Our objectives were to examine the effects
of prerigor excision and rapid chilling vs. conventional
carcass chilling of two muscles on proteolysis and
tenderness during the postmortem storage, as well as
the effects of fast and slow rates of cooking on myofibrillar
characteristics and tenderness. The longissimus
thoracis (LT) and triceps brachii (TB), long head muscles
were removed 45 min after exsanguination from
the left side of 12 carcasses and chilled in an ice bath
to induce cold shortening (excised, rapidly chilled). At
24 h postmortem, the corresponding muscles were removed
from the right side (conventionally chilled). All
muscles were cut into 2.54-cm-thick steaks and assigned
to one of two postmortem times (1 or 14 d), and
to raw and cooking treatments. Steaks were cooked at
260°C(FAST) or 93°C(SLOW) in a forced-air convection
oven to an internal temperature of 70°C. Cooking loss,
cooking time, and Warner-Bratzler shear force (WBSF)
were measured on cooked steaks. Sarcomere length
(SL) and the extent of proteolysis of desmin were measured
on raw and cooked steaks. As expected, the excised,
rapidly chilled muscles had a much more rapid
(P < 0.05) temperature decline than those that were
conventionally chilled. The excised, rapidly chilled treatment resulted in shorter (P < 0.05) SL, and SL was
shorter (P < 0.05) in LT than in TB steaks. Raw steaks
had longer (P < 0.05) SL than cooked steaks, regardless
of chilling treatment. The FAST cooking resulted in
shorter (P < 0.05) SL thanSLOWcooking in conventionally
chilled steaks, but cooking rate had no effect (P >
0.05) on SL of rapidly chilled steaks. Generally, TB
steaks required longer (P < 0.05) cooking times and had
higher (P < 0.05) cooking losses than LT steaks, and
FAST-cooked steaks had greater (P < 0.05) cooking
losses than SLOW-cooked steaks. Rapidly chilled
steaks had less (P < 0.05) degradation of desmin than
conventionally chilled steaks (31 vs. 41%). Aging for
14 d increased (P < 0.05) desmin degradation. Rapid
chilling of muscles resulted in much higher (P < 0.05)
WBSF values, whereas aging resulted in lower (P <
0.05) WBSF values. The SLOW-cooked TB steaks were
more tender (P < 0.05) than FAST-cooked TB steaks
and LT steaks cooked at either rate. Excised, rapidly
chilled muscles underwent proteolysis, but it occurred
at a slower rate during the first 24 h postmortem than
it did in conventionally chilled muscles. Cooking rate
did not affect tenderness of LT steaks, but SLOW cooking
resulted in more tender TB steaks.
