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Ultimate pH (pH u ) is an indicator that influences post-mortem meat quality. We studied physiological and biochemical changes of steaks obtained from Nellore bulls (Bos indicus) during post-mortem ageing. To this, Longissimus lumborum (LL) muscles were classified into three groups: Normal-pH u (≤5.79), Intermediate-pH u (5.80-6.29) and High-pH u (≥6.30) groups, portioned into steaks, vacuum packaged and matured at 2°C for 0, 7, 14, 21 and 28 days. High-pH u steaks exhibited impaired colour stability and were darker compared to the other groups. High-and Normal-pH u steaks showed improved tenderness and myofibrillar fragmentation linked to proteolysis. Intermediate-pH u steaks were associated with a lower meat tenderness and decreased collagen solubility. High-pH u steaks retained a high pH during ageing and increased water-holding capacity. These findings provide evidence that highlight pH u as a strategy for the classification of pH u -dependent beef quality from Nellore bulls that can be adopted by the Brazilian meat industry.

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Bos taurus indicus temperament is variable and affects beef tenderization. Our objective was to investigate temperament and performance of non-castrated Nellore and identify groups based on Longissimus lumborum (LL) pH decline as well as beef characteristics produced by those groups. We investigated 94 animals with a subset of carcasses (n = 24) selected based on LL pH at 24 h postmortem (pm) to represent two groups: resistant to pH decline (> 5.8 called pH-Res; n = 10) and normal (< 5.7 called pH-Nor; n = 14). Steaks were fabricated from the LL muscle and randomly assigned to aging (2, 7, 14, and 21 days). Sarcomere length, cooking loss, myofibrillar fragmentation index (MFI), and Warner-Bratzler shear force (WBSF) were determined.Data on temperament were investigated in a multivariate approach, while beef data were compared between groups using the analysis of variance. Rectal temperature at the beginning of the finishing phase and total weight gain were greater and related to animals in the pH-Res group (p < 0.01 and p = 0.03, respectively). Temperature and pH decline curves, sarcomere length, and cooking loss revealed that pH-Res produced beef with lower quality compared to the pH-Nor group. Results for MFI and WBSF did not show differences between groups within each time pm; however, overall steaks from pH-Res were tougher (p = 0.06). Incidence of LL pH between 5.8 and 5.9 at 24 h pm did not compromise the tenderization rate or extension; however, it affected the water holding capacity in this population of Nellore cattle.

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