PRESSURE CANNING
Home canning season is nearly upon us, and the boiling water and pressure canners are being dusted off and readied for use. The goal of home canning is to preserve food for future use by preventing spoilage. The high water content of foods makes them very perishable for a number of reasons including: the growth of microorganisms, the activity of food enzymes, reactions with oxygen, and moisture loss. Most microorganisms (bacteria, yeasts, and molds) are difficult to remove from food surfaces. Washing helps, peeling and blanching help even more, but it is vital to use the most current recommended processing procedures and times. Whether a food should be processed using a pressure canner or boiling water canner depends on the acidity of the food. Low-acid foods include high protein foods, and ALL fresh vegetables except tomatoes and must be processed using a pressure canner.
Pressure canners for home use were extensively redesigned in the 1970’s. Earlier models were heavy-walled kettles with clamp-on or turn-on lids. Today’s models are lighter weight, thin-walled kettles, most have turn-on lids fitted with gaskets, have removable jar racks, a dial-gauge, an automatic vent/cover lock, a vent pipe covered with a safety valve and a safety fuse. Only use canners that have the Underwriter’s Laboratory (UL) approval to ensure their safety.
In Nebraska home canners need to check the elevation where they will be canning. For elevations above sea level, it is necessary to add additional time or pressure when processing food to obtain a safe product. Canning directions for each food will give proper processing times and pressures for elevation adjustments.
There are two kinds of gauges to indicate pressure, dial and weighted.
Weighted gauges indicate and regulate the pressure and are usually designed to ‘jiggle’ several times a minute or to keep rocking gently when they are maintaining a pressure of 5, 10, or 15 pounds. Reading your manufacturer’s directions is the only way to know how to use your weighted gauge. These gauges do not need to be tested annually.
Dial gauges indicate the pressure and usually have a counterweight or pressure regulator for sealing off the vent pipe to pressurize the canner. This weight should not be confused with a weighted gauge, it will not rock or jiggle. Pressure reading on a dial gauge canner are the only way to know the pressure in the canner.
Pressure canners are deep enough for one layer of quart or smaller jars or deeper to hold two layers of pint or smaller size jars. The USDA recommends canner be large enough to hold at least 4 quart jars to be considered a pressure canner.
Accurate dial gauge readings are a vital part of successful pressure canning at home and need to be checked for accuracy every year.
Gauges can be tested for accuracy at most Nebraska Extension Offices. Call your local Nebraska Extension Office to see if testing is done there. Generally, canner lids and gauges can be dropped off at one of the office locations and they will be tested and return to you a few days later. Do call the office you will be taking your gauge to know their hours and availability to test your gauge.
For more information on current home canning procedures, contact your local Nebraska Extension Office or on the web at go.unl.edu/canning Nebraska Extension, In Our Grit, Our Glory.