Pyridinoline (PYR) and Ehrlich's chromogen (EC) are well-known
mature collagen crosslinks associated with the toughness of high
connective tissue beef. The hypothesis that the concentration of
PYR increases and that of EC decreases with cattle age was investigated in a study involving calf-fed steers (n = 14), yearling-fed
Hereford–Aberdeen Angus or Charolais–Red Angus steers (n = 14)
and similarly bred mature cows (n = 12) slaughtered at 12, 20 and
73 months of age, respectively. Semitendinosus (ST) and gluteus
medius (GM) muscles were harvested 24 h post mortem and stored
frozen until meat quality and connective tissue analyses. Meat quality analyses indicated that for the ST mean muscle ultimate pH
values did not differ among age groups and cow ST showed lower
purge loss and L* (increased darkness) and b* values (decreased yellow)
and higher a* values (increased redness) than calf and yearling ST. For
the GM, mature cows had lower mean ultimate pH, L* (darker meat)
and b* (decreased yellowness) values, and lower purge and cooking
losses than yearling and calf GM. Intramuscular fat was significantly
(P b 0.05) lower in cow than in calf and yearling muscle for both ST
and GM muscles. Shear force did not differ between age groups for
the GM but ST shear force values were significantly higher for mature
cows. Total collagen content for the GM was not different between
age groups but yearling cattle showed higher total collagen in the ST
than in the other age groups and ST mean total collagen content was
higher than that in the GM. PYR concentration (mol PYR/mol collagen)
did not change with animal age in the ST or GM, although total amounts
of PYR in each muscle increased with age due to increases in total collagen with age. EC concentrations (mol EC/mol collagen) in both ST and
GM decreased with animal age and were negatively correlated with
shear force. Results indicated that total collagen rather than PYR
crosslink density increases meat toughness with animal age and the decline in EC concentration suggests that it may be replaced by another
crosslink as muscles mature.