Postmortem Oxygen Consumption by Mitochondria and Its Effects on Myoglobin Form and Stability

Abstract

The objective of this study was to assess the morphological integrity and functional potential of mitochondria from postmortem bovine cardiac muscle and evaluate mitochondrial interactions with myoglobin (Mb) in vitro. Electron microscopy revealed that mitochondria maintained structural integrity at 2 h postmortem; prolonged storage resulted in swelling and breakage. At 2 h, 96 h, and 60 days postmortem, the mitochondrial state III oxygen consumption rate (OCR) and respiratory control ratio decreased with time at pH 7.2 and 5.6 (p < 0.05). Mitochondria isolated at 60 days did not exhibit ADP-induced transitions from state IV to state III oxygen consumption. Tissue oxygen consumption also decreased with time postmortem (p < 0.05). Mitochondrial oxygen consumption was inhibited by decreased pH in vitro (p < 0.05). In a closed system, mitochondrial respiration resulted in decreased oxygen partial pressure (pO(2)) and enhanced conversion of oxymyoglobin (OxyMb) to deoxymyoglobin (DeoMb) or metmyoglobin (MetMb). Greater mitochondrial densities caused rapid decreases in pO(2) and favored DeoMb formation at pH 7.2 in closed systems (p < 0.05); there was no effect on MetMb formation (p > 0.05). MetMb formation was inversely proportional to mitochondrial density at pH 5.6 in closed systems. Mitochondrial respiration in open systems resulted in greater MetMb and DeoMb formation at pH 5.6 and pH 7.2, respectively, vs controls (p < 0.05). The greatest MetMb formation was observed with a mitochondrial density of 0.5 mg/mL at both pH values in open systems. Mitochondrial respiration facilitated a shift in Mb form from OxyMb to DeoMb or MetMb, and this was dependent on pH, oxygen availability, and mitochondrial density.

Metabolite Profile Differences between Beef Longissimus and Psoas Muscles during Display

“…The addition of succinate can limit MetMb formation by electron transport mediated metmyoglobin reduction (Tang et al, 2005) and also by reverse electron transport (Belskie et American Meat Science Association.…”

“…Although various pre-and post-harvest factors can increase myoglobin oxidation, meat has an inherent capacity to delay metmyoglobin accumulation by a process called metmyoglobin reducing activity (MRA; Ledward, 1985). The concentration of reduced nicotinamide adenine dinucleotide (NADH), myoglobin chemistry, and mitochondrial activity play a significant role in metmyoglobin reduction (Tang et al, 2005;Ramanathan and Mancini, 2010;Nerimetla et al, 2017). In postmortem muscle, enzymes involved in the glycolytic and tricarboxylic acid cycle (TCA) retain activity.…”

“…However, the metabolite concentration decreases with postmortem time. Various studies have shown that the addition of metabolites such as lactate, pyruvate, and succinate to meat or isolated mitochondria can regenerate NADH and can influence beef color (Tang et al, 2005;Kim et al, 2006;Ramanathan et al, 2011). Therefore, characterizing TCA and glycolytic substrate changes in postmortem muscle is critical to understand the fundamental basis for meat discoloration.…”

Exogenous and Endogenous Factors Influencing Color of Fresh Meat from Ungulates

“…Wiklund et al (2006) found that deer meat from animals fed pellets had a lower pH and greater a* values than the meat from grazing animals. The lower pH results in lower mitochondrial activity and lower oxygen consumption (Tang et al, 2005), which subsequently lead to rapid Mb oxygenation, increased blooming, and deeper penetration of the cherry-red OxyMb layer (Ramanathan et al, 2013).…”

Mitochondrial respiratory and antioxidative enzyme activities in broiler meat in relation to age and gender of the animals

“…This assumption is supported by the presented TBARS results and partly by the antioxidative enzyme activities. The determination of the MRA is a method to investigate O 2 consumption of the tissue and has been analysed in muscle/meat samples from pigs (Brooks and Cassens, 1973;Campion et al, 1975;Wicke et al, 2000;Werner et al, 2010), cattle (Ashmore et al, 1972;Bendall, 1972;Lanari and Cassens, 1991;Tang et al, 2005b;Ramanathan et al, 2009) or poultry Opalka et al, 2004;Bottje and Carstens, 2009), also in relation to the muscle-tomeat transition after slaughter of the animals. Many of these studies were carried out with mitochondria isolated from the muscle/meat samples before and after slaughter.…”