Meat color is an important aspect of a consumer’s purchase decisions regarding meat products. Perceived meatcolor results from the interaction of light, a detector (i.e., human eye), and numerous factors, both intrinsic and extrinsic tothe muscle, that influence the chemical state of myoglobin. The complex nature of these interactions dictates that decisionsregarding evaluations of meat color be made carefully and that investigators have a basic knowledge of the physical andchemical factors affecting their evaluations. These guidelines were compiled to aid investigators in navigating the pitfalls ofmeat color evaluation and ensure the reporting of information needed for the appropriate interpretation of the resulting data.The guidelines provide an overview of myoglobin chemistry, perceptions of meat color, details of instrumentation used inmeat color evaluation, and step-by-step protocols of the most common laboratory techniques used in meat color research.By following these guidelines, results of meat color research may be more clearly presented and more easily replicated.

In postmortem muscle, mitochondria remain active and can influence beef color by oxygen consumption and metmyoglobin reduction. Enzymes involved in glycolysis and the tricarboxylic acid cycle can generate reducing equivalents such as succinate or NADH. Mitochondrial activity is critical to maintain steaks that are bright cherry-red and improve color stability. This review seeks to characterize the role of mitochondria in beef color; more specifically to understand the effects of mitochondrial function on myoglobin redox stability.

Any deviation from a bright-red color leads to a discounted price or beef is discarded. Limited data are currently available on the economic losses due to retail beef discoloration. Therefore, the objective of the study was to estimate economic losses, the amount of beef discarded, natural resource wastage, and environmental impact due to beef discoloration. One-year data of total beef sales, total beef discarded, and discounted sale values were collected from 2 national retail chains and 1 regional retail chain located in the Southern United States, representing data from 5,034 stores and 44 states. The US beef system life cycle parameters from published literature were used to calculate the impact of discarded meat on water and energy use and greenhouse gas emissions. The study noted that approximately 2.55% of beef is discarded because of discoloration. The results indicate that the US beef industry loses $3.73 billion annually owing to discoloration. The total amount of beef discarded per year in the US corresponds to 194.70 million kg, which represents wasting 780,000 animals and the associated natural resources used in their production. A 1% decrease in discolored beef in the US could reduce natural resource waste and environmental impact by 23.95 billion L of water, 96.88 billion MJ of energy consumed, and 0.40 million tons of carbon dioxide equivalent emission along the beef upstream value chain. Therefore, improving the color stability of meat could increase the sustainability of beef production and limit the waste of nutritious beef, so the application of novel technologies to mitigate color deterioration should be imperative.

Deviation from a bright cherry-red color of fresh meat results in less consumer acceptance and either discounted or discarded products in the value chain. Tissue homeostasis changes immediately after exsanguination, leading to acidification of muscle. Any alteration in pH drop can influence both muscle structure and enzymatic activity related to oxygen consumption and the redox state of myoglobin. This review focuses on both fundamental and applied approaches to under-stand the effects of pH on biochemical changes, oxygen diffusion, and its impact on meat color. Recent updates utilizing high-throughput “omics” approaches to elucidate the biochemical changes associated with high-pH meat are also dis-cussed. The fundamental aspects affecting fresh meat color are complex and highly interrelated with factors ranging from live animal production to preharvest environmental issues, muscle to meat conversion, and numerous facets along the merchandising chain of marketing meat to consumers.

Interrelationship between mitochondria and myoglobin function influence beef color. NADH level in postmortem muscle is an important determinant of mitochondrial activity and metmyoglobin reduction. Increased aging time promotes discoloration of steaks; however, the mechanism of this effect is not clear. The objective was to characterize the role of wet‐aging in beef longissimus lumborum muscle mitochondrial function and to characterize the global metabolome to determine the mechanism of that can regenerate NADH. Beef longissimus lumborum muscles were randomly assigned to 3, 7, 14, 21, and 28 days aging periods. Surface color, biochemical, mitochondrial, and metabolite profiles were determined at each aging period and at the end of 6‐day display. During 6‐day display, sections aged for 28 days had 30.4% decrease in redness than sections aged for 3 days. Aging time decreased ( P <0.05) muscle oxygen consumption, mitochondrial protein content, and antioxidant capacity. Metabolites such as fumaric acid, creatinine, and fructose, that can take part in glycolytic/TCA cycle and regenerate NADH decreased ( P <0.05) with aging and display time. In support, NADH levels also decreased ( P <0.05) with aging time, but aging time had no effect ( P = 0.44) on NADH‐dependent reductase activity. The results suggest that decreased color stability in aged beef can be attributed to increased mitochondrial damage, depletion of metabolites that can regenerate NADH, and increased oxidative stress. Practical Application: Beef aging time results in increased discoloration of steaks under retail display. The current research determines the fundamental basis of lower color stability in aged beef. The results indicate that mitochondrial degeneration, depletion of metabolites that produce NADH, and increased oxidative stress can limit shelf‐life of aged steaks. Hence, application of post‐harvest strategies to minimize mitochondrial damage and oxidative changes may have the potential to increase shelf‐life of aged beef.