Note: Descriptions are shown in the official language in which they were submitted.
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PRESERVATION OF MEAT PRODUCTS
Background of the Invention
1. Field of the Invention
The present invention relates to the preservation of
foodstuffs, and more particularly but not by way of
5 limitation, to the preservation of meat products utilizing
infrared radiation.
2. Brief Discussion of the Prior Art
Meat products, especially cured meat products such as
ham, bacon, smoked sausage and the like, remain edible for
10 only a relatively short period of time. Thus, preservation
of meat products has engaged the attention of mankind since
prehistoric times. As the biological causes of food deteri-
oration have become better understood over the centuries,
man has developed various methods for dealing wlth the caus-
15 ative agents.
Most foodstuffs, especially meat products, carry oracquire bacteria, mold or yeast; and such microorganisms are
the ma;or cause of food spoilage. Other factors leading to
deterioration or spoilage of food products are enzymes which
20 occur naturally in some foods, as well as chemical reactions
such as oxidation.
Meat products, even though cured, are susceptible to
reinfestation with microorganisms; and meat products must be
subjected to additional processes in order to retard the
25 proliferation of additional colonies of bacteria as well as
to achieve maximum shelf life.
Methods currently employed in the preservation of meat
products include desiccation, salting and pickling, smoking,
thermo-processing, cold storage, freezing and the use of
30 chemical preservatives. Thus, the prior art is replete with
various methods and apparatus for treating and packaging
food products and other microbiologically labile products to
preserve such products against microbiological spoilage.
Dunn et al. in U.S. Patent No. 4,871,559 disclose a
35 method and apparatus for the preservation of food products
by inactivation of microorganisms and enzymes wherein the
surface of the food product is sequentially illuminated with
very short pulses of intense polychromatic incoherent light
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having a duration of from about 0.001 to about 100
milliseconds. The polychromatic incoherent light employed
has an energy density in the range from about 0.01 to about
50 joules per square centimeter at the surface of the food
5 product and a wave length distribution such that at least
about seventy percent of the energy of the pulse of intense
polychromatic incoherent light is distributed at wave
lengths of from 170 nanometers and 2600 nanometers. The
illumination of the surface of the food product, which
10 results in heating a superficial surface layer thereof
through absorption of the short intense polychromatic inco-
herent light pulse, provides a temperature effective to
inactivate enzymes and microorganisms at the superficial
surface layer of the food product before substantial
15 thermoconduction occurs from the superficial surface layer
to the interior of the food product.
U.S. Patent No's. 2,072,417 and 2,072,416, issued to
E.C. Berndt et al., disclose a cyclic method for treating
or irradiating a partially opaque liquid substance, such as
20 milk, with ultraviolet rays to reduce the bacterial content
of the substance while producing a high percentage of the
potential amount of vitamin D in the substance without det-
rimental effects, such as an unpleasant taste or odor. The
cyclic method of treating the liquid substance includes
25 exposing only a portion of the substance to ultraviolet rays
at one time, discontinuing the exposure and thereafter mix-
ing the treated portion of the substance with the untreated
portion while the treatment is discontinued. Thereafter,
the liquid substance is sequentially treated with the active
30 rays until the summation of the amount of treatment received
during the cyclic exposures is less than the time required
to impart undesirable properties to the substance.
Rentschler et al. in U.S. Patent No. 2,482,507 disclose
the use of radiant energy, such as ultraviolet light and x-
35 ray, for destroying organisms by contacting the fluid hostwith radiant energy for a period of about eight hours.
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Wood, U.S. Patent No. 3,814,680, discloses the purification
of materials, such as liquids, by subjecting the material to
ultraviolet radiation where the ultraviolet light source is
operated at high frequency while maintaining the germicidal
5 wave length.
Hiramoto, U.S. Patent No. 4,464,336, also discloses a
method of sterilization wherein a flash discharge of ultra-
violet light is employed to provide a large instantaneous
luminous output so as to destroy microorganisms, such as
lOAspergillus Nigger and other organisms in the lower layers
of the substrate; and Moulton, U.S. Patent No. 2,930,706,
discloses the use of ultraviolet radiation to kill or inac-
tivate deleterious organic life, such as enzymes, spores and
yeast encountered in the preparation of citric vices
DiGeronimo, U.S. Patent No. 4,424,188, discloses a
method for sterilizing packaging material used in the asep-
tic packaging of food stuff. The method includes the steps
of (l) subjecting the packaging material to ultrasonic
vibrations through a liquid medium; and (2) subjecting the
20packaging material to ultraviolet radiation. The bacterial
effect when carrying out the method in the sequence of steps
(l) and (2) is purportedly greater than if practiced in the
reverse order. The packaging material sterilized can be a
moving web of packaging material, and after sterilization
25treatment, the web can be fed through conventional machinery
for forming, filling and sealing.
United Kingdom Patent No's. 1,052,513, 1,346,521,
1,448,411, 1,548,997 and 1,581,998 disclose various flash
lighting devices for generating short wave radiation flashes
30Of high intensity which can be used in the sterilization of
substrates or for curlng polymerizable coatings or sealants.
The substrates, coatings and sealants, as well as the use of
the rapid pulse ultraviolet light devices, have particular
utility in the fields of printing, medicine and dentistry.
Sterilization systems have also been suggested in the
prior art wherein a plasma generated by a laser is employed
o
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to kill or inactivate microorganisms and thereby sterilize
foods, beverages, medicines, medical supplies, water and the
like. Laser energized sterilization methods and apparatus
are disclosed in Atwood US Patent No. 3,817,703),
5 Tensmeyer (U.S. Patent No. 3,955,921), Tensmeyer (U.S.
Patent No. 4,042,325), and ~opa et al. (U.S. Patent No.
4,265,747)-
Dell'Acqua et al., U.S. Patent No. 4,810,508, disclose a
process for the preservation of food products of animal
10 origin, such as milk, meat and by-products thereof, so that
such food products are free of Listeria bacteria. The proc-
ess to achieve Listeria-free food products comprises adding
(in an acidic environment of pH 4.5 to 6.5) an efficacious
quantity of lysozyme or its non-toxic salt to the food
15 products.
Brody et al., U.S. Patent No. 4,391,080, dislcose a
method for providing a sterile inert atmosphere in an asep-
tic packaging machine wherein an inert gas is passed through
a microbiological filter and then sparged through a bath of
20 hot sterilizing liquid. A portion of the sterile inert gas
is withdrawn from the interior of the machine by means of a
pump or blower, and the withdrawn sterile inert gas is sepa-
rated into three parts. The first part of the withdrawn gas
is passed through a heater and then over the flange areas of
25 containers passing through the machine to dry same prior to
heat sealing operations; the second part of the withdrawn
gas is directed to the machine filler to provide a back-up
microbiological barrier for the filler; and, the third part
of the withdrawn gas is passed through jets aligned on
30 either side of a web of cover material as the cover material
emerges from the sterilizing bath, the jets being arranged
to blow off liquid sterilant adhering to the material.
High energy electromagnetic radiation, such as x-rays,
gamma rays and beta rays have also heretofore been employed
35 in a sterilization process to destroy or kill
microorganisms, especially in the medical field. However,
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the equipment necessary to effect sterilization using such
high energy electromagnetic radiation is expensive and
requires specialized equipment, and extensive shielding must
be provided to protect personnel from harmful side effects
5 from such radiation.
Summarv of the Invention
According to the present invention an improved method
and apparatus for preserving meat products is provided
wherein living microorganisms present on the surface of meat
10 products are essentially destroyed. Broadly, the method
comprises the steps of exposing the meat products to intense
infrared radiation for a period of time effective to heat
the surface of the meat product to at least about 180F.
(without adversely affecting the palatability and appearance
15 of the treated meat products), and thereafter immediately
encapsulating the infrared treated meat products in an
essentially air-impervious aseptic material.
The apparatus employed in carrying out the preservation
of meat products comprises an infrared radiation oven having
20 an entrance at one end and an exit at an opposed end, and a
conveyor for moving the meat products therethrough at a con-
trolled rate of speed. A plurality of heating elements are
supported in the infrared radiation oven which are capable
of generating sufficient heat so that the surface of the
25 meat traveling through the oven is heated to at least about
180F. An encapsulation packaging unit, a conventional unit
generally known in the industry as a "shrink wrap" machine,
is located immediately adjacent the exit of the infrared
radiation oven so that the infrared radiation-treated meat
30 products can be packaged in a sterile packaging material
before the surface of the radiation-treated meat products
can be recolonized with bacteria or other microorganisms.
The rate at which the conveyor moves through the infra-
red radiation in order to expose the meat products to the
infrared radiation to destroy living microorganisms on the
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surface of the meat products can vary, but in order to
effectively kill the microorganisms without substantially
effecting the palatability and visual appearance of the meat
products so treated, the rate of travel of the conveyor is
5 controlled so that the meat products are exposed to a sur-
face temperature of at least about 180F. in the infrared
radiation oven for a period of time no longer than about
fifteen seconds.
An object of the present invention is to provide an
10 improved method for preserving meat products without signif-
icantly altering the characteristics of the treated meat
products.
Another object of the present invention, while achieving
the before-stated ob;ect, is to provide an improved method
15 and apparatus for treating meat products so that living
microorganisms present on the surface thereof are essen-
tially killed without adversely affecting the palatability
and visual attractiveness of the treated meat product.
Another object of the present invention, while achieving
20 the before-stated objects, is to provide a method and appa-
ratus for treating cured meat products wherein the shelf
life of such products of is substantially enhanced.
Other ob;ects, features and advantages of the present
invention will be apparent from the following detailed
25 description when read in conjunction with the drawings and
appended claims.
Brief Description of the Drawings
FIG. 1 is a semi detailed side elvational view of a meat
preserving apparatus constructed in accordance with the pre-
30 sent invention.
FIG. 2 is a partially cutaway view of the infrared radi-
ation oven of the meat preserving apparatus of FIG. 1 show-
ing a portion of the infrared elements thereof.
FIG. 3 is a cross-sectional view taken along 3-3 in FIG.
35 2.
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FIG. 4 is a partially cut-away, isometric view of one
end portion of the infrared radiation oven of FIG. 2.
FIG. 5 is a partially cut-away, isometric view of an
opposed end portion of the infrared radiation oven of FIG.
5 2.
Detailed Description
Referring now to the drawings, and more particularly to
FIG. 1, shown therein is a meat preserving apparatus 10 for
preserving meat products constructed in accordance with the
10 present invention. The meat preserving apparatus 10 com-
prises an oven 12 having a first or entrance end 14, a sec-
ond or exit end 16 and a heating chamber 18 (FIG. 2 )
disposed therebetween. conveyor frame 19 for supporting
an endless conveyor 20 extends through the oven 12 substan-
15 tially as shown.
The oven 12 is supported in an elevated position rela-
tive to the supporting surface by a frame assembly 22. The
oven 12 iS provided doors 24 and 26 which are pivotally con-
nected to a sidewall 28 of the oven 12 by any suitable
20 means, such as hinges 30, 32, respectively, so as to provide
access to the heating chamber 18 for maintenance of the oven
12.
In order to enhance opening and closing of the doors 24
and 26, the door 24 is provided with a latching handle 34
25 and the door 26 iS provided with a latching handle 36.
Connection ox the handles 34, 36 to the doors 24, 26, as
well as their locking engagement with the sidewall 28 of the
oven 12, is in a conventional manner.
A trough 38 containing a cooling liquid, e.g. water, is
30supported on the frame assembly 22, so as to be disposed
below the oven 12. The conveyor 20 is passed through the
trough 38 and into contact with the liquid therein so that
the conveyor 20 is cooled after passage through the oven 12.
To prevent heat build-up in the liquid as the conveyor
3spasses through the troush 38, the trough 38 is provided with
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an outlet port (not shown) and an inlet port (also not
shown). The outlet port of the trough 38 is connected to
the input side of a pump 39 via a conduit 40; and the output
of the pump 39 is connected to a heat exchanger 42 via a
5 conduit 44. The heat exchanger 42 is then connected to the
input port of the trough 38 via a conduit 46. Thus, the
liquid in the trough 38 can be passed through the pump 39
and the heat exchanger 42 wherein it is cooled prior to
being recirculated to the trough 38.
The meat preserving apparatus lo further comprises a
drive pulley 48 (shown in phantom) which is operably con-
nected to a motor 50 supported by the frame assembly 22 in a
conventional manner. A plurality of idler or support pul-
leys 52 are supported by the frame assembly 22 for support-
15 ing the endless conveyor 22 and for directing the conveyor22 through the oven 12. The motor 50 is a variable speed
motor so that the rate of travel of the conveyor 20 through
the oven 12 can be controlled. Thus the length of time that
meat products positioned on the conveyor 20 are exposed to
20 heat within the oven 12 can readily be controlled.
It has been determined that in order to effectively kill
microorganisms on the surface of meat products using the
meat preserving apparatus 10, while at the same time pre-
venting unsightly burn marks on the meat products or deteri-
25 oration of the meat products during the infrared heating ofsame within the oven 12, the rate of travel of the conveyor
20 should be such that meat products placed thereon remain
in the oven 12 for a period of time of from about 10 to
about 15 seconds, and more desirably about eleven seconds.
To generate the desired temperature in the chamber 18 of
the oven 12, the meat preserving apparatus 10 further com-
prises a plurality of heating elements 54 extending into the
chamber 18 so as to be disposed above the conveyor 20; and a
plurality of heating elements 56 extending into the chamber
35 18 so as to be disposed below the conveyor 20. The heating
elements 54 and 56 extend substantially the width of the
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g
chamber 18 so that the chamber 18 can be substantially uni-
formly heated. The heating elements 54 and 56, and their
relationship to the conveyor 20 are illustrated in FIGS. 2
and 3.
The heating elements 54 and 56, which provide the infra-
red radiation for heating the surface of the meat products
to the desired temperature of at least 180F. as same passes
through the oven 12 on the conveyor 20, are connected to a
power source (not shown) through an input controller panel
10 58 supported on an upper surface side 60 of the oven 12 by
an auxiliary frame 62. The input control panel 58 is opera-
bly connected to and responds to a temperature sensing unit
64 disposed within the chamber 18 of the oven 12. Thus, the
intensity of infrared radiation is a function of the radi-
15 ated heat from the heating elements 54, 56; and the infraredradiation is controlled indirectly by the input controller
panel 58 in response to the temperature in the chamber 18 of
the oven 12 as sensed by the temperature sensing unit 64.
Meat products, especially cured meat products, which
20 have been treated with the infrared radiation generated by
the heating elements 54 and 56 in the chamber 18 of the oven
12 are transported immediately through a shrinkwrap unit 66
in order to be protected from external contamination, thus
prolonging the shelf life of the treated meat product. The
25shrinkwrap unit 66 is a conventional commercially available
unit. Thus, no further description of the shrinkwrap unit
66 is believed necessary to enable one to understand and
practice the inventive concept set forth herein.
Referring now to FIG. 4 the meat preserving apparatus 10
30further comprises a door housing 70 having an opening 72
extending therethrough such that the opening 72 openly com-
municates with the chamber 18 of the oven 12. The conveyor
frame 19 is disposed adjacent a lower end 74 of the opening
72 substantlally as shown. An entrance door 76 is pivotally
3sconnected to an upper portion 78 of the housing 70; and the
entrance door 76 extends downwardly therefrom and terminates
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substantially adjacent the conveyor frame 29, and thus the
conveyor 20 supported thereon. The entrance door 76 is
dimensioned so as to have exterior dimensions substantially
corresponding to the intarior dimensions of the opening 72.
5 Thus, when meat products are placed on the conveyor 20 and
the motor 50 is actuated, the meat products will engage a
lower portion of the entrance door 76 and pivotally move the
entrance door inwardly into the housing 70 so that the meat
products can enter the chamber 18 of the oven 12 via the
10 conveyor 20. It should be noted that the entrance door 76
can be fabricated of any heat resistant material. Further,
the entrance door 76 substantially reduces the amount of
heat exiting the chambers 18 through the opening 72 in the
housing 70 which permits one to more readily control the
15 temperature within the oven 12.
Referring now to FIG. 5, the meat preserving apparatus
10 further comprises a housing 80 having an opening 82
extending therethrough so as to openly communicate with the
chamber 18 of the oven 12. The conveyor frame 19 is dis-
20 posed adjacent a lower portion 84 of the opening 82 substan-
tially as shown. An exit door 86 is pivotally connected to
an upper portion 88 of the housing 80; and the exit door 86
extends downwardly therefrom and terminates substantially
adjacent the conveyor frame 29, and thus the conveyor 20
25 supported thereon. The exit door 86 is dimensioned so as to
have exterior dimensions substantially corresponding to the
interior dimension of the opening 82. Thus, as meat prod-
ucts exit the chamber 18 of the oven 12 via the conveyor 20,
the meat products strikingly engage the exit door 86 causing
30 same to move outwardly so that the meat products can pass
thereunder. After passage through the opening B2 of the
housing 80, the meat products are directly passed to the
shrinkwrap unit 66 as heretofore discussed.
The method of preserving meat products, especially cured
35 meat products, employing the meat preserving apparatus 10 of
the present invention will now be described with reference
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to the drawings. Initially, the oven 12 is heated by actua-
tion of the heating elements 54 and 56 so that the chamber
18 of the oven 12 is heated to a temperature of approxi-
mately 650F. The motor 50 is actuated so that the conveyor
5 20 travels through the chamber 18 of the oven 12 at a con-
trolled rate of speed. That is, the rate of travel of the
conveyor 20 is controlled such that meat products placed on
the conveyor 20 will pass through the chamber 18 of the oven
12 in a period of time of from about ten to fifteen seconds,
10 and more desirably, in about 11 seconds. By controlling the
time which the meat products are exposed to the temperature
within the oven 12 (as well as the temperature in the cham-
ber 18 of the oven 12) one can more easily heat the surface
of the meat products to a temperature of at least 180, so
15 that any microorganisms present on the surface of the meat
products will be effectively killed and destroyed. Further
by controlling the heating of the surface of the meat as
specified above, as well as the dwell time of the meat prod-
ucts in the chamber 18 of the oven 12, meat exiting the oven
20 12 appears in its natural state and the palatability of the
meat is substantially uneffected.
The treated meat products, upon exiting the oven 12, are
immediately passed to the shrinkwrap unit 66 so that the
treated meat products can be sealed by wrapping same in an
25 air-impervious material. The conveyor 20, onto which the
meat was placed, travels a predetermined path and defined by
the pulleys 52 and is directed through the cooling medium,
such as water, in the trough ~8. The conveyor 20 is thus
cooled and rinsed. By cooling the conveyor 20 meat products
30placed thereon do not become "branded" because of hot spots
formed on the conveyor 20 as same is heated during the
travel of the conveyor 20 through the chamber 18 of the oven
~2.
Experience has shown that when treating meat products,
3sespecially cured meat products, using the meat preserving
apparatus 10 of the present invention, substantially all
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microorganisms present on the surface of cured meat products
are destroyed without noticeably affecting the taste, smell
or appearance of the treated meat products. Further, by
immediately packaging the treated meat products in an air-
impervious material employing the shrinkwrap unit 66, thetreated meat products are not only protected from external
contamination but also have extended shelf life.
It will be clear that the present invention is well
adapted to carry out the objects and obtain the advantages
10 mentioned as well as those inherent therein. While a pres-
ently preferred embodiment of the invention has been
described for the purposes of this disclosure, numerous
changes can be made which will readily suggest themselves to
those skilled in the art and which are encompassed within
the spirit of the invention disclosed and as defined in the
appended claims.
