A pressure cooker is the only safe way to can green beans and other low-acid vegetables at home. Killing spoilage organisms on green beans requires a water temperature of 240 degrees Fahrenheit, which is well above the 212 degrees Fahrenheit where water normally boils. This superheated water temperature can only be achieved in a Presto or other pressure cooker because the pressure raises the boiling point of water.
Selection and Preparation
For pressure-canning green beans, you should select young, tender, slightly immature beans that are free of blemishes. Spoilage organisms grow faster on bruised and blemished beans than on unblemished beans. Wash and prepare your beans as you would for cooking. Remove stems and blossom ends and any strings in string beans. You can leave beans whole or cut into 1-inch pieces. For the best flavor and color, prepare your beans for canning as soon as possible after picking.
Get Your Jars
Only use glass Mason jars intended for home canning. These reusable jars are made of heat-tempered glass that can withstand the temperatures required for canning. Mason jars also have a deep neck and wide sealing surface to ensure an airtight seal. These canning jars come in standard half-pint, pint and quart sizes. Don't use the jars from commercially prepared foods for home canning. These jars aren't intended for reuse and are likely to fail.
You can pack green beans raw or precooked. The raw pack produces a crisper bean, while the precooked hot pack increases the shelf life of your beans. For a raw pack, pack your beans tightly in a hot sterilized Mason jar, then fill the jar with boiling water, leaving an inch of headroom, and put on the sealing lid. For a hot pack, precook your beans by placing them in boiling water for 5 minutes. Pack the hot beans loosely in the jar and fill with the water you boiled the beans in, leaving an inch of headroom, and put on the lid. With either pack, you can add 1 tsp. of canning salt if desired.
A pressure cooker has an interior rack to keep the jars from touching the vessel's bottom. Pour about 3 inches of hot water in the bottom of the cooker. Arrange the filled jars on the rack and seal the pressure cooker. Apply heat and allow steam to vent for 10 minutes before pressurizing. If using a dial-gauge cooker, process at 11 lbs. pressure (12 lbs. above 2,000 feet altitude) for 20 minutes for pint jars and 25 minutes for quart jars. With a weighted gauge cooker, process at 10 lbs. pressure (15 lbs. above 1,000 feet altitude) for 30 minutes for pint jars and 40 minutes for quarts. Turn off heat and allow cooker to cool completely before opening lid.