Connective tissue sheaths serve as the scaffolds in skeletal muscle, and they allow for the growth and development of muscle tissue. However, these connective tissues also cause the “background toughness” in meat. Therefore, meat tends to be less tender when there is a high amount of connective tissue present. Collagen is the main component of connective tissue, and it is stabilized by both immature and mature crosslinks. The heat-labile immature crosslinks mainly exist in younger animals, and they transform into heat-stable mature crosslinks as animal age. Pyridinoline (PYD) and deoxypyridinoline (DPD) are major mature collagen crosslinks. PYD is mainly found in muscles, while DPD is found in bones. PYD and DPD densities vary among muscles depending on their location and functionality.
Some collagen forms are immediately solubilized upon heat treatment, and there are collagen structures that cannot be solubilized even with extensive heat treatment. These heat insoluble collagen tissues that remain in meat after cooking are the main contributor to the “background toughness” of the meat. However, the heat insoluble collagen is not well characterized, and the factors affecting collagen solubility are not well understood. Asian consumers were selected to participate in the sensory panel of the current study due to their culture and familiarity to beef shank cuts. Although beef shank cuts are not well sought after in the U.S., stewed beef shank is widely consumed in many Asian cultures, particularly in China in the form of “sauced beef.” Therefore, our goal was to investigate mature collagen crosslink densities and their relationship to cooked beef tenderness and connective tissue texture by using a stewed beef shank model.