Mitochondria play a significant role in beef color. However, the role of oxidative stress in cytochrome c release and mitochondrial degradation is not clear. The objective was to determine the effects of display time on cytochrome c content and oxidation-reduction potential (ORP) of beef longissimus lumborum (LL) and psoas major (PM) muscles. PM discolored by day 3 compared with LL. On day 0, mitochondrial content and mitochondrial oxygen consumption were greater in PM than LL. However, mitochondrial content and oxygen consumption were lower (P < 0.05) in PM than LL by day 7. Conversely, cytochrome c content in sarcoplasm was greater on days 3 and 7 for PM than LL. There were no significant differences in ORP for LL during display, but ORP increased for PM on day 3 when compared with day 0. The results suggest that muscle-specific oxidative stress can affect cytochrome c release and ORP changes.

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.

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Sample preparation is an important step in forensic toxicological analysis. With the technological advancements and the availability of mass spectrometers with increasing sensitivities, the need to remove potential interferences, such as matrix components or non‐relevant analytes to the analysis, is essential to optimizing an analytical method. Forensic toxicological analysis involves diverse analytes with a variety of chemical properties that need to be considered when selecting an appropriate sample preparation technique. The push for broad standards and best practice documents for forensic toxicology demonstrates the need for laboratories to ensure they meet the required capabilities to not only detect specific classes of drugs commonly encountered in forensic case work, but also ensure method validity. The objective of this article is to provide the forensic toxicology community a high‐level overview of biological matrices and their relevant components that should be considered during sample pre‐treatment as well as traditional and non‐traditional sample preparation techniques and present general applications. This article is categorized under: Toxicology > Drug Analysis