You may want to roast some fresh in-the-shell peanuts at home. But if you just threw them in the oven, you’d be missing one crucial ingredient: salt. Yet, salting shelled peanuts before roasting would surely be futile. The salt would not even stick to the shells, let alone get inside the actual peanuts. How do they salt peanuts in the shell? How can salt even get through the shells to season the peanuts inside? It involves another cooking step and a pressure cooker!
A clever cook might think of wetting down the peanuts before salting them. This would work if you wanted a salty shell, but it still would not affect the taste of the peas (yes, peas) inside.
Yet, roasted peanuts, like the kind you get at the ballgame, bars, and Five Guys Burgers, have salt in them. How do they get the salt inside the shells?
The truth is, unless you are okay with unsalted peanuts, you’d have a hard time reproducing the taste of commercial roasted peanuts in the shell. This is not to say you can’t make good peanuts at home; they just won’t taste like ballpark peanuts.
Wait, Are They Actually Nuts? Since we’re talking about the science of “peas,” you might be surprised to learn how they actually grow. Check out our deep dive: Are Peanuts Actually Roots or Seeds?
The Science of Brining: How Pressure Forces Salt Through the Shell
To salt peanuts in the shell, they cook the peanuts in a brine solution under pressure for about ten to twenty minutes. The pressure forces the salty water into the shell. Peanut shells are actually a bit spongy and are not water-tight. For this reason, you can make boiled peanuts even with peanuts that aren’t “green,” although it takes longer.
After they are pressure-cooked, there is excess water inside the peanut. The peanuts are drained and then roasted in a very hot and very dry oven at around 800° F. Some roasters insert an extra drying step in between.
Regardless, once the peanuts are dry and roasted, there is a coating of salt left behind to flavor the peanuts inside. The browning of the peanuts produces flavor in the same way as browning other foods, via changes in the sugar and amino acids.
The Five Guys Secret: Why Are Their In-Shell Peanuts So Salty?
If you’ve ever cracked open a peanut at Five Guys Burgers and Fries, you know they have a distinct, salty punch that home-roasted peanuts usually lack. Many fans wonder if the salt is sprayed on the outside or if there is a special variety of “salty” peanut being grown.
The reality is much more scientific. Five Guys uses the same industrial pressure-brining method described above. This method ensures that the salt doesn’t just sit on the shell, but actually permeates it to season the nut inside. Because the brine is forced into the shell under pressure before roasting, the salt becomes “locked in” once the moisture is evaporated in the oven. This creates that consistent, savory flavor that has become a hallmark of the Five Guys experience.
Why Traditional Home Roasting Fails (And the Alton Brown Method)
The above is how they salt peanuts in the shell on a commercial level. Could you duplicate this at home?” You may be able to use a pressure cooker for the brining step and then roast the peanuts in a convection oven turned up to its highest setting. I’ve certainly never tried this, and I don’t know if it will work!
A quick search for recipes turned up in-shell peanuts that would be salted on the outside only. I also found one “curious” recipe by Alton Brown. His method calls for coating the shells in peanut oil and then salting them. Unfortunatley, this would only result in very brown and salty peanut shells at best, but no actual salty taste on the peanuts themselves.
If you plan to eat the peanut shell and all, you may like this. Yes, people do eat them that way! But usually with deep-fried peanuts. The oil and salt method would work well for shelled peanuts, but the peanuts would not be ‘dry-roasted,’ and the texture is not quite the same.
How to Salt Peanuts in the Shell at Home
While commercial roasters rely on industrial pressure vessels, you can replicate the method in a home kitchen with a small batch in a stovetop pressure cooker or an Instant Pot. Start by dissolving half a cup of salt in a gallon of water, submerging the raw in-shell peanuts completely, and weighing them down with a heavy plate so they stay beneath the surface. Cook the peanuts under pressure for 15 to 20 minutes in a 15-PSI stovetop cooker, or for 25 to 30 minutes in a lower-pressure Instant Pot (10 to 12 PSI), so the salty brine penetrates the shells. Drain the peanuts thoroughly and spread them in a single layer on a rimmed baking sheet to dry in a low oven at 170°F to 200°F for two to three hours, propping the oven door slightly ajar so steam can escape.* Skipping this drying phase traps water inside the hull and leaves the nuts soggy instead of crisp. Once the shells feel dry and brittle to the touch, raise the oven temperature to 325°F to 350°F and roast for 20 to 30 minutes until the kernels inside are lightly browned.
*Alternatively, the pressure-brined peanuts can be spread out and air-dried for at least 24 hours.
Further Reading
- Are Peanuts Roots Or Seeds?
- The Real Reason Canned Foods Are Packed in Water
- How Handheld Smokers Work: The Science of Cold Smoke Infusion