WO2005058060A1

WO2005058060A1 - A plant for enzymatic hydrolysis of a batch of animal or vegetable components and method for using the plant

Info

Publication number: WO2005058060A1
Application number: PCT/DK2004/000870
Authority: WO
Inventors: Stig Voldbjerg SØRENSEN
Original assignee: Danflavour Aps
Priority date: 2003-12-18
Filing date: 2004-12-16
Publication date: 2005-06-30
Also published as: DK176496B1; DK200301878A

Abstract

A plant (1) and method for enzymatic hydrolysis of a reaction mixture (23) comprising a batch of at least partly hydrolysable animal or vegetable components (26) or a mixture of these components. The plant comprises a reactor (2) having a feed orifice (7) and a base section (6) having a bottom orifice (9), a pump (11) and a mixer (12) provided in or close to the bottom orifice (9) for leading a partial volume of the reaction mixture (23) out through the bottom orifice (9) of the reactor (2) when the pump (11) is in operation. The reaction mixture is recirculated for a hydrolysis period through a recirculation pipe (16) to the base section (8) of the reactor (2) in such a way that the hot fat phase settles uppermost in the reactor and is kept intact while the pump and mixer are in operation. After hydrolysis the reaction mixture (23) is left for phase separation into a solid phase (26), an aqueous phase (25), and a fat phase (24), respectively. The liquid phases (24, 25) are drained off as pure, clear phases through the solid phase (26) which functions as a filter.

Description

A plant for enzymatic hydrolysis of a batch of animal or vegetable components and method for using the plant

The invention relates to a plant for enzymatic hydrolysis of a reaction mixture comprising a batch of at least partly hydrolysable animal or vegetable components or a mixture of these components and of the kind comprising a reactor having an upper section with a feed orifice and a base section with a bottom orifice.

The invention also relates to a method for using the plant.

A large part of the food industry, such as slaughterhouses and the finished product industry, produce large quantities of waste products through the processing of for example meat, fish, and poultry. Such waste products are removed by burning or they can, to a certain extent, be transformed and be used again to for example bone meal or animal food.

The hydrolysable part of the waste products can however be hydrolysed and used in the production of for example aromatics, stocks, and soups.

A continual hydrolysis demands large space-demanding plants, large investments and large quantities of raw material in order to be profitable. With smaller or small raw material quantities smaller batch plants advantageously can be used.

The known small batch plants consist of a vertical reactor with a heating jacket and a mixer which keeps the reaction mixture mixed. The reactor typically has a conical bottom with a bottom outlet, through which the finished hydrolysed mass, that is to say the mixture of hydrolysate, fat, and bone is removed in one step for subsequent separation in for example a decanter. One of the disadvantages of these known plants is that the bottom outlet is easily clogged since the bones are packed together in the bottom outlet, while the reactor is emptied.

In some batch reactors, it is attempted to solve this problem by means of an auger rotating over the bottom outlet. The auger lifts, to a certain amount, the bones away from the bottom outlet but only partly lowers the risk of clogging of the bottom outlet since the auger rotates relatively slowly.

As a consequence of the operating problems of the batch plant, the hydrolysable waste products are only utilized in a limited amount .

The waste products from meat processing are a directly available raw material, which furthermore also is expensive to get rid of. Utilisation of this waste for production of a hydrolysate, which can be used as for example soups, stock, and aroma-concentrates, can therefore be an advantageous source of income, as long as the operation of the batch plant can be optimised.

In a first aspect according to the present invention a batch plant is provided for enzymatic production of a hydrolysate, where the batch plant has a simple, reliable operation, and is easier to maintain and use than previously known.

In a second aspect according to the present invention a batch plant is provided for utilisation of enzymatic hydrolysable by-products from foodstuffs and foodstuff processing.

The novel and unique feature according to the invention, whereby this is achieved, is the fact that the plant furthermore comprises a pump and a mixer provided in or close to the bottom orifice for keeping the reaction mixture in dispersion and forcing the dispersed reaction mixture through the bottom orifice of the reactor when the pump is in operation.

In known batch reactors for similar purposes, particulate matter of large density has a tendency to be deposited in and around the bottom orifice of the reactor, which therefore can be difficult to keep open during e.g. unloading of the reactor.

This disadvantage is overcome in a simple manner by providing the suction necessary to maintain a continuous flow out through the bottom orifice by means of the pump. The dynamic pressure that the pump has to supply varies depending on the dimensions of the reactor and the composition of the reaction mixture and can be determined empirically.

In addition, the mixer keeps the particulate matter in the reaction mixture in continuous dispersion in the area around the bottom orifice. The work of the pump is therefore not made difficult by accumulations of particulate matter in and around the bottom orifice.

During hydrolysis components rich in protein will cleave into smaller peptides and amino acids. On heating of the reaction mixture, fat and lipids are separated and deposited on top of the water phase as a fat phase uppermost in the reactor. The size of the fat phase increases during the hot enzymatic reaction as the fat melts and oils and lipids are separated.

The type of mixer and the rotational speed of this mixer are chosen so that the fat phase is kept intact as far as possible during the rotation of the mixer and suction of the pump.

In a preferred embodiment of the plant according to the present invention the mixer is a mixing propeller which can keep at least the partial volume of the reaction mixture, which is in the area near the bottom orifice, continuously mixed. Hydrolysable matter will naturally continuously move towards the bottom section due to gravitation and form part of this partial volume.

Alternatively, the mixer can be formed as a rotating knife to thereby also be able to divide larger particles in the reaction mixture at the bottom orifice.

Other kinds of mixers, such as e.g. a disc mixer with blades or a blade mixer, are also comprised within the scope of the invention.

A very high-speed mixer will be inclined to put the entire reaction mixture into rotation about its axis. If the reaction mixture builds up along the interior wall of the reactor, this together with the suction effect of the mixer in axial direction could result in formation of a vortex. Such a vortex will emulsify fat phase and water phase, which is undesirable. The rotational speed of the mixer is therefore calibrated to keep a partial volume of reaction mixture between the bottom orifice and the fat phase in a dispersed mixture without the fat phase being mixed into the water phase.

A good contact between substrate in form of hydrolysable components, such as bone from meat waste, and enzyme will cause the reaction to pass off under optimum reaction conditions .

For this purpose the plant according to the present invention comprises a recirculation pipe having a first end extending at least a distance up through the base section of the reactor between the mixer and the interior wall of the reactor. Through this recirculation pipe the pump can pump reaction mixture from the bottom orifice of the reaction back to the reactor, and the mixer and pump can keep the reaction mixture in constant movement .

Thereby better agitation intensity, mixing speed and heat transfer are obtained than in known batch reactors. The desired good contact between enzyme and substrate gives optimum rate of reaction. In addition the bottom orifice of the reactor is prevented from clogging.

The fluid flows in the recirculation pipe can advantageously be controlled by means of a first valve in the first end of the recirculation pipe and a second valve in the other end of the recirculation pipe.

Recirculated reaction mixture passes through the first open valve during a first period, for example corresponding to the desired hydrolysis duration. At the end of this first period, the first valve is closed.

The second valve is kept closed for the entire first period and a subsequent phase separation period, during which a phase separation into fat phase, aqueous phase and solid phase can take place in the reaction mixture .

The second valve is then opened, and the phases are successively drained off via the bottom orifice of the reactor and out through the second end of the recirculation pipe. First, the aqueous phase is drained off, then the fat phase is drained off, and finally a solid phase is let off that mainly consists of bone, bone particles and other non- hydrolysable particulate matter and residual components.

During the draining off of the above liquid phases, the solid phase functions as a filter and retain the impurities that might be in the liquid phases. The drained off aqueous phase can have a small content of fat and lipids and can therefore be passed further through a fat separating tank.

A small part of the fat will, during the draining off of the fat phase, settle as residual fat on bone and particulate matter in the solid phase. This residual fat can be leached out from the solid phase if reuse of the residual fat is desired.

By means of the plant according to the present invention, the fat phase can be kept intact outside the field of action of the mixer if the first end of the recirculation pipe is made with a screen extending in a plane perpendicular to the rotational axis of the mixer so that the recirculated reaction mixture can be forced in towards the centre of the reactor for contact again with the mixer.

If the screen has a length which is greater than or equal to the diameter of the recirculation pipe, the recirculated reaction mixture can then, in a simple manner, be prevented from being pressed up in the reactor due to the pump pressure. The fat phase can therefore be kept intact during the entire first period.

In an alternative embodiment of the present invention the first end of the recirculation pipe can be bent an angle of between 70° and 110°, preferably between 75° and 105°, but especially between 80° and 100° to thereby send the recirculated reaction mixture tangentially into the reactor.

The reactor can furthermore comprise an agitator located above the mixer for keeping an additional part of the reaction mixture in mixing. Such an agitator must be mounted on the reactor in such a way that the fat phase on the surface of the reaction mixture is not contacted. Furthermore, the agitator must not form a vortex or contribute to the increase the vortex of the mixer.

The plant and method will be described in more detail in the following with reference to the accompanying drawing and example, in which

Fig. 1 is a longitudinal sectional view through an empty plant according to the present invention,

Fig. 2 is the view in fig. 1 in an initial hydrolysis stage in which the reactor has been filled with a batch of reaction mixture, and

Fig. 3 is the view in fig. 1 showing the hydrolysed reaction mixture after phase separation and during draining off of aqueous hydrolysate.

In the following it is assumed that the batch plant 1 in figs. 1, 2, and 3 is used for proteolytic hydrolysis of a mixture of water and divided bone .

The plant 1 is comprised of a cylindrical reactor 2 with a lid 3. The reactor 2, typically a tank 2 of acid-proof stainless steel, is encapsulated in a heating jacket 4, around which a heat-insulating jacket 5 is mounted. The lid 3 is here shown to be a simple lid 3 with an insulating cover 6. On filling of the reactor 2 through the feed orifice 7, the lid is taken off, and the reactor is filled with a batch of reaction mixture consisting of water and bone. The enzyme is added either at once or after heating of the reaction mixture to the hydrolysis temperature.

The reactor 2 has a conic bottom section 8 with a bottom orifice 9 connected to a pump 11 by means of an outlet pipe 10, by way of example the pump is here a centrifugal pump. A mixer 12 in form of a mixing propeller 12 for keeping the reaction mixture in rotation above the bottom orifice 9 is mounted directly above the bottom orifice 9. The reactor 2 furthermore has an agitator 13. The agitator 13 is exemplarily shown in fig. 1 as a flat-bladed impellor driven by an external motor 14 and sweeps a large partial volume of the reaction mixture in the centre section 15 and base section 8 of the reactor 2.

The pump 11 pumps reaction mixture 23 from the bottom orifice 9 of the reactor 2 out through the outlet pipe 10 and further out into the recirculation pipe 16 which has a first end 17 with a first valve 18 and a second end 19 with a second valve 20 which has an discharge outlet 27. The first end of the recirculation pipe 16 has an upper orifice 21 which is screened by means of a screen 22 for directing the flow of recirculated reaction mixture in over the mixing propeller 12.

Fig. 2 shows a plant 1 according to the invention full of reaction mixture 23 and enzyme. The reaction mixture 23 is heated and a fat phase 24 has been separated on the surface of the water phase 25 of the reaction mixture 23, in the water phase bone fragments 26 are seen dispersed by means of the agitator 13 and mixer 12, respectively. The first valve 18 is open and the second valve 20 is closed.

The mixer 12 keeps the reaction mixture 23 sufficiently mixed so that the bone fragments 26 do not block the bottom orifice 9 and the outlet pipe 10 when the reaction mixture, by means of the pump 11 as indicated with the arrows, is continuously recirculated back to the base section 8 of the reactor 2 through the recirculation pipe 16. The pump 11 forces the recirculated reaction mixture through the open valve 18 and out through the orifice 21 of the recirculation pipe 16. The recirculated reaction mixture under pressure, shown with the arrow, glances off from the screen 22. The recirculation takes place in the base section 8 so that the fat phase 24 can be kept intact during the course of the entire reaction. An intact fat phase 24 can be separated or skimmed off as an independent fraction without the reaction mixture needing additional treatment by e.g. centrifugation. The constant recirculation ensures the best possible contact between enzyme and substrate and heat transmission.

After termination of the hydrolysis, the agitator 13, mixer 12, and pump 11 are stopped. The hydrolysed reaction mixture 23 is left until it, as shown in fig. 3, has been divided into three phases: a fat phase 24 at the top of the reactor 2, a solid phase 26 in the base section 8 of the reactor 2, and a aqueous phase between the fat phase 24 and the solid phase 26.

Fig. 3 shows the plant 1 after phase separation and with a partly emptied reactor 2.

The solid phase 26 functions as a filter during the draining off of the liquid phases 24,25. Particulate matter in the liquid phases will be caught and retained in the pore volume of the filter during the draining off, and the liquid phases can be drained off as pure, clear phases.

The reactor is emptied, as shown in fig. 3, by closing the first valve 18 and opening the second valve 20. First the liquid phases 24,25 are drained off. The pump 11 is activated, and liquid phase in form of aqueous hydrolysate 25 is pumped, as indicated with the arrows, via the second open valve 20 out through the discharge outlet 27 of the second end 19 of the recirculation pipe 16 and collected. After draining off of the hydrolysate 25, the fat phase 24 is drained off in a similar manner and collected. Within the scope of the invention, the liquid phases can also be drained off of the reactor as a result of the pressure from the liquid column in the reactor.

Then, the second valve 20 is closed, the reactor 2 is filled with water, the mixer 12, agitator 13 and pump 11 are activated, and the solid phase and reactor are rinsed by recirculation, as described above, for a desired period of time. Then, the second valve 20 is opened again, and the suspension of solid phase and water is pumped out of the reactor.

ILLUSTRATION EXAMPLE

An approximately 4 m³, insulated, cylindrical reactor equipped with a heating jacket, having a diameter of 1.4 m, has a conic bottom with a bottom orifice of a diameter of 0.10 m. The valves of the recirculation pipe are closed. The reactor is filled with a batch of raw material - reaction mixture of 1,800 kg beef bone from slaughterhouse waste (divided into pieces of a length of approximately 2.5 cm) and 1,200 kg water. Agitator and mixer are activated, and the mixture is heated to an average temperature of 55°C by means of the heating jacket which contains hot vapour at 2 bars. The pump is activated, the mixer is activated, and the first valve is opened, and recirculation begins. 1,800 g Novozyme 2.4 Alcalase (protease) is added, and stirring is maintained for a hydrolysis period of 60 minutes. The Alcalase is inactivated by heat denaturation, the temperature of the reaction mixture being raised to 95°C for 30 min. by means of heat from the heat jacket. Stirring and pumping are stopped. The first valve is closed. The reaction mixture is left for 10 min. The bone fraction settles to the bottom of the base section of the reactor. The second valve is opened, and approximately 3,000 1 clear liquid is first drained off that has a protein content of 6 w% calculated on basis of the mass of beef bone. Then 12 w% clear liquid fat is drained off, calculated on basis of the mass of beef bone.

The second valve is closed, 1,000 1 water is added, the first valve is opened, and the agitator, mixer, and pump are activated, and the water and the solid phase are mixed to a wash mixture. After 5 minutes the first valve is closed, and the second valve is opened. The wash mixture is pumped out.

The content of proteins, peptides, and amino acids can be extracted from the aqueous phase. Alternatively, the savoury, aqueous phase is used as it is for e.g. soups or meat extract.

Fats, oils, lipids, and bone can be utilized in a known manner.

Claims

Claim

1. A plant (1) for enzymatic hydrolysis of a reaction mixture (23) comprising a batch of at least partly hydrolysable animal or vegetable components (26) or a mixture of these components, and of the kind comprising a reactor (2) having an upper section with a feed orifice (7) and a base section (6) having a bottom orifice (9) , characterized in that the plant (1) furthermore comprises a pump (11) and a mixer (12) provided near the bottom orifice (9) for leading a partial volume of the reaction mixture (23) out through the bottom orifice (9) of the reactor (2) when the pump (11) is in operation.

2. A plant (1) according to claim 1, characterized in that the bottom orifice (9) of the reactor is connected, via the pump (11), to a recirculation pipe (16) having a first end (17) extending at least a distance up through the base section (8) of the reactor between the mixer (12) and the interior wall of the reactor (2) , and a second end (19) , through which the content of the reactor (2) is drained.

3. A plant (1) according to claim 2, characterized in that the first end (17) of the recirculation pipe (16) has a screen (22) extending in a plane mainly perpendicular to the rotational axis of the mixer (12) .

4. A plant (1) according to claim 3, characterized in that the screen (22) has a length greater than or equal to the diameter of the recirculation pipe.

5. A plant (1) according to claim 2 or 3 , characterized in that the first end (17) of the recirculation pipe (16) is bent in an angle of between 70° and 110°, preferably between 75° and 105°, but especially between 80° and 100°.

6. A plant (1) according to any of the claims 2 - 5, characterized in that the first end (17) of the recirculation pipe (16) has a first valve (18) , - that the second end (19) of the reaction pipe (16) has a second valve (20) , that the first valve (18) is open for a first period, during which the reaction mixture (23) is recirculated to the reactor (2) by means of the pump (11) , and then is closed, that the second valve (20) is closed during the first period and is open when the reactor (2) is emptied.

7. A plant (1) according to any of the claims 1 - 6, characterized in that the mixer (12) is a mixing propeller or a rotating knife.

8. A plant according to any of the claim 1 - 7, characterized in that the reactor (2) furthermore comprises an agitator (13).

9. A method for, by means of a plant (1) according to any of the claims 1 - 8, producing a hydrolysate (25) rich in protein of an aqueous mixture of a reaction mixture (23) in form of a batch of at least partly hydrolysable animal or vegetable components (26) or a mixture thereof, said method comprising the steps of heating the mixture (23) to a hydrolysis temperature, adding a protease or a mixture of proteases to hydrolyse the content of the reaction mixture (23) of hydrolysable matter, keeping the reaction mixture (23) dispersed for a determined period of hydrolysis, inactivating the protease or the mixture of proteases, characterized in that the method furthermore comprises that the second valve (20) is closed during the hydrolysis period, that the first valve (18) is open during the hydrolysis period, that the reaction mixture (23) during the first period corresponding to the hydrolysis period is recirculated to the reactor (2) by means of the pump (11) through the first open valve (18) of the recirculation pipe (16) , that the pump (11) is stopped after the first period, - that the reaction mixture (23) is left for phase separation into at least three phases, a solid phase (26) , an aqueous phase (25) , and a fat phase (24) , respectively, that the first valve (18) is closed, - that the second valve (20) is opened, that the aqueous phase (25) is drained off through the discharge outlet (27) of the second end (19) of the recirculation pipe (16) . that the fat phase (24) is drained off through the discharge outlet (27) of the second end (19) of the recirculation pipe (16) .

10. A method according to claim 9, characterized in that the solid phase (26) is pumped out through the discharge outlet (27) of the recirculation pipe (16) , optionally after addition of wash water.