Rigor

Rigor means muscle rigidity or stiffness, as in rigor mortis. After slaughter, muscles pass through a phase of stiffening driven by biochemical changes in the fibres, and understanding this phase is essential in meat science because it determines tenderness, water-holding capacity, and processing behaviour. How carcasses are chilled, hung, and handled during rigor affects the final eating quality. Meat that is processed or frozen at the wrong stage can become tough, so timing operations around rigor is a core skill in slaughter and butchery.