--Of all the attributes of eating quality, tenderness is rated the most important factor affecting beef palatability--

Slow cooked meals are generally easier to make and very cost effective using cuts of meat that improve in texture and flavor when cooked for long periods of time at low temperatures. These tough cuts of meat contain large amounts of collagen which require long cooking times to break down into a rich gelatin.

HOW DOES SLOW COOKING WORK?

When you cook, collagen begins to melt at about 160F and turns to a rich liquid,gelatin. This gives meat a lot of flavor and a wonderful silky texture. When cooking it is important to liquify collagen.

Denatu r ation of the collagen molecule is a kinetic process, and hence a function of both temperature and duration of heating. Cooking at low temperatures require long periods of time to liquify collagen.

COOKING MEAT TEMPERATURES

105F/40C - 122F/50C--Calpains begin to denature and lose activity till around 105F, cathepsains at 122F. Since enzyme activity increases up to those temperatures, slow cooking can provide a significant aging effect during cooking. Meat should however be quickly seared or blanched first to kill surface microbes.

120°F/50°C -- Meat develops a white opacity as heat sensitive myosin denatures. Coagulation produces large enough clumps to scatter light. Red meat turns pink.

Rare Meats: 120°F/50°C is the early stages of juiciness in meats as the the protein myosin, begins to coagulate . This lends each cell some solidity and the meat some firmness. As the myosin molecules bond to each other they begin to squeeze out water molecules that separated them. Water then collects around the solidifyed protein core and is squeezed out of the cell by connective tissue. At this temperature meat is considered rare and when sliced juices will break through weak spots in the connective tissue.

140°F/60°C -- Red myoglobin begins to denature into tan colored hemichrome. Meat turns from pink to brown-grey color.

140°F/60°C -- Meat suddely releases lots of juice, shrinks noticebly, and becomes chewy as a result of collagen denaturing which squeezes out liquids.

Medium -- Well Meats: Collagen shrinks as the meat tmeperature rises to 140/60 more of the protein coagulates and cells become more seggregated into a solid core and surrounding liquid as the meat gets progressively firmer and moister. At 140-150 the meat suddenly releases lots of juices, shrinks noticeably and becomes chewier as a result of collagen shrinkage. Meat served at this temperature is considered medium and begins to change from juicy to dry.

160°F/70°C -- Connective tissue collagen begins to dissolve to gelatin. Melting of collagen starts to accelerate at 160F and continues rapidly up to 180F.

Well Done Slow Cooked Meats: Falling apart tenderness collagen turns to gelatin at 160/70. The meat gets dryer, but at 160F the connective tissues containing collagen begins to dissolve into gelatin. With time muscle fibers that had been held tightly together begin to easily spread apart. Although the fibers are still very stiff and dry the meat appears more tender since the gelatins provide succulence.

NOTES: At 140°F changes are caused by the denaturing of collagen in the cells. Meat served at this temperature med-rare is changing from juicy to dry. At 160°F/ 70°C connective tissue collagen begins to dissolve to gelatin. This however is a very lengthy process. The fibers are still stiff and dry but meat seems more tender. Source: Harold McGee -- On Food and Cooking