CA2030760A1 - Preservation of meat products - Google Patents

Abstract

Abstract of the Disclosure A method and apparatus for preserving and extending the shelf life of cured meat products by exposure of the surface of the meat products to infrared radiation for a controlled duration of time to achieve a surface temperature of about 180°F. not to exceed about 15 seconds. Immediately after exposure to the infrared radiation the cured meat products are encapsulated in a substantially air-impervious packaging material.

Description

203~7~0 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 2~3076~

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 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, 2~30761D

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 2~3~7~

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 203~7~

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 2!~3a7~

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 203076~3 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 20307go 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 20307~

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.

Claims (8)

1. A method for preserving and extending the shelf life of cured meat products by destroying living organisms which may be present on the surface of the cured meat products, the method comprising the steps of:
heating the surface of the cured meat products to a tem-perature of at least about 180°F. for a period of time of up to about 15 seconds; and immediately thereafter encapsulating the heated cured meat products in a substantially air-impervious packaging material.

2. A method for preserving and extending the shelf life of cured meat products of claim 1 wherein the period of time the cured meat products are heated is from about 10 to about 15 seconds.

3. A method for preserving and extending the shelf life of cured meat products by destroying living organisms which may be present on the surface of the cured meat products, the method comprising the steps of:
heating an oven with a plurality of electrical heating elements, a portion of the heating elements being disposed in a lower portion of the oven and a por-tion being disposed in an upper portion thereof;
passing the cured meat products to be treated through the oven on a conveyor such that the heating ele-ments in the upper portion of the oven are disposed above the cured meat products and the heating ele-ment in the lower portion of the oven are disposed below the cured meat products;
controlling the travel rate of the conveyor such that the cured meat products positioned on the conveyor are heated on the surface thereof to a temperature of at least about 180° during travel through the oven; and encapsulating the cured meat products with a substan-tially air-impervious packaging material immedi-ately upon exiting the oven.

4. A method for preserving and extending the shelf life of cured meat products of claim 3 wherein the oven is heated to a temperature of at least about 650°F and the conveyor is controlled so that the travel rate of the conveyor is such that the cured meat products are exposed to heat in the oven for a period of time of from about 10 to about 15 seconds.

5. A method for preserving and extending the shelf life of cured meat products of claim 3 further comprising cooling the conveyor upon exiting the oven and prior to reentry into the oven so as to eliminate hot spots on the conveyor and thereby prevent branding of the cured meat products by the conveyor.

6. A method for preserving and extending the shelf life of cured meat products of claim 3 wherein the oven is heated to a temperature of at least about 650°F., the conveyor is controlled such that cured meat products placed thereon travel through the oven in a time period of from about 10 to 15 seconds so that the surface of the cured meat products is heated to a temperature of at least about 180° F. while pre-venting alteration of the appearance and palatability of the cured meat products.

7. An apparatus for preserving and extending the shelf life of cured meat products comprising:
a radiant furnace having an entrance opening at one end and an exit opening at an opposed end thereof;
conveyor means extending through the oven via the entrance opening and the exit opening;
infrared radiation means disposed within the oven so as to be positioned above and below the conveyor means;
control means for adjusting the rate of travel of the conveyor through the oven and thus the time the cured meat products positioned thereon are exposed to heat generated by the infrared radiation means;
and encapsulating means for encapsulating the cured meat products immediately upon exiting the oven with a substantially air-impervious packaging material.

8. An apparatus for preserving and extending the shelf life of cured meat products of claim 7 further comprising:
trough means for containing a cooling liquid such that the conveyor means is passed through the cooling liquid upon exiting the oven and prior to reentry into the oven.