The present invention relates to a method of monitoring the temperature of a fryer and to a temperature probe.

A number of foodstuffs are produced by a frying process in which the foodstuffs are conveyed along a fryer containing a body of heated oil. Many snack foods, such as potato chips, are produced using such a frying process. The frying parameters can vary along the product flow path and also across the product flow path. For example, the oil temperature can vary along the flow path, or transversely across the flow path at any given longitudinal location. Such frying parameters may vary as a result of a variations in the oil heating apparatus, and/or variations in the properties of the input foodstuffs to be fried. Any uncontrolled or undetected variations in the frying parameters can lead to non-uniform products.

In a fryer, one primary frying parameter which may have a large impact on product quality is oil temperature. It is known to use fixed temperature sensors. in a fryer to monitor the production process. However, these sensors are laborious to install and provide rather limited information on the temperature profile of the oil in the fryer, and the temperature to which the products are subjected during the frying process.

For some industrial fryer applications, it is desirable to model or simulate the frying process using software. However, an accurate representation of the frying process requires accurate input data, for example the temperature profile along the fryer, and optionally across the fryer. Existing fryer temperature monitoring systems provide inadequate data for fully simulating the temperature variations to which the products are subjected during the frying process in any given fryer.

It is an aim of the present invention to provide a method of monitoring the temperature of a fryer, and to a temperature probe which may be used in such a method, which is easy and inexpensive to install and provides a very versatile device for measuring temperature within the fryer at various locations. Accordingly, in one aspect the present invention provides a method of monitoring the temperature of a fryer, the method comprising the steps of:

(i) providing a temperature probe comprising a temperature sensor within a hermetically sealed casing;

(ii) providing a fryer, the fryer containing a body of heated oil, the fryer having a product input end and a product output end with a product flow path therebetween;

(iii) floating the temperature probe on the oil along at least a part of the product flow path of the fryer, the temperature probe having a density less than the specific gravity of the oil; and

(iv) recording a temperature profile corresponding to the temperature sensed by the temperature sensor of the temperature probe along the respective part of the product flow path.

Optionally, the fryer fries a foodstuff and steps (iii) and (iv) are carried out by conveying the temperature probe together with the foodstuff along the product flow path of the fryer during the foodstuff frying process.

Typically, the foodstuff comprises snack foods, for example potato chips.

Optionally, in step (iii) the temperature probe is floated along a selected longitudinal flow path at a selected transverse position relative to a centre line of the product flow path.

Typically, the temperature sensor is adapted to measure a temperature of at least 200°C and the heated oil is at a temperature of at least 200°C.

Optionally, in step (iv) a plurality of temperature values sensed by the temperature sensor over a period of time is transmitted by a wireless transmitter within the casing and connected to the temperature sensor.

In one embodiment, the wireless transmitter transmits series of wireless signals in step (iv), each wireless signal including information associated with a respective temperature value sensed during step (iv), to provide a series of temperature values associated with the respective part of the product flow path. Typically, the temperature probe has a density of no more than 925g/dm ³ .

In another aspect, the present invention further provides a temperature probe comprising a temperature sensor within a hermetically sealed casing, the temperature sensor being adapted to measure a temperature of at least 200°C and the hermetically sealed casing being thermally resistant to a temperature of at least 200°C, and a wireless transmitter within the casing and connected to the temperature sensor, the wireless transmitter being adapted to transmit a plurality o temperature values sensed by the temperature sensor over a period of time, the temperature probe having a density of no more than 925 /dm ³ .

In one embodiment, the casing has a substantially spherical exterior surface. Optionally, the casing is comprised of two hemispheres interconnected by an annular seal member. Typically, each hemisphere comprises an annular outer flange and the two flanges are affixed together, e.g. bolted together by a plurality of bolts. In one embodiment, the casing has an external diameter of from 5 to 15 cm, optionally from 8 to 12 cm, further optionally about 10 cm. Typically, the casing is composed of stainless steel.

Optionally, the temperature sensor comprises a thermocouple. Typically, the temperature sensor is mounted within a polymer capsule, for example a PTFE capsule. Optionally, thermal insulation within the casing at least partly surrounds the polymer capsule.

Optionally, the temperature sensor is fixedly mounted within the casing.

Embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings, in which:

Figure 1 is a schematic perspective view of a temperature probe in accordance with an embodiment of the present invention;

Figure 2 is a schematic perspective view of a temperature sensor in the probe of Figure 1 ; and

Figure 3 schematically illustrates a plan view of a fryer used in the monitoring method of an embodiment of the present invention. Referring to Figures 1 and 2, there is shown a temperature probe 2 in accordance with an embodiment of the present invention.

The temperature probe 2 comprises a temperature sensor 4 within a hermetically sealed casing 6.

The temperature sensor 4 is adapted to measure a temperature of at least 200°C. in this embodiment, the temperature sensor 4 comprises a thermocouple 10. The temperature sensor 4 is mounted within a polymer capsule 8, for example composed of PTFE, part of which is shown in Figure 2. Thermal insulation (not shown) within the casing 6 at least partly surrounds the polymer capsule 8. The temperature sensor 4 is fixedly mounted within the casing 6.

The casing 6 is thermally resistant to a temperature of at least 200°C, and typically the casing 6 is composed of stainless steel. In this embodiment, the casing 6 has a substantially spherical exterior surface 12. The casing 6 is comprised of two hemispheres 14, 16 interconnected by an annular seal member 18, for example composed of a thermally resistant elastomer. Each hemisphere 14, 16 comprises an annular outer flange 20, 22 and the two flanges 20, 22 are bolted together by a plurality of bolts 24. Typically, the casing 6 has an external diameter of from 5 to 15 cm, for example from 8 to 12 cm, such as about 10 cm.

A wireless transmitter 26 is located within the casing 6 and is connected to the temperature sensor 4. The wireless transmitter 26 is adapted to transmit a plurality of temperature values sensed by the temperature sensor 4 over a period of time. The transmissions are receiver by a receiver and recorded.

The temperature probe 2 has a density of no more than 925g/dm ³ . This provides that the temperature probe 2 can float in an edible oil which is typically used for frying, for example sunflower oil which is used for frying many snack foods such as potato chips and has a specific gravity of about 920g/dm\

The temperature probe 2 can be used in a method of monitoring the temperature of a fryer. Referring to Figure 3, in the method, the fryer 50 contains a body of heated oil 52. Typically, the temperature sensor 4 is adapted to measure a temperature of at least 200°C and the heated oil 52 is at a temperature of at least 200°C. The fryer 50 has a product input end 54, at which foodstuffs 58 to be fried are added to the fryer oil 52, and a product output end 56, at which fried foodstuffs 58 are removed from the fryer oil 52, with a product flow path 60 therebetween. The foodstuffs 58 may comprise snack foods, for example potato chips

The temperature probe 2 is disposed in the fryer 50 so as to be within the body of heated oil 52. Since the density of the temperature probe 2 is lower than the specific gravity of the oil 52, the temperature probe 2 floats on the surface of the oil 52. The temperature probe 2 is floated on the oil 52 along at least a part of the product flow path 60 of the fryer 50. The temperature probe 4 is conveyed together with the foodstuff 58 along the product flow path 60 of the fryer 50 during the foodstuff frying process. A temperature profile corresponding to the temperature sensed by the temperature sensor 4 of the temperature probe 2 along the respective part of the product flow path 60 is recorded. The fryer 50 includes conventional conveying apparatus 62, such as a helical screw, paddles, flights, etc. to convey the product through the fryer 50.

The temperature probe 2 may be floated along a selected longitudinal flow path 64 at a selected transverse position relative to a centre line 66 of the product flow path 60.

A plurality of temperature values sensed by the temperature sensor 4 over a period of time is transmitted by the wireless transmitter 26 within the casing 6. The transmissions are received by a receiver 68 and recorded to provide a temperature profile along the fryer 50.

Typically, the wireless transmitter 26 transmits series of wireless signals in step (iv), each wireless signal including information associated with a respective temperature value sensed by the temperature sensor 4, to provide a series of temperature values associated with the respective part of the product flow path 60.

By providing a temperature probe 2 which can float in the fryer oil and is dimensioned so as to be substantially the same size as the foodstuff being fried, the temperature probe 2 is able to follow the path taken by products through the fryer, including floating on the surface of the oil and being temporarily partly or wholly submerged in the oil when urged downwardly by any conveying apparatus in the fryer, and thereby provide a substantially continuous temperature profile which is actually experienced by the foodstuff during its passage through the fryer.

The temperature probe 2 permits the temperature of a fryer easily to be monitored using a temperature probe which is inexpensive to manufacture and deploy. The temperature probe 2 provides a very versatile device for measuring temperature within the fryer at various locations.

The preferred embodiment of the present invention can therefore provide a wireless 'floating ball' data logger will enables the measurement of temperature along all or part of the journey that the foodstuffs, such as potato slices wen manufacturing potato chips, take in the fryer by mimicking the slices and whilst doing so it builds a temperature profile. The wireless data logger can be selectively flowed along the left, centre and/or right of the fryer to understand how the temperature profile differs in the different transverse zones across the transverse width of the fryer. This can provide information on how the cooking process differs for slices that enter the fryer in the three different transverse zones too. Furthermore, the wireless data logger can also provide temperature information that can be employed to minimise product defects, because the data logger can provide temperature data indicating hotspots or cool oil regions and hence be employed to avoid overcooking or undercooking the foodstuffs during the frying process.

Various modifications to the present invention as defined in the appended claims will be apparent to those skilled in the art.