If you wanted to roast some fresh in-the-shell peanuts at home, and you 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 to the actual peanuts.
A clever cook might think of wetting down the peanuts before salting them. This would work if you wanted a salty shell but 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 at 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.
Commerical Roasted In-Shell Peanut Process
To get salt into peanut shells peanuts are cooked 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, something you know if you’ve ever made boiled peanuts.
But now 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 above is how it’s done 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 basically be salted on the outside only and one “curious” recipe by Alton Brown which calls for coating the shells in peanut oil and then salting them, a method which would 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 peanuts shell and all maybe you’d like this. Yes, it’s done, 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.