Paleron (shoulder blade)

Shoulder muscles work constantly, so they are rich in collagen, the protein of connective tissue. Cooked fast, collagen tightens and the meat is chewy. Collagen dissolves into gelatine over a wide range of temperatures, very slowly when the meat is merely warm and faster the hotter it gets. Held for hours at a bare simmer, so that the inside of the meat sits well above 70 °C, it slowly turns to gelatine, which lubricates the fibres and thickens the cooking liquid. That is why paleron is braised rather than grilled, and why a bourguignon made with it has a glossy, clinging sauce.

The muscle fibres themselves still tighten and squeeze out moisture as they heat, so the art is to keep the liquid at a bare simmer — boiling hard makes fibres dry and stringy even as the collagen melts.