EFFECT OF PRERIGOR FREEZING AND POSTRIGOR CALCIUM-CHLORIDE INJECTION ON THE TENDERNESS OF CALLIPYGE LONGISSIMUS

The effect of rapid prerigor freezing and postrigor freezing and postr igor calcium chloride injection on the tenderness of callipyge longiss imus was studied. Ewe and wether lambs (n = 49; 1/2 Dorset x 1/2 Roman ov) were grain-fed and slaughtered at approximately 250 d of age. Base d on leg conformation scores, 23 of the carcasses had the callipyge ph enotype. Within each phenotype, approximately one-half of the carcasse s were chilled conventionally (24 h at -2 degrees C). At approximately 17 min postmortem, the remaining carcasses were submersed in liquid n itrogen for 15 min and then held at -2 degrees C for 4 d. At 1 d postm ortem for carcasses chilled conventionally and at 4 d postmortem for c arcasses frozen in liquid nitrogen, the longissimus muscles from both sides were removed. The longissimus from one side of each carcass was vacuum-packaged and aged (1 degrees C) conventionally for 7 or 14 d. T he remaining muscles were injected with a 2.22% solution of food-grade calcium chloride at 5% by weight, vacuum-packaged, and aged as above. Liquid nitrogen freezing was effective in limiting sarcomere shorteni ng (1.99 vs 1.63 mu m; P < .05). Warner-Bratzler shear force values of callipyge longissimus were 222 and 232% of that of normal longissimus after 7 and 14 d postmortem, respectively(P < .001). Also, trained pa nel tenderness rating was decreased by 49.4% in untreated callipyge lo ngissimus after 14 d postmortem. Liquid nitrogen, calcium chloride inj ection and their combination did not affect d-14 longissimus shear for ce and sensory tenderness for normal lambs because untreated muscles w ere already tender. Liquid nitrogen freezing improved the shear force and sensory tenderness rating of callipyge longissimus by 30 and 86.2% after 14 d postmortem, respectively. Calcium chloride injection impro ved the shear force and sensory tenderness of callipyge longissimus by 36.7 and 86.2% after 14 d postmortem, respectively(P < .001). The mos t effective treatment for mitigating the callipyge effect on tendernes s was the combination (freezing and calcium chloride injection) treatm ent, which improved the shear force and sensory tenderness by 51.2 and 124.2% after 14 d postmortem, respectively (P < .001). We conclude th at either treatment can effectively mitigate the negative effect of ca llipyge phenotype on longissimus tenderness. Callipyge lamb carcasses subjected to the combination of prerigor liquid nitrogen freezing, pos trigor calcium chloride injection, and 14 d postmortem storage had ten derness similar (P > .05) to that of normal, untreated carcasses after 14 d of postmortem storage.