Rachel Forrest attended the canning demonstration at the Portsmouth Farmers’ Market and wrote about the things she learned:
Recently, I got some information on how to can correctly at the Portsmouth farmers market from Claudia Boozer-Blasco, extension educator in Family and Consumer Resources, with the University of New Hampshire Cooperative Extension in Rockingham County.
Now, I know how to can veggies and sauces. I’ve done it before, but one thing I never learned were some of the reasons why certain processes are done to avoid illness in canning. I’m one of those people who always asks, “OK, so why did you do that?”
The water bath process is for high acid foods — your jams, applesauce, pickled beets, tomatoes. First thing I didn’t know — the acid and the boiling point work together to eliminate the botulism. With pressure cooking canning, used with lower acid foods like beans and corn, it’s temperature and pressure. The recipe will tell you which one to use.
Second thing I didn’t know — use a book with canning recipes published after the mid-1980s because it reflects the changes made in recipes since the USDA et al tested the recipes and let us know the science behind canning.