Reusing cooking oil is a common practice for many home cooks looking to save money and reduce waste. However, concerns about the safety and nutrition of reused oil may make some cooks hesitate. Here is a look at the pros and cons of reusing cooking oil, along with tips for how to reuse oil safely.
Quick Answers
Can you reuse cooking oil? Yes, cooking oil can be reused if stored and filtered properly. However, reused oil deteriorates in quality and nutrition with each use.
Is reused cooking oil bad for you? Reused oil is not inherently bad for you, but does degrade in quality and absorb more free fatty acids and potential toxins with each reuse. Moderation is key.
How many times can you reuse cooking oil? Experts recommend reusing oil no more than 2-3 times. The more times oil is reused, the more it degrades.
Can you reuse cooking oil after frying fish? It’s not recommended to reuse oil after frying fish or other seafood containing omega-3 fatty acids, as they oxidize faster.
The Benefits of Reusing Cooking Oil
There are a few potential benefits that make reusing oil an attractive option for home cooks:
- Cost savings – Oil can be expensive, so reusing it a few times helps cut down on costs.
- Reduced waste – By reusing oil several times, you generate less waste from single-use oil.
- Retained flavors – Reused oil absorbs flavors from previous cooking, which can enhance dishes.
During times of economic hardship, reusing cooking oil instead of buying new bottles for each use can certainly help stretch a grocery budget further. If waste reduction is a priority, reuse also helps eliminate some single-use oil bottles from landfills. Reused oil’s absorbed flavors may benefit some dishes as well, like fried chicken or french fries.
The Potential Downsides of Reusing Oil
However, there are also some downsides associated with reusing cooking oil multiple times:
- Reduced nutrition – Heating and reheating oil degrades vitamins like vitamin E.
- Harmful oxidation – With each reuse, oil oxidizes faster, generating free radicals.
- Higher smoke points – More reused oil is needed to fry properly as smoke points drop.
- Off flavors – Absorbing flavors can also make undesirable tastes in reused oil.
- Food residue – Bits of batter or debris left in oil can turn rancid or burn.
The biggest concerns with reusing oil are oxidation and reduced nutrition. Heating oil, especially for frying, degrades fatty acid chains and generates free radicals that are harmful in excess. And the more times oil is reheated, the fewer vitamins like vitamin E remain. Reused oil also tends to absorb more contaminants from food residue.
How Many Times Can You Reuse Cooking Oil?
Most recommendations from health organizations suggest reusing cooking oil no more than 2-3 times. Reusing oil only once or twice minimizes oxidation and nutrient loss.
Here is a look at reused oil with each successive fry:
- 1st use – Fresh oil ideal for frying
- 2nd use – Very small reduction in quality
- 3rd use – Significantly more oxidation; 20-27% loss of nutrients
- 4th+ uses – Drastic degradation in quality and nutrition
As you can see, the first reuse still maintains pretty good freshness and nutrient levels. But after the third reuse, oxidation and degradation accelerate rapidly. Reusing oil more than 3 times is not recommended.
Tips for Safely Reusing Cooking Oil
To make the most of reused cooking oil, follow these best practices:
- Refrigerate oil after each use. Colder temps slow oxidation.
- Strain oil through cheesecloth after each use to remove food bits.
- Avoid reusing oil from deep frying fish or other omega-3 rich foods.
- Avoid mixing different types of oil together when reusing.
- Store oil in an airtight container away from light or heat.
- Look for dark color and an off smell, signs oil should be discarded.
- Don’t reuse oil more than 2-3 times.
Proper storage and filtering between uses helps maximize how long oil can be reused while maintaining some freshness. Discard at any signs of smoking, foaming, or an off appearance or odor.
Healthier Reuse Oil Alternatives
For those concerned about reusing cooking oil but wanting to reduce waste, there are a couple healthier options:
- Use high oleic oils – Varieties like sunflower withstand more reuse.
- Fry at lower temperatures – Less degradation occurs at 325-350°F.
- Use oil for non-frying – Use old oil for roasting veggies, etc.
Choosing more stable high oleic oils like sunflower allows for slightly longer reuse with less oxidation. Lower frying temps also preserves freshness longer. You can also repurpose older degraded oil for uses like roasting vegetables where lower temperatures minimize further degradation.
Health Risks of Reusing Cooking Oil
Reused cooking oils rich in polyunsaturated fats are most worrisome for health. With each successive reuse, these oils develop:
- More free radicals that damage DNA
- Higher levels of trans fats from hydrogenation
- Increased concentration of lipid oxidation products
- More peroxide compounds linked to cancers
- Potential acrylamide formation above 250°F
Deep frying causes the most free radical generation and trans fat production at high heat. But even oven heating can degrade oils each time. There are elevated risks of conditions like heart disease, inflammation, diabetes, and cancer when reusing oil excessively.
Signs Your Reused Oil Has Gone Bad
Watch for these signs that reused cooking oil is no longer safe and should be discarded:
- Darkening color – From clear yellow to dark golden brown
- Thick, syrupy texture – Increased viscosity from polymerization
- Strong, unpleasant smell – Rancid odors indicate spoilage
- Visible smoke early while heating – Lower smoke points
- Bubbling foam in the pan – Deterioration during frying
Oil that appears dark, sticky, or greasy or gives off foul odors should not be consumed. Excess foaming when frying along with rapid smoking are other clear signs deteriorated oil should be thrown out based on safety and quality.
Storing Reused Cooking Oil Properly
To best preserve reused oil between uses, be sure to:
- Filter out food debris with cheesecloth or filter
- Transfer to an airtight, opaque container
- Store in a dark cabinet away from heat or light
- Refrigerate for up to 1 month to slow oxidation
- Avoid transferring back and forth between fridge and pantry
- Never mix fresh and reused oil together
- Discard after signs of deterioration appear
Proper storage maximizes reuse lifespan. Though refrigeration isn’t required, it does help prolong stability further. Just avoid temperature fluctuations that can accelerate degradation.
Disposing of Used Cooking Oil Properly
When it’s finally time to discard reused oil, be sure to get rid of it the right away:
- Avoid pouring down drains – Can clog pipes and sewer systems.
- Don’t dump in the trash – Can leak and contaminate landfills.
- Find a recycling center – Some municipalities accept used oil.
- Use curbside collection – If such cooking oil recycling programs exist.
- Turn into biodiesel fuel – DIY converter kits available online.
Because pouring used oil down drains or placing in the trash has negative environmental impacts, look for recycling programs in your community. Some cities offer curbside pickup for used cooking oils. And you can purchase systems to make biodiesel fuel at home.
Reusing Cooking Oil for Other Purposes
If you don’t want to reuse old cooking oil for frying or sautéing, there are several other applications for it, like:
- Conditioning cast iron cookware
- Lubricating kitchen tools and hardware
- Polishing wood finishes
- Waterproofing fabrics or boots
- Creating soaps and candles
- Mixing with bird seeds or pet food
- Controlling dust on gravel roads or paths
- Killing insect pests on garden plants
So even after cooking with reused oil, it still has purposes other than eating. You can take advantage of its lubricating and water-resistant properties in particular. Just don’t coat anything that will contact food later.
The Bottom Line
Here are the key takeaways on reusing cooking oil:
- Reusing oil can provide some cost savings and less waste, but reduces nutrition and freshness.
- Don’t reuse cooking oil more than 2-3 times due to increased oxidation and free radicals.
- Store reused oil properly in a cool, dark place in an airtight container.
- Discard reused oil once it becomes dark, foamy, sticky or smelly.
- Look for recycling options when disposing used cooking oil.
- Limit consumption of foods cooked in reused oil due to health risks.
While reusing oil in moderation has financial upsides, it also carries safety and nutrition downsides. Limit oil reuse to just a couple times and monitor carefully for signs it’s time to discard. And try to consume reused oil fried foods only occasionally as part of an otherwise healthy diet.
