Garlic and olive oil have always had an affinity for one another, but combining them in an infusion creates an intense melding of flavors. Unfortunately, when fresh garlic is placed in olive oil, the microorganism Clostridium botulinum can grow, causing botulism food poisoning, a serious and potentially deadly illness. Stick with commercially prepared infusions or follow strict guidelines for making homemade versions.
Commercially prepared olive oil infused with garlic goes through a special process to acidify the garlic before it is added to the oil. Because the botulism bacterium grows in alkaline conditions, this acidifying process ensures a safe product. Store commercial olive oil infusions at room temperature in a cool, dry, dark location. Use them within three months. Olive oil can become rancid after three months. You probably won't detect any changes in taste or odor, but consuming rancid oil has been associated with cancer and premature aging.
The safest way to make infused olive oil at home is by using dried garlic, rather than fresh, in the infusion. The botulism bacteria need water, present in fresh garlic, to grow. Using dried garlic considerably reduces your risk of foodborne illness. Homemade oil prepared with dried garlic can be stored in a dry, cool location at room temperature. Use it within three months.
If you opt to use fresh garlic in a homemade infusion, take extra precautions to ensure a safe product. Place two or three fresh garlic cloves in a container. Pour 1/4 cup of vinegar in a pan and bring it to a boil. Pour the hot vinegar over the garlic cloves and allow it to cool to room temperature. Add the oil and place the lid on the container. Refrigerate the olive oil immediately and use it within one month. Olive oil will harden in the refrigerator. Warm it in a pan or set it at room temperature for 30 minutes to soften it.
Garlic-infused olive oil, when used properly, adds zest and flavor to myriad foods. Place it on the table as a dipping sauce for crusty breads, or drizzle it over hot pasta and add a sprinkling of hard cheese. Saute vegetables with it at a low temperature or make it a base for salad dressings. In addition to garlic, you can also add dried herbs or peppers to olive oil. Follow the safety guidelines for these foods, just as you would garlic.