Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/24/2012
Publication Date: 2/1/2012
Citation: Shackelford, S.D., King, D.A., Wheeler, T.L. 2012. Chilling rate effects on pork loin tenderness in commercial processing plants. Journal of Animal Science. 90:2482-2849.
Interpretive Summary: The present experiment determined that there are significant tenderness differences among pork packing plants due to differences in carcass chilling systems. These data show that there is a need to identify optimal chilling systems for pork and/or develop early postmortem treatments that mitigate the deleterious effects of blast chilling on tenderness while making use of the favorable impacts of blast chilling on production efficiency and microbiological quality.
Technical Abstract: The present experiment was conducted to provide a large-scale objective comparison of pork LM tenderness and other meat quality traits between packing plants that differ in stunning method and carcass chilling rate. For each of two replicates, hogs were sourced from a single barn of a commercial finishing operation that fed hogs from a single terminal crossbred line. On each day, three trucks were loaded, with each of those trucks delivering the hogs to a different plant. Plant A utilized CO2 stunning and conventional spray chilling, Plant B utilized CO2 stunning and blast chilling, and Plant C utilized electrical stunning and blast chilling. The boneless, vacuum-packaged, loin was obtained from the left side of each carcass (n = 597; 100/plant/rep). As expected, hot carcass weight, LM depth, and LM IMF did not differ among plants (P > 0.05). By 1.67 h postmortem (one h after the carcasses exited the harvest floor), the average deep LM temperature was more than 10ºC higher for Plant A than Plants B and C and deep LM temperature continued to be more than 10ºC higher for Plant A until 4.17 h or 6.33 h postmortem than for Plants C and B, respectively. Both plants that utilized blast chilling produced loins with higher LM slice shear force at 15 d postmortem than did the plant that utilized conventional spray chilling (P < 0.0001). The frequency of loins with excessively high (> 25 kg) LM slice shear force values was much greater for Plant B than Plant A (14.7% vs. 1%; P < 0.01). Among all the traits studied, including visual and instrumental evaluations of LM color, ultimate pH, marbling score, and lean color stability, the only other difference between Plants A and B was that purge loss during 13 d (from d 1 to d 14) of vacuum-packaged storage was higher for Plant B (P < 0.05). That is, with this sample of hogs and CO2 stunning, no loin quality advantages were detected for blast chilling. Regardless of chilling method, CO2 stunning resulted in darker LM lean color and higher LM water-holding capacity than did electrical stunning (P < 0.05). This research shows that differences in chilling systems among pork packing plants can have a strong influence on loin chop tenderness.