Tough aged meat presents greater expression of calpastatin, which presents postmortem protein profile and tenderization related to Nellore steer temperament.

Eighteen Nellore steers were classified as either excitable (high index) or calm (low index) temperament, and high or low WB Shear Force (SF) in Longissimus lumborum at 16 days postmortem, with a subset assigned to four groups: HTHS-high temperament and SF (n = 5); HTLS-high temperament and low SF (n = 4); LTHS-low temperament and high SF (n = 4); LTLS-low temperament and SF (n = 5). Only the second calpastatin peak was detected at 48 h in the all samples, and the calpastatin activity only differed (P < .05) between shear force groups.