EFFECT OF FREEZING ON CALPASTATIN ACTIVITY AND TENDERNESS OF CALLIPYGE LAMB

The longissimus muscles (LM) from 12 lambs (eight = callipyge [CLPG] a nd four = normal [NML]; 48 kg) were used to 1) assess the effect of fr eezing with or without prior immersion in liquid nitrogen on calpastat in activity (CA) and on Warner-Bratzler shear force (WBS) in CLPG, 2) determine the freezing time required to reduce CA and WBS of CLPG to t hat of NML, and 3) compare sensory panel ratings for CLPG that is aged fresh to CLPG that is aged after freezing. At 24 h postmortem, chops (.64 and 2.54 cm) were removed from each CLPG LM and randomly assigned within side to one of six freezing times (0, 2, 4, 8, 20, and 42 d). Left-side chops were vacuum-packaged and frozen at -20 degrees C for t he assigned time (FROZEN) and right-side chops were treated similarly, except that they were frozen in liquid nitrogen first (FLASH). After freezing for the assigned time, the.64-cm chop was immediately assayed for CA, and 2.54-cm chop was thawed, aged at 2 degrees C for 14 d, an d refrozen for subsequent WBS measurement. Chops (.64 and 2.54 cm) wer e also removed from the longissimus of NML lamb carcasses. The d-0 CLP G and NML chops (2.54 cm) were vacuum-packaged, aged at 2 degrees C fo r 14 d, and frozen for subsequent WBS measurement. Calpastatin activit y did not differ between freezing treatments (P =.99) or with the free zing treatment x freezing time interaction (P =.80). Freezing reduced (P =.01) CA in CLPG by 44% from d 0 to d 42. Calpastatin activity for CLPG was similar (P >.05) to that of NML lamb after freezing for 8, 20 , or 42 d. Freezing at -20 degrees C for 42 d and then aging for 14 d reduced(P =.01) WBS in CLPG by 44% from d-0 values. Shear force values for CLPG-FROZEN were similar (P >.05) to NML after 8, 20, or 42 d of freezing. Sensory panel tenderness scores were higher (P <.05) for CLP G aged after freezing 42 d than for those aged fresh. Juiciness and fl avor ratings did not differ (P >.05) between CLPG aged fresh or after freezing. Freezing for at least 8 d before aging seems to be a viable method for increasing the tenderness of CLPG LM without reducing juici ness or flavor ratings.