I have the iron kadhai and gas stove.
When I roast the peanuts (without exterior shell) they get the brown spots on them. Of course I do keep on moving the peanuts in the kadhai but still I can't move my arm terribly fast since I have to move it continuously for 10 minutes. I get tired.
What can be done so that they do get roasted properly without the brown spots?
Roasting peanuts in a pan on a stove cooks them primarily via conduction (i.e., the surface of the peanuts touching the hot surface of the pan). Since peanuts are round, each part of the peanut must touch the pan for an equal amount of time during the cooking process to be evenly roasted. That's nearly impossible without something like a barrel roaster (which very few people will have in a home kitchen).
Cooking with convection (i.e., hot air) will produce much more even results since the heat will transfer to all sides of the peanut relatively evenly. Roast the peanuts at 175°C/350°F for 30 to 35 minutes, rotating the pan half-way. You can also try putting the peanuts on a wire rack (as opposed to directly on the sheet tray), which will help the hot air to more evenly cook their bottoms.
If it does not interfere with your ultimate use of the peanuts, you can also try coating them in peanut oil before cooking (roughly 30ml of oil per kilo of peanuts). The oil will help the heat transfer more evenly to the peanuts.
Finally, you can also use the Chinese method of deep-frying the peanuts in your kadhai; roughly 15 to 20 minutes. Immersion in hot oil will cook the peanuts evenly.
Use salt in the kadhai - about 300-400 gramms or more.
Heat it, then add peanuts and roast until they smell for about 6-8 minutes on medium gas. Your peanuts will not burn as heat is transferred to all parts of the peanuts.
You can roast the peanuts on a gas stove by simply leaving the seed coat on while roasting the peanuts. The seed coat will prevent the actual nut inside from burning and producing those brown spots. You’ll also have to keep on stirring the peanut as usual however.
Use washed, clean, dry, fine sand. Heat the sand and peanuts (shelled/unshelled) in a kadhai over stove stirring with a steel spatula. The stirring need not be so continuous that it tires your arm. Use a steel spoon with holes as used for frying pakoras to separate the sand and peanuts. Store the sand for future use (of course after it has cooled off)
The process of roasting is to remove moisture from the peanut by heating. The heating starts from the outer surface. The temperature starts increasing slowly, bringing the inner moisture to the surface and then evaporating it.
The heat transfer is by conduction through the contact point of the peanut and the kadhai. The larger the size of the peanut, the higher is the temperature required.
Usually, the peanut turns black indicating a high temperature at the contact point. It is necessary to turn the peanut contineously so that the black spot does not appear.
For the moisture to come out, I did several experiments by piercing the peanut. With this hole, it was easier for the moisture to come out with a lower temperature. The time required was reduced by about 40%.
And when salted, the taste of peanut was very good as the salt has entered in the peanut. We prepared a small manufacturing gadget which could make holes in for 30-40 peanuts at a time. There were no black spots on the peanut.
