How Long Do Infused Cooking Oils Last?

Think about the most flavorful cooking oil in your pantry right now. Maybe it's a jar of rich, unrefined coconut oil, or perhaps a pricey bottle of extra-virgin olive oil. As wonderful as these oils are, they can't quite match the concentrated flavors and aromas of infused oils. They're exactly what they sound like – regular cooking oil infused with extra herbs and spices. While they can be found in specialty stores, nothing beats homemade. But once you've made a bottle for your own, though, one important question pops up: how long will it stay fresh?

The short answer is about one month – quite a contrast to regular cooking oils that can last a year or longer. The reason's got to do with all the extra ingredients you added to the oil. While they carry fragrant essential oils that impart that lovely smell and taste to your base oil, they also introduce bacteria or mold spores that'll fast-track your oil's spoilage. It should also be noted that, considering vegetable oils contain more polyunsaturated fatty acids, canola and olive oils will spoil at a slower rate.

You can extend the oil's shelf-life by keeping it in a dark, cool spot like your pantry, or keeping it in the fridge where the cool temperature will help slow down the oil's degradation. But even with perfect storage conditions, try to use your oil within a month for the best flavor and safety. There's no shortage of great uses anyhow, from homemade popcorn to roasted vegetables — this shouldn't be a problem!

The bacteria and spores in your infusion don't just spoil it, they're also safety risks, too. For instance, the airless environment in the oil is a great spot for botulism to develop. Fortunately, there are a couple of tricks you use to minimize contamination.

Pick a clean, dark-colored container (to protect the oil from light) and sterilize it in a pot of boiling water for about 10 minutes. For the lid, simmer it separately in a pan of hot water (around 180 degrees Fahrenheit, so not boiling) to protect the rubber seal. The heat will kill the bacteria and give your infusion a spanking-clean starting point.

When it comes to the ingredients, dried herbs and spices are your best bet since they contain little of the moisture that bacteria need to grow. If you prefer fresh ingredients, per the University of Idaho (via PennState Extension), you can make them safer through acidification. Simply soak fresh herbs and spices for 24 hours in a solution of citric acid (one teaspoon per two cups of water). You'll know the acidification is complete when the ingredients begin to change color, or if you have a pH meter handy, when they reach 4.6 or below. This acidic environment prevents harmful bacteria, including botulism, from growing. Just make sure to only use the herbs and spices you've acidified and not add any fresh herbs to the mix, and your flavored oil is ready to elevate your homemade mayo.