Abstract:
A method and a device is provided for increasing the shelf life of an oxygen sensitive product such as ground meat by injecting an inert gas or blend of inert gases into the ground meat through a stopper as meat is being pushed toward the stuffer outlet and a conveyor to a chub packager. By introducing the inert gas at this early stage in the chub packaging operation. the oxygen content within each chub is reduced from about 7% using the prior art method to 0.5% and less using the present invention. The inert gas forces substantially all of the ambient air away from the entire surface area of the ground meat as it is being circulated in the lower portion of the stuffer hopper and prior to being forced out through the stuffer outlet.

Description:
FIELD OF INVENTION  
         [0001]    The present invention relates to a method and device for increasing the shelf life of oxygen sensitive products such as ground beef and other meat. More particularly, the invention relates to an improved stopper for attachment to the hopper of a stuffer used in the packaging of such oxygen sensitive food products. The stopper has means for purging the ambient air surrounding the product during the stuffing operation and means for disassembling and cleaning the stopper between periods of use.  
         BACKGROUND OF THE INVENTION  
         [0002]    As the global demand for processed meat increases, processors continue to demand equipment, supplies, and raw material to enhance their ability to increase productivity, profits, customer satisfaction, and most importantly sanitation measures. One high-speed packaging system for ground meat is a combination of a stuffer with a high-speed chub packaging machine. In this system, the meat, such as beef, is coarsely ground, i.e., about 9.5 mm to 19.0 mm diameter die cut, and dumped or otherwise conveyed into a hopper of the stuffer or a stuffing pump; see U.S. Pat. Nos. 4,417,434 and 5,830,050, respectively. The coarsely ground meat is then conveyed to the chub packaging machine; see U.S. Pat. Nos. 4,085,778; 4,085,779; and 4,939,885. An example of a commercially available high-speed chub packaging machine is a 4000 series KartridgPak chub packager. The chub packager packages the meat, with or without added an inert gas, e.g., carbon dioxide, into oxygen-impermeable casings; see U.S. Pat. No. 4,707,444.  
           [0003]    The chubs usually range from about 4.5 kg to 9.0 kg and have a fat content ranging from about 7% to 30%. The chubs are then shipped and stored under refrigeration until needed. In the case of ground beef, they may be distributed to supermarkets that regrind the ground beef from the chubs and repackage them in Styrofoam trays, which are over wrapped with a clear plastic film for sale to the consumer. The shelf life of the repackaged product is relatively short. This is primarily due to the prolonged exposure of the meat product to the residual oxygen present in the entire packaging system. It is well known that the prolonged exposure of the meat product to oxygen also bacterial decay and discoloration of the meat.  
           [0004]    It is known to use a modified atmosphere environment whereby a preservation-enhancing gas mixture, typically containing a bacterial inhibitor such as carbon dioxide, is introduced into the casing during the chub packaging operation. This method has led to increases in the maximum shelf life of the product of about twenty days.  
           [0005]    It would be desirable to be able extend the shelf life of the packaged meat within chubs beyond the present maximum shelf life of about twenty days, and preferably, up to a maximum shelf life of sixty or even ninety days.  
           [0006]    One type of commercially available stuffer, e.g., Henry &amp; Sons&#39; AC-20 Continuous Vacuum Stuffer; see web site: http://www.dhenrvandsons.com/index.html for specifications and other details, which information is incorporated herein by reference. The stuffer comprises a funnel-shaped hopper, a scraper for keeping the ground meat from sticking to the inside of the hopper and a stopper attached to the top of the hopper. The scraper is attached to a ring gear connected to a drive mechanism. The ring gear is located in the bottom of the hopper adjacent the outlet and has either a right or a left spiral. The ring gear causes the scraper to rotate usually in a counterclockwise direction. The combination of the scraper and ring gear forces the ground meat in a downward spiral manner toward the hopper outlet and the mechanism that feeds the ground meat to the chub packaging machine. In the commercially available continuous vacuum stuffers, the hopper, ring gear, and stopper are stainless steel and the scraper is an industrial plastic, such as nylon.  
           [0007]    The stopper is usually constructed of hollow tubing, closed at each end, and protrudes down into the bottom of the hopper adjacent, but not touching, the ring gear. The stopper stops, or at less slows down, the meat from continuing to spin or rotate around the lower portion of the hopper and allows the scrapper and ring rear combination to function more efficiently to force the meat out through the stuffer outlet and into the conveyer to the chub packager. A commercially available stopper consists of a straight rod extending along the longitudinal axis of the hopper and has extensions, called a paddle, attached to the lower end of the rod that is angled at least 15 degrees from vertical. The stopper also attachment means for fixedly attaching the stopper to the hopper  
         SUMMARY OF THE INVENTION  
         [0008]    The device and method of the present invention dramatically increases the shelf life of oxygen sensitive food products by introducing an inert gas during the stuffing stage of the packaging process.  
           [0009]    The present invention comprises an improvement in the stuffer in which the stopper has means for injecting an inert gas or blend of inert gases into the food product as it is being pushed toward the stuffer outlet. By introducing the inert gas at this early stage in the chub packaging operation, the oxygen content within each chub is reduced from about 7% using the prior art method to 0.5% and less using the present invention. Without being bound by the theory of the mechanism, it is believed that inert gas forces substantially all of the ambient air away from the entire surface area of the product as it is being circulated in the lower portion of the stuffer hopper and prior to being forced out through the stuffer outlet.  
           [0010]    Preferably, the inert gas or blend of gases is heavier than air. Therefore, the inert gas injected from the stopper displaces the ambient air surrounding the meat entering the hopper and purges the air away from the meat. The remaining oxygen present in the stuffer outlet and conveyor to the chub packager has been found to be dramatically reduced from the current operation of adding an inert gas down flow from the stuffer.  
           [0011]    As discussed in further detail in the Examples section below, measurements of the oxygen content in the chubs leaving the packaging machine has been found to be in the range of about 0.2 to 0.5 volume % oxygen using the device of the present invention. The resulting shelf life of the ground meat has been found to increase to about 90 days using the apparatus and method of the present invention.  
           [0012]    In contrast, introducing an inert gas into the casing as the chubs are being formed in the chub packager results in reducing the ambient oxygen level from 21% to only about 7-volume %. The resulting shelf life of the ground meat has been found to be about 21 days using the apparatus and method of the prior art.  
           [0013]    Various means can be used injecting or otherwise introducing the inert gas during the stuffing operation. One injection means is to place a mesh screen in the hollow stopper connected to a source of inert gas where the mesh size of the screen is designed to avoid becoming plugged with the product. Another injection means is to place the plurality of orifices along the lower section of the stopper connected to the inert gas source. Preferably, nozzles are placed in the orifices to avoid clogging them with product. Anther injection means is to place either the orifices or the nozzles in the paddle adjacent to the lower end of the stopper.  
           [0014]    A still further injection means is to construct the hollow stopper connected to an inert gas supply in at least two sections; (1) the upper section connects to the support at the top of the hopper; and (2) the bottom section having the plurality of holes. A suitable coupling joins the two sections. The coupling permits the lower section to be easily detached from the upper section for cleaning and sanitation procedures. A further modification of this injection means is to add a vertical section that is coupled to the upper section and fixedly attach to the bottom section that includes a paddle. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    Further features and advantages will become apparent from the following and more particular description of the preferred embodiments of the invention, as illustrated in the accompanying drawings in which:  
         [0016]    [0016]FIG. 1 is a top and side perspective view of an apparatus of the present invention in line with a chub packager and show a stuffer having a hopper and a stopper in fluid communication with a gas cylinder;  
         [0017]    [0017]FIG. 2 is a top view of the hopper shown in FIG. 1;  
         [0018]    [0018]FIG. 3 is a partial sectional side view of the hopper shown in FIG. 1 that has been enlarged to show one embodiment of the present invention;  
         [0019]    [0019]FIG. 4 is a front and side prospective view of the support and flat stopper combination shown in FIG. 3;  
         [0020]    [0020]FIG. 5 is a partial sectional side view of the hopper to show a preferred embodiment of the present invention;  
         [0021]    [0021]FIG. 6 is top and side perspective view of a modification of the preferred embodiment of the present invention as it is being assembled;  
         [0022]    [0022]FIG. 7 is a perspective top and side view of the assembled stopper of FIG. 6 with a nut lock being slid into place; and  
         [0023]    [0023]FIG. 8 is a partial sectional side view of the hopper to show another modification of the preferred embodiment of the present invention.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0024]    Referring now to FIGS.  1 - 3 , packaging system  1  includes improved stuffer  10  upstream of chub packager  20  and cylinder  30  containing an inert gas or a blend of inert gases in fluid communication with stopper  40 . The inert gas is fed via gas inlet line  44  to funnel shaped hopper  50 , designed to move ground meat in a downward motion, and is injected into the ground meat in stuffer  10  through stopper  40 . Preferably hopper  50  is at least ¾ th  full of product and is always maintained at or above product level  52  shown in FIG. 1.  
         [0025]    Stopper  40  is mounted to attachment means or support  54  attached to rim  56  of hopper  50  by means of bolts  58 , welding or other similar means, so that stopper  40  is in a stationary position along the longitudinal axis through the center of hopper  50 .  
         [0026]    In FIG. 3, the internals of hopper  50 , in which scrapper  60  and ring gear  66  are operably mounted within hopper  50  for movement in a counterclockwise rotation to screw the ground meat toward hopper outlet  70  and screw conveyor  74 .  
         [0027]    A suitable hopper, scraper, Part #114-080-001 (A-46a), and stainless steel ring gear. Part #114-051-000 (A-32), are designed for the Continuous Vacuum Stuffer A 20  discussed under the Background of the Invention section, and are commercially available from Henry &amp; Sons; see web site for additional details, the details of which are incorporated herein by reference: http://www.dhenrvandsons.com/rings.htm#Scraper.  
         [0028]    Stopper  40  having paddle  80  is mounted within hopper  50  to prevent the ground meat from continuing to rotate in a counterclockwise manner within hopper  50  and to direct the product into outlet  70 .  
         [0029]    In the embodiment shown in FIGS.  1 - 4 , gas inlet line  44  may be connected to stopper  40  in the following manner. For example, ⅜ inch polymeric tubing  44  is connected to quick connect fitting  84  inserted in ½ inch NPT (National Pipe Thread) nipple  86  treaded into a hole drilled into 1-⅝ inch stainless steel tubing  88  adjacent to one of connections  90  bolted to rim  56  with bolts  58 . Support  54  consists of tubing  88  welded at each end to tee connections  90 . For example stopper  40  is 1-½ inch stainless steel tubing and is welded at right angles in the middle of tubing  88 . Stopper  40  in this embodiment is basically in the form of a right angle elbow with horizontal section  92   a  extending a foot from its connection to tubing  88  to the center of hopper  60  and vertical section  92   b  extending along the longitudinal axis of hopper  50 .  
         [0030]    In the embodiment shown in FIGS.  3 - 4 , paddle  80  includes flat piece  94  of stainless steel, i.e., approximately 2-4 inches by 6-8 inches, welded to rod  96  that is in turn is welded to end of vertical section  96 . Paddle  80  is at an angle of about 15 to 20 degrees off the longitudinal axis of stopper  40 .  
         [0031]    A section is removed from vertical section  92   b  where it connects to paddle  80  and screen  100  is welded in its place. In this specific embodiment, screen  100  is a tubular section approximately one foot in length. The tubular section is formed by rolling a multi-mesh screen that is commercially available from MAP Systems, Inc. into a 1⅝ inch tube to match the diameter of stopper  40 . Screen  100  is designed so that the product in hopper does not interfere with the passage of the gas. It is apparent that a number of other types of screens be used to serve this purpose. Various other means for injecting an inert gas into the hopper are described below.  
         [0032]    Vacuum line  120  is operably connected to a means for generating a vacuum in conveyor  74  to packager  20 . Although stuffer  10  is designed to operate under vacuum, the device of the present invention is not limited to vacuum stuffing operations.  
         [0033]    In FIGS.  5 - 7  a preferred embodiment of stopper of the present invention is shown in which flat stopper  140  consists of upper section  150 , vertical section  156 , and paddle section  158  having a plurality of nozzles  160  screwed into holes  166  drilled into the sides of paddle section  158  or vertical section  156  or both sections as shown Upper section  150  forms a smooth arc from its connection to tubing  88  of support  54  to vertical section  156 .  
         [0034]    Sanitary connection locking mechanism  170  consists of nut  174  that encircles upper section  150  against collar  180 , two O-rings  184  for sealing nut  174  to threaded section  190  welded or otherwise fixedly attached to end  194  of lower section  156 .  
         [0035]    In the embodiment shown in FIG. 6, alignment pin  196   a  is built into threaded section  190  and alignment notch  196   b  is built into collar  180  adjacent the lower end of upper section  150  for aligning vertical and upper sections. In addition, locking mechanism  170  includes nut lock  198  to prevent accidental uncoupling of sealing nut  174  that could result in as number of apparent consequences.  
         [0036]    Flat paddle  200  is welded to rod  210  attached to the end of vertical section  156 . In FIG. 5 nozzles  160  are only shown in paddle  200 , whereas in FIGS. 6 and 7, nozzles are inserted along vertical section  156  and in paddle section  158 . Although the device of the present invention is operable for periods of time using only orifices  160 , the product would tend to plug orifices  160  and require frequent shutdowns for cleaning.  
         [0037]    Nut lock  198  in this embodiment is constructed of ¼ inch hexagonal plate  210  that has 1-½″ hole  212  in the center and 2 tabs  214  welded 180° from each other. Hexagonal plate  210  has a ¼″ notch machined as shown in FIG. 6 to accept ¼ inch locking strip  218  that is welded to 1-½ inch upper section  150 . Hexagonal plate  210  is shown in FIG. 7 sliding down locking strip  218  by gravity to encapsulate nut  174  and to lock it in place.  
         [0038]    The method of operating the device of the present invention shown in FIGS.  1 - 4  is as follows: As the product is dumped into hopper  50  from meat carts or on a conveyor, valve  220  is opened on cylinder  30  containing an inert gas under pressure. The inert gas comprises carbon dioxide, or a blend of inert gases, preferably containing sufficient carbon dioxide. For example, a blend of 50 vol. % carbon dioxide and 50 vol. % nitrogen can be used. The gas is pressurized though inlet gas line  44 , quick connect  84 , nipple  86  and tubing  88 , to stopper  140  from which the gas exits through the plurality of nozzles  160  into the product being rotated in the bottom of hopper  50 . The rate of inert gas passing into hopper  50  should be in the range of about 20 to about 100 cubic feet per hour. The rate of product from stuffer  10  is in the range of about 100 to about 1000 pounds of product per hour. The desired ratio of inert gas to the flow rate of product from stuffer is about 0.05 to about 0.2 cubic feet per pound of product.  
         [0039]    Typically the product is ground meat that enters hopper  50  is at a temperature slightly below freezing. At these temperatures, it is preferred that the stopper is spiral stopper  230  having helical or spiral paddle  240  attached to its sides in place of flat paddles  80  or  158  as discussed above. FIG. 8 shows spiral stopper  230  in which spiral paddle  240  consisting of stainless steel in the shape of spiral is attached to the sides of hollow vertical tube  242 . A number of holes are drilled along vertical section  242  and nozzles  250  are mounted within the holes as shown in FIG. 8.  
         [0040]    The comparative example and example of the preferred embodiment of the present invention that follows illustrates the unexpected results from practicing the apparatus of the present invention over that of the prior art. The examples are for illustrative purposes only and are not meant to limit the scope of the claims in any way.  
       EXAMPLE  
     Comparative Example  
       [0041]    A Henry &amp; Sons&#39; AC-20 Continuous Vacuum Stuffer was placed in line with a KartridgPak 4000 packaging machine substantially as shown in FIG. 1, but without the modification of the inert gas being injected into the stuffer as described above. In this comparative example, ground beef was dumped into the hopper and fed to chub packager  20  at a rate of about 400 pounds per hour. The hopper w as maintained from about 75% to 100% full of product at all times during the operation. Carbon dioxide under a pressure of about 20 psig was pressurized at a rate of 30 to 60 cu. ft./hr. into the rope sections of the filled tubular casing prior applying the clips to from the chubs in the packaging machine. The oxygen levels in the exterior voids of the chubs leaving the packaging machine were measured with an oxygen meter and found to be 7 vol. % oxygen.  
       Example  
       [0042]    The comparative example was repeated using the embodiment of the present invention described in the Detailed Description section above in connection with FIGS.  1 - 4   e . In this example illustrating the present invention, ground beef was dumped into the hopper and fed to chub packager  20  to maintain the same product level in the hopper and at the same rate as in the comparative example. Carbon dioxide was injected at the same rate used in the comparative example into the product in the lower section of hopper  50  as discussed in detail above. The oxygen levels in the exterior voids of the chubs leaving the packaging machine were measured with the same oxygen meter and found to be in the range from 0.27 to 0.5 vol. % oxygen, over an order of magnitude less than that of the comparative example. This low level of oxygen was found to increase the shelf life of the resulting chubs from 21 days to 90 days.  
         [0043]    Without departing from the spirit and scope of this invention, one of ordinary skill in the art can make various changes and modifications to the device of the present invention to adapt it to various usages and conditions. As such, these changes and modifications are properly, equitably, and intended to be, within the full range of equivalents of the following claims.