About Botulism

Of Canning, Bargains, and Safety: Canning is a bargain compared to buying store food. Being a frugal-minded person, in previous editions of this book I used to look for ways to make canning even cheaper. No more. I understand better now the risk of botulism. Over 700 people have died of botulism since folks started canning in this country. (In 1992 in the United States, 10,000 persons were killed by handguns, which puts that in some perspective.) Last year [1976] in the United States, there were 20 reported incidents of botulism involving 30 persons and resulting in 7 deaths. One death from botulism is one too many, because they could all be prevented by following proper canning procedures. In this new edition I've painstakingly given you only the safest procedures, and the canning instructions scattered throughout the book have all been reviewed by true experts (which I am not) and either approved, changed so as to be approved, or dropped. How Botulism Grows: Botulism poisoning is caused by a certain kind of bacteria (Clostridium botulinum) that is practically everywhere in the soil. The food poisons specialists call the beastie "bot" for short. You're safest, and most likely correct, to assume that bot is present on your garden food too. The bacteria themselves are not poisonous. But it's a good idea to keep your baby out of the dirt because children under age 1 don't handle them as effectively as older people do. Bot won't grow in the refrigerator. When cooked, bot bacteria die easily, but their seed forms, called "spores," are extraordinarily resistant to heat. They aren't resistant to high acid and sugar, however; those inactivate the bot spores. (We're beginning to learn that botulism can survive in mildly acid products.) That's why high-acid foods, sweet preserves, and pickled foods can be canned using a boiling-water bath.

But if bot spores get a combination of insufficient heating, no air, low acid, and low sugar content, then they are in bot heaven. The area inside a sealed jar is a no-air place. And if it isn't jam or pickles or fruit, it's a low-acid food. In that case, you have to pressure-can. That extra heat is the only remaining line of defense. Bot spores can resist a lot of boiling, but they are reliably killed by the 240°F temperatures achieved by heating under pressure— "pressure canning."

"High Acid" or "Low Acid"? Different foods naturally contain varying amounts of acid. As the acid strength increases, the temperature or time needed to kill the beasties decreases. High-acid foods can be processed more quickly than low-acid foods. High-acid foods can also be processed at a slightly lower temperature—merely the boiling point of 212°F—whereas low-acid foods must be processed at 240°F to be safe. And only inside a pressure canner can you get a sustained temperature that high. So low-acid foods such as beans and corn must be pressure-canned to destroy the spores of the bot bacteria. Spores are the most resistant seed form of the beasties. Unless you roast to death all the spores of the bacillus botulinus in low-acid foods, the remaining spores grow As they grow they give off an invisible, tasteless, but powerful toxin (poison).

"Bot" toxin: This toxin is one of the most deadly poisons known on earth. If you merely touch a finger to it and touch that finger to your lips to taste, you could get enough to kill you. It is said that 16 ounces of bot toxin would be enough to kill the entire world's population. The toxin itself doesn't trumpet its presence. You can open the jar and it may look and smell fine. It is, however, destroyed by heat. That's why it is recommended that all low-acid home-canned foods be boiled 15 minutes with the lid on before tasting or serving.

The symptoms ordinarily appear within 18 to 36 hours of poisoning but have been known to take as long as 8 days to become evident. What are the symptoms? At first nausea and vomiting, later blurred vision, dry throat, and difficulty swallowing. Then comes progressive weakness that can paralyze the respiratory tract as well as the limbs. The poison does that because it affects the nervous system, breaking down communication between motor nerves and the muscles.

The botulism cases that I've heard about involved pickled beets, tomatoes (for which pressure canning has not in the past been recommended), spicy tomato products such as salsas and taco sauce (the problem being the false assumption that the "hotness" will preserve the food), mushrooms, olives, asparagus, beans, cabbage, carrots, and peppers. In rare cases, it has also happened with pressure-canned food.

Researchers are just now discovering that bot bacteria can survive in the presence of more acid than had previously been believed. Some standard canning directions used to say to simply bring pickled beets, for example, to a boil and then hot-pack them. Some people got bot poisoning from doing that. Now we know it's not safe to can pickled foods without a water-bath canning time. So therein lies the risk of using old recipes. Some cooks thought that because salsa was so hot, it could be canned without much processing. Again, now we know better because of a bot case. Spicy hot doesn't bother bot.

Now that I've practically scared you to death, let me revive you with success stories. Many's the family that cans 700 or more quarts a year, year after year, with great success. Florence Ward, Quilcene, WA, wrote me, "I have canned for over 50 years. When we lived on a dairy ranch for 17 years, I used to can around 600 quarts of fruit and meats each year. Pickles too. We had five children—all married long since. Fruit, such as peaches and apricots, cherries and pears—I've canned thousands of quarts of them."

Sandra Oddo, Hurley, NY, wrote me, "A year ago I got a pressure canner from Sears for $24 (can 4 quarts, hold 8) and now I wouldn't be without it. It's too small for mass canning, but perfect for what's left of the lentil soup after we've had a ham—canned soup heats faster than frozen, too—and for food deliberately mass-cooked so there will be leftovers for pressure canning, which saves later work. It saves enormously on fuel. Would you believe that 45 minutes turns a 3-year-old rooster into a tender stew?"

From Maureen Darby, Leslie, AK: "The cost of the canner is easily offset by the fact that it requires far less fuel to operate than it would to can in boiling water. I even can fruit under pressure. I do have to watch it closely, but it's better than waiting to boil the quantity of water needed to cover the jars in a water bath. We don't own a freezer. The initial cost and the cost of the electricity to run them make them impractical—besides the constant worry of power shortage."

So be careful when you can. But bot poisoning is rare—an average 7-30 cases a year nationwide among about 100 million canners. It's rare because of all the careful home canners who read the rules that come with canning equipment and in good canning books, and follow them, and use pressure canners. Still, that's 7-30 too many sick people. Those safety rules are all very clearly stated here, too. Please, better safe than sorry. Follow them!

Continue reading here: Canning Methods and Supplies

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