By Andrew Skousen – Originally at World Affairs Brief and reprinted here by permission.
Most canning sites err on the side of caution and recommend long processing times and, preferably, a steam canner. As I noted in the last preparedness tip, I prefer steam bath canning for faster processing with less energy, but you have to know its limits and the bacteria you are fighting. For home canning the main fear is botulism and here’s why:
Cl. botulinum is a bacterium that is all around us in soils and the environment. It survives difficult conditions by forming spores that are resistant to heat, chemicals and drying. Under favorable conditions the spores develop into bacteria (germination) and the bacteria grow in the food. During growth they produce a potent neurotoxin (nerve toxin called botulinum toxin) that causes the illness [botulism].
The botulinum bacteria itself is not the problem—our own gut can handle them in small amounts—it is their neurotoxic byproduct, especially when it accumulates in food under the right conditions: no air, room temperatures, neutral pH, low salt, and low sugar. Unfortunately, some bottled preserves (principally meat and vegetables) sitting on the shelf have these exact conditions. Botulism symptoms include blurred or double vision and gradual muscle paralysis. In extreme cases it can paralyze the lung muscles and cause death (artificial respirators are used now to save most patients). Recovery can take months while the body regrows the damaged nerve endings.
Some sites report that botulinum bacteria may not always cause a bad smell or taste. But don’t fear this invisible threat yet. To ensure botulinum spores are killed all portions of the food must be heated to 250 deg F (121 deg C) for 3 minutes. These temperatures can only be reached with a pressure canner. So why didn’t our great-grandparents get sick more often using water bath and steam canning? They found other ways of inhibiting the spores: Acidic environments (pH less than 4.6), high sugar (>50%) and/or high salt (>7%) inhibits the spores from developing. That is a lot of sugar or salt, so acid is really your best bet.
Many of our great grandmothers canned meat and veggies without a pressure canner, but I suspect they usually cooked these when adding to a meal. The botulism bacteria and its neurotoxin are both neutralized by heat—even just simmering the jar’s contents at 176 deg F (80 deg C) for a few minutes does the job. Don’t throw out suspicious food in hard times, just cook it well. Unfortunately the fear of putting a recipe or instruction out there that might allow for botulism has caused many to throw out their old family recipes and processing instructions so we are mostly stuck with pressure canner instructions for these products.
Fruit and most tomatoes are acidic enough for atmospheric steam canning (despite what you hear), but some hybrid tomatoes are bred to be so sweet they need two tablespoons of lemon juice per quart jar to get the pH level low enough. Many people also add lemon juice to applesauce for the same reason.
A hand-crank applesauce/tomato sauce mill is very useful in home canning. We also pull out the steam juicer for grape and berry juices. Other tools are also extremely valuable depending on your produce: a cherry pitter, pear corer, jar lifter to avoid scalding when removing hot jars and a large-mouth funnel (that fits small and large mouth jars) as seen on Victorio’s website. They are available at kitchen supply stores (and hardware stores seasonally). Next week I’ll cover the options for canning lids including some that are reusable