As a general rule, it’s the acidity of an ingredient that determines the method of canning that should be used. Low acid foods (ph greater than 4.6), such as vegetables and meat, require processing in a pressure canner in order to be preserved safely at home. Unless you have unlimited freezer space, learning to use a pressure canner expands the options for the winter pantry.

With 18 pounds of green beans from Fairwinds Farm in Bowdoinham, ME, on hand, the fourth class in the Master Food Preserver Program focused on several different ways of preserving this low acid vegetable — through freezing, pressure canning (raw and hot pack), and pickling.

The raw pack process, also known as cold pack is just what it sounds like — packing the jars with uncooked beans  — and goes quickly. Simply wash the beans, trim and cut, and pack the jars tightly until you run out of beans or jars, whichever comes first.

A quarter teaspoon of canning salt was added to each pint-sized jar for flavor, with boiling water following, and leaving a 1 inch headspace. Once the jars were covered, they were placed in the pressure canner. Above, you can see the pressure canner being loaded with a second tier, another canning rack placed in between to keep the two levels separate. These raw-packed green beans were then processed at 10 pounds of pressure for 20 minutes.

Our teacher, Kathy Savoie, brought in two different types of weighted-gauge pressure canners for us to use. The one above is from Presto and is designed to rock gently, while the one below is from Mirro and “jiggles” several times a minute once they’re up to pressure. It can be mystifying what these terms mean and, as both these canners came up to pressure, we appreciated the opportunity to experience firsthand what “rocking gently” and “jiggling” sounds like.

Another way to regulate the pressure in a canner is through a dial gauge. I use what’s called a dual-gauge canner, which has both a dial and weighted gauges, and allows the user to track pressure visually as well as by sound.

These are the hot-packed green beans being carefully removed from the canner and set aside to cool. Notice how Kathy is lifting the jar straight up from the pot before setting it down; the liquid in the jars was still boiling inside, and tilting the jars may interfere with the vacuum seal as it forms.

Rather than packing the jars raw, these hot-packed beans were covered with boiling water and left to boil for 5 minutes before transferring to jars. The extra step preshrinks the beans, allowing more to fit in the jar; it also helps to prevent floating once the jars of beans are processed. Hot-packing as a technique also improves shelf life, further preserving color and flavor, especially with foods that are processed with a boiling water canner.

After processing, these jars were left to cool undisturbed for at least 12 to 24 hours. The two jars of raw-packed beans on the left seem indistinguishable from the hot-packed one to the right. Once the rings were removed, the hot-packed jars were noticeably more full than the raw-packed ones; the raw-packed beans had shrunk more during processing.

Also known as the “olive of Maine,” dilly beans are another way of preserving green beans, especially if you don’t have access to a pressure canner. The inclusion of vinegar brings up the amount of acidity, allowing these spicy pickles to be processed safely with a boiling water canner.

There seem to be two distinct camps when it comes to preserving green beans — some prefer them canned, while others prefer them frozen. In a side by side comparison, there didn’t seem much difference between the raw-packed (left) and hot-packed (middle) beans, while the frozen ones had retained both more color, flavor and texture. The closest in texture to fresh were the dilly beans, which were raw-packed and processed for only 5 minutes, compared to 20 minutes for the pressure-canned ones.

Resources:
– Preserving Food: Freezing Vegetables
– Preserving Food: Canning Vegetables
– USDA Canning Guide: Selecting, Preparing and Canning Vegetables

This is one in a series of posts following the Master Food Preserver Program offered by the University of Maine Cooperative Extension.