Influence of ultimate pH on bovine meat tenderness during ageing

The aim of this work was to evaluate the influence of ultimate pH and agein g at 2+/-2 degrees C on the tenderness of beef. The m.long-issimus thoracis et lumborum from 23 young bulls excised at 28 h post mortem were grouped i nto: Normal (pH 5.5 to 5.8) moderate DFD (mod DFD) (5.8 < pH < 6.2) and DFD (pH 6.2 to 6.7). The toughness as measured by Warner-Brattier shear force (WBSF) and sensory evaluation, was significantly (p < 0.05) lower in the DF D group than in the Normal one and a significant (p<0.001) linear relations hip was found between ultimate pH and tenderness as evaluated by both metho ds. The myofibrillar protein solubility (MPS) at pH 7.0 was significantly h igher in the DFD group at all post mortem times whereas for myofibrillar fr agmentation index (MFI) higher values (p < 0.05) were only found in the DFD group at day I. In all three groups toughness decreased (p < 0.05) from 1 to 6 days, with no further decrease to 13 days. This decrease in toughness was associated with an increase of MFI in all pH groups. Collagen solubilit y in all three groups was not affected by ageing. No significant (p>0.05) d ifferences in soluble collagen and myofibrillar protein solubility (MPS) at pH 5.5 were found between the pH groups at any time. The tenderness evalua ted by both methods was significantly (p <0.05) related to MFI, MPS at pH 7 .0, cooking loss and juiciness. Total and soluble collagen, sarcomere lengt h, intramuscular fat and MPS at pH 5.5 were not significantly (p > 0.05) re lated with tenderness. (C) 1999 Elsevier Science Ltd. All rights reserved.