THE SCIENCE OF MEAT COLOR INCLUDING THE INFAMOUS SMOKE RING
Barbecue is one of those methods of cooking that is loved by many but not truly understood by those who love it! I’m always entranced by the fact that barbecue gets mingled with the word grilling when the reality is, these two methods of cooking mean very different things. One common denominator though is the meat used for these cooking methods that simply becomes a variant of color so completely different from traditional cooking methods like the frying pan, slow cooker, and oven.
Let’s take a closer look first, at what meat is and then how color develops when cooked.
You likely define meat as an animal protein that is derived from an animal like cattle, pig, chicken, lamb, goat, etc., and you would be correct in a very abbreviated definition. But there is so much more to meat that most don’t understand.
Meat is mostly the muscle tissue of an animal which is made up of 75% water, 20% protein, and 5% fat, carbohydrates, and various other protein. The muscles themselves are made of bundles of cells called fibers. Each cell is comprised of thread-like fibers made of two proteins: actin and myosin.
The purpose of these protein fibers is to make muscles contract and relax, which requires an immense amount of energy, which the fibers derive from the energy-carrying molecule ATP -adenosine triphosphate. To produce ATP there must be oxygen which muscles get from circulating blood. When an animal is killed, blood circulation stops resulting in all muscles exhausting their supply of oxygen. When oxygen is halted it halts the production of ATP, resulting in the sugar stored in muscles known as glycogen, to be broken down without oxygen support. The result is the production of lactic acid that builds up in the muscle tissue. If this acid level is too high, the meat loses its water-binding ability and becomes pale and watery. Too low, and the meat will be tough and dry. Add to this the calcium release that occurs when the lactic acid builds up, and the myosin and actin proteins become fixed. It’s important not to freeze animal meat too soon after slaughter or the meat will become tough. The meat needs to age to allow the enzymes in the muscle cells to break down these overlapping proteins and produce tender meat.
Why We Cook Meat
Denaturing is the process of breaking, unwinding, and coagulating the protein molecules when meat is heated. When heated, muscle fibers release water. Remember, meat is roughly 75% water when raw. You can retain moisture or water content of meat by using some specific techniques including brining, steaming, braising or poaching, and tenderizing using acid.
Here’s a summary of what happens at specific cooking temperatures to meat:
105°F/40°C — 122°F/50°C: blanch or sear meat first kills surface microbes then allow the proteins to denature at these temperatures giving an aging effect to the meat
120°F/50°C: meat has a white opacity as the myosin protein denatures. Red meat begins to turn pink. This is known as the “rare” stage of meat cooking and when sliced, the juices will break through the weak spots in the connective tissue.
140°F/60°C: Red myoglobin begins to denature and turns tan colored. Myoglobin is another protein store in muscle that is water soluble. You would know this protein as the red juice in meat packaging when you purchase store bought product. It’s not blood but it does receive oxygen and iron from hemoglobin in blood. At this temperature, meat releases a lot of juice, shrinks in size, and becomes chewy. It is known as “medium” in doneness.
160°F/70°C: Connective tissue is what binds muscles to bone. Throughout the muscle is a softer connective tissue called collagen. When cooked, collagen dissolves or melts and becomes gelatin. This melting is what gives meat a silky texture and moisture. Collagen starts to accelerate the melting stage at 160°F and continues rapidly until 180°F. Despite the meat drying out at this temperature, melted collagen is what makes meat seem more tender. Just remember, lean meats as well as chicken and turkey don’t have much collagen so don’t over-cook them.
The Smoke Ring
Before we discuss the smoke ring, I need to mention the Maillard reaction. This is the reaction that occurs between amino acids and reducing sugars in meat that is exposed to dry heat such as a frying pan. What results is that beautiful, brown exterior that gives meat a rich, deep flavor. This only occurs with a temperature above 300°F and with dry heat.
Now to the pink ring that commonly occurs just under the surface of a smoked meat. The smoke ring is caused by gases in the smoke that preserve the myoglobin and interact with the nitric oxide (NO) and carbon monoxide (CO) in combustible material like charcoal and wood. The gases react with the iron in myoglobin and result in the telltale ring of pink just under the surface, while the rest of the meat will turn gray due to the NO and CO only having limited penetration ability in the meat. This chemical reaction is similar to what happens to meats exposed to curing salts which also produce a pink coloring. The ring stops growing when the meat hits about 170°F and myoglobin loses its oxygen retaining ability.
If you want a smoke ring then you must incorporate cold meat into a low-temperature equipment. This will allow the meat to remain below 140°F for a longer time which is the temperature at which myoglobin begins turning brown.
As a final note, keep in mind that any meat that goes to black in color is never good. That means the meat’s surface has essentially turned to carbon and the ingestion of carbon laced foods has been proven to be a carcinogen. If you take your meat to this stage, do everyone a favor and throw it away. No one needs to know you took the meat too far!
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