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.
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ABSTRACT: The shelf life of packaged fresh red meats is most frequently determined by the activity of microorganisms, which results in the development of off-odors, gas, and slime, but it is also influenced by biochemical factors such as lipid radical chain and pigment oxidation causing undesirable flavors and surface discoloration. The predominant bacteria associated with spoilage of refrigerated meats are Pseudomonas, Acinetobacter/Moraxella (Psychrobacter), Shewanella putrefaciens, lactic acid bacteria, Enterobacteriaceae, and Brochothrix thermosphacta. The spoilage potential of these organisms and factors influencing their impact on meat quality are discussed. High O 2 -modified atmosphere (80% O 2 + 20% CO 2) packaging (MAP) is commonly used for meat retail display but vacuum packaging remains the major MAP method used for meat distribution. Two-step master packaging (outer anoxic-20% CO 2 + 80% N 2 /inner gas-permeable film) is used for centralized MAP distribution, but CO use (0.4%) in low O 2 packaging systems is limited by consumer uncertainty that CO may mask spoilage. Active packaging where the film contributes more than a gas/physical barrier is an important technology and has been studied widely. Its application in combination with MAP is very promising but impediments remain to its widespread industrial use. The influence of processing technologies including modified atmospheres on lipid oxidation and discoloration of meats are analyzed. Because both organic acids and antioxidants have been evaluated for their effects on microorganism growth, in concert with the prevention of lipid oxidation, work in this area is examined.Comprehensive Reviews in Food Science and Food Safety 07/2012; 11:340-354. · 5.05 Impact Factor
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ABSTRACT: Protein degradation that occurs in tissue during post-mortem interval or sample preparation is problematic in quantitative analyses as confounding variables may arise. Ideally, such artefacts should be prevented by preserving the native proteome during sample preparation. We assessed the efficacy of thermal treatment (TT) to preserve the intact proteome of mouse heart and brain tissue in comparison to standard snap-freezing with liquid nitrogen (LN). Tissue samples were collected, either snap frozen (LN), subjected to TT, or snap frozen followed by thermal treatment, and subsequently analysed by 2-DE. In heart tissue, following quantitative image analysis, we observed 77 proteins that were significantly altered across the three treatment groups (ANOVA, p<0.05). Principal component and clustering analyses revealed LN and TT to be equally beneficial. These findings were confirmed by MS identification of the significantly altered proteins. In brain tissue, 189 proteins were significantly differentially expressed across the three treatment groups (ANOVA, p<0.05). Brain tissue appeared to be more responsive to TT than heart and distinct clusters of differentially expressed proteins were observed across treatments. Overall, TT of brain tissue appears to have beneficial effects on protein stabilisation during sample preparation with preservation of high-molecular-weight proteins and reduction in protein fragmentation.Proteomics 08/2009; 9(19):4433-44. · 4.43 Impact Factor
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ABSTRACT: The aim of this research was to characterize the lamb M. longissimus dorsi (LD), M. semitendinosus (ST), and M. psoas major (PM) muscles for differences in instrumental colour, tissue oxygen consumption rate (OCR), mitochondrial respiration control ratio (RCR), metmyoglobin reductase activity (MRA), and the relative proportions of myoglobin (Mb) redox forms. LD, ST, and PM muscles were stored for 6 days at 4 °C. Changes in the instrumental colour (CIE L*-value, a*-value, b*-value, Chroma-value, and Hue-value), OCR, RCR, MRA, and relative proportions of Mb redox forms during storage were evaluated. LD revealed the lowest MetMb accumulation and highest colour stability. Muscles with higher colour stability had lower levels of OCR, higher MRA, and less MetMb accumulation. Colour stability and MRA for the lamb muscles were LD > ST > PM. The correlation coefficients among the main parameters were also investigated in this research. The correlation coefficients between a*-value and OxyMb within the same muscle were highly significant (r = 0.951, 0.974, 0.828; P < 0.05). MRA of the muscles was negatively correlated (r = −0.810, −0.942, −0.971, P < 0.05) with the relative percentage of MetMb. The results of the present study suggested that OCR, RCR and MRA contribute to variation in colour stability of different lamb muscles.European Food Research and Technology 236(4). · 1.39 Impact Factor