The smoke ring is a pink layer underneath the surface of done meat that is created when the meat is exposed to smoke during smoking. However, based on multiple sources, we can learn that it is a slightly more complicated process that depends on many factors.
A smoke ring is made as a result of reactions occurring between Carbon Monoxide ( CO ), Nitric Oxide ( NO ) and a protein that is also called myoglobin.
If you think about it for a while, you’ll agree with me that each type of meat has a different color. This is caused by a protein (myoglobin) that gives meat its color (red).
In its natural state, myoglobin has a purple and red color, but all of that changes when you expose the meat to oxygen. As soon as you cut a piece of beef the color of the meat starts to change. The reason behind this is the ability of myoglobin to react with oxygen.
The fresher the meat, the redder the color. If meat gets exposed to fresh air for too long, it will change its color to a not very aesthetic brown (oxymyoglobin) while also starting to give off a different (and quite unpleasant) smell (metimyoglobin). If this is the case, you can be sure that the meat was cut many days earlier and is simply not fresh.
This phenomenon is perfectly shown in this picture
All of that slightly complicated theory might only lead you to one question – what does it have to do with the smoke ring?
Burning wood generates gas (nitrogen dioxide) that in turn dissolves on the moist surface of the meat, combining with myoglobin. Such a reaction prevents a situation where the myoglobin turns into metmyoglobin upon longer exposure to oxygen.
That’s how the smoke gets trapped inside the pink color, creating the smoke ring.
You also need to know that nitric gas penetrates from the inside, which is why the pink ring is only created right underneath the meat’s surface. Most pink rings get at the depth of 1/8 to 1/2 inches.