Abstract:
A cooking oven system and related method for cooking a batch of food items having any number of potential substrate characteristics, e.g., beef, pork, chicken, etc., wherein an indirect cooking chamber having a high humidity is transitioned into a direct cooking chamber having a high temperature. A process control system connects the indirect cooking chamber with the direct cooking chamber to ensure proper operating conditions depending upon the substrate.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     This invention relates to a indirect and direct heated continuous impingement oven system to deliver desired food attributes on substrates requiring different treatments.  
         [0003]     2. Description of Prior Art  
         [0004]     Cooking ovens for cooking food typically include a heat source, air mover and heat exchanger are typically provided within the cooking chamber for cooking the food provided on the conveyor. A uniform and consistent cooking environment for different food items, such as beef, pork and chicken, is difficult to maintain in existing cooking ovens because of a lack of proper operating conditions including air flow, moisture content, recirculation, heat exchange and other factors. As such, it is desirable that when beef, for example, is cooked in a cooking oven designed for chicken, the final cooked product achieves the desired taste, appearance, waste and/or safety characteristics.  
         [0005]     In general, different substrates require very specific application treatments to deliver the sensory attributes desired by consumers. Food processors strive to deliver these specific home cooked food attributes through continuous large-scale industrial cooking systems. These systems have considerable flexibility in the preparation steps that lead to altering the flavor profile or adding value through coating and seasonings during the raw and partially cooked stages. However, heat treatment steps determine the final food item outcome in terms of product quality, flavoring, color development, and food safety.  
       SUMMARY OF THE INVENTION  
       [0006]     It is therefore an object of this invention to provide a cooking oven system that is capable of cooking a wide variety of food items having varying substrate characteristics.  
         [0007]     It is one object of this invention to provide a cooking oven system that provides uniform and controllable cooking conditions.  
         [0008]     It is one object of this invention to provide a cooking oven system having an adjustable cooking cycle that has flexibility to deliver proper conditions required for a given substrate.  
         [0009]     It is another object of this invention to provide a cooking oven system having a combination of hardware and controls to deliver energy to the food item optimally and efficiently to produce food items at a lower cost per pound in relation to existing ovens.  
         [0010]     It is yet another object of this invention to provide an indirect cooking chamber having a thermal fluid heat exchanger heating an air-vapor mixture within the indirect cooking chamber.  
         [0011]     It is still another object of this invention to provide a direct cooking chamber having one or more gas-fired burners.  
         [0012]     A cooking oven system according to a preferred embodiment of this invention includes an indirect cooking chamber cooking at a high humidity and a transition from the indirect cooking chamber and into a direct cooking chamber cooking at a high temperature, preferably using direct gas-fired burners.  
         [0013]     In most cooking processes involving humidity, such as in the indirect cooking chamber of the present invention, there is a certain percentage of moisture that condenses on the surface of food items. The energy that is delivered to the surface during this process occurs through the change of phase in the steam. This energy subsequently migrates to the core of the food items through conduction. This translates to a corresponding increase in the internal core temperature of the food items. Of course, the thicker and/or dryer the food items, the longer it will take to reach a steady state core temperature which can be measured. Another key variable that influences the time constant is the composition of the substrate itself.  
         [0014]     Therefore, the greater the amount of steam available for condensing, the larger the rise in the core temperature of a given food item. This generally holds true so long as the surface of the food item is below the dew point temperature of the surrounding atmosphere. Once the surface reaches the dew point temperature there is generally no energy delivered to the surface of the food item through condensation. At this point, depending on the temperature of the surrounding atmosphere, there is a possibility for food item surface cooling caused by evaporative cooling. In order to continue to drive energy to the surface, the heating mechanism should be changed to convection or high velocity impingement combined with higher temperature heating.  
         [0015]     The above two parameters combined with high humidity can deliver better control of food item yield. The optimum mix of parameters for this step following condensation is dependent on the substrate and desired sensory attributes of the food item.  
         [0016]     A preferred embodiment of the present invention involves a cooking oven system with an indirect heating chamber or zone and a direct heating chamber or zone. A transition is preferably positioned between the indirect heating chamber and the direct heating chamber to maintain correct operating conditions within the respective cooking zones. A process control system preferably links the indirect heating chamber with the direct heating chamber to provide optimum operating conditions depending upon the substrate characteristics of the food item.  
         [0017]     The cooking oven system according to this invention may additionally include a transport mechanism, such as a conveyor, that extends entirely, or partially, through the indirect heating chamber, the transition and the direct heating chamber and between an inlet and an outlet of the cooking oven system. An air distribution system may be positioned in fluid communication with the indirect cooking chamber and the direct cooking chamber and may include one or more blowers or other devices for circulating conditioned air throughout the respective cooking chambers. The process control system may additionally control the transport mechanism, the air distribution system, steam flow, top and bottom air flow distribution and the heat transfer penetration rate. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]     The above-mentioned and other features and objects of this invention will be better understood from the following detailed description taken in conjunction with the drawings wherein:  
         [0019]      FIG. 1  is a schematic view of a cooking oven system according to one preferred embodiment of this invention; and  
         [0020]      FIG. 2  is a schematic view of a cooking oven system according to another preferred embodiment of this invention. 
     
    
     DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0021]      FIG. 1  shows a cooking oven system according to one preferred embodiment of this invention. Cooking oven system  10  is preferably a stand-alone or modular oven which may have any desired number of modules joined together in an end-to-end relationship. Cooking oven system  10  preferably includes indirect and direct heated continuous cooking chambers to deliver desired food attributes on substrates requiring different treatments.  
         [0022]     Different substrates that are desirable for use in such cooking oven system  10  may include beef, pork, fish, bakery items and any other such item or combination requiring unique operating conditions to produce cooked food items having optimal attributes.  
         [0023]     The current state of the art cooking systems lack flexibility in extracting the flavor profile and mouth feel that is unique to a given substrate. This is primarily due to the lack flexibility in the cooking system to deliver the precise conditions needed at the right time in the cooking process. Simply applying heat does not necessarily produce the desired home cooked attributes. Several interrelated factors typically bring about the desired flavor profile. For example, heat processing conditions, sequences and equipment needed for poultry, beef, pork and bakery items can vary significantly. Therefore, flexibility of heat treatments, the timely application of appropriate heat transfer mechanisms and overall equipment and system design are crucial to bringing about the qualities that are inherent and unique to the respective substrates. Furthermore, food item appeal and texture associated with coatings external to the substrate are also enhanced through precise control and conditioning of heat delivery.  
         [0024]     The current invention describes the design and use of a non-dedicated system for multiple substrates that require different processing treatments. For example, this system can produce food items of different substrates such as beef, pork, fish, poultry and bakery items to deliver improved quality without having to re-arrange hardware for cooking. This involves a combination of an indirect and direct heated system with highest humidity heat conditioning upstream and dryer conditioning coupled with direct flame induced heat downstream respectively.  
         [0025]     As shown in  FIG. 1 , and briefly described above, cooking oven system  10  preferably includes: (1) indirect cooking chamber  20  for cooking a continuous batch of food items in a high humidity; and (2) direct cooking chamber  30  for cooking the continuous batch of food items at a high temperature. As shown schematically in  FIGS. 1 and 2 , indirect cooking chamber  20  and direct cooking chamber  30  may comprise two separate “boxes” or alternatively comprise a single “box.” In each alternative, the distinct cooking chambers are preferably separated with transition  50 .  
         [0026]     The air-vapor mixture in indirect cooking chamber  20  is preferably heated using thermal fluid from a thermal fluid heat exchanger  25  located within indirect cooking chamber  20 . The thermal fluid heat exchanger  25  may be heated externally with heater  28 . Indirect cooking chamber  20  preferably operates at a temperature less than 450 degrees F. and at a moisture by volume greater than 80% and more preferably greater than 90% and more preferably at greater than 95%. The ability to maintain a higher moisture volume may be attributable, in one preferred embodiment of this invention, to the lack of combustion air in produced by thermal fluid heat exchanger  25 . In addition, minimizing air infiltration into indirect cooking chamber  20  may result from improved containment. The humidity content of indirect cooking chamber  20  may be changed through the use of a moisture control device such as a Humitrol®, manufactured by FMC Technologies, Inc.  
         [0027]     Direct cooking chamber  30  preferably includes one or more gas-fired burners  35 . Direct cooking chamber  30  preferably operates at a temperature exceeding 400 degrees F. and more preferably exceeding 450 degrees F. and more preferably exceeding 500 degrees F. The direct flame induced heat during the final stages of the subject process thereby allows for achieving flavor profiles not possible with indirect only systems especially for food substrates having beef and pork origin. In addition, such a direct cooking chamber  30  having one or more gas-fired burners improves browning capability at lower operating cost over existing systems. Higher and dry processing capability at the final stages within cooking oven system also enhances food color development and flavor profile.  
         [0028]     Transition  50  is preferably positioned between indirect cooking chamber  20  and direct cooking chamber  30 . As shown schematically in  FIG. 1 , transition  50  may comprise tunnel  55 , preferably approximately 2 feet in length that extends between indirect cooking chamber  20  and direct cooking chamber. Alternatively, as shown schematically in  FIG. 2 , transition  50  may comprise partition  60  that divides a unitary indirect cooking chamber  20  and direct cooking chamber  30 . In each alternative, transition  50  preferably isolates indirect cooking chamber  20  from direct cooking chamber  30 . Such isolation may be effected with at least one seal  53  positioned within transition  50  for isolating the operating conditions of indirect cooking chamber  20  from direct cooking chamber  30 . Seal  53  may be a mechanical seal, a steam curtain or any means for isolating the operating conditions of the separate cooking chambers known to those having ordinary skill in the art.  
         [0029]     Transition  50 , in part, improves process safety of the operation, such as explosion protection. In addition, an independent transition  50  structure, such as tunnel  55 , simplifies handling the overall stress distribution.  
         [0030]     Each of indirect cooking chamber  20  and direct cooking chamber  30  may include an independent air distribution system  90  for controlling air flow within the respective chamber. Precise distribution and control of the top and bottom air flow in each cooking chamber delivers improved food item quality through more finite and regulated distribution. Preferably, air distribution system  90  is coupled with a heat exchanger and air manifolds are positioned in fluid communication with a respective chamber, particularly indirect cooking chamber  30  to produce, direct and recirculate air flow through indirect cooking chamber  30 . Air distribution system  90  preferably includes one or more air plenums, fans, blowers and/or other devices for circulating conditioned air to air manifolds which upon impinging on food items returns through air distribution system  90 . Air distribution system  90  may include a combination of forced draft air flow and induced air flow to generate proper and uniform conditions throughout cooking oven system  10 .  
         [0031]     As used in this specification and claims, air flow is defined as conditioned air, vapor, gas and/or fluid used to circulate through cooking oven system  10 . According to one preferred embodiment of this invention particularly in reference to indirect cooking chamber  20 , air flow comprises steam of varying temperatures and moisture content. As such, the energy is delivered predominantly through the condensation of a thermal fluid on the surface of a food item. This method of energy delivery allows for optimum control of the overall process resulting in increased food item throughput, yield and improved quality, especially during the indirect stage.  
         [0032]     According to one preferred embodiment of this invention, process control system  80  is connected with indirect cooking chamber  20  and direct cooking chamber  30 . Process control system  80  preferably maintains the desired operating conditions within indirect cooking chamber  20  and direct cooking chamber  30 . According to a preferred embodiment of this invention, process control system  80  may selectably control the operating conditions within indirect cooking chamber  20  and/or direct cooking chamber  30  depending upon a particular substrate to be cooked. For example, the operating conditions, such as temperature, thermal fluid flow, humidity, air flow, top and bottom distribution of air and/or heat penetration rate may be adjusted depending upon whether the substrate comprises beef, pork, chicken, bakery items and/or any other desired substrate.  
         [0033]     Process control system  80  thereby enables precise control of moisture conditioning in each chamber (zone) of cooking oven system  10  to pre-established conditions irrespective of changes in the external conditions or seasonal variations. Process control system  80  may additionally control steam flow, top and bottom air flow distribution and the heat transfer penetration rate within cooking oven system  10 .  
         [0034]     Transport mechanism  70 , such as a conveyor, is preferably positioned at least partially, and preferably entirely, through indirect cooking chamber  20 , transition  50  and direct cooking chamber  30 . Transport mechanism  70  is used to transport food items through cooking oven system  10  and may include a single unitary belt or numerous transport segments or belts. Transport mechanism  70  is preferably a pervious belt thus permitting air and liquid to flow through.  
         [0035]     In addition, cooking oven system  10  may further include infeed conveyor  73  connected to an inlet of indirect cooking chamber  20 . Infeed conveyor  73  preferably supplies the uncooked substrate/food items to indirect cooking chamber  20  at a desired mass flow rate. Accordingly, outfeed conveyor  77  is preferably connected to an outlet of direct cooking chamber  30 . Outfeed conveyor  77  preferably discharges fully cooked and/or pre-cooked substrate/food items from cooking oven system  10 . The length and configuration of infeed conveyor  73  and outfeed conveyor  77  may be determined by food item throughput and quality requirements of the individual processor.  
         [0036]     Transport mechanism  70  preferably includes controllable speed along at least a portion of its length. According to one preferred embodiment of this invention, process control system  80  may electronically control, or otherwise communicate with, transport mechanism  70 .  
         [0037]     According to a preferred embodiment of this invention, transport mechanism  70  operates continuously whenever cooking oven system  10  is in operation. Thus, cooking oven system  10  may be referred to as a continuous oven. Uncooked food items, preferably in batches, are loaded onto transport mechanism  70  continuously at an inlet of indirect cooking chamber  20  and transported through the respective chambers  20 ,  30  and preferably emerges treated and/or cooked, at an outlet of direct cooking chamber  30  of cooking oven system  10 .  
         [0038]     Accordingly, a method of cooking a batch of food items within cooking oven system  10  includes the steps of moving the batch of food items through indirect cooking chamber  20  operating at a high humidity; moving the batch of food items through transition  50  at an outlet of indirect cooking chamber  20 ; and moving the batch of food items through direct cooking chamber  30  operating at a high temperature. Operating conditions, including temperature, humidity and air flow, are continuously maintained in indirect cooking chamber  20  and direct cooking chamber  30  based upon the substrate characteristics of the food items using process control system  80  connected with the respective cooking chambers. Additional conditions such as speed of transport mechanism  70  and the effectiveness of transition  50  may further be controlled using process control system  80 . In addition, process control system  80  may adjustment the heat penetration rate into the food-items by varying the distance of jets, burners and/or other heating means to the food items  
         [0039]     Finally, a substrate characteristic of the food item to be processed may be entered into process control system  80  which may then responsively adjust the humidity content of indirect cooking chamber  20  and/or the temperature of direct cooking chamber  30  and/or the top and bottom airflow to obtain the desired surface characteristics.  
         [0040]     The resulting apparatus and method thereby permits improved latitude to optimize throughput, yield and flavor and/or other sensory properties. For instance, the precise conditioning capability afforded by process control system  80  allows minimizing damage to the food casing during processing of sausage. Also, distinct processing zones enable very specific sensory attributes on dough based bakery items.  
         [0041]     In addition, a single system (and sequence of processing steps) according to a preferred embodiment of this invention arranged to produce food items of different substrates delivers improved quality without the need to rearrange, reconfigure or replace hardware for cooking. Avoidance of such changes in hardware results in improved overall process economics and lower initial cost. Such economics are further benefitted by the improved food item throughput relative to a direct gas only and improved yield relative to an indirect heated only process. Such improved food item throughput results in lower emissions and substrate rendering waste.  
         [0042]     While in the foregoing specification this invention has been described in relation to certain preferred embodiments thereof, and many details have been set forth for purpose of illustration, it will be apparent to those skilled in the art that this invention is susceptible to additional embodiments and that certain of the details described herein can be varied considerably without departing from the basic principles of the invention.