Year of Publication

2017

Degree Name

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation

College

Agriculture, Food and Environment

Department

Animal and Food Sciences

First Advisor

Dr. Surendranath P. Suman

Abstract

Fresh beef color is critical to consumers’ purchase decisions, and beef color stability is muscle-specific. Sarcoplasmic proteome plays a critical role in beef color stability. This dissertation focuses on the proteome basis of inter- and intra-muscular variations in beef color.

The first experiment examined the sarcoplasmic proteome of three beef muscles with differential color stability, i.e., longissimus lumborum (LL), psoas major (PM), and semitendinosus (ST), during wet-aging. LL, PM, and ST (n = 8) were subjected to wet-aging for 0, 7, 14, and 21 days. On each aging day, steaks were fabricated, and color and other biochemical attributes were evaluated on days 0, 3, and 6 of storage. Sarcoplasmic proteome was analyzed using two-dimensional electrophoresis, and differentially abundant proteins were identified using mass spectrometry. Muscle source and aging influenced color and biochemical attributes. Proteome analysis identified 135 protein spots differentially abundant (P < 0.05) and indicated muscle-specific changes during wet-aging. These proteins are categorized as glycolytic enzymes, proteins associated with energy metabolism, antioxidant proteins, chaperones, and transport proteins. The results characterized the muscle-specific changes in sarcoplasmic proteome profile of beef muscles during wet-aging.

The second experiment was carried out to characterize the proteome basis for intramuscular color stability variations in beef semimembranosus. Semimembranosus muscles from eight carcasses (n = 8) were fabricated into color-labile inside (ISM) and color-stable outside (OSM) steaks. Color attributes were evaluated instrumentally and biochemically on 0, 2, and 4 days, and steaks frozen during fabrication were used for sarcoplasmic proteome analysis. ISM steaks demonstrated greater (P < 0.01) abundance of glycolytic enzymes than their OSM counterparts. Possible rapid post-mortem glycolysis in ISM could lead to rapid pH decline during early post-mortem, which in turn could compromise its color stability.

The third experiment examined the changes in color attributes and sarcoplasmic proteome of beef ISM and OSM during wet-aging. Semimembranosus muscles from eight carcasses (n = 8) were subjected to wet-aging for 0, 7, 14, and 21 days. At each aging point, ISM and OSM steaks were fabricated, and color and other biochemical attributes were evaluated on days 0, 3, and 6 of storage. Sarcoplasmic proteome analysis was done using steaks frozen on day 0 and 21 of aging. The results indicated that the color attributes of ISM and OSM steaks were influenced by aging. Aging influenced the sarcoplasmic proteome profile of ISM and OSM, and the differentially abundant proteins were associated with glycolysis and energy metabolism.

The fourth experiment examined the functionality of mitochondria isolated from ISM and OSM (n = 5). Mitochondrial oxygen consumption rate (OCR) measured using succinate as substrate (at pH 5.6, 25°C) indicated greater (P < 0.05) OCR in OSM than ISM. The results indicated the existence of intramuscular variation in mitochondrial functionality in beef semimembranosus. The observed differences in mitochondrial OCR between ISM and OSM steaks could be contributing to the intramuscular color variations in beef semimembranosus.

Digital Object Identifier (DOI)

https://doi.org/10.13023/ETD.2017.217

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