Effect of prerigor freezing and postrigor calcium chloride injection on the tenderness of callipyge longissimus.

Abstract

The effect of rapid prerigor freezing and postrigor freezing and postrigor calcium chloride injection on the tenderness of callipyge longissimus was studied. Ewe and wether lambs (n = 49; 1/2 Dorset x 1/2 Romanov) were grain-fed and slaughtered at approximately 250 d of age. Based on leg conformation scores, 23 of the carcasses had the callipyge phenotype. Within each phenotype, approximately one-half of the carcasses were chilled conventionally (24 h at -2 degrees C). At approximately 17 min postmortem, the remaining carcasses were submersed in liquid nitrogen for 15 min and then held at -2 degrees C for 4 d. At 1 d postmortem for carcasses chilled conventionally and at 4 d postmortem for carcasses 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. The 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 shortening (1.99 vs 1.63 microm; 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 panel tenderness rating was decreased by 49.4% in untreated callipyge longissimus after 14 d postmortem. Liquid nitrogen, calcium chloride injection and their combination did not affect d-14 longissimus shear force and sensory tenderness for normal lambs because untreated muscles were 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 improved the shear force and sensory tenderness of callipyge longissimus by 36.7 and 86.2% after 14 d postmortem, respectively (P < .001). The most effective treatment for mitigating the callipyge effect on tenderness was the combination (freezing and calcium chloride injection) treatment, which improved the shear force and sensory tenderness by 51.2 and 124.2% after 14 d postmortem, respectively (P < .001). We conclude that either treatment can effectively mitigate the negative effect of callipyge phenotype on longissimus tenderness. Callipyge lamb carcasses subjected to the combination of prerigor liquid nitrogen freezing, postrigor calcium chloride injection, and 14 d postmortem storage had tenderness similar (P > .05) to that of normal, untreated carcasses after 14 d of postmortem storage.