[FONT="]This is from
www.Amazingribs.com [/FONT]
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It is important to understand that the reddish color in meat and its juices is not blood.[/FONT] That was pretty much all drained out in the slaughter house. The ruddiness comes from a pigment called
[FONT="]myoglobin.[/FONT]
At about 120F, some of the fluids begin to get milky. As the meat gets approaches 140F, cell walls begin to break open and release liquids. This is what makes meat juicy. Raw meat isn't very juicy because the cell walls are all intact. After the fibers break down the juices release more easily as you chew. That's why a rare steak is juicier than raw steak.
At about 140F red meat begins to turn pink as the myoglobin begins to change. As the temperature rises and the myoglobin changes, the juices go from pink to clear, and the meat turns tan. Also at about 140F, the heat causes the sheaths around the muscle cells to shrink rapidly and squeeze out moisture much like wringing out a wet wash cloth. It can happen suddenly, and the meat will rapidly shrink, stiffen, and become chewier. Juices will bead and pool on the surface. That's why medium rare steak cooked to about 130F is much juicier than well-done steak cooked to 160F. This drying process even happens when meat is boiled. You would think that boiling meat would keep it moist, but boiled meat can get as dry as cardboard. Poaching or braising meat by submerging it in liquid below 212F, the boiling point, will not drive off the moisture as rapidly.
As the hot air circulates in an oven (and all covered grills, smokers and outdoor cookers are ovens), the moisture on the surface runs off and evaporates. The lower the oven temp, the less evaporation, and the juicier the ribs. Evaporation is not a problem with a big roast like a pork butt. If the exterior is a bit dry and crusty on a
pork butt or
brisket, no sweat. The interior is so far away that the moisture cannot escape. But when it comes to ribs, the secret to moist meat is to cook it low and slow. But low and slow has benefits for even thick cuts. It seems to allow more flavor to develop.
Further cooking transforms more of the compounds in the meat. Some of them begin to escape as enticing aromas. This is no great loss. We smell powerful scents even if some aromatic compounds are as low as a few parts per billion. These aromas can cause a problem however. It will attract the neighbors. Ladies, if you want to catch a man, forget the expensive implants and get a smoker!
The melting of collagen really starts to accelerate as the meat hits 160F and it continues rapidly on up to 180F. By now lean meat like steak or pork loin is well done and beginning to dry out. On collagen and fat laden cuts such as ribs, pork shoulder, or brisket, although the muscle fibers are drying and toughening, the collagen that held them together as bundles begins to turn to liquefy; the meat gets easier to chew and the gelatinous collagens makes the texture more pleasing.
[FONT="]Meanwhile the fat is softening, rendering, spreading through the meat to lubricate it, and dripping out. As it softens, fat absorbs the aromas and flavors from spices in the rub, marinade, or brine if you used them. Most important, the fat absorbs the smoke flavor if you are using a smoker. If the meat gets too hot, all the fat will render out and rob the meat of much of their flavor and texture. [/FONT]