Selecting the Correct Processing Time

Michigan State University Extension
Preserving Food Safely - 01600947

Selecting the Correct Processing Time

     When canning in boiling water, more processing time    
is needed for most raw-packed foods and for quart jars      
than is needed for hot-packed foods and pint jars.          

     To destroy microorganisms in acid foods processed in   
a boiling-water canner, you must:                           

     *  Process jars for the correct number of minutes in   
        boiling water.                                      
     *  Cool the jars at room temperature.                  

     The food may spoil if you fail to add process time     
for lower boiling-water temperatures at altitudes above     
1,000 feet, process for fewer minutes than specified, or    
cool jars in cold water.                                    

     To destroy microorganisms in low-acid foods processed  
with a pressure canner, you must:                           

     *  Process the jars for the correct number of minutes  
     *  Allow canner to cool at room temperature until it   
        is completely depressurized.                        

     The food may spoil if you fail to select the proper    
process times for altitudes above 1,000 feet, fail to       
exhaust canners properly, process at lower pressure than    
specified, process for fewer minutes than specified or      
cool the canner with water.                                 

  Process times for half-pint and pint jars are the same,   
as are times for 1-1/2 pint and quart jars. For some        
products, you have a choice of processing at 5, l0, or l5   
PSIG. In these cases, choose the canner pressure (PSIG)     
you wish to use and match it with your pack style (raw or   
hot) and jar size to find the correct process time. An      
example of how to select the proper process follows.        


     Suppose you are canning peaches as a hot-pack in       
quarts at 2,500 feet above sea level. Since specific        
process times may vary with (l) the type of canner          
Used,(2) the style of pack,(3) the jar size and (4) the     
altitude where you live, follow these steps to find the     
recommended process time from one of the three following    

     1.  Locate the correct table for your type of canner.  
         Look down the column labeled "Style of Pack" on    
         the left side of the table and locate the correct  
         line for hot-pack and quart jars.                  
     2.  Look across the top to find your altitude. To      
         determine the correct time for you, look down the  
         altitude column until you intersect the row you    
         selected in Step 1.                                
     3.  The process pressure is 10 PSIG.                   
     4.  Look under process time. All jar sizes and styles  
         of pack require 10 minutes.                        
     5.  Therefore, at 2,500 feet, process peaches for 10   
         minutes at 10 PSIG in a weighted gauge pressure    

PRESSURE CANNER                                             

Style                Canner Pressure (PSI) at Altitudes of  
of        Jar       Process        0-                Above  

Pack      Size      Time         1000 ft.        1001 ft.   

Hot       Pints     10 min.         5 lb.           10 lb.  
Hot       Quarts    10              5               10      

Raw       Pints     10              5               10      
Raw       Quarts    10              5               10      
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