Consumers often associate a bright-red color with beef freshness and wholesomeness. Higher-than-normal-pH conditions are an example of a color deviation in which beef failed to have a bright-red color, leading to discounted carcasses and economic losses to the meat industry. High-pH beef or dark-cutting beef is one of the most prominent beef-quality defects worldwide. Dark-cutting beef is characterized by elevated muscle pH, increased water-holding capacity, a dry-sticky texture and an undesirable very dark lean color. The 2011 National Beef Quality Audit reported that 3.2 percent of carcasses graded were assessed as dark-cutting. Although the etiology of dark-cutting beef is not clear, it is widely accepted that pre-harvest stress leads to depletion of glycogen reserves prior to slaughter, which hinders the formation of lactic acid in postmortem muscle. The average postmortem muscle pH in normal beef ranges from 5.4 to 5.6 because of lactic acid formation. In dark-cutting beef, however, pH ranges from 6.0 to 6.8 because of limited lactic acid from glycogen.
Various factors such as the plane of nutrition, cattle temperament, climate variation, misuse of growth promotants/implants, mishandling practices and shipping are all potential contributors for dark-cutting carcasses. All these factors can affect stress and glycogen levels prior to animal harvest. In recent years, beef producers have optimized various factors such as feedlot management, good handling practices and proper transportation practices to minimize losses from dark-cutting beef. Still, dark-cutters continue to be a quality defect around the world. Therefore, understanding the fundamental basis of high-pH beef is critical to developing post-harvest strategies to improve color and value of high-pH beef.
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