Food grade oils are plant-based oils that are safe for human consumption. Common food grade oils include olive oil, vegetable oil, coconut oil, avocado oil, sunflower oil, and others. These oils are extracted from crops through pressing, crushing, and refining processes.
Food grade oils have a wide range of culinary applications and are commonly used for cooking, baking, salad dressings, marinades, and more. However, there is often confusion around whether these oils have an expiration or best-by date, and if so, how long they are safe to consume after opening.
Do food grade oils expire?
Yes, food grade oils do expire and have a limited shelf life. However, the timeframe depends on the type of oil.
Here are some general guidelines on how long common food grade oils last:
| Type of Oil | Unopened Shelf Life | Opened Shelf Life |
|---|---|---|
| Vegetable oil | 6-12 months | 6-8 months |
| Canola oil | 2 years | 6-12 months |
| Coconut oil | 2-3 years | 18-24 months |
| Olive oil | 2-3 years | 6-12 months |
| Avocado oil | 6-12 months | 6-9 months |
| Grapeseed oil | 6-12 months | 3-6 months |
As you can see, the shelf life depends on the oil’s properties and growing conditions of the source crop. Oils with higher saturated fat content, like coconut oil, tend to last longer than others. Refined oils also tend to have a longer shelf life compared to unrefined, virgin oils like extra virgin olive oil.
Once opened, the clock starts ticking on an oil’s freshness. Exposure to oxygen, light, and heat can cause oils to go rancid. For best quality, store oils in a cool, dark place and make sure lids are tightly sealed. Refrigerating after opening can help prolong shelf life.
How to tell if food grade oil has expired
Because food grade oils have a definite shelf life, it’s important to learn how to determine if an oil has expired and is no longer safe to consume. Here are some signs of expired oils:
– Change in color: Fresh oil should have a clear, consistent color based on the oil type. Yellow or brown discoloration can indicate oxidation and rancidity.
– Change in smell: Rancid oils give off a distinct, unpleasant odor that is often described as paint-like or crayony. If the fragrance is off, don’t use it.
– Change in taste: Expired oils taste stale, bitter, or unpleasant. You may feel a tingling, burning sensation on your tongue.
– Change in texture: Oil may become thick and gummy, or foam excessively when shaken.
– Cloudiness: Oils turn cloudy as triglycerides solidify and clump together.
– Mold growth: Visible mold spots or growth on the surface of the oil.
– Date on packaging: If oil is past the recommended best-by date, it should be discarded.
If you notice any of the above signs, the oil should be thrown out. Consuming rancid oils can cause negative health effects, so it’s not worth taking a chance.
Health risks of consuming rancid oils
Rancid oils contain free radicals and oxidation products that are potentially harmful if consumed. Some health risks and effects associated with eating expired, oxidized oils include:
– Increased inflammation: Compounds in rancid oil are pro-inflammatory and may worsen conditions like arthritis, heart disease, and diabetes.
– Decreased antioxidant status: Oxidized lipids deplete protective antioxidants like vitamin E in the body.
– Organ toxicity: Compounds in oxidized oil may cause damage to tissues and organs over time.
– Negative effects on heart health: Studies link consuming oxidized fats to increased risk of atherosclerosis and heart attack.
– Gastrointestinal irritation: Stomach pains, cramping, and nausea are common after ingesting rancid oils.
– Accelerated aging: The oxidative stress caused by rancid oils may contribute to accelerated cellular aging.
While occasional consumption of slightly oxidized oils is unlikely to cause harm in healthy adults, it’s best to avoid consuming oils that have clearly gone rancid. Certain populations like young children may be more sensitive to the negative effects.
Tips for extending food grade oil shelf life
To get the most out of your food grade oils and extend shelf life, follow these tips:
– Buy small bottles: Once opened, oil starts to degrade. Buying small bottles ensures it gets used up quickly.
– Check best-by dates: Don’t purchase oils that are close to expiring. Look for furthest dates out.
– Store oils properly: Keep oils in a cool, dry pantry out of direct light. Refrigeration after opening can help.
– Limit oxygen exposure: Use bottles with minimal headspace. Don’t transfer back and forth between containers.
– Watch for signs of spoilage: Frequently check oils for changes in smell, taste, color, etc.
– Cook with oils you buy: Don’t just collect oils for occasional use. Incorporate them into regular cooking.
– Buy quality oils: High quality, fresh oils resist spoilage better than old, lower grade oils.
– Don’t cook with rancid oils: Heating further accelerates oxidation, so only use fresh, non-rancid oils.
With proper storage methods and care, most food grade oils can easily last until their best-by date and remain safe for consumption. Follow common sense precautions, and your cooking oils should retain their quality and freshness.
Can you use expired food grade oil?
It is not recommended to use food grade oils past their expiration or best-by date. As discussed above, oxidized and rancid oils can have negative effects on health, flavor, and overall quality. Consuming spoiled oils is an unnecessary risk.
However, depending on storage conditions and how far past the best-by date, very recently expired oils may still be suitable for certain uses. Here are some potential exceptions:
– Using the expired oil very quickly in high heat cooking like stir-fries where any off flavors likely won’t be detected.
– Using small amounts of the expired oil combined into a flavorful dish or baked good where oxidation compounds may be diluted.
– Using the oil for non-edible purposes like lubricating equipment, moisturizing hair/skin (for non-rancid oils), oil lamps, etc.
– Running the oil through high heat processes like deep frying repeatedly, which may render any potentially harmful compounds inactive. However, the oil may still impart unpleasant flavors.
Again, it’s impossible to make a blanket determination if an expired oil is safe or not. Use your best judgment evaluating the oil’s smell, taste, color, etc. Only use oils you’re confident have not spoiled. When in doubt, throw it out. The small amount potentially saved isn’t worth the risk.
Can you restore spoiled cooking oil?
Once an oil has clearly gone rancid, there is no reliable way to reverse the chemical breakdown and make it safe for consumption again. However, there are a few methods that claim to temporarily “restore” oxidized cooking oils:
– Filtering: Passing used cooking oil through a fine filter using diatomaceous earth or activated charcoal. This can remove some particles, but not oxidation.
– Heating: Heating spoiled oil to high temperatures may help reduce rancid odors and alter the chemistry, but creates further loss of nutritive value.
– Combining oils: Mixing small amounts of rancid oil into fresh oil is sometimes suggested to dilute the compounds. This is not recommended, as it can spoil the new oil.
– Citric acid: Adding vitamin C is said to counteract the breakdown. However, this does not improve nutrition or fully eliminate rancidity.
– Exposure to UV light: Some claim that subjecting oxidized oil to UV radiation can extend shelf life. This method is not well studied or proven effective.
While these home remedies may mask rancidity temporarily, they do not reverse the chemical breakdown, eliminate potentially harmful compounds, or make spoiled oils suitable for reuse. Once an oil goes rancid, it’s best to discard and use fresh oil.
Frequently Asked Questions
Does frying shorten oil’s shelf life?
Yes, frying significantly shortens an oil’s shelf life and accelerates oxidation. Frying raises the temperature of the oil and exposes it to moisture, oxygen, and degraded food particles. This causes chemical changes that quickly lead to rancidity. Only use fresh, high quality oils for frying and promptly discard after use.
Do cloudy oils always mean they’ve expired?
Not always. Some oils like coconut oil naturally solidify at cooler temperatures and turn cloudy or semi-solid when refrigerated. However, if an oil is cloudy at room temperature or when heated, that likely signals chemical changes are occurring and expiration is imminent or has already happened.
How do you dispose of rancid cooking oil?
Never pour expired oils down the sink drain. The best way to dispose of rancid oil is to first solidify it by refrigerating or freezing, then double bag and throw it in your regular trash. Some municipalities may have oil recycling programs as well. Avoid dumping oil outside.
Can you eat food cooked with expired oil?
It’s best to avoid eating anything cooked with rancid, oxidized oil whenever possible. However, cooked foods likely pose less direct risk than consuming the expired oil itself. Use caution and common sense if eating something cooked in overused oil, especially for vulnerable populations. Ideally, always cook with fresh oil.
Do all oils need refrigeration after opening?
Not necessarily. Most standard cooking oils like vegetable, canola, or olive oil can be safely stored in a cool, dry place after opening. Heartier oils like coconut and avocado oil are also shelf stable for over a year. Refrigeration can help slow oxidation, but isn’t critical for short-term storage. Some oils like toasted sesame oil should always be refrigerated.
Conclusion
All food grade oils eventually expire and should not be consumed after going rancid. Telltale signs of spoiled cooking oil include changes in color, smell, taste, and texture. While the shelf life varies by oil type and storage methods, opened cooking oils typically begin to oxidize within 6 to 12 months. Though some try to revive used oils, there is no reliable way to safely reverse the chemical degradation once it spoils. To avoid any potential health risks and unpleasant flavors, it’s best to discard expired cooking oils and use fresh ones. With proper handling, most oils can easily last until their expiry date printed on the packaging.
