow rate, the product is temporarily stored in the tank 1140 Second, should a user desire to retain the product in a liquid form, it may be temporarily stored in the tank _g _ 1 3 1 ~56 114. To preserve the product stored in the tank 114, acids (preferably H3PO4) may be added. The ~3PO4 is added in a quantity sufficient to lower the pH of the material to approx. 3Ø Antioxidant preservative agents, including potassium sorbate, may also be added. The material not entering the tank 114 proceeds through valve 117, centrifugal pump 118 and through line 120 (flow rate of 660 lb/hr) to a high-pressure pump 122 (Gaulin Co., model 300SE, 5 H.P. high-pressure type). The pump 122 is designed to increase product pressure for atomization.

The protein product is then passed through line 124 (3/8"
diameter) at a pressure of approx. 3000 psig into atomizing nozzle 125. The temperature [T6] at the top of the spray dryer 126 (DeLaval Co. model 72-12) is approximately 425 F. Air flows through the spray dryer at approximately 3000 ft3/min. The concentrated product is sprayed into the top of dryer 126 at a rate of 660 lb/hr and released from the bottom of the dryer 126 in powder form at a temperature [T7] of 180 F at 200 lb/hr.
The following examples describe proximate composition data for various marine fish digested in the above-described invention. Column A shows the composition of raw waste fish, column B is the composition of the digested fish (with bones removed by passage of the digested product through a 40 mesh screen), and column C
is the composition of the digested fish after concentration to a moisture level of 50%. (The columns may not add up to 100% in view of proximations made during analysis of the data.

Proximate Analyses of 5 species of Marine Scrap Fish A B C
Digested Deboned Concentrated Raw Fi=h Product Product English Sole Moist 79.32~ 82.75% 50~00 Protein 13.40 13.~8 40.52 Fat 2.64 2.75 7.97 Ash 4.94 .52 1.51 Petrale Sole Moist 73.44% 76.28% 50.00 Protein 14.58 15.14 31~91 Fat 7.76 8.06 16.99 Ash 4.42 .52 1.10 Orange Rockfish ~oist 70.30% 74.59% 50.00 Protein 16.19 17~18 33.81 Fat 7.26 7.70 15.15 Ash 6.53 .53 1.04 Yellowtail Rockfish Moist 71.61% 75.44~ 50.00%
Protein 15.79 16.64 33.86 Fat 7.02 7.40 15.06 Ash 5.78 .53 1.08 True Cod Moist 78.92% 81.28~ 50.00 Protein 15.60 16.07 42.90 Fat 2.09 2.15 5.74 Ash 4.33 .51 1.36 While I have shown and described a preferred embodiment of my invention, it will be apparent to those skilled in the art that changes and modifications may be made without departing from my invention in its broader aspects. I therefore intend the appended claims to cover all such changes and modifications as follows in the true spirit and scope of my invention.

Claims (19)

1. A method for continuously digesting animal materials and producing concentrated protein products therefrom comprising:
reducing said animal materials to a finely ground condition;
combining said ground materials with enzymes in a mixing vessel to form a pre-digestion mixture;
heating said pre-digestion mixture;
digesting said heated pre-digestion mixture in a successive arrangement of individual digester units each having an agitator therein to form a protein digestion product, whereby said successive arrangement of digesters provides increased agitation and mixing of said mixture, resulting in decreased digestion time, uniform digestion time, and controlled protein hydrolysis;
recycling a portion of said protein digestion product to said mixing vessel, whereby said recycling provides heat and additional enzymes to said pre-digestion mixture in said mixing vessel, dilutes said pre-digestion mixture, and reduces the viscosity of said mixture;
pasteurizing the non-recycled portion of said protein digestion product to inactivate enzymes and destroy pathogenic microorganisms, and to reduce the microbial load therein; and concentrating said pasteurized, protein digestion product.

2. The method of claim 1 wherein said animal materials comprise fish.

3. The method of claim 1 wherein said animal materials comprise poultry.

4. The method of claim 1 in which said enzymes comprise proteolytic enzymes.

5. The method of claim 4 in which said proteolytic enzymes comprise papain.

6. The method of claim 4 in which said proteolytic enzymes comprise autolytic enzymes endogenous to the materials being digested.

7. The method of claim 4 in which said proteolytic enzymes comprise visceral extracts.

8. The method of claim 1 in which said pre-digestion mixture is heated in a tubular, scraped surface heat exchanger to a temperature of between about 130° and 160°F.

9. The method of claim 1 in which acids are added to said pre-digestion mixture to regulate pH and enhance enzymatic activity therein.

10. The method of claim 1 wherein said digestion is carried out for a period of between 15 to 30 minutes.

11. The method of claim 1 wherein undesired bones and solid materials are removed from said protein digestion product.

12. The method of claim 1 wherein bone removal is accomplished by passage of said protein digestion product through a vibrating screen.

13. The method of claim 1 wherein bone removal is accomplished by passage of said protein digestion product through a decanting centrifuge.

14. The method of claim 1 wherein pasteurization is accomplished by the mixture of said protein digestion product with steam in a direct steam injection heater.

15. The method of claim $ in which preservatives are combined with said pasteurized protein digestion product for the preservation thereof.

16. The method of claim 15 in which said preservatives comprise an acidic agent.

17. The method of claim 15 in which said preservatives comprise antioxidants.

18. The method of claim 15 in which said preservatives comprise mold inhibitors.

19. A method for continuously digesting animal materials as recited in claim 1, further comprising continuously feeding said materials in combination with enzymes to at least two individual digester units having agitators therein, whereby said continuous feeding and digestion of said materials in said digester units provides enhanced agitation of said enzymes in said materials, resulting in more efficient digestion and diminished reaction times.