GB2540218A

GB2540218A - Heat flux control tunnel for food preservation and removal of micro-organisms

Info

Publication number: GB2540218A
Application number: GB1512202.1A
Authority: GB
Inventors: James Handley Simon
Original assignee: Linde GmbH
Current assignee: Linde GmbH
Priority date: 2015-07-06
Filing date: 2015-07-13
Publication date: 2017-01-11
Also published as: GB201512202D0

Abstract

An apparatus 10 for chilling food product(s) 16 to at least one of preserve the food, and destroy organisms on the food. The apparatus comprises a housing 12 having a sidewall 15 defining a chamber 14 divided into a plurality of zones 22, 24, 26 and having an inlet 30 at one end and an outlet 32 at another end. Within the chamber are a plurality of spaced heat-flux sensors 36 disposed proximate an inner surface 17 of the sidewall, a plurality of spaced fans 38, a liquid nitrogen (LIN) apparatus 40, 42 providing LIN to the chamber and the food. A controller (48, fig 3) communicates signals between the heat flux sensors, the fans, and the LIN apparatus to reduce the temperature of the food. A conveyer belt 28 transports the food through the zones. The LIN apparatus may comprise a delivery pipe 42 connected to a spray bar 40 with a plurality of nozzles to spray jet streams 46 of LIN onto the food. The controller may control the amount of cooling by actuation of conveyer belt speed, fan speed and supply pressure of LIN discharged. A method for chilling a food product(s) is disclosed.

Description

HEAT FLUX CONTROL TUNNEL FOR FOOD PRESERVATION AND REMOVAL OF MICRO-ORGANISMS

BACKGROUND OF THE INVENTION

[0001] The present embodiments relate to apparatus and methods that provide cold shock treatment to denature proteins and damage cells to destroy an organism, such as bacteria, present on food products.

[0002] Every product and organism, including bacteria, has a known rate of cooling, and it is known with respect to same that there is one rate to achieve optimum destruction of the bacteria or preservation of the product. Conversely, a different rate of cooling could result in bacteria growth or maintenance of the bacteria in a frozen state only, whereupon exposure to room or ambient temperatures could cause the bacteria to become active. It is, however, difficult to achieve the optimum cooling rate for each type of bacteria, as many variations can occur regarding the size of the food product and its associated thoughput during processing, which variables can adversely impact the efficient and effective cooling rate of the bacteria for destruction.

[0003] Currently, the majority of food freezing/chilling processes rely on a temperature set point to control the operational temperature parameters of the application equipment. For example, a set point controller is usually set at -18Ό (freezing) to freeze a product. When that temperature is achieved in the equipment, the system will operate at this specific temperature to freeze the product by measuring the temperature in the tunnel and controlling the speed at which the product passes through the tunnel (usually, the speed is manually controlled). This system of setting a temperature required in the tunnel and selecting a speed for the product passing therethrough is well established and used for most food products.

[0004] However, certain products, including certain types of food products, can be damaged by being subjected to freezing or chilling at incorrect rates and, in most cases, resulting in either excessive freezing or chilling of the products or perhaps insufficient freezing or chilling. Such fluctuations can be cost detrimental, as energy is wasted on inaccurate processing or product recalls occur due to inaccurate temperatures for the products. A worst case scenario can be the potential for food safety to be compromised if microbial growth has not been reduced or eliminated. The product could also incur a shorter shelf life due to continued enzyme activity resulting in product deterioration (color changes/ tissue breakdown), whether or not such deterioration is visible.

[0005] Accordingly, it would be beneficial to be able to measure the energy present and adjust same as the energy required to remove heat from the product to achieve the ideal frozen or chilled state for each type of product in order to effectively preserve the product, and/or prevent or destroy bacteria on the product.

SUMMARY OF THE INVENTION

[0006] There is therefore provided an apparatus embodiment for chilling a food product to at least one of preserve the food product, and destroy organisms on the food product, which includes a housing having a sidewall defining a chamber therein, the chamber divided into a plurality of zones; an inlet provided at an end of the chamber, and an outlet provided at another end of the chamber; a plurality of heat-flux sensors spaced apart and disposed proximate an inner surface of the sidewall in the chamber; a plurality of fans spaced apart and disposed in the chamber; a liquid nitrogen (LIN) apparatus disposed in the chamber to provide the LIN to the chamber and the food product; and a controller operatively associated with and disposed to transeive signals between the plurality of heat flux sensors, the plurality of fans, the LIN apparatus, and the controller, the controller adapted to generate a signal responsive to the transeive signals to reduce the temperature of the food product.

[0007] There is also provided a method embodiment for chilling a food product for at least one of preserving the food product, and destroying organisms on the food product, including measuring a heat flux within a chamber of a housing; introducing the food product having a specific cooling rate into the chamber; providing liquid nitrogen (LIN) into the chamber and to the food product; measuring the heat flux with sensors for generating a signal representing any change of said heat flux; transmitting the signal to a controller for controlling the introducing of the food product and the providing the LIN into the chamber; and cooling the chamber responsive to the signal for providing the cooling rate for the food product.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] For a more complete understanding of the present embodiments, reference may be had to the following detailed description of the embodiments taken in conjunction with the drawing Figures, of which: [0009] FIG. 1 shows a side view of a heat flux control tunnel apparatus embodiment according to the present embodiments; [0010] FIG. 2 shows a partial end view of the apparatus embodiment in FIG. 1; and [0011] FIG. 3 shows a control diagram for the apparatus embodiment of FIG 1.

DETAILED DESCRIPTION OF THE INVENTION

[0012] Before explaining the inventive embodiments in detail, it is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, if any, since the invention is capable of other embodiments and being practiced or carried out in various ways. Also, it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

[0013] For purposes herein, a “product” is anything that can have its energy removed in order to reduce a temperature of the product, such as for example a food product. Reduction of the energy, such as heat, in the food product can be undertaken to preserve the food product and/or reduce if not eliminate bacteria thereon. The term “food product” denotes the singular and plural of same.

[0014] By way of example only, a food product includes a known amount of energy within its composition. By removing this energy in a controlled process, the food product can change state Damage to the product’s state by internal crystal growth from water will be minimized, as the food’s internal water mass changes from liquid to ice crystals for a frozen requirement An arrangement of a plurality of heat flux probes installed within processing equipment measure the transfer of heat from within the equipment as the product moves through same and will gradually reduce the temperature within the equipment to remove the latent energy (heat) within the food product by lowering the temperature of the food product to only that amount necessary to kill bacteria and/or chill or freeze the product without causing cellular destruction. The heat flux probes will sense when a sufficient amount of the energy has been removed from the product. Automation of the speed by which the product moves will also be controlled by signals received from the heat flux probes, as the amount of energy is measured when the food enters the equipment. To control this situation, an increase or a decrease in cooling is required.

[0015] Utilising the present embodiments to control processing with heat flux enables more accurate and efficient freezing or chilling of the product, as the apparatus and method embodiments are set for each product type. There would be less product loss, more efficient use of the cooling medium in the cooling system or apparatus, and less potential for food safety issues.

[0016] Since it is known that excessive cooling can damage food products by mechanical, chemical, osmosis and enzyme changes to the cellular structure of the food, the present embodiments can be used to reduce and eliminate the presence of microbial growth (bacterial, yeast, algae and fungi growths, for example) on foods. Ascertaining the heat transfer coefficient of microbes allows the present embodiments to remove energy from the cells in such a way that the microbial cell would be destroyed by the process. The process can be used to establish cooling rates of foods to provide best preservation of same without causing damage to cell walls and intercellular material of the food. The cooling process is also used to determine how to maximise destruction of microbial cell walls by mechanical breakdown, chemical changes or osmosis, without affecting the food product upon which the microbes are present.

[0017] Referring to FIGS. 1-3, a heat flux control tunnel apparatus is shown generally at 10. The tunnel apparatus or apparatus 10 can be a chiller or freezer for industrial applications, and includes a housing 12 having a chamber 14 or internal space therein in which products such as food products 16 are processed. A wall 15 of the housing 12 defines the chamber 14 and has an inner surface 17 exposed to the chamber. The processing of the food product 16 is to chill or freeze said products in order to preserve the product for subsequent processing and/or substantially reduce, prevent if not eliminate any organisms or bacteria, such as Campylobacter microbes, which may be present on the food products. The housing 12 includes legs 18 or supports, which may be adjustable, extending therefrom to support the housing off an underlying surface 20 in a plant of factory floor.

[0018] In one embodiment, the chamber 14 of the apparatus 10 includes a plurality of zones 22,24,26, collectively also referred to as “22-26”. The housing 12 also includes an inlet 30 opening into one of the zones 22-26, and an outlet 32 opening into another one of the zones. In FIG. 1, the zone 22 includes the inlet 30, while the zone 26 includes the outlet 32. A conveyor belt 28 travels and extends through the chamber 14 and is exposed to all of the zones 22-26. The conveyor belt 28 is initially accessed at the inlet 30 for transporting the food product 16 thereon through the chamber 14 to be removed from the outlet 32 for packaging, subsequent processing, etc. The conveyor belt 28 is shown operating in a direction represented by arrow 34, by way of example only. The conveyor belt 28 can be of any known construction and fabricated from many different types of materials, such as for example stainless steel, aluminum, plastic.

[0019] Disposed within the chamber 14 are a plurality of sensors 36 for heat flux occurring within the chamber and with respect to the food product 16, and a plurality of fans 38 for circulating liquid nitrogen (LIN) introduced into the chamber as further described hereinafter. Although the sensors 36 are represented by boxes which appear external to the chamber 14, such representation is to indicate the relationship of the sensors to the fans 38, and is not meant to represent that the sensors are external to the chamber. Each one of the plurality of sensors 36 may be a HukseFLUX® thermal sensor, such as Model HF05 industrial heat flux sensor. Reference to such a heat flux sensor is by way of example only and it is understood that other types of heat flux sensors may be employed in the chamber 14 of the present apparatus 10. The heat flux sensors 36 are mounted at or proximate to the interior surface 17 of the chamber 14.

[0020] Referring to FIG. 1, it can be seen that the heat flux sensors 36 and the rotational features of the fans 38 are disposed in corresponding ones of the zones 22-26 of the chamber 14. That is, the zone 22 including the inlet 30 has heat flux sensor 36A disposed in said zone proximate the inlet 30, and another heat flux sensor 36B disposed in the zone 22 downstream of the sensor 36A.

[0021] The zone 24 includes a plurality of the heat flux sensors 36C,36D,36E, and a plurality of the fans 38A,38B,38C,38D. The arrangement of the sensors 36 and the fans 38 in the zone 24 can be in an alternating arrangement as shown.

[0022] Referring to the zone 26, there is provided a plurality of heat flux sensors 36F,36G, with the sensor 36G disposed proximate the outlet 32 of the chamber 14.

[0023] The direction 34 of the conveyor belt 28 for transporting the food product 16 therefore denotes an “upstream” to “downstream” flow occurring from the zone 22 having the inlet 30 to a position downstream of the zone 22 to the zone 26 having the outlet 32.

[0024] The chamber 14 and the zones 22-26 have liquid nitrogen (LIN) sprayed into the chamber for contacting the food products 16. A LIN spray bar 40 is disposed in the chamber 14 at the zone 24 and extends substantially along said zone above an upper surface of the conveyor belt 28 which is supporting the products 16. The spray bar 40 functions as a manifold, and is in fluid communication with a pipe 42 connected at one end to the spray bar and at an opposite end to a source (not shown) of the LIN external to the housing 12. A control valve 44 is interposed in the pipe 42 to control a flow of the LIN through the pipe and into the spray bar 40. At least one and for most applications a plurality of nozzles 46 are connected to the spray bar 40 to release the LIN in a liquid state from the nozzles onto the food products 16 where heat flux occurs. If the pipe 42 which supplies the LIN is insulated sufficiently, the LIN (in a liquid state) will be exhausted from the nozzle 46 in jet streams. When the LIN contacts the food product 16, it changes phase from a liquid to a gaseous state and energy is expended at this stage to cool the food product.

[0025] Referring to FIG. 2, a human machine interface (HMI), controller, PLC (process logic controller) or computer 48 is connected to and receives signals regarding the spray bar 40 pressure, the heat flux sensors 36 and the control valve 44 for computation against data input regarding the apparatus 10 and the food products 16 for generating output signals to control the speed of the conveyor belt 28, the pressure and therefore the flow of the LIN through the pipe 42 to the spray bar 40, and actuation of the fans 38.

[0026] The heat flux sensors 36 will for most applications be mounted to the interior surface 17 of the wall 15 of the housing 12 at the zones 22-26. The sensor 36A is mounted at the inlet 30 where the food product enters the chamber 14. The sensor 36A for most applications is mounted directly above the belt with sufficient clearance for the food product 16 to pass thereunder. The heat flux sensor 36G is similarly mounted with respect to the outlet 32, and above the conveyor 28 so that there is sufficient clearance for the food product 16 having been treated to pass thereunder and exit the apparatus 10.

[0027] As shown in FIG. 2, there are inputs and outputs in communication with the controller 48. In particular, a user, such as for example a plant employee, can select from a menu 50 at the controller for operation of the apparatus 10 and input particulars about the product 16 to be processed in the apparatus.

[0028] Inputs to the HMI 48 include pressure 52 occurring in the liquid nitrogen spray bar 40, temperature 54 of the heat flux sensed and transmitted from the heat flux sensors 36, and particulars regarding the products 16 uploaded from the menu 50 to the controller 48.

[0029] Outputs from the controller 48 include a speed control signal 56 directed to a belt controller 58 for the conveyor belt 28, fan control signal 60 directed to the fans 38, and a LIN control signal 62 directed to the control valve 44 for the LIN. A pressure exerted at the LIN control valve 44 is sensed by the sensor 54 and accordingly transmitted to the controller 48.

[0030] In operation, the heat flux sensors 36 will measure conductive, convective and radioactive heat transfer within the zones 22-26, as well as a temperature of the zones.

[0031] The heat flux control tunnel apparatus 10 is turned on and an amount of energy and a temperature within the tunnel, i.e., within the chamber 14 and the zones 22-26 thereof, is measured as well. Similar measurements will be taken at the inlet 30 and the outlet 32 of the housing 12, and all of these readings will be signaled or transmitted to the controller 48. Transmission of the signals may be wireless. All of these readings will also be referred to as the “reference base 1 measurement”.

[0032] The particulars about information regarding the food product 16 are input into the controller 48. The food product 16 will either be chilled or frozen to preserve same and/or to substantially reduce or destroy any organisms that are on the food products. The visible screen of the menu 50 of the controller 48 can prompt a pictorial selection for use by the operator. The required cooling rates for either (i) best preservation cooling rate or (ii) best kill rate for microorganisms on the food product have already been defined by scientific analysis or reference known cooling rates and uploaded into the controller 48. The apparatus 10 then cools down to the required cooling rate having the necessary temperature in the chamber 14. When the temperature of the chamber 14 has stabilized, a series of temperature measurements are received by the controller 48 from the heat flux sensors 36 and these reference measurements will consist of “reference base 2 measurement”.

[0033] At this stage, the food products 16 are introduced onto the conveyor belt 28, either by machine or manual labor, and fed to the inlet 30. There is no necessity to set or upload size for production rate for the apparatus 10 to operate on the food product 16, because the heat flux sensors 36 will measure the amount of energy within the chamber 14, including the zones 22-26, and continue to cool the chamber 14 with LIN from the nozzles 46 to achieve the best cooling rate for the operational requirements necessary for the particular food products 16. That is, if the size or the production rate of the food products 16 is to increase, the latent heat in the tunnel will also increase and therefore more LIN will be required. The sensors 36 will generate signals to achieve the required cooling rate for the food products 16. If in fact an increase of cooling is necessary within the zones 22-26, the controller 48 can actuate one or more of the following, either alone or in combination with each other, to achieve further chilling and freezing: increased flow of the LIN from the remote source through the pipe 42 and the nozzles 46, increased rotational speed of the fans 38 and/or adjustment of the speed of the conveyor belt 28 transporting the products 16 through the chamber 14. If the size or production rate is to decrease, the latent heat in the tunnel will also decrease and therefore less LIN will be required and the controller 48 will adjust or actuate the same elements to efficiently use the LIN for preservation cooling or bacterial destruction.

[0034] The food products 16 will depart the zone 26 through the outlet 32 either at the optimal chilled/frozen state, or such that any bacterial contamination has been destroyed, such as for example any Campylobacter is destroyed that was present on the food products.

[0035] Operation of the tunnel apparatus 10 will be by use of the controller 48. By ascertaining an amount of latent heat within the tunnel chamber 14 after said chamber has cooled down to the stable set point reference base 1 measurement, said reference condition can be used to ascertain the amount of latent energy which increases in the tunnel after the food product 16 has been introduced into the tunnel. The heat flux sensors 36 signal or relay this information to the controller 48. The controller 48 then determines an amount of cooling energy necessary in relation to the cooling rates for the food products 16 to achieve the best possible conditions for either of preservation (by chilling or freezing) of the food or destruction of any bacteria on the food products. This occurs by controlling an amount of cooling energy introduced into the chamber 14 in combination with actuation of one or more of the following: the LIN control valve 44, speed of the conveyor belt 28, speed of the fans 38, and supply pressure of the LIN 42 being discharged from the nozzles 46 onto the food products 16.

[0036] It will be understood that the embodiments described herein are merely exemplary, and that one skilled in the art may make variations and modifications without departing from the spirit and scope of the invention. All such variations and modifications are intended to be included within the scope of the invention as described and claimed herein. Further, all embodiments disclosed are not necessarily in the alternative, as various embodiments of the invention may be combined to provide the desired result.

Claims

CLAIMS What is claimed is:

1. An apparatus for chilling a food product to at least one of preserve the food product, and destroy organisms on the food product, comprising: a housing having a sidewall defining a chamber therein, the chamber divided into a plurality of zones; an inlet provided at an end of the chamber, and an outlet provided at another end of the chamber; a plurality of heat-flux sensors spaced apart and disposed proximate an inner surface of the sidewall in the chamber; a plurality of fans spaced apart and disposed in the chamber; a liquid nitrogen (LIN) apparatus disposed in the chamber to provide the LIN to the chamber and the food product; and a controller operatively associated with and disposed to transeive signals between the plurality of heat flux sensors, the plurality of fans, the LIN apparatus, and the controller, the controller adapted to generate a signal responsive to the transeive signals to reduce the temperature of the food product.

2. The apparatus of claim 1, further comprising a conveyor extending through the chamber for transporting the food product through the plurality of zones.

3. The apparatus of claim 1, wherein at least one heat flux sensor is mounted proximate to said inlet, and at least another heat flux sensor is mounted proximate said outlet.

4. The apparatus of claim 1, wherein the plurality of heat flux sensors and the plurality of fans are mounted in an alternating arrangement in said chamber.

5. The apparatus of claim 1, wherein the LIN apparatus comprises a LIN delivery pipe, and a spray bar disposed in the chamber and in fluid communication with the LIN delivery pipe.

6. The apparatus of claim 5, wherein the spray bar comprises a plurality of nozzles through which the LIN is sprayed into the chamber and onto the food product.

7. The apparatus of claim 5, wherein the spray bar disposed in the chamber extends through only one of said plurality of zones.

8. A method for chilling a food product for at least one of preserving the food product, and destroying organisms on the food product, comprising: measuring a heat flux within a chamber of a housing; introducing the food product having a specific cooling rate into the chamber; providing liquid nitrogen (LIN) into the chamber and to the food product; measuring the heat flux with sensors for generating a signal representing any change of said heat flux; transmitting the signal to a controller for controlling the introducing of the food product and the providing the LIN into the chamber; and cooling the chamber responsive to the signal for providing the cooling rate for the food product.

9. The method of claim 8, further comprising conveying the food product through the chamber.

10. The method of claim 8, further comprising circulating the LIN within the chamber for contacting the food product.