Abstract:
An apparatus and method of microbiocidal gas generation includes generating a microbiocidal agent, such as lactic acid, without the need for a carrier gas. A liquid microbiocidal agent is introduced into a heat exchanger where it is heated to generate a gaseous miocrobiocidal agent without a carrier gas for use with food products, while eliminating the costs, additional equipment and additional steps associated with the use of a carrier gas in the generation of microbiocidal agents.

Description:
FIELD AND BACKGROUND OF THE INVENTION  
         [0001]    The invention relates generally to the application of microbiocidal substances to food products. More particularly, the invention relates to the generation and the use of microbiocidal agents without using a carrier gas for the treatment of food products  
           [0002]    The preservation of perishable products has been, and continues to be, the focus of considerable commercial interest. By extending the shelf life of a food product, economic value can be added to that food product. Approaches to this end are many and varied (e.g., tight control of storage conditions, packaging, post and in situ applications of preservatives) and various combinations of these and other techniques are known and in practice to one extent or another.  
           [0003]    In the context of one particular group of food products, namely baked goods (e.g., muffins, crumpets, scones, bagels, cookies, breads, etc.), all of the above techniques are in use. For example, baked goods can be placed in frozen or refrigerated storage, covered with anaerobic packaging, and/or supplemented by the addition of preservatives. When such preservatives are used, the preservative can be added to either a batter or a mix from which the baked goods are prepared. Also, the preservative can be applied to finished baked goods. With respect to the finished baked goods, application of a small amount of the preservative can extend the shelf life of the baked goods from a typical 6-8 days to an extended 14-16 days when all other conditions (e.g., packaging, storage conditions, and the like) are equal. These preservatives can include a wide variety of substances (i.e., microbiocidal substances, antimicrobial substances, etc.) such as acetic acid, carbonic acid, mixtures thereof, and the like.  
           [0004]    Current methods of generating and applying microbiocidal substances involve the use of a volatile gas, such as acetic acid, within a carrier gas. Volatile gases by nature are generally hazardous to work with, as they can be explosive under specific conditions.  
           [0005]    The nature of volatile microbiocidal agents requires carrier gases to accommodate the volatile gases. The additional measures required during the design, fabrication, installation and use of equipment to be used with volatile gases and carrier gases can decrease the efficiency and increase the cost of a microbiocidal application process. For example, in order to use volatile gases, the following must be observed: explosion-proof components must be used, adding tremendous cost to the application system; specific procedures must be observed when storing the volatile gases, such storage oftentimes occurring off-site and out of the direct control of the supplier of the volatile gases; and detailed control and strict systems must be implemented to prevent leakage and prevent exposure to those in working with the volatile gases. The leakage of volatile gases can pose a significant risk to plant personnel.  
           [0006]    The use of a carrier gas requires that the microbiocidal substance be atomized. The atomized substance is then converted to vapor by mixing it with a super-heated carrier gas. The system requires the use of a metering system on the carrier gas, a metering pump for the microbiocidal acid, a heating system for the carrier gas, as well as an atomization system from the microbiocidal agent and a mixing vessel for the process.  
           [0007]    It would be beneficial if the use of carrier gases with microbiocidal agents, specifically non-volatile agents, could be reduced or eliminated. Further, it would be desirable to provide a microbiocidal agent food treatment system that uses microbiocidal agents that are not mixed with super-heated carrier gases.  
           [0008]    Thus, an apparatus and method for providing treatment to a food product with a microbiocidal agent that is not combined with a carrier gas would be advantageous and therefore desirable, since such an apparatus and method would eliminate the need for the additional costs and equipment associated with the use of carrier gases in the treatment process.  
         SUMMARY OF THE INVENTION  
         [0009]    The present invention provides for the generation of a microbiocidal agent for the treatment of food products that overcome the aforementioned problems. In accordance with one aspect of the invention, a method of generating a microbiocidal agent is provided which includes providing a liquid microbiocidal agent, and heating the liquid microbiocidal agent to generate a gaseous microbiocidal agent. In this method, the heating step provides for the generation of the gaseous microbiocidal agent without a carrier gas.  
           [0010]    Various other features, objects and advantages of the present invention will be made apparent from the following detailed description and the drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    For a more complete understanding of the present invention, embodiments of the invention are disclosed with reference to the accompanying drawings which are for illustrative purposes only. The invention is not limited in its application to the details of construction or the arrangement of the components illustrated in the drawings. The invention is capable of other embodiments or of being practiced or carried out in other various ways. Like reference numerals are used to indicate like components unless indicated otherwise.  
         [0012]    The drawings illustrate at least one mode presently contemplated for carrying out the invention.  
         [0013]    In the drawings:  
         [0014]    [0014]FIG. 1 illustrates a flow diagram of a process for preparing a baked food product;  
         [0015]    [0015]FIG. 2 illustrates a flow diagram of another process for preparing a baked food product;  
         [0016]    [0016]FIG. 3 illustrates a schematic diagram of one treatment fluid generation system that includes the use of a carrier gas;  
         [0017]    [0017]FIG. 4 illustrates a perspective view of one embodiment of a microbiocidal agent generation system in accordance with the present invention;  
         [0018]    [0018]FIG. 5 illustrates a side cross-sectional view of the microbiocidal agent generation system of FIG. 4;  
         [0019]    [0019]FIG. 6 illustrates a front view of the microbiocidal agent generation system of FIG. 4;  
         [0020]    [0020]FIG. 7 illustrates another embodiment of a microbiocidal agent generation system in accordance with the present invention; and  
         [0021]    [0021]FIG. 8 illustrates a flowchart of a methodology associated with the generation of the microbiocidal agent in accordance with another embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0022]    Although the present invention is described below in the context of applying a preservative (e.g., a microbiocidal substance) to a baked good, the invention can also be employed with, and has applicability to, many different application processes.  
         [0023]    Referring to FIG. 1, an outline  2  is illustrated for preparation of commercial quantities of a food product, namely a baked good (e.g., muffin, crumpet, scone, bagel, cookie, bread, and the like). Batter is prepared and then poured into molds that are either carried on, or form a part of, a conveyor mechanism. The conveyor mechanism moves the batter through a baking zone in which the batter is fully baked.  
         [0024]    Upon leaving the baking zone, the baked good is de-molded, typically onto a second conveyor mechanism. The de-molding procedure typically deposits the baked goods upon the second conveyor mechanism such that the baked goods are arranged in an indexed array. The indexed array of baked goods are then conveyed through a cooling tunnel to bring the baked goods to a temperature appropriate for packaging (e.g., room temperature or slightly above).  
         [0025]    In some instances as illustrated in FIG. 1, prior to packaging, the baked goods will pass through a treatment apparatus. Prior to encountering the treatment apparatus, the baked goods are assembled into batches. In batches, the baked goods are transported through the treatment apparatus where a treatment fluid containing a preservative is applied to an external surface of the baked goods. Typical preservatives can include a wide variety of substances (i.e., microbiocidal substances, antimicrobial substances, etc.). Preservatives have the ability to radically reduce the pH of food products and, as such, can eradicate and/or eliminate bacteria present within the food product. The treatment fluid can include a preservative or a mixture containing the preservative. For example, a vaporized mixture of carbon dioxide and an application agent can be employed as the treatment fluid.  
         [0026]    In other instances, as illustrated by outline  4  in FIG. 2, placement of the cooling tunnel and the treatment apparatus are reversed. In other words, the baked goods are de-molded, assembled into batches, treated with the treatment fluid, cooled, restored to the indexed array, and then packaged.  
         [0027]    [0027]FIG. 3 illustrates a treatment fluid generation system that includes the use of a carrier gas and an example of an application agent preparation system  100 . System  100  is an example of equipment to accommodate a carrier gas, but in view of the present invention, may be in part eliminated.  
         [0028]    In system  100 , tank  101  holds liquid carbon dioxide, typically at about three hundred (300) psig. Liquid carbon dioxide is transferred to vaporizer  102  and converted to a gas substantially free of any droplets. The gas is then passed through pressure reduction valve  103  and the pressure of the gas is reduced from three hundred (300) psig to one hundred (100) psig.  
         [0029]    The gaseous CO 2  is then transferred to heater  104  and heated to substantially the same temperature as the contents of mixing/separation chamber  123  (e.g., 140° F.). Temperature control unit  126  coordinates the temperature of heater  104  and of chamber  123 . From heater  104 , the gaseous carbon dioxide at one hundred (100) psig is transferred to mass flow meter  105 , which is controlled by flow control  106 . As long as pump  107  is in proper operation, flow control  106  allows carbon dioxide to move from mass flow meter  105  into pipe  108 . Pipe  108  divides into pipes  109  and  110 . While the amount of carbon dioxide each of pipes  109  and  110  will carry can vary to convenience, typically pipe  109  will carry about ten percent (10%) and pipe  110  will carry the remaining about ninety percent (90%) by weight of the carbon dioxide. The stream of carbon dioxide passing through in pipe  110  can also pass through control valve  111  before entering mixing antechamber  112 .  
         [0030]    Liquid acid, such as lactic acid, is removed from tank  113  through check valve  114  by the action of pump  115 . When lactic acid is used, the liquid lactic acid moves through line  116  and valve  117  into metering pump  107 . If atomization nozzle  120  is operational, then the liquid lactic acid is fed into the atomization nozzle where the liquid lactic acid is atomized with carbon dioxide delivered to the nozzle through line  109 . If atomization nozzle  120  is not operative, then the liquid lactic acid is returned to tank  113  by way of line  118  and check valve  1119 .  
         [0031]    Atomized lactic acid is transferred from atomization nozzle  120  into the upper section of mixing/separation chamber  123  in which it is vaporized by contact with carbon dioxide delivered from mixing antechamber  112  through orifice plate  121 . The carbon dioxide delivered from line  110  into antechamber  112  passes through pressure reduction valve  111  in which the pressure of the carbon dioxide is reduced from one hundred (100) psig to about five (5) psig. The pressure of the atomized lactic acid as delivered to mixing/separation chamber  123  is also about five (5) psig. The temperature, pressure and volume of carbon dioxide introduced into the upper section of mixing/separation chamber  123  is sufficient such that the atomized lactic acid is essentially completely vaporized upon contact with it.  
         [0032]    Atomization nozzle  120  passes through antechamber  112  and orifice plate  121 , and opens into the upper section of mixing/separation chamber  123 . Atomization nozzle  120  can extend into the upper section of mixing/separation chamber  123  to any convenient length, but typically the end of the nozzle is flush with or extends only a short distance beyond orifice plate  121 .  
         [0033]    Further, commonly-owned, co-pending U.S. patent application Ser. No. 10/141,166, filed May 7, 2002, and entitled “Apparatus and Method for Providing Treatment to a Continuous Supply of Food Product Using a Vacuum Process,” discloses other and various embodiments and components within a fluid generation system and, therefore, the contents and disclosure of these applications are incorporated into the present application by reference as if fully set forth herein.  
         [0034]    Referring now to FIGS. 4 and 5, the microbiocidal agent generation system of the present invention is shown generally at  10 . The system  10  includes a tubular member  12  that acts as a heat exchanger. Tubular member  12  is a heat source or is associated with a heat source such that tubular member  12  is capable of being heated. A portion of the outside of tubular member  12  has been removed to facilitate understanding and explanation. Although in this embodiment a spiral tube-type heat exchanger is shown, other sizes and shapes may be employed.  
         [0035]    Disposed within tubular member  12  is insert  14 . Insert  14  is preferably of a generally spiral configuration that causes liquid flowing into tubular member  12  to be disrupted and directed away from the center of tubular member  12 , or to spirally disperse the liquid to the inner circumferential or the inner peripheral wall  22  of tubular member  12 . In this embodiment, insert  14  imparts a spiral fluid flow to the liquid microbiocidal agent as the liquid microbiocidal agent travels through the member  12 . An insert of any shape that is capable of directing the liquid to inner peripheral wall  22  may be used.  
         [0036]    Tubular member  12  includes wall  16  that is heated, directly or indirectly, to facilitate heat transfer from the wall to the liquid travelling through tubular member  12 . The general purpose of microbiocidal agent generation system  10  is to convert a liquid microbiocidal agent into a gaseous microbiocidal agent. Any suitable microbiocidal agent is contemplated, although lactic acid is preferred. Consistent with the purpose of converting the agent from a liquid phase to a gas phase, in operation liquid microbiocidal agent enters tubular member  12  at an inlet  20  in a direction indicated by arrow  18 . Once introduced at inlet  20  of tubular member  12 , insert  14  disrupts the flow of the liquid and directs the microbiocidal agent towards inner peripheral wall  22  of tubular member  12 . Because tubular member  12  is heated, contact between the wall  22  of the tubular member  12  and the liquid microbiocidal agent will cause the liquid microbiocidal agent to heat as it proceeds through tubular member  12 . Upon sufficient heating of the liquid microbiocidal agent, a gaseous microbiocidal agent is generated that exits the member  12  at outlet  24  in the direction indicated by arrow  26 . In this manner, the (gaseous) microbiocidal agent is generated for delivery without the use of a carrier gas.  
         [0037]    [0037]FIG. 6 illustrates directing of the liquid microbiocidal agent  28  from a central region  30  of tubular member  12  in a radial fashion as indicated by, for example, direction arrows  32 , such that the liquid microbiocidal agent  28  is dispersed against the inner peripheral wall  22  of tubular member  12  which is heated. In this manner, after the liquid microbiocidal agent  28  enters tubular member  12  at inlet  20 , liquid microbiocidal agent  28  is directed along the inner peripheral wall  22  of tubular member  12  such that heat energy from heated tubular member  12  is transferred to liquid microbiocidal agent  28 . This process allows the heat energy from the heated tubular shell  12  to generate the gaseous microbiocidal agent without the use of a carrier gas for the liquid agent.  
         [0038]    The embodiment of the microbiocidal agent generation system in FIG. 7 is shown generally at  50 . System  50  provides the heat energy necessary to convert the liquid microbiocidal agent into a gaseous microbiocidal agent. System  50  includes a shell and tube type heat exchanger for the purpose of transferring heat energy from a recirculation gas to another fluid, in this case the microbiocidal agent, which may be used for microbial decontamination. System  50  is shown with a portion of the outer cover removed to facilitate understanding and explanation.  
         [0039]    System  50  includes a shell  52  and a plurality of tubes  54  disposed therein. Attached to and communicating with the interior of shell  52  is gas line  56  for recirculating gas through the system  50 . The gas line  56  is in communication with a heater  58  to heat the gas traveling through gas line  56 . The gas line  56  can be constructed to contain a fluid as well to provide heating of the tubes  54 .  
         [0040]    In operation, the gas travels in a direction as indicated by arrow  60  through gas line  56 , where it is heated by heater  58 . The heated gas is introduced via gas line  56  in a direction indicated by arrow  62  into the interior  64  of shell  52 . The heated gas then travels about a series of baffles  66  within the shell  52 . Baffles  66  direct the gas in a substantially sinusoidal flow throughout the interior  64  of the shell  52 , such that the gas will flow around and contact tubes  54 , thereby transferring heat from the gas to the tubes  54 . The gas travels in a sinusoidal flow substantially as indicated by arrows  68  to then exit the shell  52  into gas line  56  where the (now cooler) gas is recirculated to be exposed again to heater  58  for the process to repeat.  
         [0041]    While the gas is flowing through the interior  64  of the shell  52 , liquid microbiocidal agent is introduced into heat exchanger inlet  69  in a direction indicated by arrow  70 . The agent is then distributed to flow into the plurality of tubes  54 . While moving through tubes  54 , the heat from the gas is transferred to the tubes  54  and ultimately to the liquid microbiocidal agent, which is heated until it becomes a gaseous or vaporized microbiocidal agent. Thereafter, the heated (now gaseous) microbiocidal agent flows to outlet  72  as indicated by arrow  74 . The gaseous microbiocidal agent exits system  50  for subsequent use, such as for treatment of food products.  
         [0042]    As shown in FIG. 7, a fluid conduit  59  is in communication with the heater  58 . The conduit  58  provides a fluid to be heated to the heater  58 . The heater  58  can include a pump, such as a self-priming pump, to circulate the fluid through the conduit  56  and into the chamber  64  of the apparatus  50 .  
         [0043]    The system  52  can include manifolds  71 ,  73  at both the inlet  69  and outlet  72 , respectively, for the plurality of tubes  54 . That is, the fluid introduced at the inlet  69  is guided into the manifold  71  which distributes the liquid in a substantially uniform manner to the plurality of tubes  54  so that all are filled with a substantially equal amount of agent to be heated and vaporized. At the outlet  72  of the system  50 , the manifold  73  is disposed in the shell  52  to receive opposite ends of the plurality of tubes  54  to substantially uniformly direct the agent to the outlet  72  where it is discharged as a gaseous microbiocidal agent.  
         [0044]    An alternate embodiment calls for the plurality of tubes  54  being constructed and arranged as a single tube having one end in communication with the inlet  69  and an opposed end in communication with the outlet  72 . An intermediate portion of the tube between the opposed ends is constructed and arranged in a sinusoidal manner to provide the agent introduced at the inlet  69  into the tube with a sufficient amount of residence time in the chamber  64  to be exposed to the heating effect of the fluid circulated through the line  56 .  
         [0045]    [0045]FIG. 8 illustrates a methodology shown generally at  200  associated with the generation of the gaseous or vapor microbiocidal agent in accordance with the present invention. The process starts  202  when it is desired to generate gaseous microbiocidal agent for application to, for example, food products. The first step is to introduce  204  liquid microbiocidal agent into a heat exchanger. A plurality of heat exchangers may be used, including those at FIGS. 4 and 7. After introducing the liquid microbiocidal agent into the heat exchanger, the liquid microbiocidal agent is heated  206  by virtue of the operation of the heat exchanger. A gaseous microbiocidal agent is generated  208  by the heating of the liquid micobiocidal agent, and this generation of the gaseous agent occurs without a carrier gas. Therefore, it is not necessary to atomize the liquid microbiocidal agent prior to heating.  
         [0046]    Since the gaseous microbiocidal agent is generated within the heat exchanger at  210 , it is necessary to recover the gaseous microbiocidal agent from the heat exchanger. Following this recovery, the gaseous microbiocidal agent is provided  212  to application equipment suitable for the intended end product to which the gaseous microbiocidal agent will be applied. It is anticipated that this process may be performed on a discrete or continuous basis and at some point in the process it is determined  214  whether more gaseous microbiocidal agent is needed. If so  216 , liquid microbiocidal agent is again introduced  204  and the process continues. If more agent is not needed  218 , the process is complete  220 .  
         [0047]    The methods described and claimed herein are set forth to provide the teachings of best mode and preferred embodiments of the invention, for purposes of clarity and particularity, and are not provided by way of limitation.  
         [0048]    The present invention has been described in terms of preferred embodiments, and it is recognized that equivalents, alternatives, and modifications, aside from those expressly stated, are possible and within the scope of the appended claims.