Method and control system for controlling pasteurization

Abstract

In a method and control system for controlling pasteurization of a food product, the internal temperature of the product, at least one pasteurization property change rate of the product based on the internal temperature of the product, and a cumulative pasteurization property change as a function of the pasteurization property change rate and time are at least periodically determined. A value of the cumulative pasteurization property change is at least periodically compared to at least one predetermined value, and a signal is generated when a predetermined relationship arises between the cumulative pasteurization property change value and the predetermined value(s). A cooked food product is preferably pasteurized at a temperature below the temperature at which it was cooked.

What is claimed is:  
     
         1 . A method of controlling pasteurization of a food product, comprising: 
 (a) at least periodically determining an internal temperature of the product;    (b) at least periodically determining at least one pasteurization property change rate in the product based on the internal temperature of the product;    (c) at least periodically determining a cumulative pasteurization property change value in the product as a function of the at least one pasteurization property change rate and time;    (d) at least periodically comparing the cumulative pasteurization property change value to at least one predetermined value; and    (e) generating a signal when the comparing reveals a predetermined relationship between the cumulative pasteurization property change value and the predetermined value.    
     
     
         2 . The method of  claim 1 , further comprising determining a nominal time of beginning of pasteurization based on the internal temperature of the product.  
     
     
         3 . The method of  claim 2 , wherein the cumulative pasteurization property change is first determined after the nominal time of beginning of pasteurization.  
     
     
         4 . The method of  claim 1 , wherein the internal temperature of the product is determined by calculation based on a time the product is enveloped by a heated fluid, the temperature of the heated fluid, an initial temperature of the product and size of the product.  
     
     
         5 . The method of  claim 4 , wherein the initial temperature of the product is determined by: 
 (a) determining the size of the product;    (b) monitoring an on-time of at least one heating element in the heated fluid until a temperature of the heated fluid after the product is enveloped by the heated fluid substantially equals a starting temperature of the heated fluid; and    (c) determining the initial temperature of the product based on the starting temperature of the heated fluid, the on-time of the heating elements and the size of the product.    
     
     
         6 . The method of  claim 4 , wherein the initial temperature of the product is determined by uniformly preheating the product to a predetermined initial temperature.  
     
     
         7 . The method of  claim 4 , wherein the initial temperature of the product is determined by monitoring a temperature of the fluid after the product is enveloped by the fluid.  
     
     
         8 . The method of  claim 1 , wherein the pasteurization property change rate is a log kill rate of at least one microorganism in the product, the cumulative pasteurization property change value is a cumulative log kill of said at least one microorganism, and the predetermined value is a total log kill of said at least one microorganism required for a desired degree of pasteurization of the product.  
     
     
         9 . The method of  claim 8 , wherein said food product is a proteinaceous food product.  
     
     
         10 . The method of  claim 9 , wherein said proteinaceous food product is uncooked.  
     
     
         11 . The method of  claim 10 , wherein said uncooked food product is meat.  
     
     
         12 . The method of  claim 10 , wherein said uncooked food product is seafood.  
     
     
         13 . The method of  claim 12 , wherein said seafood is selected from the group consisting of fin fish and shellfish.  
     
     
         14 . The method of  claim 13 , wherein said shellfish is oysters.  
     
     
         15 . The method of  claim 9 , wherein said proteinaceous food product is cooked.  
     
     
         16 . The method of  claim 15 , wherein said cooked food product is meat.  
     
     
         17 . The method of  claim 15 , wherein said cooked food product is seafood.  
     
     
         18 . The method of  claim 8 , wherein said food product is a non-proteinaceous food product.  
     
     
         19 . The method of  claim 18 , wherein said non-proteinaceous food product is selected from the group consisting of fruits and vegetables.  
     
     
         20 . The method of  claim 15 , wherein said product has been sliced, ground or mixed after cooking.  
     
     
         21 . The method of  claim 1 , wherein the predetermined value is a predetermined pasteurization property change value for a time at which the comparing takes place.  
     
     
         22 . The method of  claim 1 , further comprising controlling the temperature of the product in response to the signal.  
     
     
         23 . The method of  claim 1 , further comprising chilling the product in response to the signal.  
     
     
         24 . The method of  claim 1 , further comprising adjusting a dwell time of the product in a heated fluid in response to the signal.  
     
     
         25 . The method of  claim 8 , wherein the time at which the comparing takes place is before a predetermined time at which sufficient pasteurization is expected to be completed.  
     
     
         26 . The method of  claim 1 , wherein the product is heated in an enveloping heated fluid, the heated fluid is in at least two different temperature zones, and the product is moved from one of the temperature zones to another of the temperature zones in response to the signal.  
     
     
         27 . The method of  claim 14 , wherein the heated fluid is liquid and the different temperature zones comprise separate baths.  
     
     
         28 . The method of  claim 1 , wherein the product is heated in a liquid bath.  
     
     
         29 . The method of  claim 16 , wherein the liquid bath is vertically perturbated.  
     
     
         30 . An apparatus for controlling pasteurization of a food product, comprising: 
 (a) means for at least periodically determining an internal temperature of the product;    (b) means for at least periodically determining at least one pasteurization property change rate in the product based on the internal temperature of the product;    (c) means for at least periodically determining a cumulative pasteurization property change value in the product as a function of the at least one pasteurization property change rate and time;    (d) means for at least periodically comparing the cumulative pasteurization property change value to at least one predetermined value; and    (e) means for generating a signal when the comparing reveals a predetermined relationship between the cumulative pasteurization property change value and the predetermined value.    
     
     
         31 . The apparatus of  claim 30 , further comprising: 
 (f) means for enveloping the product by a heated fluid;    (g) means for monitoring an on-time of at least one heating element in the heated fluid until a temperature of the heated fluid after the product is enveloped by the heated fluid substantially equals a starting temperature of the heated fluid; and    (h) means for determining the initial temperature of the product based on the starting temperature of the heated fluid, the on-time of the heating elements and the size of the product.    
     
     
         32 . An apparatus for controlling pasteurization of a food product, comprising: 
 (a) a first calculator that at least periodically determines an internal temperature of the product;    (b) a second calculator that at least periodically determines at least one pasteurization property change rate in the product based on the internal temperature of the product;    (c) a third calculator that at least periodically determines a cumulative pasteurization property change value in the product as a function of the at least one pasteurization property change rate and time;    (d) a comparator that at least periodically compares the cumulative pasteurization property change value to at least one predetermined value; and    (e) a signal generator that generates a signal when the comparator reveals a predetermined relationship between the cumulative pasteurization property change value and the predetermined value.    
     
     
         33 . The apparatus of  claim 32 , further comprising a fourth calculator that determines a nominal time of beginning of pasteurization based on the internal temperature of the product.  
     
     
         34 . The apparatus of  claim 32 , wherein the first calculator determines the internal temperature of the product based on a time the product is enveloped by a heated fluid, the temperature of the heated fluid, an initial temperature of the product and size of the product.  
     
     
         35 . The apparatus of  claim 34 , further comprising: 
 (a) an on-time monitor that monitors an on-time of at least one heating element in the heated fluid until a temperature of the heated fluid after the product is enveloped by the heated fluid substantially equals a starting temperature of the heated fluid; and    (b) a fifth calculator that determines the initial temperature of the product based on the starting temperature of the heated fluid, the on-time of the heating elements and size of the product.    
     
     
         36 . The apparatus of  claim 34 , further comprising a preheater that preheats the product to a predetermined initial temperature.  
     
     
         37 . The apparatus of  claim 32 , further comprising a temperature controller for at least periodically controlling a temperature of a heated fluid in which the product is enveloped in response to the signal.  
     
     
         38 . The apparatus of  claim 32 , further comprising an unloading mechanism configured to remove the product from a heated fluid and move the product to a chiller in response to the signal.  
     
     
         39 . The apparatus of  claim 32 , wherein the predetermined value is calculated based on a total log kill required for a desired degree of pasteurization of the product.  
     
     
         40 . The apparatus of  claim 32 , further comprising a dwell time adjuster to adjust a dwell time of the product in a heated fluid in response to the signal.  
     
     
         41 . The apparatus of  claim 32 , wherein the product is heated in a heated fluid in at least two different temperature zones, and the product is moved from one of the temperature zones to another of the temperature zones in response to the signal.  
     
     
         42 . The apparatus of  claim 41 , wherein the heated fluid is a liquid and the different temperature zones comprise separate baths.  
     
     
         43 . The apparatus of  claim 32 , wherein the product is heated in a liquid in a bath containing a perturbator for vertically perturbating the liquid.  
     
     
         44 . The apparatus of  claim 32 , wherein the first, second and third calculators comprise a processor programmed to (i) at least periodically determine an internal temperature of the product, (ii) at least periodically determine at least one pasteurization property change rate in the product, and (iii) at least periodically determine a cumulative pasteurization property change in the product.  
     
     
         45 . A method of controlling pasteurization of a food product, comprising: 
 (a) preheating the product to a predetermined initial temperature;    (b) further heating the product by contact with a heated fluid while maintaining a temperature of the heated fluid at a substantially constant temperature while the product is in contact with the heated fluid;    (c) maintaining the product in contact with the heated fluid for a predetermined time, wherein the predetermined time is a function of a log kill rate of at least one microorganism in the product at the temperature of the heated fluid and a desired log kill level; and    (d) removing the product from contact with the heated fluid at an end of the predetermined time.    
     
     
         46 . The method of  claim 45 , further comprising chilling the product upon removing the product from the heated fluid.  
     
     
         47 . A method of pasteurizing a cooked food product, comprising: 
 heating said cooked food product to a pasteurization temperature (i) that kills microorganisms on or in said food product, but (ii) is lower than a minimum temperature to which the food product was cooked, for at least a time sufficient to achieve a desired level of pasteurization.    
     
     
         48 . The method of  claim 47 , wherein said pasteurization temperature is at least 10° F. below said minimum temperature.  
     
     
         49 . The method of  claim 47 , wherein said pasteurization temperature is within 10° F. of a minimum pasteurization temperature.  
     
     
         50 . The method of  claim 47 , wherein said desired level of pasteurization is at least a 3 log reduction of a selected microorganism contamination of said product throughout an entire volume of said product.  
     
     
         51 . The method of  claim 47 , wherein said desired level of pasteurization is at least a 5 log reduction of a selected microorganism contamination of said product throughout an entire volume of said product.  
     
     
         52 . The method of  claim 51 , wherein said microorganism is at least one member selected from the group consisting of salmonella,  E. coli  and Listeria.  
     
     
         53 . A method of pasteurizing an uncooked non-egg food product, comprising: 
 heating said food product to a pasteurization temperature (i) that kills microorganisms on or in said food product, but (ii) is lower than a minimum temperature at which the food product begins to lose functionality, for at least a time sufficient to achieve a desired level of pasteurization.    
     
     
         54 . The method of  claim 51 , wherein said food product is selected from the group consisting of meat and seafood.  
     
     
         55 . The method of  claim 51 , wherein said food product is selected from the group consisting of fin fish and shellfish.