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Impact of up- and down-regulation of metabolites and mitochondrial properties on pH and color of longissimus muscle from normal-pH and dark-cutting beef.

Limited knowledge is currently available on the biochemical basis for the development of dark-cutting beef. The objective of this research was to determine the metabolite profile and mitochondrial content differences between normal-pH and dark-cutting beef. A gas chromatography-mass spectrometer-based non-targeted metabolomics approach indicated down-regulation of glycolytic metabolites, including glucose-1- and 6-phosphate and up-regulation of tricarboxylic substrates such as malic and fumaric acid occurred in dark-cutting beef when compared to normal-pH beef. Neurotransmitters such as 4-aminobutyric acid and succinate semialdehyde were upregulated in dark-cutting beef than normal-pH beef. Immunohistochemistry indicated more oxidative fiber type in dark-cutting beef than normal-pH beef. In support, mitochondrial protein and DNA content were greater in dark-cutting beef. This increased mitochondrial content, in part, could influence oxygen consumption and myoglobin oxygenation/appearance of dark cutting beef. The current results demonstrate that the more tricarboxylic metabolites and mitochondrial content in dark-cutting beef impact muscle-pH and color.