Compact and high in protein and nutrients, eggs are an integral part of a healthy diet. Unfortunately, they tend to have a pretty short shelf life unless you take a few steps ahead of time to prevent them from spoilage. The easiest and most effective way I have found to do this is with mineral oil. Eggs stored in this way can last a long time even without refrigeration!
How do you preserve eggs using mineral oil?
- Wash and dry a dozen fresh eggs.
- Warm one tablespoon of mineral oil for 10 seconds in the microwave.
- Let the oil cool so it isn’t too hot to touch.
- Wearing gloves, cover each egg completely with mineral oil.
- Place each egg in an egg carton with the small end down.
These are the basic steps to preserving eggs with mineral oil, but how long will they last and what else can you do to extend their shelf life? Keep reading to find out!
Why Preserve Eggs with Mineral Oil?
While it’s true that you can always use powdered eggs or other egg substitutes, there’s just something satisfying about a big plate of fried eggs, a nice egg salad sandwich, or a hard-boiled egg in front of a blazing campfire. Good luck getting any of those with powdered eggs.
Real eggs are one of the few foods that can fill your belly, refuel your body, and replenish your nutrient stores without taking up a lot of room in your shelter or stash. The biggest issue with eggs, assuming you don’t have your own flock of healthy laying birds, is that they don’t last long without refrigeration. The last thing you need is to forget about an egg tucked in the back of your cache and have it explode in a foul-smelling bacteria bomb. Kiss your food stores goodbye.
Enter mineral oil preservation. Egg preservation with mineral oil is relatively simple, it has been used for ages, and the method in which this works has a solid basis in cold, hard science. Mineral oil is cheap, easy to find, simple to store, and a little goes a long way! A nice bonus is that it has other uses in survival situations, so it’s not a one-trick pony.
Quick Egg Science
If you’ve read any of my other articles on SuperPrepper.com you already know I love science. I believe it’s important to understand why something works, not just how to make it work. This is especially true for anything you plan to put in your body. These egg facts will help you pick the best eggs to preserve and will help you decide if a preserved egg has been compromised before you make the mistake of eating it. I’ll cover some more important points after the how-to section, so keep reading!
- Freshly-laid eggs can last several weeks to a few months outside or on your counter, depending on the temperature. This is due to the “bloom”, which is a clear layer of protection that helps regulate oxygen exchange and prevent bacterial infections. Fresh eggs don’t need to be refrigerated. I have left fresh, unwashed eggs on my counter for four months and they’ve been perfectly delicious.
- Store-bought eggs have been scrubbed and bleached, removing dirt, feces, and the bloom. They must be refrigerated since the protective bloom is gone. They can last a couple days on your counter, but not much longer.
- Store-bought eggs may have been laid more than 60 days ago. You have no idea how old those eggs are, and there’s no law stating that farmers or stores must tell you when an egg was laid.
- The older an egg is, the more likely it is to float in a glass of water. This is due to oxygen slowly seeping in through the shell, increasing the size of the air cell located at the fat end of the egg. It’s also due to moisture evaporating from the egg, making more room for air and bacteria. Store-bought eggs will get fat air cells much faster because the bloom is gone and more air can seep in through the shell.
- Store-bought eggs will go bad quickly at temperatures over 40 degrees Fahrenheit.
Preserving Eggs Using Mineral Oil
Preserving eggs in mineral oil has been done for decades. It is safe, quick, and super simple.
- Eggs—fresh or store-bought
- Mineral oil—found in grocery stores, farm stores, drug stores, or online.
- Gloves—latex, nitrile, or rubber
- Bright flashlight or egg candler
- Egg carton—plastic cartons are best for long-term storage and extra protection
- Microwave-safe bowl or small pot
- Measuring cup
Step 1 – Float Test
I always float test my eggs, even though they come from my own flock of chickens and I know how old they are. It’s just good food handling.
Fill a bowl or pot with enough cool water to fully cover two eggs stacked on top of one another (you won’t actually be stacking eggs, sadly). One at a time, place eggs in the water.
If the egg stays at the bottom, it’s fresh—happy preserving!
If the egg begins to rise to the top but doesn’t break the surface, it’s not totally fresh, but it can still be preserved.
If the egg floats to the top and bobs out of the water, it has a big air cell which means it’s pretty old and not good for preservation.
When you’re done testing your eggs, dump the water out and dry the container. If you need more clarification on performing the float test, have a look at this video which walks you through the process.
Step 2 – Prep the Eggs
Wash, dry, and gently place your eggs on a towel or in a container. Don’t put them in the carton just yet. They’ll be impossible to pull out of their little cubby holes once your hands are covered in oil. If you’re using fresh eggs, don’t scrub or rub too hard. That will remove the bloom. You can still preserve eggs with the bloom removed, but it’s better if it’s still intact.
Step 3 – Candle the Eggs
The point of “candling eggs” is to check for air cell size, embryonic development, and cracks.
In a dark room, turn on your flashlight or candler and hold the fat end of the egg against it. You should see three distinct parts:
- A little pocket of air down by the fat end
- A floating dark circle (the yolk)
- The gooey white part around the yolk.
If any of those three are missing, the egg is not good for preserving.
An unfertilized egg (or a fertilized one that hasn’t begun developing) will look mostly clear, with an obvious, darker yolk floating around. You should be able to slowly spin the egg to watch the yolk move freely inside the egg. That’s a winner!
If you see dark spider-web-like strings, that’s an early-stage embryo. No good for preservation, but you can still eat it. This video shows what fertilized eggs will look like during candling if you want to make sure you can recognize it.
Cracks will look like lightning strikes or bullet holes in glass (an impact circle with radiating cracks). These are no good for preservation and you should not eat them.
Step 4 – Measure Out the Oil
Measure about one tablespoon of mineral oil per dozen eggs you are preserving. I usually use about ¼ of a cup of mineral oil (equal to four tablespoons) since I usually preserve four dozen eggs at a time. Put the mineral oil into a bowl or pan.
Warm the oil for about 10 seconds in the microwave or a couple minutes on the stove. Let it cool slightly before you begin preservation to prevent burns.
Step 5 – Use Protection
It’s time to glove up! Mineral oil has some minor drawbacks, but gloves will keep it from affecting you. Putting gloves on now also gives the oil a little time to cool enough to handle.
Step 6 – Rub them Down
Poke your fingers in the oil, then rub it around your gloves. Once your gloves are covered in oil, pick up an egg and gently roll it around in your hands. Make sure to cover every inch of each egg in oil. You don’t need to worry about putting it on too thick. The whole point is to seal it up to prevent bacteria and oxygen from entering, so slather away.
You can also dip the egg and swirl it a bit in the bowl or pot, but you should let the excess drip off before storing them.
Step 7 – Store them Bottoms Up
When the egg is completely covered in oil, place it in the egg carton, fat side up.
That’s it! You’re done. Find a cool, dry, dark location to store your eggs.
Should You Flip Eggs Preserved in Mineral Oil?
Yes. It’s best to flip eggs that are preserved in mineral oil about once a month. This will help preserve the yolks and keep them from settling and sticking.
What Does Science Say About Oil-Preserved Eggs?
Of course, I just so happen to have a killer link to some egg-preservation science right here. The basic gist of this study is that oil preservation works, it’s safe, and you have lots of options.
This particular experiment proved that oil-preserved eggs that were kept at 25 degrees Centigrade (about 77 Fahrenheit) maintained a higher internal quality and decreased moisture evaporation over a five-week period than non-coated eggs.
Remember my egg facts earlier about evaporation and the air cell? According to the study on the NCBI website, at five weeks, the oil-coated eggs lost less than 0.8% of their weight through evaporation. The non-coated eggs lost a whopping 7.26%. That means the non-coated eggs lost more moisture and gained much more air—and guess what comes with the air? Bacteria!
How Long Will Mineral Oil-Preserved Eggs Last?
Eggs that are preserved with a mineral oil coating can last anywhere from 6 months to 1 year, depending on storage conditions and the freshness of the egg at the time of preservation.
The study I linked above only went on for five weeks and the eggs were kept at a pretty high temperature—about the temperature of an average kitchen counter. Even so, five weeks is a substantial time to hold eggs unrefrigerated.
I wish that study had gone on to test how long the eggs could remain safe to eat at that temp, but that’s not the case. A little math can help us if you don’t mind some educated speculation. If the study went on for five weeks and they only noted .8% weight loss, it’s probably safe to say that a preserved egg would only lose 1.6% at ten weeks and 3.2% by twenty weeks. I could keep going, but I think you see the pattern.
Lower the temperature, and you extend that time significantly.
Beyond educated guesses and quick math, we can look to experienced preppers, homesteaders, and survivalists for answers.
My personal experience has given about nine months in the fridge. It’s not that the eggs went bad; we just ate them all. They were delicious, kept their correct shape and weight, and didn’t have any noticeable taste or texture changes. I did note that they weren’t the best for baking though.
This lady tested year-old oil-preserved eggs and found them to be quite tasty. They were stored in the fridge and had some minor effects, but were overall in good shape. The key to keeping these eggs edible is temperature. Any cool, dry, dark location will work, but the fridge seems to be the best choice.
Should You Freeze These Eggs?
I don’t know a single egg-preserver who freezes their eggs after oil preservation. It’s a bit redundant. I have frozen eggs before, but I’ve always done it without the shells. More science here: liquids expand when frozen. It stands to reason that trying to freeze an oil-preserved egg in its shell would just result in egg explosions (egg-spolsions? Ahem, sorry…) and a giant mess.
Basically, I wouldn’t freeze oil-preserved eggs. However, if you have successfully frozen mineral oil-preserved eggs in their shells, I’d love to hear your methods in the comments.
Can You Use Coconut or Other Oils to Preserve Eggs?
Most types of oil will work, but coconut and many other oils will eventually go rancid. That’s why it is always best to preserve your eggs using mineral oil.
Using Eggs Preserved in Mineral Oil
As noted above, these eggs won’t work well for baked goods or anything that needs fluffy, whisked whites. Otherwise, they work for everything else. Just be sure to wash them well.
A Few Warnings
Mineral oil is a very refined petroleum product. It’s primarily used as a laxative, which is why you can find it in stores near the stomach medicines. Ingesting large quantities of this stuff will make you run to the latrine pretty quickly, so don’t chug it.
Mineral oil is also known to disrupt or change estrogen levels in women, so always perform mineral oil egg preservation with gloves on.
Also, while doing this it’s important to make sure you don’t burn yourself after heating the mineral oil. Oil based burns are the worst, and the oil can heat extremely well in a microwave even in a short period of time.
Some preppers have come on the scene recently throwing unsubstantiated warnings on this method—mainly about freshness, cleaning the eggs, and demonizing store-bought eggs. They mean well, I’m sure, but a lot of their advice starts to fall into the sensationalist realm. I have yet to see scientifically-backed claims, so I’m less likely to believe them. I’m more than willing to revisit their claims if and when they bring some science to the table.
I’ve been preserving eggs for many years, and the warnings of using only warm, 24-hour-old eggs is a bit silly and unrealistic for most people. The bottom line is to be smart, use common sense, and pay attention to proper food handling techniques. If you follow the steps outlined here, choose healthy, undamaged eggs, and pay attention to temperatures and storage methods, even store-bought eggs can be preserved in mineral oil.
What is your experience with preserving eggs? Share your methods and results in the comments below!