Defining the role of mitochondria in fresh meat quality development

dc.contributor.authorMatarneh, Sulaiman K.en
dc.contributor.committeechairGerrard, David E.en
dc.contributor.committeememberScheffler, Tracy L.en
dc.contributor.committeememberJohnson, Sally E.en
dc.contributor.committeememberSobrado, Pabloen
dc.contributor.committeememberShi, Haoen
dc.contributor.departmentAnimal and Poultry Sciencesen
dc.date.accessioned2017-11-09T19:41:23Zen
dc.date.available2017-11-09T19:41:23Zen
dc.date.issued2017-07-12en
dc.description.abstractDuring postmortem metabolism, hydrogen ions accumulate in the muscle and gradually lower the pH from 7.2 to an ultimate pH near 5.6. The ultimate pH of meat is widely valued as an indicator of fresh meat quality as it directly affects the quality characteristics of color, texture, and water holding capacity. Therefore, our research was conducted to identify the processes responsible for determining ultimate pH. Pigs harboring the AMPK�•3R200Q mutation produce meat with extremely low ultimate pH (pH ~ 5.3) that is detrimental to quality. This phenomenon is often attributed to a greater glycogen content in muscle from the mutant pigs compared to wild-type pigs. However, our research indicated that greater glycolytic flux in muscle from these pigs causes a lower ultimate pH rather than greater tissue glycogen deposition. On the other hand, however, AMPK�•3R200Q pigs contain more mitochondria and retain greater oxidative capacity. Hence, we hypothesized that mitochondria may contribute to the lower ultimate pH in muscle of these pigs. To test our hypothesis, isolated mitochondria were incorporated into an in vitro system the mimics postmortem glycolysis. Mitochondria enhanced glycolytic flux and pH decline in the in vitro system similar to that of AMPK�•3R200Q pigs. After a series of experiments, we found that the causative agent for enhanced glycolytic flux is a soluble mitochondrial protein. In other experiments, mitochondrial F1-ATPase was found to be responsible for the majority of this effect, principally through promoting greater ATP hydrolysis at lower pH values, thereby allowing for greater flux through glycolysis. These data suggest that variations in ultimate pH may be more thoroughly explained and predicted by the abundance of mitochondria. Broiler pectoralis major muscle, which is a highly glycolytic muscle, possesses high ultimate pH (pH ~ 5.9) compared to pork and beef. We postulated that rapid carcass chilling reduces the flux through glycolysis, thereby causing premature termination of postmortem metabolism. Yet, chilling was only partially responsible for the high ultimate pH of pectoralis major muscle. However, we showed that pectoralis major of broiler chicken exhibits lower phosphofructokinase-1 activity compared to porcine longissimus lumborum muscle, which limits the flux through glycolysis.en
dc.description.abstractgeneralConsumer demand for high quality meat has increased dramatically over the past two decades. In order to meet this demand, it is crucial to understand factors that control the development of fresh meat quality characteristics. Consumers purchase meat based on color, but repeat purchases are also influenced by meat freshness, texture, and juiciness. These quality attributes develop after the animal has been harvested during the conversion of muscle to meat through a series of biochemical reactions. This conversion results in muscle acidification (pH decline) caused by the degradation of stored muscle energy that acidifies muscle. Normally, the muscle pH drops from a neutral value in living muscle to an acid value (~5.6) in fresh meat. In some cases, however, excessive acidification occurs and this can dramatically impact fresh meat quality characteristics. Our research program focuses on the mechanisms responsible for this extended acidification. To that end, we use mutant pigs known as RN– that produce meat with extremely low ultimate pH known as “acid meat”. While most believe that the extended pH decline in muscle of these pigs is a function of elevated energy in the muscle prior to harvesting, we showed that theses pigs have different muscle prior to harvest and this difference cause increased acidification during the transformation of muscle to meat. To investigate this issue further, we also examined the contribution of mitochondria (the powerhouse of the cell) to this process mainly because muscle from the RN– pigs containing around 50% more mitochondria compared to normal pigs. Curiously, we have shown mitochondria participate in this process. Because mitochondria require oxygen to function and harvesting animals disrupts oxygen delivery to the muscle, mitochondria were considered irrelevant to the development of meat quality characteristics. Our studies have definitively proved that mitochondria can contribute to meat quality and may be key in improving fresh meat quality.en
dc.description.degreePh. D.en
dc.format.mediumETDen
dc.identifier.othervt_gsexam:12491en
dc.identifier.urihttp://hdl.handle.net/10919/80033en
dc.language.isoen_USen
dc.publisherVirginia Techen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectmeat qualityen
dc.subjectultimate pHen
dc.subjectmitochondriaen
dc.subjectAMPKy3R200Qen
dc.titleDefining the role of mitochondria in fresh meat quality developmenten
dc.typeDissertationen
thesis.degree.disciplineAnimal and Poultry Sciencesen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.leveldoctoralen
thesis.degree.namePh. D.en

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