Treatment to reduce microorganisms with carbon dioxide by multiple pressure oscillations

Abstract

Apparatus and methods to non-thermally treat goods for human consumption with carbon dioxide. Apparatus and methods rely on multiple pressure changes of carbon dioxide to affect one of three processes. A first process rapidly freezes and thaws water on the surface of the goods in rapid succession multiple times to detrimentally affect pathogens. A second process raises the pressure and temperature of carbon dioxide to supercritical conditions to detrimentally affect the lipids in the membranes of pathogens. A third process adjusts the pressure to form a dense carbon dioxide liquid with a low pH that may also detrimentally affect pathogens. All processes may be repeated or performed in succession, or in any order. Optionally, thereafter, the goods may be stored at low temperature in substantially 100% carbon dioxide for further pathogen reduction.

1 . A method for inactivating microorganisms on goods, comprising: 
 (a) introducing goods and carbon dioxide within an apparatus;    (b) raising the pressure within the apparatus to a pressure below the supercritical pressure of carbon dioxide, without elevating the temperature above 104 degrees Fahrenheit; and    (c) reducing the pressure within the apparatus to form ice crystals that affect the microorganisms on the surface of the goods in a detrimental manner, without substantially causing freezing of water below the surface.    
   
   
       2 . The method of  claim 1 , further comprising: 
 (d) raising the pressure within the apparatus to thaw the ice crystals before the water below the surface of the goods substantially freezes.    
   
   
       3 . The method of  claim 2 , further comprising, cycling steps (c) and (d) in rapid succession for more than one cycle.  
   
   
       4 . The method of  claim 1 , further comprising adjusting the pressure of the carbon dioxide to form carbon dioxide having a pH less than 3, wherein due to the low pH, the carbon dioxide affects the microorganisms in a detrimental manner.  
   
   
       5 . The method of  claim 1 , further comprising adjusting the pressure of the carbon dioxide to form carbon dioxide having a pH less than 4, wherein due to the low pH, the carbon dioxide affects the microorganisms in a detrimental manner.  
   
   
       6 . The method of  claim 1 , further comprising adjusting the pressure of the carbon dioxide to form carbon dioxide having a pH less than 5, wherein due to the low pH, the carbon dioxide affects the microorganisms in a detrimental manner.  
   
   
       7 . The method of  claim 1 , further comprising applying ultrasonic energy to separate microorganisms from the goods and mixing the goods within the chamber.  
   
   
       8 . The method of  claim 1 , further comprising, after reducing the pressure, raising the pressure and temperature of the carbon dioxide to reach supercritical conditions, and holding the supercritical conditions for a period of time sufficient for the supercritical carbon dioxide to affect the microorganisms in a detrimental manner.  
   
   
       9 . The method of  claim 1 , wherein liquid carbon dioxide is in contact with the surfaces of the goods in sufficient quantities to cause freezing of the free water in contact with the microorganisms.  
   
   
       10 . A method for treating food to reduce microorganisms, comprising: 
 (a) introducing food, water and carbon dioxide into an apparatus; and    (b) raising and lowering the pressure within the apparatus to cause freezing and thawing of water on the surfaces of the food in rapid succession for at least one cycle.    
   
   
       11 . A method for storing human edible goods, comprising: 
 (a) treating human edible goods with substantially 100% carbon dioxide at a pressure greater than 300 psig to less than the supercritical pressure of carbon dioxide and at a temperature less than the supercritical temperature of carbon dioxide; and    (b) storing the treated human edible goods in substantially 100% carbon dioxide at a low temperature and atmospheric pressure to achieve at least an additional 2 log kill rate.    
   
   
       12 . The method of  claim 10 , comprising storing the goods from 4 hours to 20 days.  
   
   
       13 . The method of  claim 10 , comprising storing the goods from 2 days to 20 days.  
   
   
       14 . Apparatus, comprising: 
 (a) a housing defining a cylindrical chamber with a first end and an opposite, second end;    (b) a first piston and a second piston disposed in a sealing manner at the opposite ends of the chamber, wherein the first piston and the second piston are driven towards one another to pressurize contents within the chamber to a first, high pressure, and withdrawn to depressurize contents within the chamber to a second, lower pressure; and    (c) a mixer disposed within the housing to mix any contents within the chamber.    
   
   
       15 . The apparatus of  claim 13 , wherein the mixer has a piston-like member disposed in the housing, wherein the piston-like member is in a sealing disposition with the inner surface of the chamber.  
   
   
       16 . The apparatus of  claim 13 , wherein the mixer has a piston-like member disposed in the housing, and the piston-like member has an opening for the passage of goods from one end of the chamber towards the other.  
   
   
       17 . The apparatus of  claim 13 , further comprising, an ultrasonic generator that transmits ultrasonic energy to the mixer to separate microorganisms from goods being processed within the chamber.  
   
   
       18 . The apparatus of  claim 13 , wherein the first and the second pistons are driven by the introduction and withdrawal of a liquid compatible with goods edible for human consumption.  
   
   
       19 . The apparatus of  claim 13 , wherein the mixer is configured to rotate and reciprocate in relation to the chamber length.  
   
   
       20 . The apparatus of  claim 13 , further comprising a first and a second end cap disposed at opposite ends of the housing to form a first chamber and a second chamber, wherein the chambers receive a fluid to drive the first piston and the second piston.  
   
   
       21 . The apparatus of  claim 13 , further comprising a first positive displacement pump to introduce goods to be treated within the chamber.  
   
   
       22 . The apparatus of  claim 13 , further comprising a second positive displacement pump to remove goods from within the chamber.