The average time to reach 10 C in M. longissimus dorsi was 7 h 45 min (4 h 25 min to 10 h 24 min). Five of seven slaughterhouses differed from each other ( p < 0 :05). When the temperature was 7 C, the pH was on average 5.89 and varied between 5.52 and 6.17. The slaughterhouses formed three distinct groups, based on the pH at 7 C ( p < 0 :05; Table 1). In some slaughterhouses the pH was close to the pHu, but in others only about a half of the pH fall had taken place.
 During this period the shear forces decreased by 18% (M. longissimus dorsi) and 8% (M. semimembranosus).By sensory evaluation the tenderness increased by 24% and 0%, respectively (results not shown).Because the correlations between shear force measurements and sensory evaluation within the slaughterhouses were on average )0.85, ranging from )0.78 to
)0.85 for M. longissimus dorsi, only the shear force
measurements are discussed later. In M. semimembranosus the changes were smaller and the correlations
were lower, being )0.69 on average, and none or hardly
any tenderisation occurred on ageing. Therefore, the M.
semimembranosus results will not be discussed further.
The correlations between the shear force measurements and different cooling rate/pH indicator values
were calculated to find the best fit. It was found that the
pH value when the temperature reached 7 C was the
most significant factor to explain the variation in shear
force. The correlation between the pH values at 7 C and
shear force values, using the slaughterhouse averages, at
5 d postmortem was r ¼ þ0 :94 ( p ¼ 0 :002). The regression equation ( N ¼ 7, R2 ¼ 87 :1%) was (Eq. (1);
Fig. 1)