| dc.description.abstract | Elevated muscle pH in dark cutting beef can enhance mitochondrial activity and stability of enzymes involved in oxygen consumption. Both processes can influence the myoglobin oxygenation, hence beef color. Limited studies have characterized the effects of extended aging on biochemical properties of dark cutting beef. Therefore, the objectives were: (1) to determine the effects of extended aging on biochemical factors involved in dark cutting beef, and (2) to quantify the mitochondrial content in normal pH and dark cutting beef using real time quantitative polymerase chain reaction (q-PCR). Ten USDA choice (pH = 5.6) and ten no-roll dark cutter (pH > 6.4) strip loins (IMPS #180) were obtained from a commercial packing plant within 3 d of harvest. Loins were cut into four equal sections, vacuum packaged, and aged for 21, 42, and 62 d at 2�C. Following aging of normal pH and dark cutting loin sections, two 2.5-cm thick steaks were cut and used to determine blooming properties, oxygen consumption, metmyoglobin reducing activity, lipid oxidation, mitochondrial quantification, and myoglobin concentration. Surface color readings were measured using a HunterLab Miniscan XE Plus spectrophotometer. Oxygen consumption rate and metmyoglobin reducing activity were measured as oxygenation capacity and initial metmyoglobin formation, respectively. q-PCR was used to quantify mitochondrial concentration. The experiment was replicated 10 times. The data were analyzed using the Mixed Procedure of SAS and significance was determined at P < 0.05. A muscle pH type x blooming time x aging interaction (P < 0.05) was found for a* values. Normal pH beef had greater a* values at all bloom time points. Metmyoglobin reducing capacity was greater (P < 0.05) for dark cutting beef compared with normal pH beef. Aging improved blooming properties of both normal and dark cutting beef. There was no effect on lipid oxidation. Mitochondria content was 2.04 fold greater in dark cutting beef compared with normal pH beef. Better understanding the biochemical properties will help to design strategies to improve blooming properties in dark cutting beef.Keywords: dark cutter, aging, bloom, mitochondria | |
