Garlic in oil. For added safety, the FDA now requires that all commercial garlic in oil products contain specific levels of microbial inhibitors or acidifying agents such as phosphoric or citric acid. Although most garlic products do contain these additives, some boutique or specialty mixes may not. Always check the label to be sure.
As for home-prepared mixtures of garlic in oil, the FDA recommends that these “be made fresh for use and not left at room temperatures.” Any leftovers should be refrigerated for use within three days, frozen for longer storage, or discarded.
The reason for the concern is that unrefrigerated garlic in oil mixtures lacking antimicrobial agents have been shown to permit the growth of C. botulinum bacteria and its toxins, without affecting the taste or smell of the products. Toxin production has been known to occur even when a small number of C. botulinum spores were present in the garlic. When the spore-containing garlic is bottled and covered with oil, an oxygen-free environment is created that promotes the germination of spores and the growth of microorganisms at temperatures as low as 50 F.
Botulism is a potentially fatal food poisoning characterized by blurred or double vision, speech and breathing difficulty, and progressive paralysis. Without prompt and correct treatment, one-third of those diagnosed with botulism may die. C. botulinum spores are widespread in the environment but cause no harm as long as oxygen is present. Also, the toxin produced by C. botulinum bacteria is readily destroyed by heat. Boiling a potentially suspect mixture for 10 minutes, plus one minute for each 1,000 feet above sea level, will destroy any botulism toxin that may be present.
Vegetables and herbs in oil. Several cases of botulism have been associated with home-prepared vegetables and herbs stored in oil. These products also should be made fresh, with leftovers refrigerated for use within 3 days, or frozen for longer storage. Vegetables have a high water activity level which further encourages the growth of C. botulinum bacteria in an anaerobic environment. Even when dried, there is still the potential for risk, unless the vegetable has been acidified to a pH of 4.6 or lower.
Just kidding.
