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.
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.)
Q and A
So no-chill brewing is bad?
The no-chill procedure is not the problem. The risk only develops if you store your wort for longer than a couple days without pitching. Also, everything in this article applies to improperly canned starter wort as well.
Where did you get your ideas? What do the experts say?
These aren’t my ideas. They are the standard recommendations for people who can their own foods, as laid out by the USDA in their 2009 canning guide. The FDA requirements for commercial food packagers mirror these recommendations. If the USDA and FDA aren’t experts, I don’t who would be. (Additionally, a homebrewing friend who recently earned a degree in food science had read my article before it was published. His major professor was an expert in food toxins.)
What about wine or mead? Wine and mead must isn’t even boiled . . . and you can’t give honey to babies because it has botulism spores in it, right?
The pH of both wine and mead musts are below 4.6 initially, and won’t support the growth of C. botulinum.
How can babies be poisoned by honey, but not adults?
Adults have gut bacteria lining their entire gastrointestinal tract. If you ingest botulism spores — and you do, on a regular basis — they will pass through your system before the spores can be activated, grow, and produce toxin. The bacteria in your gut don’t allow the C. botulinum to gain a “foothold.” In addition, the pH of your stomach is low, so the spores would not activate there. However, the pH of your lower GI tract is much higher and the spores can become active there. The pH of human fecal material is 7–7.5 for a healthy individual. (Now aren’t you glad you read this website?)
The gastrointestinal tracts of babies do not yet have a full complement of bacteria, and the botulism bacteria can colonize sections of their lower gut and kill them.
What about liquid malt extract?
Liquid malt extract is approximately 80% solids. There isn’t enough water activity to support the growth of botulism (or most other spoilage microorganisms).
What about those beer kits that are just packaged wort?
This is a great question. To get an answer, I spoke to Tim Vandergrift. When Tim worked at WineExpert, he helped develop their line of Baron’s Beer Kits. These kits contain 7.5 L (2.0 gallons) of concentrated wort, which is diluted to 23 L (6 gallons) in a sanitized fermenter and pitched with yeast. These kits are stored, unrefrigerated, on the shelves of homebrew shops until they are used.
When developing these products, botulism was a primary concern. To make the wort safe, it was subjected to two Pasteurization runs — the first to activate any botulism spores that might be present, and the second run to kill the active bacteria.
Other companies offer wort kits as well. Tim wasn’t sure how each was produced. However, if they are sold in the US, they would have to meet FDA packaging requirements and somehow address the problem of botulism. (And most countries have similar guidelines.)
What about sour beers that are “pitched” by exposure to airborne microorganisms?
As long as they start fermenting within 3 days such that the pH of the fermenting beer drops below 4.6, they will be fine. Commercially, sour beers that are spontaneously fermented are left to cool overnight, where they are inoculated by airborne “bugs.” But they are then pumped to barrels, where yeast and bacteria from previous fermentations are present.
What about E. coli and other pathogens?
Strains of pathogenic E. coli, and many other bacterial pathogens are killed by boiling temperatures. There are a few other sporulating bacteria, such as some species of Bacillus that can cause illness in humans — and will grow under the same conditions as C. botulinum — but botulism is the biggest concern.
What about adding Campden tablets? Will they kill botulism spores?
Campden tablets are used to sanitize wine musts. They are not effective at wort pH (or even beer pH).
But the risk is low, right? We all take risks everyday, don’t we?
We do face risks every day, but we can be smart about managing risk. The risk of botulism poisoning is low, but the consequences when it does happen are very high. Botulism can kill you. In addition, you can eliminate this risk simply by pitching your yeast the next day. You’ve got everything to gain — including your health, and a beer to toast your good health with — by pitching your yeast promptly. There is nothing to gain by letting it sit, or at least nothing you should risk your life over. We do face risks everyday, but intelligent people avoid deliberately taking big risks that provide no benefits.
In addition, homebrewers frequently share their beer with others. It is one thing to assume a risk for yourself, but it is unacceptable to put someone else at risk without their knowing it. If you make a beer from wort that has been stored for awhile, you should not give it to others (or send it to a homebrew contest).
Homebrewing is a fairly safe hobby. There are risks of being burned or scalded. There are risks of inhaling fumes from cleaning chemicals. In commercial brewing, there are added risks — for example, of suffocating by entering a tank filled with CO2. However, these risks are low and manageable. And, there is a point to taking the risk — you need to produce beer. In my opinion, there’s no good reason to risk your life so you can have a cube (or an improperly canned yeast starter) on hand.