Release of lysosomal enzymes during post mortem conditioning and their relationship to tenderness

Abstract
Summary: Samples of the M. longissimus dorsi were taken from beef carcasses 1 hr, 24 hr, 5 days, 7 days and 14 days post mortem. Tenderness (shear force), the amount of protein and hydroxyproline in filtered muscle homogenates, the activity of β‐glucuronidase in muscle fractions and the electron histochemical determination of acid phosphatase were measured at these post mortem times.Shear force was a maximum at 24 hr and decreased thereafter to a value less than that of the 1 hr samples by 14 days. The amount of protein and hydroxyproline in filtered muscle homogenates was a minimum at 24 hr and increased to a maximum at 14 days. The specific activity of free β‐glucuronidase (a lysosomal enzyme) increased with post mortem ageing, while the specific activity of bound (sedimentable) β‐glucuronidase decreased with post mortem ageing, suggesting that this enzyme is released during the conditioning period. Electron histochemical determination of acid phosphatase activity showed the activity to be localized in specific areas around the I‐band at early post mortem times: the activity was more dispersed throughout the cell at later post mortem times.