Michigan State University Extension
Preserving Food Safely - 01600947
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.
EXAMPLE OF USING TABLES FOR DETERMINING PROPER PROCESS TIMES
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 tables:
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 canner.
RECOMMENDED PROCESS TIME FOR PEACHES IN A WEIGHTED-GAUGE 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