IE78010B1

IE78010B1 - A process for producing a food product

Info

Publication number: IE78010B1
Application number: IE960069A
Authority: IE
Inventors: Joseph Connolly; William Gerard Connolly; John Connolly; William Vincent Connolly
Original assignee: Meadowgate Co Ltd
Priority date: 1996-01-22
Filing date: 1996-01-22
Publication date: 1998-01-28
Also published as: IE960069A1; GB9605184D0; GB2309150B; GB2309150A

Abstract

A flaked animal feed product is produced by delivering raw grain, especially maize, onto a wetting conveyor (7) and spraying 4-6% water by weight of the grain onto the raw material as it passes along the wetting conveyor (7). The wetted grain is then delivered to one or more damping bins (8) where it is soaked until the moisture content of the grain is between 14% and 17% (w/w). The soaked grain is then delivered to a cooker (26) where it is cooked at approximately 100°C for approximately 1 hour before being flaked by passage between a pair of rollers (31). The flaked material is then dried and cooked. The soaked material may be preheated before delivery to the cooker.

Description

Introduction The invention relates to a process for producing a food product, and in particular to a process for producing a flaked animal feed product.

Flaked animal feed products are well known. Usually, such products are produced by cooking a raw grain material such as maize, passing the cooked material through a flaker/roller and finally drying and cooling the flaked material. During cooking, native starch within the raw grain is gelatinised to substantially increase the susceptibility of the starch to enzymes, thus making the starch more digestible. Unfortunately, conventional cooking techniques rarely result in the complete gelatinisation of native starch into the more digestible form leaving a certain portion of the starch in the product undigested, thus decreasing the nutritional value of the product. One of the main reasons for this poor gelatinisation of native starch is the poor heat conductivity of the grain.

Further, many cereals and legumes have indigenous dangerous toxins. These toxins are susceptible to heat and may be inactivated at high temperatures. However, conventional cooking techniques tend to result in poor, if any, destruction of these toxins. Again, this is primarily due to the poor heat conductivity of raw grain.

It is an object of the invention to provide an improved process for producing flaked animal feed which will overcome at least some of these disadvantages. 7801 0 Statements of Invention According to the invention there is provided a process for producing a flaked animal feed product comprising the steps of:5 uniformly wetting grain with from 4 to 6% by weight of water and soaking the grain to achieve a moisture content in the grain of from 14% to 17% by weight; delivering the soaked material to a cooker; cooking the soaked material at a temperature of between 10 90°C and 110°C for between 50 to 60 minutes; flaking the cooked material by passing it between a pair of rollers; drying the flaked material; and cooling the dried material.

In a particularly preferred embodiment of the invention the process includes the steps of:delivering raw material onto a wetting conveyor; spraying 4-6% water by weight of the raw material onto the raw material as it passes along the wetting conveyor; delivering the wet raw material to one or more damping bins; and soaking the wet raw material until the moisture content of the raw material is between 14% and 17% (w/w); Ideally, the wet raw grain is soaked for approximately 24 hours.

Ideally, the wet raw grain is soaked until the moisture content is approximately 14.7% (w/w).

Preferably, the soaked grain is cooked at approximately 100°C for approximately 60 minutes.

In one embodiment of the invention, the soaked material is preheated before being delivered to the cooker.

Preferably, the preheating includes a preheating/ conditioning stage and a pressure heating stage.

Most preferably, the preheating/conditioning stage comprises delivering the soaked material to a bed of a preheater/conditioner and forcing hot air up through the bed.

Ideally, the preheating/conditioning stage utilises hot air from a dryer exhaust as a heat source.

Most preferably, in the preheating/conditioning stage the temperature of the soaked material is raised by between 10°C and 50°C, preferably approximately 30°C and the moisture content of the soaked material is raised by between 1% and 5%, preferably approximately 1.3%.

In another embodiment of the invention the pressure heating stage comprises delivering the preheated/ conditioned material to an autoclave and heating the preheated/ conditioned material in the autoclave.

Typically the preheated/condition material is heated in the autoclave for between two and ten minutes, preferably approximately four minutes at a pressure of between 50 and 300 lbs per square inch, preferably approximately 125 lbs per square inch.

In one embodiment of the invention the preheated conditioned material is delivered to a pre-autoclave where the preheated/conditioned material is preheated prior to delivery to the autoclave.

Preferably the preheated/conditioned material is heated in the pre-autoclave for approximately four minutes.

In a particularly preferred embodiment of the invention the pre-autoclave utilises excess heat from the autoclave as a heat source.

Ideally the autoclave is heated by means of pressurised steam.

Preferably the excess heat is provided by bleeding excess pressurised steam from the autoclave assembly to the preautoclave .

In a particularly preferred embodiment of the invention the temperature of the preheated/conditioned material is raised by between 40°C and 70°C and the moisture content of the preheated/conditioned material is raised by between 1% and 10% in the pressure heating stage.

Preferably the temperature of the preheated/conditioned material is raised by approximately 55°C and the moisture content of the preheated/conditioned material is raised by approximately 4% during the pressure heating stage.

In one embodiment of the invention the autoclaved material has a temperature of not less than 90°C and a moisture content of not less than 18% on delivery to the cooker.

Typically the autoclaved material upon delivery to the cooker has a temperature of approximately 100°C and a moisture content of approximately 20%.

Ideally, the process includes an initial step of passing 5 the raw material through a screen or mesh.

In one embodiment of the invention, the raw material is maize.

The invention also provides an animal feed product, and in particular a flaked maize product whenever produced by the process of the invention.

Detailed Description The invention will be more clearly understood from the following description thereof given by way of example only with reference to the accompanying drawings in which s15 Fig. 1 is a diagrammatic view of a plant for carrying out the process according to the invention; Fig. 2 is a diagrammatic view of a drying and cooling portion of the plant; Fig. 3 is a perspective view of a portion of a bed of 20 a dryer used in a drying process in a closed position; and Fig. 4 is a perspective view of the bed illustrated in Fig. 3 in an open position.

Referring to the drawings and initially to Fig. 1, a 25 process for producing a flaked animal feed product, in this case a flaked maize product, according to the invention comprises the step of first delivering maize from a maize storage bin 2 via a chute 3 to a rubble separator 4. In the separator 4 the maize is passed through a screen or mesh (not shown) to remove any large unwanted objects such as stones, or any other type of relatively large debris. The maize then passes to a destoner 5 which removes smaller objects such as clumps of maize, small stones, twigs or stems. From the destoner 5 the maize is fed directly onto a wetting conveyor 7. A number of spray heads (not shown) spray water onto the maize as it passes along the conveyor 7, the water being added at approximately 4 - 6% by weight of the maize. The wetted maize is delivered by the wetting conveyor 7 to one of six damping bins 8. In the bins 8, the wetted maize is soaked for approximately twenty four hours. This soaking step softens the maize grain making it more permeable to steam infusion. In addition, the water is dispersed throughout the maize grain and acts as a heat conductor during the various subsequent heating stages described below. After the damping step the maize has a moisture content of approximately 14.7% (w/w), the temperature of the maize being approximately 15°C.

The soaked maize is delivered along a conveyor 10 to a holding bin 11 where it is held until required.

In one arrangement the soaked maize is fed directly through a chute 12 into a cooker 26. A steam inlet 27 connects the cooker 26 with a steam boiler (not shown). Usually the maize is cooked for approximately one hour at a temperature of approximately 100°C. As the cooking vessel is not pressurised atmospheric pressure cannot be exceeded. However, if a greater degree of gelatinisation is required, it is possible to continue adding steam while cooking for a greater period of time.

Alternatively, the soaked maize may be preheated before cooking. In this case, the soaked maize is fed from the holding bin 11 through a chute 14 directly into a preheater/conditioner 13, having a soaked material support bed 15, the operation of which is described in more detail below. After a preset drying time during which warm air is passed up through the soaked maize, the support bed 15 is opened and the warmed maize falls onto an output conveyor 17 which delivers the maize to a pre-autoclave 18. The warmed maize is heated in the pre-autoclave 18 before being delivered by a chute 20 to an autoclave 22 where the warmed maize is heated under pressure. A connecting chute 25 in the autoclave 22 is then opened, discharging the autoclaved maize into the cooker 26 where the maize is cooked as described above.

After the cooking step, the maize is fed directly to a roller/flaker 30 which flattens the maize grains between a pair of rollers 31 before delivering them to a drying and cooling section 33 via a chute 32. The drying and cooling section 33 includes a dryer 37.

In more detail, the soaked maize resting on the support bed 15 of the preheater/conditioner 13 is wanned by passing warm air, at approximately 60°C, below the support bed 15 and up through the soaked maize. The warm air is delivered from the dryer 37 via a dryer exhaust line 16 as will be described in more detail below. The maize, which is delivered into the preheater/ conditioner 13 at an approximate temperature of 15°C and a moisture content of approximately 14.7% is heated sufficiently such that it exits the preheater/conditioner 13 at a temperature of approximately 45°C and a moisture content of approximately 16%. As the increase in temperature and moisture holding capacity of the maize is due solely to recycled energy, this results in considerable energy savings.

I In more detail, the pre-autoclave 18 is sealed as soon as the maize has been delivered, via the output conveyor 17, into the pre-autoclave 18. A connecting duct 21 connecting the pre-autoclave 18 with the autoclave 22 is then opened by means of an exit valve 19 mounted in the connecting duct 21, thus bleeding into the pre-autoclave any excess steam from the autoclave 22. The exit valve is then closed and the maize in the pre-autoclave 18 is heated under pressure for approximately four minutes. This increases the temperature and the water content of the maize by 30°C and 2% respectively. At this stage, a chute 20 connecting the pre-autoclave 18 with the autoclave 22 is opened, allowing the pre-autoclaved maize to fall into the autoclave 22. The chute 20 is then closed and a steam inlet valve 23 connecting the autoclave 22 with the boiler (not shown) is opened allowing pressurised steam pass from the boiler into the autoclave 22 up to a pressure of approximately 125 lbs per square inch. At this pressure, the temperature in the autoclave increases to approximately 130°C and the moisture content of the maize increases over time to approximately 22%. The temperature of 130°C is held for four minutes and the exit valve 19 is then reopened, reducing the pressure and bleeding excess steam into the pre-autoclave 18. The connecting chute 25 in the autoclave 22 is then opened discharging the autoclaved maize into the cooker 26.

The preheated maize entering the cooker 26 has a temperature of approximately 100°C and a water content of approximately 20%. Thus, when the pressure is released in the autoclave 22 by bleeding excess steam into the preautoclave 18, the temperature of the maize drops by 30°C and 2% moisture is instantly flashed off. The heat treatment achieved when the temperature reaches 130°C for a period of time effectively kills many of the harmful toxins in the maize grains which are not killed at conventional cooking temperatures. This raised destroys trypsin inhibitors in the grains and most spoilage and pathogenic micro-organisms including salmonella. This destruction of toxins is possible due to the fact that the heating is carried out under pressure allowing greater temperatures to be achieved.

Referring now to Fig. 2, the drying and cooling operation 33 is illustrated in more detail. Flakes of hot wetted maize are delivered from the chute 32 of the roller/flaker 30 via a dryer input 35 onto a top bed 36 of the dryer 37.

The operation of this bed is described in detail below. Hot air, at approximately 120° is delivered by an air heater 38 below the top bed 36. As the hot air is delivered up through the cooked maize on the top bed 36, it dries the maize. Spent air at substantially dew point is delivered out of the dryer 37 to the cyclone 39. The hot and wet spent air is driven by a recirculation fan 40 from the cyclone 39 into an air mixer unit 41. After drying, the top bed 36 is opened and the partially dried maize falls onto a bottom bed 42 where air at approximately 90°C is delivered from an air heater 43 below the bottom bed 42 for further drying. Air from the bottom bed 42 is exhausted by a further cyclone 44 and delivered by the recirculation fan 40 to the air mixer unit 41. It will be appreciated that at all times except at starting and stopping the plant there is a single load of maize on each of the beds 36 and 42.

After drying, the dried maize is delivered along a dryer output conveyor 45 into a cooler 46. Hot air from the cooler 46 is delivered into a further cyclone 47 and then via a cooling fan 48 into the air mixer unit 41. A certain amount of the air in the air mixer unit 41 is exhausted along the dryer exhaust line 16. Thus, in the air mixer unit 41 there is extremely hot air at a temperature of approximately 120°C and at a relatively high humidity, as delivered from the dryer by the recirculation fan 40, and warm dry air at a temperature of 40°C from the cooler 46 which is mixed the hot wet air. This air mixture is then delivered, on demand, to the air heaters 38 and 43 respectively. However, one significant aspect of this portion of the plant is that a large portion of the air from the air mixer unit 41 is diverted along the dryer exhaust line 16 for delivery underneath the support bed 15 of the preheater/conditioner. This arrangement results in a significant saving in energy costs by reusing warm wet air from the dryer 37 to preheat and precondition the maize.

The top and bottom beds 36,42 of the dryer 37 and the bed 15 of the preheater/conditioner 13 are similar and one of these is illustrated in Figs. 3 and 4. Each bed 36, 42, 15 is formed by a number of spaced-apart side by side slats 50. Each slat 50 is of stepped construction comprising a flat upper deck portion 51 and a flat lower deck portion 52 projecting on opposite sides of a central connecting web 53. Each upper deck portion 51 and each lower deck portion 52 is spaced-apart from each adjacent upper deck and lower deck portions 51,52 respectively to define a number of parallel upper slits 61 and parallel lower slits 62 in the bed. The slits 61, 62 are horizontally offset to provide a tortuous passageway for drying air.

Each slat 50 is fixed to an axle 54 which is rotatably mounted in the dryer 37. The slats 50 are movable by a ram 60 from the normally closed drying configuration illustrated in Fig. 3 to an open position as illustrated in Fig. 4 for delivery of maize from the drying bed. The ram 60 has an actuator rod 58 to which the slats 50 are connected by levers 56. Each lever 56 is pivotally mounted at a lower end to the rod 58 and fixed to the axle 54 of a slat 50 at an upper end thereof.

In use, the maize rests on the flat upper decks 51 of each bed 36,42, 15 and a certain amount of maize will fall through the upper slits 61 onto the lower decks 52.

Because of the configuration of the slats 50 the angle of repose of the maize is such that it will not flow through the lower slits 62. For example, during a drying operation, a small quantity of maize will rest on each lower deck 52 and within the upper slit 61. The hot air is delivered up through each lower slit 62 above and across the lower deck 52 into the maize on the lower deck 52 and through the upper slits 61 and the main body of maize resting on the upper decks 51.

The bed is opened by moving the ram 60 in the direction of the arrow marked X. This causes the actuating rod 58 to move the lever arms 56 to pivot each slat 50 into the open position illustrated in Fig. 4. In this position the ram 60 is operated to reciprocate the actuator rod 58 and agitate the maize to facilitate its discharge.

The fact that the raw material has been soaked before cooking provides for a much more effective, thorough and even cooking due to the presence of water throughout the body of the grain. Not only does the heat treatment effectively kill the harmful toxins in the maize grain, it also effectively destroys trypsin inhibitors in the grains and most spoilage and pathogenic micro-organisms including salmonella.

The amount of water added during the damping step is important. If too little is added, each maize grain will not absorb enough water to conduct heat effectively through the grain. If too much water is added, the handling of the maize becomes difficult during the subsequent steps of the process.

It will be appreciated that the pressure heating stage may include only an autoclave without a pre-autoclave. In this respect, the warmed maize may be delivered from the preheater/conditioner directly into the autoclave.

It will be further appreciated that the drying/cooling part of the process may comprise an integrated dryer/cooler with two beds, an upper bed through which heated air is blown in a drying operation and a lower bed onto which the dried maize falls and up through which cool air is blown in a cooling operation. The design of the individual beds in such an integrated dryer/cooler may be the same as the beds of the dryer and cooler described above.

The invention is not limited to the embodiments hereinbefore described which may be varied in both construction and detail. In particular, process sequence and parameters may also be varied without departing from the spirit of the invention.

Claims

CLAIMS?

1. A process for producing a flaked animal feed product comprising the steps of:uniformly wetting grain with from 4 to 6% by 5 weight of water and soaking the grain to achieve a moisture content in the grain of from 14% to 17% by weight; delivering the soaked material to a cooker; cooking the soaked material at a temperature

2. A method as claimed in claim 1 wherein the process includes the steps of:delivering raw material onto a wetting conveyor;

3. A process as claimed in claim 1 or 2 in which the soaked grain is cooked at approximately 100°C for approximately 60 minutes.

4. A process as claimed in any of claims 1 to 3 in which the grain is soaked for approximately 24 hours. 5. Which the raw grain material is maize. 5 approximately 30°C and the moisture content of the soaked material is raised by approximately 1.3% during preheating/conditioning.

5. A process as claimed in any of claims 1 to 4 in which the grain is soaked until the moisture content is approximately 14.7% (w/w).

6. A process as claimed in any preceding claim in which the soaked material is preheated before being delivered to the cooker.

7. A process as claimed in claim 6 in which the preheating includes a preheating/conditioning stage and a pressure heating stage.

8. A process as claimed in claim 7 in which the preheating/conditioning stage comprises delivering the soaked material to a bed of a preheater/ conditioner and forcing hot air through the bed.

9. A process as claimed in claim 8 in which the preheating/conditioning stage utilises hot air from a dryer exhaust as a heat source. 10. Any claims 1 to 25. 10 delivering the preheated/conditioned material to an autoclave and heating the preheated/conditioned material in the autoclave.

10. A process as claimed in any of claims 7 to 9 wherein the temperature of the soaked material is raised by between 10°C and 50°C and the moisture content is raised by between 1% and 5% during preheating/conditioning. 10 of between 90°C and 110°C for between 50 and 60 minutes; flaking the cooked material, preferably by passing it between a pair of rollers; drying the flaked material; and

11. A process as claimed in claim 10 wherein the temperature of the soaked material is raised by

12. A process as claimed in any of claims 6 to 11 in which the pressure heating stage comprises

13. A process as claimed in claim 12 in which the preheated/conditioned material is heated in the

14. 14. A process as claimed in claim 13 in which the for preheated/conditioned material is heated 20 approximately four minutes at approximately 125 lbs per square a pressure inch. of

15. A process as claimed in any of claims 12 to 14 in which the preheated/conditioned material is delivered to a pre-autoclave prior to delivery to 15 autoclave for between two and ten minutes at a pressure of between 50 and 300 lbs per square inch. 15 cooling the dried material.

16. A process as claimed in claim 15 in which the preheated/conditioned material is heated in the pre-autoclave for approximately four minutes.

17. A process as claimed in either of claims 15 or 16 in which the pre-autoclave utilises excess heat from the autoclave as a heat source.

18. A process as claimed in any of claims 12 to 17 wherein the autoclave is heated by means of pressurised steam.

19. A process as claimed in claim 17 or 18 in which pressurised steam is bled from the autoclave to the pre-autoclave.

20. A process as claimed in any of claims 12 to 19 in which the temperature of the preheated/conditioned material is raised by between 40°C and 70°C and the moisture content of the preheated/conditioned material is raised by between 1% and 10% during pressure heating. 20 spraying 4-6% water by weight of the raw material onto the raw material as it passes along the wetting conveyor; delivering the wet raw material to one or more damping bins; soaking the wet raw material until the moisture content of the raw material is between 14% and 17% (w/w);

21. A process as claimed in claim 20 in which the temperature of the preheated/conditioned material is raised by approximately 55°C and the moisture content of the preheated/conditioned material is raised by approximately 4% during pressure heating.

22. A process as claimed in any of claims 12 to 21 in which the autoclaved material upon delivery to the cooker has a temperature of not less than 90°C and a moisture content of not less than 18%.

23. A process as claimed in claim 22 in which the autoclaved material upon delivery to the cooker has a temperature of approximately 100°C and a moisture content of approximately 20%.

24. A process as claimed in any preceding claim including an initial step of passing the raw grain material through a screen or mesh.

25. A process as claimed in any of claims 1 to 24 in 25 the autoclave.

26. A process for producing a flaked animal feed product substantially as hereinbefore described with reference to the accompanying drawings.

27. A flaked animal feed produced by the process of

28. A flaked maize produce produced by the process of claim 26.