Beef color is an important sensory property that influences consumer purchasing decisions. Dark-cutting is a condition in which beef exposed to air does not have a characteristic bright red color. Defective postmortem glycolysis leads to greater than normal muscle pH (&gt; 6.0) in dark-cutting conditions. Dark-cutting beef is characterized by dark red color, and this beef is not sold in retail. Atypical dark-cutting beef represents darker meat at normal-pH, and this beef is not discounted and sold in retail conditions. The darker color of atypical is lower than typical dark-cutting conditions. The objective of the study was to determine the metabolite profiles of normal-pH, atypical dark-cutting, and typical dark-cutting beef. The muscles of all three types were collected from a commercial beef processing facility (n = 6 replications). The surface color was measured using a HunterLab spectrophotometer. The metabolites were extracted in methanol, dried under nitrogen, derivatized, and metabolites were separated by gas chromatography and analyzed by mass spectrometry (GC/MS). Chromatography data were analyzed using Chemstation software, and the spectra were deconvoluted using AMDIS software. The compounds were identified using the Fiehn metabolomics library and the NIST mass spectral library. The data were analyzed using MetaboAnalyst. The average pHs were 5.6 (normal-pH), 5.8 (atypical dark-cutting), and 6.4 (typical dark-cutting). The unsupervised principal component analysis indicated no differences in metabolite profiles between atypical and normal-pH beef, while different clusters were noted between typical dark-cutting and normal-pH beef. In both atypical and typical dark-cutting beef, several metabolites involved in muscle biochemistry such as glucose-6-phosphate, succinic acid, malic acid, aspartate, and citric acid demonstrated a similar trend in abundance. For example, a slight change (P &gt; 0.05) was noted between normal-pH and atypical dark-cutting beef. However, the change becomes more significant (P &lt; 0.05) between typical dark-cutting and normal-pH beef. The results suggest that darkening may be an outcome of the same etiology, but the muscle darkening and metabolite changes become more prominent with increased pH.

Gas chromatography-based metabolomics to characterize the differences between atypical and dark-cutting beef

ACS Spring 2022

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