[TomNJ]

Worth,

I read a study some years ago on the time and temperatures needed to kill botulism spores. I don’t remember where I found the study but recall that they added spores to jars filled with neutral water (pH=7) and processed them. As I recall, the spores could survive up to 20 hours in a boiling water bath! That blew my mind as I used to think boiling temperatures would kill everything.

Pressure canning at 10 lbs. (240°F) killed the spores in something like 12 minutes, and at 15 lbs. (250°F) in under three minutes. Now one must remember that the spores need to reach and hold those temperatures, and it takes some time for the heat to fully penetrate the food in the jar. The larger the jar and the thicker or chunkier the food, the longer it takes for the heat to penetrate. And if some spores are in the center of a quart jar and stuck between a couple of pieces of onion for insulation, even more time is needed. This is why canning recipes often call for processing times of 30 to 60 minutes or more, even at high pressures, to allow for these variables.

The alternative to killing the spores is to establish conditions under which they cannot hatch, such as increasing the acidity or freezing. The spores themselves are common and harmless (except to infants), but if allowed to hatch the bacteria inside the spores create the deadly toxin as they grow. Spores can hatch if they are stored at temperatures of 40-140°F, have moisture, food, little to no oxygen, and low acidity (pH >4.6). These conditions are common in many canned foods, hence the need to kill the spores by pressure canning. High acid foods, however (pH <4.6) can be canned in a boiling water bath as the acidity prevents the spores from hatching.

High acid foods include foods pickled in vinegar (>50%), acidified foods (enough added vinegar, lemon juice or citric acid) and many fruits. Low acid vegetables such as beans, asparagus, beets, carrots, potatoes, onions, garlic, meats and many more require pressure canning. Tomatoes, the most commonly canned vegetable, are on the border of high and low acidity and may need special attention.

Generally speaking, pure tomato products acidified with a little lemon juice or citric acid are safe for boiling water processing. If, however, you add low acid vegetables to the tomatoes, such as onions, peppers, celery, and garlic so common to making sauces and salsas, then you risk raising the pH to unsafe levels. These products should be acidified and pressure canned. Following approved recipes is a safe way to go, even though I do not. I have been canning my own tomato salsa recipe for over 40 years, even though it differs from approved recipes, but by acidifying with citric acid and pressure canning for 45 minutes at 15 pounds I am comfortable. Your mileage may vary, and I am not suggesting anyone just create their own recipes willy nilly. If you are going to can then you should educated yourself as to the proper procedures and risks.

Some websites in my opinion exaggerate the risks and chase people away from this rewarding hobby. A couple other points about botulism. While a very nasty disease that can leave one paralyzed, it is rarely deadly with a 96% survival rate. Usually by the time one notices the symptoms (blurry or double vision, trouble speaking, and difficulty breathing) they get themselves to a hospital where the progress of the disease can be stopped, but not reversed. It can take many months to recover.

It is also very rare with only a few cases per year among the 20+ million home canners in the USA, mostly caused by low acid foods being boiling water bath canned. And finally, the toxin if formed can be destroyed by boiling the product for 15 minutes, although one must be very careful handling such a product.

Still botulism should not be ignored and all home canners should read up on proper canning techniques rather than following grandma’s recipes and methods. Grandma may have survived, but you may not. If you are going to do it, do it right.

TomNJ/VA