GB2463893A

GB2463893A - Determining the temperature of a cooking foodstuff

Info

Publication number: GB2463893A
Application number: GB0817710A
Authority: GB
Inventors: James King
Original assignee: LYONS SEAFOODS Ltd
Current assignee: LYONS SEAFOODS Ltd
Priority date: 2008-09-26
Filing date: 2008-09-26
Publication date: 2010-03-31
Also published as: GB0817710D0

Abstract

A device is provided for monitoring the temperature of a foodstuff during a cooking process for cooking the foodstuff in a cooking liquid. The device (1) comprises a temperature sensor (3) and a means (2) of securing the foodstuff to facilitate placement of the sensor in relation to the foodstuff, wherein the device has an average bulk density of less than 1g cm-31 whereby in use the device is neutrally or positively buoyant in the cooking liquid. A method of cooking a foodstuff is disclosed, also.

Description

Method and device for the cooking of foodstuffs

Background of the Invention

The present invention relates to a device for determining the temperature of a foodstuff (particularly but not exclusively shellfish) during cooking and a method of determining the temperature of a foodstuff during cooking. The application of the present invention relates primarily to commercial cooking of food-stuff, and particularly (but not exclusively) mass-production cooking processes.

When preparing cooked foods, there is a general need to ensure that a foodstuff is properly cooked to minimise the number of bacteria in the foodstuff. There are several known ways of doing this. For example, certain shellfish change colour on cooking (the shell of a prawn turns red when heated) . It is, however, perfectly possible for the carapace to have changed colour whilst at least some of the meat of the shellfish is not properly cooked. Furthermore, such a technique is also not applicable to foodstuffs which do not change colour.

Another way of determining whether a foodstuff is cooked is to examine the density of that foodstuff. For example, certain shellfish become positively buoyant in water when cooked. Some mass-production cooking methods, however, do not lend themselves to this form of indication that the food is cooked.

A further known method comprises providing a temperature sensor in the fluid (typically a liquid) in which a foodstuff is cooked.

Whilst there is a general relationship between the temperature of the fluid and the temperature of the foodstuff, the relationship may not be sufficiently clear so that the temperature of the foodstuff can be determined with sufficient accuracy.

Furthermore, none of the methods mentioned above lend themselves to process validation in which compliance with regulations imposed by certain regulatory authorities (such as the US Food and Drugs Administration, International Organisation for Standardisation and the European Community) is required.

Validating that a particular cooking process reliably cooks a foodstuff in a complete and safe manner can be an important step to take before adopting such a process in a commercial cooking process.

A means of validating a mass-production cooking process is known.

A conveyor belt cooking process in which a foodstuff is conveyed through one or more ovens to cook the foodstuff can be validated by means of attaching a temperature probe to a temperature logging device via a wire. Such equipment is bulky and can not be used to validate other cooking processes, such as for example processes in which food is cooked in a cooking liquid, as opposed to on a conveyor.

The present invention seeks to mitigate one or more of the problems mentioned above.

Summary of the Invention

There is provided in accordance with a first aspect of the present invention, a device for monitoring the temperature of a foodstuff during a cooking process for cooking the foodstuff in a cooking liquid, the device comprising a temperature sensor and a means of securing the foodstuff to facilitate placement of the sensor in relation to the foodstuff, wherein the device has an average bulk density of less than about ig crn3 and preferably greater than about 0.7g cm3, whereby in use the device is neutrally or positively buoyant in the cooking liquid.

The device preferably has an average bulk density less than that of the cooking medium and therefore, in such cases, the device is, in the absence of the foodstuff, positively buoyant when placed in the cooking medium. The device of the present invention facilitates the sensing of the temperature of a foodstuff during the cooking process and the use of temperature sensing in cooking devices and methods (for example, using cooking chambers comprising screw conveyors) which did not previously lend themselves to temperature sensing of foodstuffs.

For example, such a device may be used with a screw conveyor which is often used to cook shellfish, such as prawns.

The foodstuff to be carried is generally of a particulate nature, for example, a sausage, piece of pasta (such as ravioli) or a shellfish (such as a prawn (known in the USA and some other countries as a "shrimp") ) . In the context of the present invention, the term "particulate" as used in relation to food-stuffs does not means that the food-stuffs are made of particles; a foodstuff that is one-piece (or a single integral morsel) such as a prawn may be described as being particulate in nature.

The size of the device is preferably such that it may be accommodated, without deforming the device, in a container having a volume no more than about 50 times (preferably no more than 20 times) greater than the typical volume of the foodstuff to be carried. The maximum dimension of the device may for example be less than 300mm, and more preferably less than 150mm. The volume of liquid displaced by the device when submerged may be between 30cm and 150cm3. The mass of the device may be less than lOOg, and may be less than 50g.

The device preferably has an average bulk density such that, in use when cooking a foodstuff held by the device in a particular liquid cooking medium, the device and foodstuff together have a substantially neutral or positive buoyancy. The cooking medium may be water. Water has a density of about 0.96-0.97g/cm3 at the temperatures at which the foodstuff is cooked, typically about 9000. The cooking medium may be oil, which has a lower density than water. Vegetable oils typically have a density of about O.90g/cm3 at cooking temperatures. The cooking medium may be a saline solution, which has a density higher than that of pure water.

The device is preferably so arranged that when an uncooked prawn having a weight of between about lOg and about 30g is secured to the device the device has a buoyancy, with reference to water at 90°C, that is neutral or positive. Preferably, when loaded with an uncooked prawn having a mass of 25g the device has a net buoyancy which is rio greater than lOg (positive buoyancy), and preferably has a buoyancy of between 3g and 9g (positive buoyancy) In certain embodiments of the invention, it is important that the foodstuff attached to the device when cooked in the liquid behaves in the liquid in a manner similar to that when cooking a foodstuff in the liquid without the device being attached. For example, prawns tend to have a neutral or negative buoyancy when raw and a neutral or positive buoyancy immediately after being cooked. There is therefore a period of time in which the prawn -5-.

floats within the body of the cooking liquid (i.e. neither at the surface of the liquid or at the bottom of the vessel containing the foodstuff and the cooking liquid) . In the case of cooking prawns, it is therefore important that the device is not so dense that the device and prawn immediately sink, never to rise again during the cooking process; and it is also important that the device is not so light that the device and prawn immediately float, with no prospect of sinking during the cooking process.

In such cases, the device preferably has an average bulk density that is greater than O.8g cm3.

When designed for use in a cooking process using water as the cooking medium, the device may have an average bulk density that is greater than O.90g cm3. The device may have an average bulk density that is less than or equal to O.98g cm3. The device may have an average bulk density about the same as that of water at 9Q0 The device may have an average bulk density that is about O.97g cm3.

When designed for use in a cooking process using oil as the cooking medium, the device may have an average bulk density that is greater than O.82g cm3. The device may have an average bulk density that is less than O.92g cm3.

The device may be provided with a float. The float comprises positively buoyant material and therefore acts to make the device more buoyant than it may otherwise have been. It will be understood that in use the device may be neutrally buoyant and that therefore the "float" may actually be submerged in the cooking medium. The float may have an average bulk density that is preferably less than O.Sg cm3, and may be less than O.5g cm3.

The temperature sensor may comprise a temperature probe. Such a probe may be configured for insertion into the foodstuff so that the internal temperature of the foodstuff may be sensed. It is often convenient for the probe to be arranged to sense the temperature of the coldest part of the foodstuff (often known as the "cold spot"), since if the temperature of the cold spot is sufficiently high during cooking, the temperature of the rest of the foodstuff will be sufficiently high.

The float may be provided with a space for receiving the temperature sensor. This is particularly useful if the temperature sensor is elongate, such as may be the case for a temperature probe which is, in use, inserted into the foodstuff.

The float may be provided with stopper. The stopper may act to retain the temperature sensor in relation to the device. The stopper may for example inhibit loss of temperature sensor from device. In such an arrangement, the float is typically provided with a space for receiving the temperature sensor and the stopper closes over one end of the space. The stopper may be made of buoyant material.

The stopper may be releasably securable to the float. For example, the stopper may be provided with a first stopper securing part and the float may be provided with a second stopper securing part complementary to the first stopper securing part so that the float and stopper are securable to one another. The first and second stopper securing parts may comprise screw threads.

The float may be substantially cylindrical. The float may be provided with one or more flanges against which the sensor may abut. The float may be provided with an annular flange.

The float may be made from nitrile rubber (Buna-N), such as Nipol, Krynac and Europrene.

The stopper may conveniently be made from a plastics material, such as nylon.

The means for securing the foodstuff to facilitate placement of the sensor in relation to the foodstuff may comprise means for securing the foodstuff to facilitate insertion of the sensor into the foodstuff.

The device may comprise a carrier for carrying the foodstuff, the carrier providing the means for securing the foodstuff to facilitate placement of the sensor. Placement of the sensor may typically involve insertion of the sensor into the foodstuff.

The sensor may be provided with a first sensor securing part and the carrier may be provided with a second sensor securing part complementary to the first sensor securing part so that the sensor and carrier are securable to one another. The first and second sensor securing parts may comprise screw threads.

The carrier may comprise a cage. The cage may be arranged to protect the foodstuff. The cage is preferably sufficiently open to allow cooking liquid to pass around the foodstuff without any significant resistance. The cage may comprise a plurality of cage members for protecting the foodstuff. The cage members may extend from a first end of the cage to a second end of the cage.

The first end of the cage may be associated with a float of the device. The cage may be provided with a connecting member for connecting the cage members together. The connecting member typically provides physical stability to the cage. The connecting member may be provided at or adjacent to the second end of the cage. The cage members and connecting member may typically be provided by wire.

In the case where the device comprises a float, the carrier may be provided with the float.

The means for securing the foodstuff may comprise one or more bias members, preferably a plurality of bias members. In use, the plurality of bias members may grip the foodstuff. The means for securing the foodstuff may be accommodated inside a cage.

In accordance with a second aspect of the present invention, there is provided a carrier for use in the device of the first aspect of the present invention.

In particular, the second aspect of the present invention provides a carrier for carrying a foodstuff in a cooking liquid, the carrier providing a means of securing the foodstuff to facilitate placement of a sensor in relation to the foodstuff, the carrier being positively buoyant.

The carrier is preferably sufficiently buoyant so that, in use, a device comprising a temperature sensor and the carrier loaded with a foodstuff is neutrally or positively buoyant.

The second aspect of the present invention also provides a carrier for carrying a foodstuff in a cooking liquid, the carrier providing a means of securing the foodstuff to facilitate placement of a sensor in relation to the foodstuff, wherein the carrier comprises a float.

The carrier of the second aspect of the present invention may comprise those features described above with reference to the device of the first aspect of the present invention. For example, the carrier preferably comprises a cage for protecting the foodstuff.

There is provided in accordance with a third aspect of the present invention a method of cooking a foodstuff, the method comprising: (a) providing a device comprising a carrier for carrying a foodstuff, (b) providing a foodstuff, (c) securing the foodstuff on or in the carrier, (d) providing a liquid for cooking the foodstuff, (e) cooking the foodstuff in said liquid, and (f) using the device to sense the temperature of the foodstuff during step (e), wherein the device with the foodstuff secured in or on it is neutrally or positively buoyant in said liquid during at least a part of step (e) For the avoidance of doubt, it is stated that steps (a) to (d) are not necessarily consecutive steps. For example, the foodstuff may be secured in the carrier prior to being introduced into the liquid. Alternatively, the step of securing the foodstuff in the device may take place in the liquid.

-10 -Step (f) may comprise contemporaneous sensing and display of the temperature of the foodstuff. Alternatively, step (f) may comprise sensing the temperature of the foodstuff and subsequently transferring the sensed temperature data, for example, to an external computer which may be used to manipulate and/or display the data.

For the avoidance of doubt, the word "during" used in relation to step (f) does not mean that temperature is sensed continuously or throughout the whole of the cooking process. For example, temperature may be sensed only once during the cooking process (although it may be desirable to sense the temperature more than once) The method may comprise providing a cooking chamber comprising a screw conveyor for moving foodstuff within the cooking chamber.

Such screw conveyors are known for the cooking of certain foodstuffs (such as prawns) The device used in the method of the third aspect of the present invention may be the device of the first aspect of the present invention.

Description of the Drawings

The present invention will now be described by way of example only with reference to the following Figures of which: Figure 1 is a side-on view of a device in accordance with a first embodiment of the present invention; Figure 2 is a cross-sectional view of the device of Figure 1 taken along arrows AA in Figure 1; and

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-11 -Figure 3 is a perspective view of the carrier part of the device of Figure 1 showing the relationship between the cage and the springs for securing an item of foodstuff.

Detailed Description

Figures 1 and 2 show a device in accordance with an embodiment of the present invention. The device, denoted generally by reference numeral 1, comprises a carrier 2 for carrying a foodstuff and a temperature sensor 3. The temperature sensor comprises a probe portion 3a for insertion into a foodstuff. In use, three sprung steel arms 11, 12, 13 retain the foodstuff in position in the device. The arms 11, 12, 13 are sprung to hold the foodstuff resiliently in place, thereby resisting unwanted removal of the foodstuff from the device.

The carrier 2 comprises a cage 4 for protecting a foodstuff and a float 5. The cage 4 is formed from three cage members 6, 7, 8 attached to a collar 9. The cage members 6, 7, 8 are made from stainless steel wire. An annular connecting member 10 made from a stainless steel band is provided at one end of the cage 4. The connecting member 10 connects the three cage members 6, 7, 8 together, thereby providing physical strength to the cage and also helping to protect the foodstuff.

The float 5 comprises Buna-N rubber, which is a buoyant material having a density of about 0.4g cm3. A space 17 is provided in the float to accommodate the sensor 3, with a stopper 16 being provided to prevent unwanted egress of the sensor 3 from the float 5. The buoyancy provided by the float 5 is such that the device is neutrally or positively buoyant even when the desired foodstuff is mounted on the device. In this embodiment, the -12 -device 1 has a mass when unloaded of about 32g. The device has an average bulk density of about 0.8g cm3.

The steel sprung arms 11, 12, 13 and cage members 6, 7, 8 are fixed to a collar 9. The collar 9 is also fixed to a sensor-receiving portion 15. The sensor receiving portion 15 is substantially cylindrical is shape and comprises a cylindrical passage therethrough for the receipt of the sensor 3.

The device 1 will now be described in more detail with reference to Figures 1 to 3. The float 5 is provided with a space 17 for accommodation of the main body of sensor 3. The space 17 is typically created by machining material from a block of Buna-N rubber. The float 5 is provided with an annular flange 18 which forms an abutment against which the shoulders 19 of the main body of the sensor 3 abut. The sensor 3 comprises an attachment portion 20 and probe portion 3a which extend through an aperture 21 in the float 5 formed by annular flange 18. Attachment portion 20 of sensor 3 is provided with a screw thread 22 which engages with a corresponding screw thread (not shown) provided on the sensor receiving portion 15 of carrier 2. The provision of the screw threads on the attachment portion 20 of the sensor and the sensor receiving portion 15 of the carrier 2 facilitates the attachment of the sensor to the carrier. Furthermore, the provision of the flange 18 on float 5 facilitates the attachment of the float 5 to the carrier 2 and the sensor 3.

A screw thread (not shown) is provided on the lower portion of the internal surface of the float which forms the space 17. This screw thread mates with a corresponding screw thread 23 provided on stopper 16. The stopper 16 is machined from nylon and helps -13 -secure the sensor 3. It has a density of about 0.5g cm3 and thus further provides buoyancy to the device.

The sensor used in the present device is an Ellab� TS temperature micro logger with a 25mm probe (Ellab A/S, Roedovre, Denmark or Ellab UK Ltd., Bawburgh, Norwich, UK).

The length of the device is about 100mm and has a maximum diameter of about 45mm. The device may thus be wholly accommodated in a sealed container having an internal volume of cm3. The volume of water displaced by the device when unloaded but submerged in water is about 40 cm3.

The device shown is particularly designed for use with prawns, having a mass of between about lOg and about 25g. Those skilled in the art will realise that the device may be adapted for use with one or more of a whole range of foodstuffs, in particular particulate foodstuffs, such as shellfish, sausages and ravioli.

An example of the use of the exemplified device will now be described. The device 1 is assembled according to the description provided above and a foodstuff (in this case, a raw prawn) is mounted onto the device by pushing the prawn onto the probe portion 3a. The steel, sprung arms 11, 12, 13 retain the raw prawn in place.

The 1oaded" device is then subjected to the same processing as raw prawns. The loaded device is introduced with the other raw prawns into a cooking chamber comprising a screw conveyor, such as those supplied by Innotec Systems By, Werkendamn, The Netherlands.

-14 -The water in the cooking conveyor is at a temperature of about 95°C. Rotation of the screw causes prawns and the loaded device to be moved through the cooking chamber towards a cooking chamber exit.

It is important that the loaded device is not negatively buoyant for the following reason. The cooking chamber typically comprises one or more heating inlets for the introduction of steam and/or heated water into the cooking chamber. The heating inlets are typically located in the bottom of the cooking chamber, below the screw conveyor. There is therefore a region of cooking liquid located below the conveyor. Anything which is negatively buoyant will sink into the region of liquid below the conveyor, and will not be conveyed to the exit (at least not in the same amount of time as it takes the foodstuff to be conveyed to the exit) . It is worth noting that the exit is typically located above the region of liquid associated with the heating inlets. A negatively buoyant device will, therefore, tend to sink into the region of liquid below the conveyor, and even in the event that such a device was to be delivered to the exit, the timescale for delivering the device would not be characteristic of a foodstuff which is not mounted to a device.

Once the prawns have passed through the cooking chamber, they should be cooked and the cold-spot of the prawn should have reached a pre-determined level. The sensor measures the temperature of the prawn (typically the temperature of the cold spot of the prawn) throughout the cooking process.

The loaded device is positively buoyant, but not excessively so.

The buoyancy of the loaded device is selected to emulate the buoyancy of a raw prawn not held in the device so that the device

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-15 -acts like a raw prawn in the conveyor, so far as this is possible. For example, in the present case, the mass of the device without the prawn is 32g, and such a device is typically used to carry a prawn having a mass of 10-23g. Ideally, the loaded device would be neutrally buoyant, but this may not be possible, given that the mass of prawns may differ from one prawn to another.

Cooked prawns (including the prawn mounted in the device) are transferred from the cooking screw conveyor to a cooling screw conveyor (such as one provided by Innotec Systems By, Werkendam, The Netherlands) . Low temperature water (typically at about 1°C) is used to cool the prawns.

The cooled prawns are then transferred to a dewatering belt to remove excess water from the prawns. Innotec Systems By (Werkendam, The Netherlands) provides such a dewatering belt.

The dewatered prawns are then frozen using a blast freezer.

The temperature of the prawn mounted in the device is sensed throughout the production process i.e. throughout cooking, cooling, dewatering and freezing.

Once the prawn in the device has been subjected to the full production process, the device is removed from the freezer and the sensor removed from the device. The data stored in the sensor is uploaded to a computer using known, conventional means and the computer may be used to manipulate and display the collected temperature data. The data may be compared to pre-determined temperatures to determine whether the production process is satisfactory. For example, the temperature data -16 -acquired during cooking may be compared to a pre-determined temperature which indicates that the prawn has been properly cooked.

Whilst the present invention has been described and illustrated with reference to particular embodiments, it will be appreciated by those of ordinary skill in the art that the invention lends itself to many different variations not specifically illustrated herein.

The densities specified for the various parts of the device may be different from those mentioned above. In another embodiment, not separately illustrated, the bulk density for the device (including all parts such as the float, cage, sensor and probe) is 0.97g cm3. The bulk density for just the float in that embodiment is 0.43 cm3.

For example, whilst the sensor used in the device of the present invention does not allow temperature data to be displayed and monitored in real-time, it should be recognised that a different sensor may be used to enable real-time monitoring and display of temperature data.

Where in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present invention, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of -17 -the independent claims. Moreover, it is to be understood that such optional integers or features, whilst of possible benefit in some embodiments of the invention, may not be desirable, and may therefore be absent, in other embodiments.

Claims

I-18 -Claims 1. A device for monitoring the temperature of a foodstuff during a cooking process for cooking the foodstuff in a cooking liquid, the device comprising a temperature sensor and a means of securing the foodstuff to facilitate placement of the sensor in relation to the foodstuff, wherein the device has an average bulk density of less than ig cm3, whereby in use the device is neutrally or positively buoyant in the cooking liquid.
2. A device according to claim 1 wherein the temperature sensor comprises a temperature probe which arranged for insertion into the foodstuff so that the internal temperature of the foodstuff may be sensed.
3. A device according to claim 1 or claim 2 wherein the device is provided with a float.
4. A device according to 3, wherein the float has a shape which defines a space for receiving the temperature sensor.
5. A device according to claim 4 wherein the float is provided with a stopper to retain the temperature sensor in the space in the float.
6. A device according to claim 5 wherein the stopper has an average bulk density of less than O.8g crn3.
7. A device according to any of claims 3 to 6 wherein the float is substantially cylindrical.I

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8. A device according to any of claims 3 to 7 wherein the float is provided with one or more flanges against which the sensor may abut.
9. A device according to any preceding claim wherein the means for securing the foodstuff to facilitate placement of the sensor in relation to the foodstuff comprises means for securing the foodstuff to facilitate insertion of the sensor into the foodstuff.
10. A device according to any preceding claim wherein the device comprises a carrier for carrying the foodstuff, the carrier providing the means for securing the foodstuff to facilitate placement of the sensor.
11. A device according to claim 10 wherein the sensor is provided with a first sensor securing part and the carrier is provided with a second sensor securing part complementary to the first sensor securing part so that the sensor and carrier are securable to one another.
12. A device according to claim 10 or claim 11 wherein the carrier comprises a cage for protecting the foodstuff.
13. A device according to claim 12 when dependent on claim 3 wherein the cage comprises a plurality of cage members for protecting the foodstuff, the cage members extending from a first end of the cage to a second end of the cage, the first end of the cage being associated with the float.
14. A device according to claim 13 wherein the cage is provided with a connecting member for connecting the cage membersI-20 -together, the connecting member being provided at or adjacent to the second end of the cage.
15. A device according to any one of claims 10 to 14 when dependent on claim 3 wherein the carrier is provided with the float.
16. A device according to any preceding claim wherein the means for securing the foodstuff comprises a plurality of bias members which, in use, grip the foodstuff.
17. A carrier for use in the device of any one of claims 10 to 15.
18. A carrier for carrying a foodstuff in a cooking liquid, the carrier providing a means of securing the foodstuff to facilitate placement of a sensor in relation to the foodstuff, the carrier being positively buoyant.
19. A carrier for carrying a foodstuff in a cooking liquid, the carrier providing a means of securing the foodstuff to facilitate placement of a sensor in relation to the foodstuff, wherein the carrier comprises a float.
20. A method of cooking a foodstuff, the method comprising: (a) providing a device comprising a carrier for carrying a foodstuff, (b) providing a foodstuff, (c) securing the foodstuff on or in the carrier, (d) providing a liquid for cooking the foodstuff, (e) cooking the foodstuff in said liquid, andI

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21 - (f) using the device to sense the temperature of the foodstuff during step (e), wherein the device with the foodstuff secured in or on it is neutrally or positively buoyant in said liquid during at least a part of step (e) 21. A method according to claim 20 comprising providing a cooking chamber provided with a screw conveyor for moving foodstuff within the cooking chamber.
22. A method according to claim 20 or claim 21, wherein the cooking liquid is at least 90% by weight water.
23. A method according to any of claims 20 to 22, wherein the foodstuff is a single shell-fish having an uncooked mass of between lOg and 35g.