Ageing only had a slight effect on ST tenderness
(P 6 0.05; Table 2), but significantly improved the tenderness
values of SM and GB (Table 3). Thus, the percentage
of improvement in tenderness [(maximum
tenderness – tenderness at 1 day of ageing)/(tenderness
at 1 day of ageing)] was lower than 15% in seven out
of nine cases (3 breeds · 3 slaughter weights) in ST,
while it was higher than 35% in eight out of nine and
in seven out of nine cases (3 breeds · 3 slaughter
weights) in SM and GB, respectively. This probably
means that ST is tender enough without ageing. Consumers
perceived it as very tender at short times of ageing
(1–2 days), so further ageing may not improve ST
tenderness substantially. However, GB and SM could
require longer ageing (8–16 days) to reach the same tenderness
as ST. According to the results in Table 3, long
ageing times tend to attenuate differences among muscles
(mainly between ST and the others). In suckling
lambs, the maximum difference among muscles was
45.6% at 1 day of ageing and 30.2% at 16 days. In light
lambs these values were 40.0% and 32.5%, and 43.3%
and 32.9% in early fattening lambs, respectively.
In contrast with our results, Boleman et al. (2004)
found that Warner–Bratzler values of ST and SM improved
with ageing by a similar percentage (from 5 to
15 days of ageing). This may be due to differences in
tenderisation rate in the first days of ageing, which were
not considered in their study.