Method for Preserving Foodstuffs

Abstract

A method for preserving foodstuffs, in which the foodstuffs are heated in the moist state in a container suitable for transport and storage with ventilation openings. The foodstuffs are heated for a defined period by a microwave, for at least such a time as hot steam forms in the container and exits through the ventilation openings. Gas is injected into the container after the heating process for at least partial compensation of the pressure drop in the container.

1 . A method for stabilizing foodstuffs in which the foodstuffs are in a moist state inside a container, having a wall, suitable as a shipping and retail package, the packing having a vent opening, said method comprising the steps of:
 heating the foodstuffs with microwaves for a limited period of time, but at least until hot steam has formed in the container and escapes through the vent opening; and   injecting a gas into the container for at least partial compensation of the pressure drop in the container after the end of the step of heating the foodstuffs.   
   
   
       2 . The method according to  claim 1 , wherein the gas is at least one of an oxygen-free gas, nitrogen and CO 2 . 
   
   
       3 . The method according to  claim 1 , wherein said step of injecting the gas comprises injecting the gas at an excess pressure of 1-5 bar. 
   
   
       4 . The method according to  claim 1 , comprising the step of precooling the gas to be injected to a temperature of less than 12° C. 
   
   
       5 . The method according to  claim 1 , wherein said step of injecting the gas comprises injecting the gas within 150 seconds after the end of said heating step. 
   
   
       6 . The method according to  claim 1 , wherein said step of injecting the gas comprises injecting the gas for 1-20 seconds. 
   
   
       7 . The method according to  claim 1 , wherein said step of injecting the gas into the container comprises flushing the container with the gas, to expel steam through the vent opening. 
   
   
       8 . The method according to  claim 1 , wherein said step of injecting the gas comprises using a cannula to inject the gas. 
   
   
       9 . The method according to  claim 8 , wherein said step of injecting the gas comprises puncturing the wall of the container with the cannula to form a puncture hole. 
   
   
       10 . The method according to  claim 9 , wherein the wall of the container that is punctured with the cannula comprises a plastic film having a thickness in the range between 40 and 220 μm. 
   
   
       11 . The method according to  claim 9 , further comprising the steps of:
 retracting the cannula; and   sealing the puncture hole in the container wall after retracting the cannula.   
   
   
       12 . The method according to  claim 11 , wherein said step of seal the puncture hole comprises applying an adhesive patch to the container wall. 
   
   
       13 . The method according to  claim 1 , further comprising the step of sealing the vent opening after injecting the gas. 
   
   
       14 . The method according to  claim 13 , wherein said vent opening comprises a valve that opens automatically under excess pressure and closes again automatically after the excess pressure drops. 
   
   
       15 . The method according to  claim 14 , further comprising the step of sealing said valve with an oil as a sealing agent, wherein the oil is at least one of a silicone oil, has a viscosity of 1000-20,000 Centipoise at 20° C. and is present in an amount of 4-8 mg. 
   
   
       16 . The method according to  claim 13 , wherein said step of sealing the vent opening comprises applying an adhesive patch. 
   
   
       17 . The method according to  claim 16 , wherein the same adhesive patch is used for sealing the puncture hole and the vent opening. 
   
   
       18 . The method according to  claim 12 , wherein the adhesive patch is applied within 60 seconds after injection of the gas. 
   
   
       19 . The method according to  claim 1 , wherein at least one of a temperature of at least 100° C. is created in the steam and 80° C. in the core zone of the foodstuff within 7 minutes during heating in the container. 
   
   
       20 . The method according to  claim 1 , wherein said step of heating the foodstuffs comprises passing the container through a device selected from the group consisting of a microwave tunnel and a microwave chamber. 
   
   
       21 . The method according to  claim 1 , further comprising the steps of:
 passing the container through an injection station; and   injecting the gas during said step of passing the container through the injection station.   
   
   
       22 . The method according to  claim 21 , wherein said step of applying the adhesive patch occurs during the step of passing the container through the injection station. 
   
   
       23 . The method according to  claim 21 , comprising the step of conveying the container on a conveyor system through the microwave tunnel and the injection station. 
   
   
       24 . The method according to  claim 23 , wherein said conveyor system comprises a conveyor device for conveying multiple containers simultaneously in several rows side-by-side. 
   
   
       25 . The method according to  claim 1 , wherein the foodstuffs are packaged in the container in a raw fresh state. 
   
   
       26 . The method according to  claim 1 , wherein the foodstuffs are packaged in the container under reduced pressure and/or in a protective gas atmosphere having a low oxygen content. 
   
   
       27 . The method according to  claim 1 , further comprising the step of supplying the container to a refrigeration chain having refrigeration temperatures between 1 and 8° C. after injection of the gas. 
   
   
       28 . The method according to  claim 1 , wherein said container withstands temperatures up to 150° C. during heating. 
   
   
       29 . The method according to  claim 1 , wherein said container withstands an excess of up to 1.5 bar absolute during heating. 
   
   
       30 . The method according to  claim 1 , wherein said vent opening of said container has a defined flow resistance which does not change even under the stresses occurring during heating and has a flow cross section of 1-20 mm 2 . 
   
   
       31 . The method according to  claim 2 , wherein the gas is a mixture of nitrogen and CO 2  in a volume ratio of 80:20 to 70:30. 
   
   
       32 . The method according to  claim 3 , wherein said step of injecting the gas comprises injecting the gas at an excess pressure of 3 bar. 
   
   
       33 . The method according to  claim 6 , wherein said step of injecting the gas comprises injecting the gas 8 seconds. 
   
   
       34 . The method according to  claim 10 , wherein said a plastic film comprises multiple layers. 
   
   
       35 . The method according to  claim 30 , wherein said vent opening has a flow cross section of 3-7 mm 2 .