Cooking oil is one of the most essential items to have in your pantry, but it is also one of the hardest items to store long-term. Here’s what you need to know about long-term storage of cooking oil, shelf life, and how to tell if your oil has gone bad.
Does Cooking Oil Go Bad?
With most foods, such as milk or eggs, “going bad” means dangerous bacteria has started growing on the food. Bacteria generally cannot grow in cooking oils. However, cooking oil can become rancid. Rancidity makes oils taste and smell bad, destroys vitamins, and can even create toxic compounds.
There are three main reasons cooking oil becomes rancid:
In some cases, oil can also go bad if it gets mixed with water. Water contamination of cooking oil is highly unlikely though, even in humid areas, so long as the bottles is not opened.
How to Store Cooking Oil
If you want cooking oil to last a long time, you need to keep it away from oxygen, heat, and light. These storage conditions will keep cooking oil fresh the longest.
Don’t Open the Bottle
When you open a bottle of cooking oil, oxygen in the air will react with molecules in the oil and cause them to go rancid. As a general rule, you should use any opened bottles of cooking oil within 6 months.
So long as the bottle stays closed, the oil will stay safe from oxidation. One long-term study found virtually no change in rancidity levels in olive oil stored in a closed bottle for 3 years.
Avoid Plastic Bottles
Cheap cooking oils usually come in plastic bottles. These bottles are not completely airtight. Over time, tiny holes form in the plastic and allow air through. If you store the oil long enough, you might even end up with an oily mess in your pantry as the oil leaks out.
Thus, it’s better to choose oil in glass bottles or even metal tins if you want to store it long-term. These bottles will do a better job of keeping air out.
Keep Away from Light
Exposure to light causes some types of cooking oils to go bad faster. Light also makes antioxidants and other healthy parts of cooking oil to degrade faster. To make your oil last longer, keep it somewhere dark and away from windows. Good brands of oil will package their products in dark bottles to keep it fresh longer.
Keep It Cool
Heat has a huge effect, one long-term study found that olive oil stored at 59F barely had any changes to rancidity even after 3 years. When stored at 70F, the olive oils were still mostly okay after 3 years. But, when stored at 98.6F, the oils went rancid within just 6-8 months, even though they were not exposed to air or light.
This shows how important it is to keep your cooking oil cool. Ideally, keep it at temperatures under 60F. If you can’t keep the oil cool, then you should use it within 6 months.
Should I store oil in the refrigerator or freezer?
Refrigerating or freezing oil is a good way to keep it fresh for longer. Highly-sensitive oils, such as almond oil or truffle oil, should always be refrigerated because they are so sensitive to heat.
Note that the cooler temperatures will cause the oil’s molecules to slow down and the oil will become cloudy. This does not mean the oil went bad: cloudy oil is still fine to use. Just let the oil come to room temperature and the cloudiness will go away. Try to keep a consistent temperature though as repeated cooling-heating will make the oil go bad faster.
Look for Nitrogen-Flushed Bottles
Certain oils, such as flaxseed and nut oils, are very susceptible to oxidation. Even the small amount of oxygen in the bottle headspace could cause the oil to go bad faster. To help their products last longer, some manufacturers will use nitrogen-flushing to remove all oxygen from the bottle before sealing it.
Because most cooking oils will go bad within 1-2 years, don’t stockpile more than you can rotate through in this amount of time. If your storage space is warm, then you’ll need to rotate through them even faster than this (aim to rotate through everything within 6 months). As with all items in your survival food list, put the newest bottles in the back and take from the front.
Cooking Oil Shelf Life
Stored at room temperature in a pantry, most cooking oil will last 1-2 years. Once opened, the oil should be used within approximately 6 months. When stored properly in an air-tight bottle in a cool, dark place, some types of cooking oil can last 5 years.
Which cooking oils last the longest?
Some types of cooking oil last much longer than others because of the types of fats they contain. Oils with more polyunsaturated fats (such as canola oil) have more carbon-carbon double bonds, so are more susceptible to going bad than oils with mostly monounsaturated fats (such as olive or peanut oil). Oils with more polyphenols (antioxidants) will also last longer.
Shelf Life of Cooking Oils (Unopened and Stored in Cool, Dark Place)
Cooking oils don’t go rancid all at once; it’s a gradual process. At a certain point the oil will become too rancid to eat. Here’s approximately how long it takes for various oils to go bad if stored in an airtight container in a cool, dark place. The oils could last longer if kept somewhere cold.
- Hydrogenated oils (such as Crisco): 5 years
- Peanut: 3-4 years
- Olive: 3 years
- Palm: 2-3 years
- Safflower: 1-2 years
- Sunflower: 1-2 years
- Canola: 1-2 years
- Coconut oil: 1-2 years
- Soybean: 1 year
- Corn: 1 year
- Lard and tallow: 9 months
*Note: There have been numerous studies which looked at shelf life of cooking oils and fats. The results don’t always line up. For example, some studies will show corn oil lasting longer than safflower.
Antioxidants to Preserve Oil
Antioxidants protect oils against oxidation, so some manufacturers will add them to their oils to improve shelf life. Vitamin E is one common antioxidant you might find in oils.. However, synthetic antioxidants (such as butylated hydroxyanisole or phosphoric acid) generally last longer than natural antioxidants. You can often find these synthetic preservatives in large containers of corn oil.
If you want to store cooking oil long-term, it’s worth looking for brands which have added antioxidants. This can increase shelf life to 5 years if stored properly.
How to Tell if Cooking Oil is Bad
If cooking oil has a sweet or fermented odor to it, then it has probably gone bad. Rancid oil will also lose its flavor and change color.
Unfortunately though, it’s very hard to detect the taste and smell of rancid cooking oils. You might not be able to detect any difference until the oil was very rancid. Note that it’s usually easier to detect rancidity with animal fats than vegetable oils.
Is It Safe to Eat Rancid Oil?
Rancid cooking oil tastes bad, has an off-putting smell, and doesn’t have as many healthy components like antioxidants. But rancid oil is still generally considered safe to consume. It will not give you food poisoning or make you sick like eating expired meat or rotting vegetables would.
However, there have been some studies which show that rancid cooking oil might have broader long-term health effects. Animal studies found that rancid oil harmed the immune system, slowed growth, and even increased likelihood of tumor growth.
The bottom line? In a SHTF situation where I had nothing else, I would have no qualms eating rancid oil. But, in everyday life, you should try to only eat fresh oil. Store it properly and keep your stockpile rotated!
For further information on long term food storage see the following:
- How to store nuts long term
- How to store flour long term
- How to store salt long term
- How to store yeast long term
- How to store baking soda long term
- How to store sugar long term
- How to store dried milk long term
- How to store rice long term
- How to store beans long term