Dr. Chris R. Calkins
Date of this Version
Herrera, N.J. 2020. The Impact of Oxidative Stress on Postmortem Meat Quality. Master's Thesis, University of Nebraska-Lincoln, Lincoln, NE.
Tenderness is the primary factor to influence consumer palatability in fresh meat. The tenderization of muscle is dependent on proteolytic mechanisms, including calcium dependent, non-lysosomal endogenous enzymes such as calpains and proteasomes. These mechanisms have been indicated alongside apoptosis early postmortem as cascades of apoptotic events promote ideal conditions for postmortem tenderization. Recent literature has identified oxidative stress-mediated events to be linked to apoptotic activity. Oxidative stress is defined as the overwhelming production of reactive species compared to homeostatic, endogenous antioxidants present within muscle systems. These conditions exhaust antioxidant function and facilitate reactive species to alter protein, lipid, or nucleic morphology and functionality. Perhaps, the generation of oxidative stress can alter muscle tissue, resulting in changes in the overall quality of fresh meat postmortem. This study examined the impact of different levels of oxidative stress in vivo on postmortem muscle quality of lambs, with emphasis towards elements of proteolytic mechanisms responsible for meat tenderness. Lipopolysaccharides (LPS) are endotoxins used to induce acute stress for this experiment. Effects of inducing lambs with an injection of either a saline control, 50 ng of LPS per kg of bodyweight (LPS50), or 100 ng of LPS per kg of bodyweight (LPS100). Injections were administered every 72 hours across a nine-day immune challenge. Treatments used examined changes in biomarkers of oxidative stress (RNA Transcriptomics and isoprostanes), pre-harvest stress conditions (rectal temperature), free calcium concentration, proximate composition, color and lipid oxidation, and tenderness. In this study, lambs administered LPS50 tended to be more tender early postmortem, and had a greater degree of Troponin T degradation compared to control samples (P < 0.05). The LPS-treated lambs exhibited noticeable upregulation of gene pathways responsible for cell growth, differentiation, degradation, and generation of oxidative species and antioxidants (Praw < 0.05). While not significant, LPS treated samples exhibited more oxidative biomarkers present in muscle tissue (isoprostane content). The LPS treatments had no detrimental effects of color or lipid oxidation (P > 0.05). Oxidative stress may impact early postmortem tenderization of meat.
Key words: apoptosis, lamb, meat quality, oxidative stress, proteolysis, tenderization
Advisor: Chris R. Calkins