Patent Publication Number: US-11659844-B1

Title: System for increasing antimicrobial efficacy in a poultry processing tank

Description:
PRIORITY CLAIM 
     The present continuation application claims priority to U.S. application Ser. No. 15/676,622 filed Aug. 14, 2017, now U.S. Pat. No. 11,350,640 issued Jun. 7, 2022, which claims priority to U.S. Provisional Application No. 62/374,468 filed Aug. 12, 2016 and entitled “METHODS AND RELATED APPARATUS FOR MEASURING AND ADJUSTING PROCESSING SOLUTION pH FOR POULTRY PROCESSING”, which is hereby incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The present invention is related to processing systems and related methods of operation during poultry processing. More specifically, the present invention is directed to methods and related apparatus for increasing antimicrobial efficacy during poultry processing by reducing concentration gradients of antimicrobial agents within a processing tank. 
     BACKGROUND 
     Commercial poultry processing plants include variety of processing and handling steps that can allow for the retention, transportation and transfer of bacteria from carcass to carcass throughout the processing plant. Of particular concern are human pathogenic microorganisms and those whose metabolism result in rapid spoilage of meat. These microorganisms, brought into the plant in or on live carcasses, are disseminated throughout the plant as the post-kill carcasses are handled by processing personnel, touch briefly together during traverse of the shackle lines, or are dipped for periods of time in various aqueous solutions, like scald baths and chill water. 
     In response to the presence of bacteria, most processing plants have implemented various processes that expose poultry carcasses to desirable antimicrobial chemistries in order to reduce bacterial populations on the carcasses. While prior chemistries including sodium hypochlorite, trisodium phosphate, various organic acids, ozone, chlorine dioxide and acidified sodium provided benefits, these older technologies suffered from undesirable effects and limitations. Newer antimicrobial chemistries include the use of peroxycarboxylic acids (“PCA”), such as peroxyacetic acid (“PAA”). PAA is a highly efficacious antimicrobial that was originally used as a hard surface sanitizer, but has more recently been recognized as possessing superior antimicrobial intervention chemistries for poultry carcasses. PAA provides a broad spectrum of kill of pathogenic and spoilage bacteria while producing no undesirable chemical by-products as the PAA degrades. 
     PAA, which is also sometimes called peracetic acid, is a peroxycarboxylic acid and is a well known chemical for its strong oxidizing potential, has the molecular formula CH 3 COOOH, and has a molecular structure as follows: 
                         
An equilibrium PAA solution is produced from an equilibrium mixture of hydrogen peroxide, acetic acid and water (“equilibrium PAA solution”), which often uses an acid catalyst, e.g., sulfuric acid.
 
                         
PAA has a pKA of about 8.4, such that about half the PAA is active (free) and about half is dissociated (bound) at a pH of about 8.4. For example, a 100 ppm solution of PAA at a pH of about 8.4 has about 50 ppm of active (free) PAA and about 50 ppm of peracetate ion, which is about 5 to about 10 times less effective than active PAA.
 
     U.S. Pat. No. 5,632,676, which pertains to the application of equilibrium PAA solutions to fowl at an application concentration of about 100 ppm to about 2000 ppm, discloses such equilibrium solutions having a pH around 3. 
     Hydrogen peroxide is always present in excess in the natural equilibrium formulation of PAA solutions (and other equilibrium PCA solutions). Both the excess hydrogen peroxide and the PCA produced in the equilibrium PCA solution (such as PAA) are the sources of the oxidative chemistry that can create undesirable organoleptic effects on poultry skin and flesh, such as extremity darkening and skin bleaching. To mitigate the development of these undesirable effects, processing plants have reduced either concentrations of equilibrium PAA solutions (and other equilibrium PCA solutions) or restricted contact times. 
     U.S. Pat. No. 5,632,676 includes numerous examples of equilibrium PAA solutions and concludes that the examples show that effective sanitation occurs within a narrow peracetic acid concentration range. This patent also discusses bleaching that is apparent in unadjusted or NaOH adjusted PAA solutions compared to a solution adjusted to pH 5 with disodium phosphate. Published Patent Application No. 2012/0244261 also discusses providing a solution of PAA-containing water in a reservoir, measuring the pH in the reservoir, and then pH adjustment before processing with a source of alkali, pH determination in the reservoir during processing with pH adjustment as necessary during processing with a source of alkali to increase the weight of the processed poultry product, with the alkali adjusted PAA solutions having a pH between about 6 to about 9 in the processing reservoir before processing begins and during the processing. 
     Because of the importance of pH in driving the equilibrium equation to proper concentrations of PAA, it would be advantageous to improve upon the accuracy of pH measurement and consistency within the processing systems. It would also be advantageous to properly monitor and maintain the pH of PAA during processing to determine the proper active PAA compared to peracetate ions in the solution during processing. Still further, due to the amount of organic material in the processing tank, it would be advantageous to have accurate monitoring of the pH of the processing solution without having to routinely clean the pH probes that can be fouled by the organic material. Finally, it would be advantageous to improve upon existing processing systems so as to reduce concentration gradients across a processing tank, as well as to increase the antimicrobial efficacy of intervention processing solutions in processing tanks. 
     SUMMARY 
     Various aspects of the present invention include both methods and related apparatus as well as systems for improving the efficacy of antimicrobial agents within processing tanks. Typically, methods, apparatus and systems of the present invention will involve the use of side streams to add appropriate antimicrobial agents into the processing tanks. Within these side streams, the antimicrobial agents will be added to a source solution and mixed to form a processing solution within the side stream. In some embodiments, the source solution is fresh water, while in some other embodiments the source solution may be a recycled, reclaimed and/or reused processing solution comprising one or more intervention solution components, such as a peroxycarboxylic acid, PAA, sodium hypochlorite or other processing chemistries. Depending upon the application, additional actions can be conducted on the processing solution within the side stream including any and or all of heating, for example, with heat exchangers, pumping, sampling, measuring, testing and/or pH adjusting the processing solution. 
     The invention may generally further comprise the processing solution having at least two distinct streams, for example, a first and second processing solution stream, wherein the at least two distinct streams will be introduced at two different and distinct locations within the processing tank. For instance, the first processing solution stream can be introduced proximate a carcass introduction location of the processing tank, while the second processing solution stream can be simultaneously introduced at a carcass removal location of the processing tank. In some embodiments, the first and second processing streams are provided by separate processing stream sources. For instance, the first processing stream may be a source of fresh water mixed with an intervention chemistry, while the second processing stream may be a recycled, reclaimed or reused processing source mixed with an intervention chemistry. In some other embodiments, a single processing solution is provided that can be divided into the first and second processing streams. In some embodiments, the processing solution can be divided into additional streams that can be introduced at various locations between the carcass introduction location and the carcass removal location of the processing tank. By simultaneously introducing at least two processing solution streams at different locations of the processing tank, large concentration gradients can be avoided with the processing tank such that each animal carcass is exposed to sufficient amounts of the antimicrobial agent across a length of the processing tank. Furthermore, reduced amounts of antimicrobial agent can be utilized as there is no longer the necessity to add excessive amounts of the antimicrobial agent at an upstream side of the processing tank to ensure that adequate levels of the antimicrobial agent are present at the downstream side. Various aspects of the present invention have been found to be especially useful when the processing tank comprises a poultry chiller tank for cooling poultry carcasses. 
     In another aspect, the present invention improves upon pH control and consistency within processing systems having an antimicrobial solution by adding a pH adjusting product and/or peroxycarboxylic acids, such as PAA, to the inlet piping system or to a tank in a side or ancillary system, such that the pH adjusting product is thoroughly mixed with the peroxycarboxylic acid prior to its introduction into a processing tank system, such as a chiller tank. 
     In some embodiments, the ancillary system can comprise one or more of the various piping of the processing tank system, for example, inlet flow piping, makeup flow piping, and tank recirculation piping. In such aspects, the processing water can have a pH between about 7 and 12 prior to addition of the peroxycarboxylic acid, in other aspects a pH between about 7.5 and 9. Once the peroxycarboxylic acid is added to the processing water, the solution is thoroughly mixed before pH determination and introduction of the processing solution into the processing tank. 
     In some other embodiments, the ancillary system can comprise one or more stand-alone tanks, for example, a mixing tank or similar reservoir, which supplies the processing solution having the desired pH to the processing tank system. Through the mixing of the processing water with the peroxycarboxylic acid and pH determination in an ancillary system, pH need only be measured once (in the ancillary system) as the velocity of the water in the ancillary system (either piping or stand-alone mixing tank) and the associated high Reynolds number, resulting in the processing solution having the desired pH between about 7 and about 12, in some other instances between about 7.5 and 11, and other instances between about 8.0 and 10.0, being thoroughly mixed prior to being introduced into the process tank. As all of the water entering the tank (either incoming, rinse, or recirculation) is at the same pH, consistent pH contacts each poultry carcass as the birds travel from a front end to a back end of the processing tank. 
     In some embodiments, the pH of the processing solution can also be determined in the overflow of the processing tank. As all of the water entering the tank travels from the front end to the back end of the processing tank, the overflow at the back end of the processing tank will provide an accurate pH determination after the carcasses travel the entire distance of the processing tank. In other words, determining the pH of the processing solution after it exits the processing tank will provide a more accurate determination of the pH than in the tank itself where processing has not been completed or organic material can build-up. 
     The above summary is not intended to describe each illustrated embodiment or every implementation of the subject matter hereof. The figures and the detailed description that follow more particularly exemplify various embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Subject matter hereof may be more completely understood in consideration of the following detailed description of various embodiments in connection with the accompanying figures, in which: 
         FIG.  1    is a schematic illustration of a poultry carcass dip tank according to a representative embodiment of the present invention. 
         FIG.  2    is a schematic illustration of a poultry carcass water chiller tank with red water loop system according to a representative embodiment of the present invention. 
         FIG.  3    is a schematic illustration of a poultry carcass water chiller tank red water loop system according to a representative embodiment of the present invention. 
         FIG.  4    is a schematic illustration of a poultry carcass water chiller tank red water loop system according to a representative embodiment of the present invention. 
         FIG.  5 A  is schematic illustration of a poultry carcass water chiller tank according to the prior art. 
         FIG.  5 B  is a schematic illustration of a poultry carcass water chiller tank according to a representative embodiment of the present invention. 
         FIG.  6    is a schematic illustration of a poultry carcass water chiller tank according to a representative embodiment of the present invention. 
     
    
    
     While various embodiments are amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the claimed inventions to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the subject matter as defined by the claims. 
     DETAILED DESCRIPTION OF THE DRAWINGS 
     Representative embodiments of the present invention provide methods and systems for improving the efficacy of antimicrobial agents in processing tanks by eliminating large concentration gradients across the length of the processing tank. In some embodiments, the invention can include consistently exposing poultry carcasses to a process solution having a similar concentration prior to introduction into a first end of a processing tank and upon exiting a second end of a processing tank. While the processing solution of the present invention is discussed in reference to a peroxycarboxylic acid, such as PAA, one of ordinary skill in the art will appreciate that the present invention is applicable to one or more antimicrobial components used in processing poultry. 
     In some embodiments, the invention can include consistently exposing poultry carcasses to process solution having similar pH prior to introduction into a first end of a processing tank and upon exiting a second end of a processing tank. Representative embodiments of the present invention utilize one or more ancillary systems for introducing a processing solution having at least one peroxycarboxylic acid in a processing water having a pH of about 7 to about 10 that is thoroughly mixed prior to introduction into the processing tank, such that the processing tank will not experience zones having different pH levels. In some embodiments, the ancillary system can comprise a piping inlet or piping recirculation loop in which the peroxycarboxylic acid is added to a processing water having a desired pH and thoroughly mixed prior to its introduction to the processing tank. In some embodiments, the ancillary system can comprise a storage tank or similar style reservoir into which the peroxycarboxylic acid is added to the processing water having a desired pH and mixed prior to its introduction to the processing tank. In some aspects, a pH adjustment component may need to be added to either the processing water or processing solution in the ancillary system to obtain the desired pH of the processing solution. Regardless of the design, the ancillary system will have high velocities and corresponding high Reynolds numbers such that the processing water, peroxycarboxylic acid, and any pH adjustment product is adequately mixed providing a processing solution having a desired pH and concentration of the peroxycarboxylic acid, such as PAA, prior to introduction into the processing tank. The present invention can further include measuring the pH within the ancillary system to accurately determine pH prior to introduction into the processing tank and without concern for fouling of a pH probe that is a common occurrence due to organic material from carcasses within the processing tank itself. 
     In a first embodiment as illustrated in  FIG.  1   , a poultry processing system  100  of the present invention can comprise a process tank  101  such as, for example, a dip tank including a processing solution  102 . The processing solution  102  generally comprises a processing water containing a peroxycarboxylic acid, preferably PAA, wherein the processing water was provided at a desired pH that is advantageous for processing and rinsing poultry carcasses and mixed with the peroxycarboxylic acid prior to being provided in the process tank  101 . The process tank  101  generally comprises a first end  104  and a second end  106 , wherein an inflow pipe  108  introduces the processing solution  102  into the process tank  101  and an outflow pipe  110  removes the processing solution  102  from the process tank  101 . 
     As illustrated in  FIG.  1   , the inflow pipe  108  can comprise an ancillary water inflow portion  112 , and one or more ancillary systems  114   a  and  114   b  can be used to supply a pH adjustment product and intervention chemistry, such as peroxycarboxylic acid, preferably PAA, to the inflow pipe  108  prior to the processing solution being introduced into the process tank  101 . For example, the inflow pipe  108  can comprise a water supply  112  into which the pH adjustment product is directly added by ancillary system  114   a , to the extent necessary, to provide a processing water. The processing water having the desired pH can then have the intervention chemistry, such as peroxycarboxylic acid, preferably PAA, added by ancillary system  114   b . For example, the pH of the water inflow supply  112  can be measured such that the pH adjustment product can be added to the water supply  112  through the use of a conventional metering pump or through a venturi injector or the like to obtain the desired pH of the processing water, preferably between about 7 and about 10. Generally, the flow of the water supply  112  with respect to ancillary system  114   a  should have a high enough velocity and correspondingly, Reynolds number to thoroughly mix the pH adjustment product into the water supply  112  to provide a processing water  112   a  having the desired pH before it is introduced into the inflow pipe  108 . The pH of the supply water  112  and/or the processing water  112   a  can be determined in the inflow pipe  108  prior to the introduction of any intervention chemistry, such as peroxycarboxylic acid. Similarly, the flow of the processing water  112   a  having the desired pH with respect to ancillary system  114   b  should have a high enough velocity and correspondingly, Reynolds number to thoroughly mix the intervention chemistry, such as peroxycarboxylic acid, preferably PAA, into the processing water  112   a  to provide a processing solution  112   b  before it is introduced into the inflow pipe  108 . The pH of the processing solution  112   b  can be measured in the inflow pipe  108  prior to the introduction of the processing solution  112   b  into the processing tank  101  to confirm the desired pH of the processing solution  112   b . Alternatively, the pH of the processing water  112   a  and the processing solution  112   b  can both be measured in the inflow pipe  108 . 
     Alternatively, ancillary system  114   a  can comprise a mixing tank or similar reservoir into which the pH adjustment product is added to a water supply and thoroughly mixed before being introduced into the inflow pipe  108 . Similarly, ancillary system  114   b  can comprise a tank or similar reservoir of the intervention chemistry. In this way, the pH of the processing water  112   a  is precisely controlled and maintained as the inflow pipe  108  delivers the processing solution  112   b  into the first end  104  of the process tank  100 . Since the processing solution  112   b  contains the processing water  112   a  at a desired pH thoroughly mixed with the intervention chemistry, the pH of the processing solution  112   b  will be consistent prior to introduction into the processing tank  101 . As such, pH will remain consistent throughout the process tank  101  and there will not be localized areas of higher or lower pH within the process tank  101  as a result of mixing the components within the process tank  101  that would limit the effectiveness of the processing solution in rinsing, chilling or otherwise treating the poultry carcasses. Furthermore, pH can be monitored in either the inflow pipe  108  or the ancillary systems  112   a ,  112   b  such that a pH probe/sensor is not exposed to potential fouling within the process tank  101 . 
     With reference to  FIGS.  2 ,  3  and  4   , various embodiments of a chiller tank with red water loop processing system  200  are illustrated. As will be described, the water chiller tank with red water loop processing system  200  can comprise varying levels of complexity based upon specific processing conditions, and as such, a variety of methods and system designs can be implemented to control pH within the water chiller tank with red water loop processing system. 
     In all of the illustrated embodiments, the chiller tank with red water loop processing system  200  comprises chiller tank  202 , a heat exchanger  204  and an optional tempering box  206 . In each of the embodiments, a make-up water stream  208  is supplied to a first end  210  of the chiller tank  202  while an overflow stream  212  is removed at a second end  214  of the chiller tank  202 . In order to maintain temperature of a pH adjusted processing solution  216  within the chiller tank  202 , a red water recirculation loop  218  supplies pH adjusted processing solution  216  from the chiller tank  202  to the heat exchanger  204 , wherein the temperature of the pH adjusted processing solution is modified to the desired temperature and subsequently returned to the chiller tank  202 . 
     With reference to  FIG.  2   , one or more ancillary systems  220   a ,  220   b  can supply the intervention chemistry and pH adjustment product and into the recirculation loop  218 , wherein the processing solution  216  is thoroughly mixed and at the desired pH and temperature prior to introduction into the chiller tank  202 . For example, ancillary system  220   b  can comprise a processing water supply having a pH adjustment product or the pH adjustment product that is directly added to the recirculated processing solution  216  in the red water recirculation loop  218 . For example, the pH adjustment product can be added to the recirculated processing water through the use of a conventional metering pump or through a venturi injector or the like. Generally, the flow of the recirculated processing water in ancillary red water recirculation loop  218  should have a high enough velocity and correspondingly, Reynolds number to thoroughly mix the pH adjustment product into the recirculated processing water before it is introduced into the heat exchanger and chiller tank  202 . Alternatively, ancillary system  220   b  can comprise a mixing tank or similar reservoir into which the pH adjustment product is added and thoroughly mixed with a water supply to provide a processing water supply  220   b  before being introduced into the red water recirculation loop  218 . In this way, the pH is precisely controlled and maintained as the red water recirculation loop  218  delivers the pH adjusted processing solution  216  into the chiller tank  202 . Similarly, the flow of the recirculated processing water  222   b  having the desired pH with respect to ancillary system  220   b  should have a high enough velocity and correspondingly, Reynolds number to thoroughly mix the intervention chemistry, such as peroxycarboxylic acid, preferably PAA, into the recirculated processing water  222   b  to provide a refreshed processing solution  222   a  having a desired concentration before it is introduced back into the chiller tank  202 . The pH of the processing solution  222   b  can be measured in the inflow pipe  218  prior to the introduction of the processing solution  222   a  into the chiller tank  202  to confirm the desired pH of the processing solution  222   a . Alternatively, the pH of the recirculated processing water  222   b  and the processing solution  222   b  can both be measured in the inflow pipe  218 . 
     In a variation to the embodiment shown in  FIG.  2   , the chiller tank with red water loop processing system  200  of  FIG.  3    can comprise additional ancillary systems  220   c ,  220   d  that supply the intervention chemistry and pH adjustment product, respectively, into the make-up water stream  208 , such that the processing solution  216  is added at the first end  210  of the chiller tank  202  in a manner similar to that as previously described with respect to the processing solution  112   b  of the poultry processing system  100 . In this manner, the processing solution  208   c  having the desired pH and intervention chemistry concentration is added to the chiller tank  202  at the first end  210  to provide a processing solution  216  within the chiller tank  202 . 
     Finally in the embodiment illustrated in  FIG.  4   , the chiller tank with red water loop processing system  200  can further comprise a bypass loop  230  that introduces additional residence time and consequently, mixing of the pH adjustment product before it is introduced into the chiller tank  202 . As illustrated, the bypass loop  230  can fluidly interconnect the make-up water stream  208  with the recirculation loop  218 . In this way, one or more ancillary systems  220   a ,  220   b ,  220   c ,  220   d  can be utilized to introduce the intervention chemistry ( 220   a ,  220   c ) and pH adjustment product ( 220   b ,  220   d ) at an advantageous location prior to its introduction into the chiller tank  202 . For example, ancillary systems  220   d  can be utilized to supply the pH adjustment product directly into the water within the bypass loop  230 , while ancillary system  220   b  can supply the pH adjustment product into the recirculation loop  218  at a point upstream of the connection to the bypass loop  230 . In an embodiment, ancillary system  22   c  can add intervention chemistry to the processing water  222   d  to provide a processing solution  222   c  before being introduced into the recirculation loop  218 . In yet another alternative embodiment, ancillary system  220   a  can add all or additional intervention chemistry to the recirculation loop  218  at a point downstream of the connection to the bypass loop  230  containing processing solution  222   c  and recirculated processing solution  222 B. The location of the ancillary systems in the chiller chiller tank processing system  200  can be advantageously selected to make use of high velocities and Reynolds numbers to thoroughly mix the pH adjustment product and/or intervention chemistries prior to its introduction and/or reintroduction into the chiller tank  202 . 
     In all of the variations of the chiller tank with red water loop processing system  200  described herein, a pH sensor/probe can be positioned in locations remote from the chiller tank  202 . For example, the make-up water stream  208 , the recirculation loop  218  and/or the bypass loop  230  can contain pH sensor/probes that are not exposed to fouling and/or contamination that can result from exposure to poultry contaminants within the chiller tank  202 . Further, the pH sensor/probes can be located after the pH adjustment product is added to provide the processing water and/or after the intervention chemistry to provide the processing solution. In this way of the pH sensor/probes maintained outside of the chiller tank, maintenance is eliminated or otherwise reduced and operators can have a higher level of confidence that pH of the processing solution and concentration of intervention chemistry is at the desired levels before being introduced into the chiller tank  202 . 
     In each of the embodiments shown in  FIGS.  1 - 4   , the overflow  110 ,  212  can also have pH probe/sensors to precisely determine the pH of the processing solution  102 ,  216  after it exits the respective tank. By determining the pH of the processing solution after it exits the tank, the amount of active PAA can be determined as a result of the organic material in the tank, which may determine the pH level and amount of intervention chemistry in the inlet prior to being introduced into the tank. 
     In some aspects, the processing solution in the inlet or red water recirculation loop prior to introduction into the tank has a pH above 7.0 and below 10, in other aspects between about 7.5 and about 9.5 and in other aspects between about 7.2 and 8.6. 
     In certain aspects, the processing solution has a concentration of peroxycarboxylic acid from about 1 ppm to about 5000 ppm, preferably from about 5 ppm to about 1000 ppm, preferably from about 10 ppm to about 200 ppm, and more preferably from about 15 ppm to about 100 ppm. In some aspects, the concentration of active peroxycarboxylic acid in the processing solution is from about 1 ppm to about 5000 ppm, preferably from about 5 ppm to about 1000 ppm, preferably from about 10 ppm to about 200 ppm, and more preferably from about 15 ppm to about 100 ppm. In some other aspects, the concentration of active peroxycarboxylic acid and active peroxycarboxylic acid ion in the processing solution is from about 1 ppm to about 5000 ppm, preferably from about 5 ppm to about 1000 ppm, preferably from about 10 ppm to about 200 ppm, and more preferably from about 15 ppm to about 100 ppm. In some aspects, the concentration of the PAA in the processing solution is between about 15 ppm and about 100 ppm, preferably between about 15 ppm and about 75 ppm, and in some other aspects between about 20 ppm and 50 ppm. 
     In certain aspects, the poultry tank design of the present invention having at least a first and a second processing stream is capable of maintaining less than about a 10 ppm concentration gradient across the processing length of a processing tank, in some aspects less than about an 8 ppm concentration gradient, less than about 6 ppm concentration gradient, less than about 5 ppm concentration gradient, less than about 4 ppm concentration gradient, and in other aspects less than about a 3 ppm concentration gradient across the processing length of the processing tank. In certain aspects, the concentration gradient across the processing length of the processing tank of the present invention is between about 1 ppm and about 10 ppm, between about 2 ppm and 8 ppm, and in some other aspects between about 3 ppm and 5 ppm. 
     Testing 
     In order to evaluate the efficacy of the present invention, a test was conducted to compare the performance of a conventional poultry chiller tank as represented by  FIG.  5 A  and an improved poultry chiller tank utilizing a side stream to introduce an antimicrobial agent as represented by  FIG.  5 B . In each case, an antimicrobial agent comprising PAA was introduced into a poultry chiller tank  300  with a target PAA concentration of 30 ppm in the poultry chiller tank  300 . Poultry chiller tank  300  comprised a 65 foot long tank with a volume of 40,000 gallons. Poultry chiller tank  300  had a poultry carcass load of greater than 34,000 and the carcass processing rate was the same for both tests. 
     With the conventional poultry chiller tank as represented by  FIG.  5 A , a concentrated antimicrobial solution  302  was added at a carcass introduction end  304  of the poultry chiller tank  300 . In the present case, antimicrobial solution  302  comprised a solution of water and PAA. During a production shift, samples of a chiller tank solution  306  were taken at the carcass introduction end  304 , a carcass removal end  308  and a chiller tank midpoint  310 . The time weighted average of 5 samples at each location were: 
     
       
         
           
               
               
               
             
               
                   
                   
               
             
            
               
                   
                 Carcass Introduction End: 
                 35 ppm 
               
               
                   
                 Chiller Tank Midpoint: 
                 26 ppm 
               
               
                   
                 Carcass Removal End: 
                 15 ppm 
               
               
                   
                   
               
            
           
         
       
     
     As can be seen in the sample measurements, a significant length of poultry chiller tank  300  experienced concentrations of PAA significantly below the desired level of 30 ppm. More specifically, poultry carcasses near that carcass removal end  308  were exposed to chiller tank solution having half of the desired concentration of PAA. The carcass introduction end  304  experienced a slightly higher level of PAA due to the injection of the concentrated antimicrobial solution  302  as well as PAA carryover on poultry carcasses from the prior processing step. 
     With the poultry chiller tank design of the present invention as show in  FIG.  5 B , a PAA solution  320  is introduced and mixed into a side stream  322  to form a processing solution  324  having a PAA concentration of 30 ppm. Processing solution  324  comprised a first processing solution  326  that was introduced into the chiller tank  300  at the carcass introduction end  304  while a second processing solution  328  was introduced into the chiller tank  300  at the carcass removal end  308 . During a production shift, samples of the chiller tank solution  306  were taken at the carcass introduction end  304 , the carcass removal end  308  and the chiller tank midpoint  310 . The time weighted average of 5 samples at each location were: 
     
       
         
           
               
               
               
             
               
                   
                   
               
             
            
               
                   
                 Carcass Introduction End: 
                 32 ppm 
               
               
                   
                 Chiller Tank Midpoint: 
                 28 ppm 
               
               
                   
                 Carcass Removal End: 
                 27 ppm 
               
               
                   
                   
               
            
           
         
       
     
     As can be seen in the sample measurements, the poultry chiller tank design of the present invention had a much lower concentration gradient across the length of the poultry chiller tank  300  with the chiller tank solution  306  at the chiller tank midpoint  310  and carcass removal end  308  being much closer to the desired concentration level of 30 ppm. As measured, the poultry chiller tank design of the present invention is capable of maintaining plus or minus 3 ppm of PAA within the chiller tank solution  306  across the length of the poultry chiller tank  300 . 
     While the design illustrated in  5 B utilized introduction of only a first processing solution  326  and a second processing solution  328 , processing solution  324  can be further divided into additional processing solution streams that can be introduced at additional locations within the poultry chiller tank  300 . For example, processing solution  324  could be further divided into a third processing solution also having a PAA concentration of 30 ppm and said third processing solution could be introduced, for example, at the chiller tank midpoint  310 . 
     Another representative embodiment of a poultry chiller tank  400  is illustrated generally in  FIG.  6   . In a manner similar to the previously described embodiments, poultry chiller tank  400  can include a recirculation line  402  for introducing a PAA solution  404  to one or more locations of the poultry chiller tank  400  between a carcass introduction end  406  and a carcass removal end  408 . In addition to recirculating a tank solution  410  from the poultry chiller tank  400 , a downstream processing stream  412  can be used to supply make-up water through the recirculation line  402 . Downstream processing stream  412  can comprise an aqueous solution that can include an anti-microbial component, such as PAA, from a downstream operation  413 , for example, a de-boning station or final rinse/bath prior to packaging, wherein the organic load is reduced as compared to the upstream poultry chiller tank  400 . Recirculation line  402  can comprise a recirculation pH adjustment stream  414  as well as a recirculation PAA adjustment stream  416  such that the PAA solution  404  has a desired PAA concentration, for example, between 15 ppm and about 100 ppm, preferably between about 15 ppm and about 75 ppm, and in some other aspects between about 20 ppm and 50 ppm. In addition, poultry chiller tank  400  can comprise another source of PAA solution, for example, a fresh PAA solution  420 . Fresh PAA solution  420  can comprise a tank or piping system where a source of fresh or otherwise filtered water  422  is adjusted with a fresh PAA adjustment stream  424  and/or a fresh pH adjustment stream  426  such that the fresh PAA solution  420  has a desired PAA concentration that is substantially equivalent to PAA solution  404 . Through the introduction of both PAA solution  404  and fresh PAA solution  420  having equivalent PAA concentrations, the PAA concentration gradient within the poultry chiller tank  400  can be reduced. 
     In some aspects, the pH adjustment product is an alkalizing agent approved for direct food contact. In some aspects, the alkalizing agent is chosen from alkali metals and alkali earth metals, including sodium hydroxide and/or potassium hydroxide and/or the sodium and/or potassium salts of carbonic acid and/or phosphoric acid and/or silicic acid and/or other alkaline chemistries. 
     Various embodiments of systems, devices, and methods have been described herein. These embodiments are given only by way of example and are not intended to limit the scope of the claimed inventions. It should be appreciated, moreover, that the various features of the embodiments that have been described may be combined in various ways to produce numerous additional embodiments. Moreover, while various materials, dimensions, shapes, configurations and locations, etc. have been described for use with disclosed embodiments, others besides those disclosed may be utilized without exceeding the scope of the claimed inventions.