Vegetables are low in acid and must be processed in a steam pressure canner at the number of pounds needed to achieve 240 degrees F. The pressure required at sea level is 10 pounds. For higher elevations, add ½ pound of pressure for each 1,000 feet above sea level. For example, at 5,000 feet, 12.5 pounds of pressure is required to reach 240 degrees F. This is necessary to supply enough heat to destroy bacteria that cause botulism. Do not take short cuts in recommended preparation or processing procedures. Failure to properly process low-acid foods in a pressure canner can result in botulism, which, if not treated, can be fatal.
Prepare Equipment and Jars
Pressure canner. Make sure your pressure canner has a tight-fitting cover, clean exhaust vent (or petcock) and safety valve, and an accurate pressure gauge. There are two types of pressure gauges; weighted and dial gauges. Weighted gauges need only to be cleaned before using. Dial gauges need to be checked for accuracy. Clean them each season before use, more frequently if used often.
Use a pressure canner that holds at least 4 quart jars. Smaller pressure canner-saucepans are not recommended for home canning as they heat up and cool down too quickly to ensure adequate heat penetration using the processing schedules specified in this fact sheet.
Canning jars and lids. Discard any jars and closures with cracks, chips, dents of rust. Defects prevent airtight seals. Use jars designed specifically for home canning. Commercial food jars (mayonnaise, coffee, etc.) breaks easily in pressure canners and may not seal. Use only the half-pint, pint, and quart sizes. Wash jars in hot, soapy water and rinse well before using. Prepare metal lids as manufacturer directs.
Elect only fresh, young, tender vegetables for canning. The sooner you can get them from the garden to the jar, the better. For ease of packing and even cooking, sort the vegetables fro size and ripeness. Wash all vegetables thoroughly, whether or not they will be pared. Dirt contains some of the bacteria hardest to kill. Don’t let vegetables soak; they may lose flavor and nutrients. Handle them gently to avoid bruising.
Fill and Close Jars
The hot-pack method is recommended for all low-acid foods, including vegetables. Some vegetables may also be packed raw. See individual directions in Table 1 to determine which method to use.
Raw pack. Put cold, raw vegetables into jars and cover with boiling water. Pack most raw vegetables (except for starchy ones) firmly into the jars. Loosely pack starchy vegetables such as corn, peas and lima beans, because they expand during processing.
Hot pack. Heat your vegetables in water or steam them before packing. Then cover with the boiling booking liquid or water. Loosely pack the hot food.
Either pack. Use enough liquid to fill around and cover the food. Read the directions for each vegetable for the amount of space to leave between the top of the food and the top of the jar. This head space is important to obtain a good seal.
Salt may be added to each jar, if desired. Salt is added only for seasoning and does not help preserve the food. If salt is used, canning salt is recommended to prevent the liquid from turning cloudy. Use ½ teaspoon salt per pint.
To remove any trapped air, insert a nonmetal spatula between the food and the jar. Slowly turn the jar and move the spatula up and down to allow air bubbles to escape. Add more liquid if necessary to obtain the proper headspace. Wipe the jar rim with a clean damp paper towel to remove any food particles. Place pretreated lid on the jar. Screw on the band fingertip tight.
Process in Pressure Canner
Read the manufacturer’s instructions for your pressure canner. General directions for using steam pressure canners are as follows:
Put 2 to 3 inches of hot water in the canner. Place filled jar on the rack, using a jar lifter. Fasten canner lid securely. Leave weight off vent port or open petcock.
Maintain a high heat setting and exhaust steam after 0 minutes. Place weight on vent port or close petcock. The canner will pressurize in the next three to five minutes.
Start timing the process when the pressure reading on the dial gauge indicates that the recommended pressure for your altitude has been reached, or when weighted gauge begins to jiggle or rock. Regulate heat under the canner to maintain a steady pressure at or slightly above the correct gauge pressure. Quick and large pressure variations during processing may cause unnecessary liquid losses from jars. Weighted gauges should jiggle or rock slowly throughout the process.
When the timed process is completed, turn the heat, remove the canner from the heat if possible, and let the canner depressurize. Do not force cool the canner by pouring cold water over it. When the pressure registers zero, wait a minute or two, then slowly open the petcock or remove weighted gauge. Unfasten the cover and tilt the far side up so steam can escape away from you.
Carefully remove jars from canner and place on rack, dry towels or newspaper. Allow jars to cool untouched, away from drafts, for 12 to 24 hours before testing seals.
Day-After Canning Jobs
Test the seals on the jar lids. Press flat metal lids at the center of the lid. Lids should be slightly concave and should not move. Remove screw bands. Label sealed jars with contents, canning method and date. Store in a clean, cool, dry and dark place.
Treat unsealed jars of food as fresh. The food can be eaten immediately, refrigerated, frozen or reprocessed. If you reprocess the food, repeat the entire process.
On Guard Against Spoilage
Bulging lids of leaking jars are signs of spoilage. When you open the jar, look for other signs, such as spurting liquid, an off odor or mold.
Low-acid canned vegetables and meats can contain botulism toxin without showing signs of spoilage. As a safety precaution before tasting, boil all home-canned vegetables in a saucepan for 10 minutes, plus 1 minute for each 1,000 feet above sea level (15 minutes at 5,000 feet). Boil home-canned spinach or corn for 20 minutes. If the food looks spoiled, foams or has an off odor during heating, discard it.
Dispose of all spoiled home-canned food where it will not be eaten by people or pets. Boil all spoiled low-acid canned food for 30 minutes before disposing of it. This destroys any toxin present and prevents its spread.