We hear all about botulism in garlic oil and the needed preventive measures. Is this only true of garlic or is it just more common. For example I make a oil packed fish (oil, salt onions, jalapeño, fish) I’ve been making this for years with no problems. Have I just been lucky or is my keeping it in the fridge what’s saved me and if so how long is safe?
Any low-oxygen low-acid environment with sufficient moisture can lead to the growth of botulism (see page 6 of this USDA guide to canning). Botulism spores are present throughout your kitchen, not just on garlic. To can low-acid foods safely, you need to use a pressure canner for a sufficiently long processing time.
Refrigeration slows down the growth of botulism. The CDC recommends storing garlic or herb infused oils in the fridge for at most 4 days. You should be at least this cautious with your oil-packed fish.