What Is Collagen?

• Collagen is a protein formed by amino acids and appears in the body in the form of tendons, ligaments and muscle-sheathing. Sometimes referred to as the body's glue, collagen binds muscles to bones and accounting for much of the final shape of an animal's or human's frame. Its connective capacities mean that in raw form collagen is stringy, tough and tenacious. Its presence has a direct relationship to the tenderness of meat. Low-work muscles, like the belly or saddle, contain less collagen than hard-work muscles like those in the legs, neck, shoulders and rump. Meat from the low-work area includes loin and tenderloin and cuts around the ribs, where meat is solid and soft. Meat from hard-work areas, like shoulder or chuck, involves several muscles joined with lacings of collagen and is therefore generally tougher.

Breaking Collagen Down

• Proteins examined under a microscope appear as tightly tangled or twisted fibers. Exposed to heat, tangles relax and stretch in a process called denaturing. Denatured meat proteins tend to be easier to chew, or tenderer, than raw ones. Beginning at approximately 120 degrees Fahrenheit, meat proteins begin the denaturing process, relaxing fibers, releasing moistures and becoming edible meat. After several other stages, at approximately 160 F, tough collagen melts into soft, viscous gelatin, which coats muscle fibers. Food scientists note, however, that the denaturing of collagen protein is a kinetic process, requiring time as well as temperature, and the softening of collagen-rich meat can be expected to take hours rather than minutes.

Slow Cooking and Collagen

• The mechanics of slow cooking are ideal for tenderizing collagen-rich meat because they expose proteins to low-moderate temperatures in a moist environment over a sustained period of time. The six to 10 hours specified by many slow-cooker recipes let denaturing follow its necessary course and supports the process with the presence of liquid.

The Results

• Both pork shoulder and beef chuck are relatively inexpensive cuts of meat known for good flavor but less than ideal texture. Each is composed of several muscles, held together with abundant connective tissue and marbled with some fat. In each cut, connective tissue, or collagen, makes meat seem stringy, tough and generally unpleasant to chew. Depending on the brand, your slow cooker may offer cooking temperatures in a range from under 200 F to over 212 F. Recipes may add seasonings and liquids beyond released meat juices to enhance flavor, but the bulk of the tenderizing work is done by slow, steamy heat over a period of six or more hours. Melted connective tissue gives meat a coat of glossy juice, and your pulled pork or pot roast emerges fork-tender.