Muscle of dark and normal beef differs metabolically.

Reduction in muscle glycogen triggered by adverse antemortem handling events alters postmortem energy metabolism and results in a high ultimate pH and dark, firm and dry beef, often referred to as 'dark-cutting'. However, the relationship between atypical dark (AT) beef, postmortem energy metabolism and underlying tissue characteristics remains somewhat unclear. Cattle harvested in the US and Canada representing normal (pH < 5.6), AT dark (pH 5.6-5.8) and dark cutting (DC; pH > 5.8) beef were analyzed for tissue characteristics related to energy metabolism. Results show AT dark beef is more oxidative but similar to normal beef in glycolytic potential and nucleotide abundance. Mitochondria DNA content (P < 0.05, Canada; P < 0.005, US) and oxidative enzymes for DC and AT dark beef were greater (P < 0.01; Canada and US) compared to normal beef. Myoglobin tracked (P < 0.01) with color classification. These findings show both DC and AT beef are inherently more oxidative and raise the possibility that more oxidative muscle may be more prone to develop dark beef.

Time of dehairing alters pork quality development.

Studies investigating the effect of scald time on pork quality are confounded with time of dehairing. To understand better pork quality development and two-toning in hams, twenty-four carcasses were assigned to an 8- or 16-min dwell time prior to the dehairing, with or without scalding (n = 6 per trt). Semimembranosus (SM) muscles were collected following dehairing and at 24 h postmortem. Protracted time to dehair improved ultimate pH (pHu; P < 0.005) and reduced (P < 0.05) color variation. One hundred forty-two carcasses were then subjected to protracted (control, 10-min) dwell times (15-min, or 20-min) in an industrial setting. Lightness was improved with 15-min dwell times compared to control, however 20-min dwell decreased the pHu (P < 0.001), increased lightness (P < 0.05), and percent purge (P < 0.001) in the SM. Also, lightness of the longissimus muscle (LM) increased (P < 0.001) with dwell time. These data show time to dehairing impacts pork quality development and suggest dehairing may be critical to quality development in a muscle-dependent manner.