Tuesday, October 2, 2007

Canning

This week Court and I decided to try a new cooking experience (new for me not for her): Canning. For those of you who don't really know how it works, canning is actually fairly straightforward. The goal is to generate relatively sterile goods that have a long shelf life. We chose two recipes that come from my relatives in New Brunswick, Canada. The first recipe is an old family favorite that my grandmother makes: dilly beans (really they are called dilled beans but we always called them dilly beans as kids). The second recipe we canned was my Aunt Kathy and Uncle Lenny's tomato salsa. We were lucky enough to get to try some of this salsa when we were recently up in Canada for my cousin Megan's wedding.

To begin with, we heated water in a large (18 qts. I think) pot to 180 degrees Fahrenheit. Into this water we added all of the canning jars and lids we were going to use. The reason for not boiling the jars is that the lids have a rubberized seal that doesn't like temperatures that high. However, 180 degrees is sufficient to kill most bacteria (there is a notable exception that I will discuss later). We held the jars at 180 for 10-15 minutes (until immediately before we needed them). We then added the ingredients into the jars. The ingredients were all either boiled or covered with a boiling liquid to about 1/2" from the top. Being careful not to touch the inside or the seal of the lids we put a lid on each jar and then screwed on the threaded lid until they were finger tight. The jars are then dropped into boiling water in the big pot for several minutes (5 in our case) to "process" the jars. Basically you are raising the temperature in the jar to do two things. First you are essentially Pasteurizing the contents of the jar to kill any bacteria that have snuck in, and second you are heating the air in the jar, which expands and when the jar cools creates a vacuum seal. The jars are then allowed to cool and you now have a canned food with a longer shelf life.

The type of canning we used is boiling canning. This type of canning is good for high acid foods like tomatoes, pickles, jams and jellies and acidic fruits. For low acid foods like vegetables you have to use a pressure canning method. Pressure canning utilizes what is essentially a pressure cooker to raise the temperature of the cans above the 212 degrees Fahrenheit. The reason for this is that nastiest of nasties, Clostridium botulinum. C. botulinum is the causative agent of botulism, a deadly form of food poisoning. Why is the boiling method of canning not sufficient to combat C. botulinum? It has to do with the biology of this specific bacteria. Clostridia family members belong to a group of bacteria that under adverse environmental conditions form what is called a "spore". This spore is highly resistant to the things we like to use to kill bacteria. As a side note Bacillus anthracis, the causative agent of anthrax also belongs to this group of bacteria. Boiling is not sufficient to kill C. botulinum spores, which if they get into your canned goods will hatch out into mature bacteria that will produce the toxin that gives you botulism. High acid foods are safe because C. botulinum can't grow in acidic environments, so boiling is sufficient.

We are waiting to see how the dilly beans turn out (they need some time to pickle) but we know the salsa is good. If I get a chance I'll put the recipes we used up on the blog sometime in the future.