A
pressure canner is the special piece of equipment you will need for processing
low-acid food (i.e. non-pickled vegetables, meat, etc.) safely at home.
They
operate similarly to a pressure cooker – in that food is heated at a high
pressure (thus high temperature) environment.
Instead of cooking the food directly in a pressure cooker, the food is
packed into jars then processed at a certain pressure and time period (varies
with different food items). This processing mimics commercial canneries, where
food is heat treated to remove contaminants, cook food and vacuum seal at the
same time.
Modern
pressure canners are MUCH safer than older models – they are lighter and have a
safety fuse (to release pressure when it climbs too high). They have 1-2 racks
inside, one for the base (to prevent jars bouncing on the base) and a second
rack if double stacking jars (to prevent jars bouncing against one another).
The major brands are also easy to find replacement parts – such as dial gauges,
rubber gaskets (which sit inside the lid), weights, etc.
Always refer to your
manufacturing booklet to learn how to operate your pressure canner, as models
and brands do vary and ALWAYS follow a pressure canning recipe.
Fresh
produce naturally contains bacteria, if acid is not present then pressure
canning is required to prevent botulism. This high temperature (created by the
higher pressure level) is what kills these microorganisms. Pressure canners
process your low acid food at 240°F (115°C) at sea
level, which is why pressure levels (thus the temperature) is changed for
different altitudes, as water boils at different temperatures at higher/lower
altitudes.
BEFORE starting pressure canning, ensure you understand how
your canner works (you can run a small practice batch of vegetables or even
water in jars the first time) and allow enough time to prepare, heat jars and
process them before removing them from the canner.