U.S. patent application number 11/716989 was filed with the patent office on 2007-10-11 for process for the extension of microbial life and color life of fresh meat products.
This patent application is currently assigned to Mitec Incorporated. Invention is credited to Brian T. Dalziel, Von Kennedy, Steven E. Koenck.
Application Number | 20070237866 11/716989 |
Document ID | / |
Family ID | 38575615 |
Filed Date | 2007-10-11 |
United States Patent
Application |
20070237866 |
Kind Code |
A1 |
Dalziel; Brian T. ; et
al. |
October 11, 2007 |
Process for the extension of microbial life and color life of fresh
meat products
Abstract
The microbial life and color life of fresh meat products are
extended by placing fresh meat in a tray, sealing the fresh meat in
the tray in an atmosphere that excludes oxygen and contains carbon
monoxide, and applying ionizing radiation to the tray containing
the fresh meat. The color life of the fresh meat in the tray may be
controlled (such as to be equal to or less than the microbial life)
by employing a permeable element and an impermeable element to seal
the fresh meat in the tray. The impermeable element is removed at a
time after ionizing radiation has been applied, so that the
atmosphere that excludes oxygen and contains carbon monoxide is
exchanged for ambient atmosphere, resulting in predictable limiting
of color life of the fresh meat.
Inventors: |
Dalziel; Brian T.; (Marion,
IA) ; Kennedy; Von; (Cedar Rapids, IA) ;
Koenck; Steven E.; (Cedar Rapids, IA) |
Correspondence
Address: |
KINNEY & LANGE, P.A.
THE KINNEY & LANGE BUILDING
312 SOUTH THIRD STREET
MINNEAPOLIS
MN
55415-1002
US
|
Assignee: |
Mitec Incorporated
101 2nd Street S.E. Suite 600
Cedar Rapids
IA
52401
|
Family ID: |
38575615 |
Appl. No.: |
11/716989 |
Filed: |
March 12, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60781529 |
Mar 10, 2006 |
|
|
|
Current U.S.
Class: |
426/129 |
Current CPC
Class: |
B65B 25/067
20130101 |
Class at
Publication: |
426/129 |
International
Class: |
B65B 25/06 20060101
B65B025/06 |
Claims
1. A method of providing fresh meat products, comprising: placing
fresh meat in a tray and sealing the fresh meat in the tray in an
atmosphere that excludes oxygen and includes carbon monoxide; and
applying ionizing radiation to the tray containing the fresh
meat.
2. The method of claim 1, wherein the atmosphere that excludes
oxygen further includes nitrogen and carbon dioxide.
3. The method of claim 2, wherein the atmosphere that excludes
oxygen consists of 70% nitrogen, 29.6% carbon dioxide and 0.4%
carbon monoxide.
4. The method of claim 1, wherein the step of applying ionizing
radiation to the tray containing the fresh meat is performed in an
environment that is controlled to exclude oxygen.
5. The method of claim 1, further comprising: unsealing the fresh
meat in the tray in a retail environment after ionizing radiation
has been applied.
6. The method of claim 5, wherein the step of sealing the fresh
meat in the tray comprises: applying a permeable lid film to the
tray to secure the fresh meat in the tray; and enclosing the tray
and permeable lid film in an impermeable bag.
7. The method of claim 6, wherein the step of unsealing the fresh
meat in the tray comprises: removing the tray containing the fresh
meat secured by the permeable lid film from the impermeable
bag.
8. The method of claim 7, wherein the permeable lid film has a
permeability that provides a color life to the fresh meat in the
tray that has a known correspondence to a microbial life of the
fresh meat in the tray that is based on a dose of ionizing
radiation applied to the fresh meat.
9. The method of claim 5, wherein the step of sealing the fresh
meat in the tray comprises: applying a permeable lid film to the
tray to secure the fresh meat in the tray; and applying a peelable
impermeable film over the permeable lid film.
10. The method of claim 9, wherein the step of unsealing the fresh
meat in the tray comprises: peeling the impermeable film off of the
permeable lid film.
11. The method of claim 10, wherein the permeable lid film and the
peelable impermeable film are multiple layers of a single film.
12. The method of claim 10, further comprising: applying a
notification label on the peelable impermeable film to provide
notification that the peelable impermeable film has not yet been
removed.
13. The method of claim 10, wherein the permeable lid film has a
permeability that provides a color life to the fresh meat in the
tray that has a known correspondence to a microbial life of the
fresh meat in the tray that is based on a dose of ionizing
radiation applied to the fresh meat.
14. A method of providing fresh meat products, comprising placing
fresh meat in a tray and sealing the fresh meat in the tray in an
atmosphere that excludes oxygen and includes carbon monoxide;
applying ionizing radiation to the tray containing the fresh meat;
and distributing the fresh meat in the tray for sale to consumers
in a retail environment.
15. The method of claim 14, further comprising: unsealing the fresh
meat in the tray in the retail environment after ionizing radiation
has been applied.
16. The method of claim 15, wherein the step of sealing the fresh
meat in the tray comprises: applying a permeable lid film to the
tray to secure the fresh meat in the tray; and providing an
impermeable seal over the permeable lid film.
17. The method of claim 16, wherein the step of unsealing the fresh
meat in the tray comprises: removing the impermeable seal over the
permeable lid film.
18. The method of claim 17, wherein the permeable lid film has a
permeability that provides a color life to the fresh meat in the
tray that has a known correspondence to a microbial life of the
fresh meat in the tray that is based on a dose of ionizing
radiation applied to the fresh meat.
19. The method of claim 16, wherein the impermeable seal over the
permeable lid film comprises an impermeable bag enclosing the tray
and the permeable lid film.
20. The method of claim 16, wherein the impermeable seal over the
permeable lid film comprises a peelable impermeable film over the
permeable lid film.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/781,529 filed Mar. 10, 2006 for EXTENDED STORAGE
LIFE FRESH MEAT by B. Dalziel, V. Kennedy and S. Koenck.
INCORPORATION BY REFERENCE
[0002] The aforementioned U.S. Provisional Application No.
60/781,529 is hereby incorporated by reference in its entirety.
BACKGROUND
[0003] The present invention relates to a method of preserving the
freshness and color life of meat products, and also to a method of
matching the color life to the microbial life of the meat
products.
[0004] An increasingly popular method of providing fresh meat in
the retail environment is case-ready packaging, whereby the meat
product is processed and packaged in a retail package by a meat
packer that may be quite distant from the retail facility.
Case-ready packaging is especially appealing to large retail
organizations that specialize in highly efficient logistics and
supply chain management, because it enables them to provide an
otherwise relatively perishable product in their stores with
minimum investment in special infrastructure. The challenge for
these organizations, even with their world-class distribution
capability, is shelf life. The time between processing fresh meat
until the product is sold to the consumer averages over 10 days,
and may be as high as 21 days.
[0005] It is quite difficult to provide good quality and good
looking fresh meat products to consumers with a shelf life as high
as 21 days. The dual challenges for shelf life of this magnitude
are microbial growth and product color. Microbial growth is related
to the geometric multiplication of spoilage bacteria that causes
fresh meat products to spoil. Product color is related to the shift
in color spectrum of the myoglobin constituents in fresh meats.
[0006] Meat scientists have researched the effect of the oxidative
states of myoglobin on the color of fresh meat. Fully fresh,
recently processed meat is dominated by the presence of
oxymyoglobin, which has oxygen attached to the myoglobin base
molecule and is bright pink-red in color in the so-called "bloomed"
state. If fresh meat is placed in an oxygen-depleted environment,
the oxygen is lost and the myoglobin turns to the deoxymyoglobin
state, which takes on a deep purple-brown color. This product may
still be very fresh, but its color is not familiar, and consumers
may be reluctant to purchase product with this appearance. As fresh
meat ages, the myoglobin progressively turns to the metmyoglobin
state that is characterized by the brown color familiarly
associated with old and possibly spoiled meat.
[0007] In the ongoing efforts to provide increased shelf life fresh
meats, it has been learned that various modified atmosphere
case-ready packages may be employed to mitigate the previously
mentioned effects of microbial growth and color loss. Microbial
growth in fresh meat can be suppressed by the use of atmospheres
that spoilage bacteria do not thrive in. For example, many spoilage
bacteria are aerobic, so they don't multiply well in an
oxygen-deprived atmosphere. Case-ready modified atmosphere
packaging (MAP) with a low oxygen atmosphere can delay spoilage in
fresh meats. Unfortunately, low oxygen packaging causes the color
of the fresh product to be dominated by deoxymyoglobin, with its
characteristic purple-brown color. Case-ready MAP products with a
high oxygen atmosphere can delay spoilage due to a high
concentration of carbon dioxide, and the oxygen concentration
extends the oxymyoglobin state to maintain the preferred pink-red
color state. High oxygen MAP is generally more successful for
delivery of case-ready fresh meat in the retail distribution
marketplace than low oxygen MAP, but even with its better
characteristics, it is generally limited to less than 10 days of
shelf life.
[0008] In the ongoing search for methods of extending the shelf
life of fresh meats, scientists have discovered that carbon
monoxide is capable of extending color life. Carbon monoxide reacts
with myoglobin in a way very similar to the way it reacts with
hemoglobin--the basic oxygen and carbon dioxide carrying
constituent in blood. Carbon monoxide has high affinity for the
oxygen-carrying site in both hemoglobin and myoglobin, and binds
approximately 240 times more strongly than oxygen or carbon
dioxide. In the case of hemoglobin, a concentration of carbon
monoxide may lead to death because the body may be deprived of
necessary oxygen. In the case of myoglobin, the presence of carbon
monoxide forms a special state of myoglobin labeled
carboxymyoglobin. Carboxymyoglobin has a color spectrum that is
nearly identical to oxymyoglobin, and causes meat to look identical
to fresh meat that is dominated by the presence of oxymyoglobin.
Meat processors and retailers have discovered that carbon monoxide
as a MAP additive, even in low concentrations, lessens the color
loss in fresh meat for significantly extended periods of time. A
popular MAP atmosphere called "low oxygen" or "low ox" includes 70%
nitrogen, 29.6% carbon dioxide and 0.4% carbon monoxide, with very
minute levels of oxygen (if any) being present.
[0009] Iradiation technology has been utilized for decades as a
means for reduction of micro flora in fresh and frozen food
products. Applications of irradiation have included reduction of
harmful food borne pathogens such as E. coli 0157:H7, Salmonella,
and Listeria, as well as common spoilage bacteria for extension of
shelf life. Irradiation has more recently been employed in systems
and processes that package the irradiated meat products with
modified atmosphere packaging to extend shelf life for case-ready
retail applications.
[0010] While the combination of these technologies has generally
extended the shelf life of fresh meat products, the desired 21 days
(or more) of shelf life has been elusive, primarily due to color
life limitations. What is needed is a process for extension of both
the shelf (microbial) life and color life of fresh meat
products.
SUMMARY
[0011] The microbial life and color life of fresh meat products are
extended by placing fresh meat in a tray, sealing the fresh meat in
the tray in an atmosphere that excludes oxygen and contains carbon
monoxide, and applying ionizing radiation to the tray containing
the fresh meat. The color life of the fresh meat in the tray may be
controlled (such as to be less than or equal to the microbial life)
by employing a permeable element and an impermeable element to seal
the fresh meat in the tray. The impermeable element is removed at a
time after ionizing radiation has been applied, so that the
atmosphere that excludes oxygen and contains carbon monoxide is
exchanged for ambient atmosphere, resulting in predictable limiting
of color life of the fresh meat.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a flow diagram illustrating a process for
extending both the shelf life and color life of fresh meat products
according to an embodiment of the present invention.
[0013] FIG. 2 is a cross section view of a prior art case-ready
modified atmosphere package for meat.
[0014] FIG. 3 is a cross section view of a case-ready modified
atmosphere package for meat according to one embodiment of the
present invention.
[0015] FIG. 4 is a cross section view of a case-ready modified
atmosphere package for meat according to another embodiment of the
present invention
DETAILED DESCRIPTION
[0016] In order to extend both the shelf life and color life of
fresh meat products, a process according to the present invention
is employed. This process is illustrated in FIG. 1. Initially, meat
is placed in a tray or another type of container. The
meat-containing tray is then sealed with a modified atmosphere gas.
For example, the modified atmosphere gas may be a low oxygen blend
comprising 70% nitrogen, 29.6% carbon dioxide and 0.4% carbon
monoxide, which is a gas blend that is generally recognized as safe
(GRAS) by the Federal Food and Drug Administration. The sealed
meat-containing, modified atmosphere tray is then irradiated with
ionizing radiation. The benefit of applying ionizing radiation to
fresh meat products in the absence of oxygen is explained in U.S.
Pat. No. 6,885,011 (assigned to Mitec Incorporated of Cedar Rapids,
Iowa). In the process of the present invention, the fresh meat
product is maintained in an oxygen-free environment by virtue of
the modified atmosphere present in the sealed tray that holds the
fresh meat product. The chamber in which ionizing radiation is
applied may also be kept substantially free of oxygen in some
embodiments, as described in the aforementioned U.S. Pat. No.
6,885,011. After irradiating the fresh meat product in the
oxygen-excluding tray, the product will experience extended
microbial shelf life due to the effect of the ionizing radiation on
food borne pathogens and spoilage bacteria in the fresh meat
product. In addition, the color life of the fresh meat product will
also be extended by the low oxygen, carbon monoxide-containing
modified atmosphere that is provided in the sealed tray. In some
scenarios, the microbial life and color life of the fresh meat
product may extend as long as 90 days.
[0017] In one particular embodiment, the low oxygen, carbon
monoxide-containing modified atmosphere is introduced into the tray
containing the fresh meat product and is allowed to dwell there for
an extended period of time before the fresh meat product is
irradiated. Allowing the carbon monoxide of the modified atmosphere
gas to dwell sets the color of the fresh meat product to a greater
extent than would otherwise occur, so that a higher dose of
irradiation can be applied to the fresh meat product without
causing discoloration.
[0018] In some embodiments, it is desirable to control the length
of the color life of fresh meat products to ensure that the color
life fails before the microbial life, so that consumers have a
reliable indication that the product may be spoiled and should not
be consumed. Experience has shown that carbon monoxide MAP
packaging may be so successful at preserving the color life of
packaged fresh meat products such as ground beef, that in some
cases these products may have a very wholesome looking fresh
appearance, but may in fact be quite spoiled. This situation is
addressed as discussed below with respect to FIGS. 2-4.
[0019] FIG. 2 is a cross section view of a prior art case-ready
modified atmosphere package for meat. The tray 1 is typically
formed of thermoplastic material such as styrofoam into a shape
with a cavity, sidewalls and a flat upper lip surface 5 that serves
as a sealing surface for a lid film 2. Lid film 2 is typically a
clear plastic sheet material that allows a consumer to view the
meat packaged inside the tray 1. Meat 3 may be ground meat of
either loaf or patty form, a whole muscle cut of meat such as a
steak, roast or filet, or the like. A headspace 4 above and around
the meat provides a volume that may be filled with a gas
combination different from ambient air to advantageously affect the
storage characteristics of the meat packaged and sealed inside the
tray.
[0020] The tray of FIG. 2 may be processed in a number of different
ways. A typical process is to simply place a meat product in the
tray and seal the tray with a modified atmosphere package (MAP)
tray sealer (not shown). MAP tray sealers are well known in the
meat packaging industry, and operate by removing the ambient
atmosphere around the meat product in the tray, replacing the
atmosphere around the meat product in the tray in the headspace 4
with a modified atmosphere, and applying and sealing the lid film 2
to the tray lip 5 to form a gas tight seal that persistently
contains the modified atmosphere in the interior of the tray.
[0021] An alternate process for the tray of FIG. 2 is to place a
meat product in the tray, expose the meat product to ionizing
radiation in an open tray before affixing the lid film to the tray,
preferably in an atmosphere that excludes oxygen as disclosed in
U.S. Pat. No. 6,885,011 (assigned to Mitec Incorporated of Cedar
Rapids, Iowa), and seal the tray with a modified atmosphere package
(MAP) tray sealer (not shown). This alternate process has the
benefit of reducing the population of micro flora including both
food borne pathogens and spoilage bacteria, and will extend the
storage life of meat products by delaying spoilage. Irradiation
does not extend the color life of fresh meat products, however. The
use of either high oxygen MAP or low oxygen with low concentration
carbon monoxide MAP may be used to extend the color life of fresh
meat products as described earlier. Unfortunately, there is no
correlation or coordination between the spoilage life and the color
life of the meat with this process, so it is possible that the
color life might be longer than the spoilage life, which could lead
to the undesirable situation where a consumer does not have a
reliable indication that the product may be spoiled and should not
be consumed.
[0022] Referring now to FIG. 3, a cross section view of a
case-ready modified atmosphere package for meat according to the
present invention is shown. The tray and meat product is identical
to the prior art tray of FIG. 2, however, the lid film 12 is of a
type that is gas permeable and allows the modified atmosphere gas
constituents to slowly diffuse across the lid film barrier 12. A
completely enclosing gas impermeable bag 10 is filled with an
equivalent or complementary modified atmosphere 1, so there is an
equilibrium state of gas transfer across the gas permeable film 12
as long as the enclosing impermeable bag 10 is in place. In an
exemplary embodiment, the modified atmosphere gas placed inside the
tray headspace 4 may be a low oxygen blend comprised of 70%
nitrogen, 29.6% carbon dioxide and 0.4% carbon monoxide. In an
exemplary embodiment, the gas blend placed inside the enclosing
impermeable bag may be an identical low oxygen blend, so there will
be no gas exchange across the impermeable lid film 12 as long as
the enclosing impermeable bag is in place.
[0023] The tray of FIG. 3 may be processed in the same ways as tray
of FIG. 2, including either ordinary MAP processing or processing
with irradiation and MAP. If the modified atmosphere includes low
concentrations of carbon monoxide, the color of the fresh meat
product will be maintained for a longer period of time in the
bright pink-red color preferred by consumers as long as the
enclosing impermeable bag is in place.
[0024] In addition, the tray of FIG. 3 allows further processing
alternatives to employed. In one embodiment, the meat product may
be placed in tray 1 and permeable lid film 12 may be applied to
tray 1 before ionizing radiation is applied (in an atmosphere that
excludes oxygen, the benefits of which are disclosed in U.S. Pat.
No. 6,885,011 referenced above). In this embodiment, no oxygen is
present in the irradiation environment because of the fact that the
atmosphere in tray 1 (sealed by permeable lid film 12) is a low
oxygen blend that substantially excludes oxygen, and in some
embodiments, the irradiation environment around the product is also
controlled to exclude oxygen.
[0025] In another embodiment, the meat product may be placed in
tray 1, permeable lid film 12 may be applied to tray 1, and gas
impermeable bag 10 may enclose tray 1 and permeable lid film 12
before ionizing radiation is applied (in an atmosphere that
excludes oxygen, as mentioned above). Again, in this embodiment, no
oxygen is present in the irradiation environment because of the
fact that the atmosphere in tray 1 (sealed by permeable lid film
12) is a low oxygen blend that substantially excludes oxygen, the
atmosphere within gas impermeable bag 10 is filled with a low
oxygen blend that substantially excludes oxygen, and the
irradiation environment around the product is also controlled to
exclude oxygen in some embodiments.
[0026] This configuration is ideal for extended storage life of
fresh meat products. When it is time for the fresh meat product to
be placed on the retail shelf, the enclosing impermeable bag is
removed. At this point, the modified atmosphere begins to diffuse
across the permeable lid film and the concentrations of MAP gas are
exchanged with ambient air until they reach ambient air
concentrations. Of particular interest is the concentration of
carbon monoxide, as well as the characteristics of the fresh meat
that has been exposed to the carbon monoxide. Research has shown
that the carbon monoxide binds to myoglobin in a manner very
similar to the way it binds to hemoglobin in blood. While the
affinity of carbon monoxide to hemoglobin is approximately 240
times greater than oxygen, this binding is reversible with a
half-life of approximately 4.5 hours.
[0027] In retail applications, it is desirable for the rate of
release of carbon monoxide to be controlled to match the required
display shelf life expected while being coordinated with the
spoilage life of the fresh meat product. For example, in relatively
high volume retail environments such as super stores, it may be
desirable to have a week of display shelf life. To achieve one week
of display shelf life, the gas permeable lid film should be
selected so that enough carbon monoxide is exchanged with the
ambient atmosphere that the carbon monoxide level is below the
color maintenance level 7 days after the enclosing impermeable bag
is removed. Other retail applications such as convenience stores
may require longer display shelf life, such as two weeks. In such
applications, the gas permeable lid film should be selected with a
lower permeability to cause a slower exchange of carbon monoxide
with the ambient atmosphere.
[0028] FIG. 4 is a cross section view of an alternate version of
the extended storage life fresh meat tray according to the present
invention. Rather than placing the entire tray 1 inside an
enclosing gas impermeable bag 10 of FIG. 3, a peelable gas
impermeable film 30 is placed immediately over a gas permeable lid
film 22 that is sealed to the tray lip 5. In some embodiments, gas
permeable lid film 22 and peelable gas impermeable film 30 may be
dual layers of a single film. This package has the benefit of a
standard tray configuration, which is convenient for processing,
shipping and handling. The film peeling step involves some
additional labor, but this labor is generally similar to removing
the gas impermeable bags 10 of FIG. 3. The primary disadvantage of
the possibility that store personnel might forget to remove the
peelable gas impermeable film may be mitigated by placing a label
on the exterior of the impermeable film that is visible to store
personnel as an indication that the film has not been properly
removed.
[0029] As in the tray configuration of FIG. 3, the tray of FIG. 4
may be processed with or without irradiation. All of the processing
options discussed above with respect to the tray configuration of
FIG. 3 are also available for the tray configuration of FIG. 4. The
tray of FIG. 4 may also include any variety of MAP gas. An
exemplary MAP gas is a blend of 70% nitrogen, 29.6% carbon dioxide
and 0.4% carbon monoxide. This MAP gas blend can maintain the color
of fresh meat products for up to 40 days or more. Irradiation
processing can provide microbial life up to 50 days or more.
[0030] Management of shelf life expiration of fresh meat products
processed and distributed according to the present invention is
essentially the same as any other perishable product with a posted
expiration date. The expiration date affixed or printed on the
trays is determined by the microbial life of the product. The color
life of fresh meat in storage according to the present invention is
generally longer than the microbial storage life of the product
until the gas impermeable bag or film is removed. Once this step is
completed, the color life of the product is very predictably
limited so that the color of the product becomes a meaningful
indication of the state of freshness of the product. Specifically,
in many embodiments it is desirable for the permeability of the
permeable film to be selected in a way that provides a color life
of a particular length of time, and for the dose of ionizing
radiation to be selected in a way that provides a microbial life of
a particular length of time that has a known relationship to the
color life. For example, in some embodiments, it is desirable for
the color life to match the microbial life. In other embodiments,
it is desirable for the color life to be slightly less than the
microbial life. The permeability of the permeable film over the
tray and the dose of ionizing radiation are controllable variables
that allow this correspondence between microbial life and color
life to be achieved.
[0031] Although the present invention has been described with
reference to preferred embodiments, workers skilled in the art will
recognize that changes may be made in form and detail without
departing from the spirit and scope of the invention.
* * * * *