My recent article on botulism generated some discussion among homebrewers. I’ve gathered most of the questions I’ve been asked in the comments section and via email here. I’ve also added a couple that might occur to someone with an interest in the subject. The original article also answers some potential questions.
Background Information
Clostridium botulinum, the bacteria that produces the botulinum toxin, can grow in environments from 40–120 °F (4.4–49 °C) when the pH is above 4.6, the oxygen level is below 2%, and the water activity is above 0.85. (Solutions with 22 g of salt per 100 g of water or 67 g of sugar (sucrose) for each 100 g of have water activities less than 0.85.) The conditions for the growth of C. botulinum are met by boiled wort stored in a sealed container, but not beer.
Botulism bacteria can grow and produce enough toxin to kill a person in 3 days. And, the spores of C. botulinum are not killed by boiling. Commercial food packagers are required to heat low-acid foods (foods over pH 4.6) to 250 °F (121 °C) for 3 minutes to kill all the botulism spores. Boiling the liquid at 240 °F for 20 minutes, which can be done at sea level with a pressure cooker set to 10 PSI, and subsequently heating the food to above 185 °F (85 °C) for more than 5 minutes before serving are the guidelines given for home canners.
So, to be on the safe side, wort should be pitched the day after it is made. This way, the pH of the fermenting beer can drop below 4.6 and you will be safe. There is not a single case of botulism attributed to making beer in the normal manner. (Prison “brewers” have concocted batches of pruno that has been tainted, but these cases usually involve the use of root vegetables stored improperly before the beverage is fermented.)
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