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Garlic has widely recognized health benefits, performing as a seemingly endless broad-spectrum natural medication. Once cooked, however, garlic compounds lose much of their beneficial properties. The best way to take advantage of garlics’ versatility is to consume it raw, but many people find the searing pungency of raw garlic overwhelming, especially as a daily requirement. Instead of consuming raw garlic, garlic oils make a good alternative for both cooking and medicinal supplements. You’ll still get some of the associated garlic odor as it leaves your lungs and your pores, but oils are still a very palatable and effective substitute.
Garlic oil is processed mainly by using the fleshy cloves of the bulb itself, but the spathe and umbel, the flowering seed head found on hardneck varieties, can also be used. There are two main ways to produce garlic oil: steam distillation and maceration. Both of these methods cause the decomposition of the sulfur compound allicin, which subsequently produces diallyl disulfide (DADS) and diallyl trisulfide (DATS). If you are allergic to garlic, then DADS is the likely culprit. If not, DADS and DATS have excellent therapeutic properties, working as antimicrobial and anti-inflammatory agents. And because they detoxify cells, they also help to protect against cardiovascular disease and colon cancer.
In steam distillation, steam is passed though chopped garlic and captured after it has condensed. This process produces an extremely concentrated reddish-brown oil, and is the method by which pharmaceutical-grade garlic oil is manufactured. Since the resulting oil is so concentrated, it is diluted before being used in culinary or medicinal applications. For example, in garlic oil tablets, the garlic oil is diluted with vegetable oil to produce a more palatable and less expensive product. Garlic oil produced by steam distillation can also be combined with carriers such as salt, sugar and dextrose, to produce salts and pastes that are used in cooking.
Maceration is carried out by chopping or crushing garlic cloves and steeping them in oil. The garlic is left in the oil for a minimum of 24 hours, before the oil is strained and the garlic discarded. Since this method is easy to perform and produces a much less concentrated product than distillation, it is more popular for home-production and culinary use. Although macerated oil contains lower levels of DADS and DATS than steam distilled oil, it is a major source of ajoene, an unsaturated disulfide which is not present in distilled oils. Ajoene functions as an antioxidant, antimicrobial, antibiotic, and antithrombotic, making it a useful supplement for a variety of medical conditions.
If you are producing garlic oil via the maceration method, you must make sure to remove the garlic from the oil. Garlic is a low-acid vegetable, which with the right atmosphere – room temperature, low oxygen, low-acid, and high moisture – can result in the growth of Clostridium botulinum, a bacteria which subsequently yields the botulinum toxin. This toxin can be produced even if the oil and garlic mixture is refrigerated. If you want to store garlic in oil, it must be frozen (Preserving Gourmet Garlic: Freezing Garlic in Oil) to ensure it is safe to eat. Macerated oils should be refrigerated and consumed within a week.