Factors influencing internal color of cooked meats.

This manuscript overviews the pertinent research on internal color of uncured cooked meats, biochemical processes involved in meat cookery, and fundamental mechanisms governing myoglobin thermal stability. Heat-induced denaturation of myoglobin, responsible for the characteristic dull-brown color of cooked meats, is influenced by a multitude of endogenous (i.e., pH, muscle source, species, redox state) and exogenous (i.e., packaging, ingredients, storage) factors. The interactions between these factors critically influence the internal cooked color and can confuse the consumers, who often perceive cooked color to be a reliable indicator for doneness and safety. While certain phenomena in cooked meat color are cosmetic in nature, others can mislead consumers and result in foodborne illnesses. Research in meat color suggests that processing technologies and cooking practices in industry as well as households influence the internal cooked color. Additionally, the guidelines of many international public health and regulatory authorities recommend using meat thermometers to determine safe cooking endpoint temperature and to ensure product safety.

Proteome basis for intramuscular variation in color stability of beef semimembranosus.

The objective of the present study was to characterize the proteome basis for intramuscular color stability variations in beef semimembranosus. Semimembranosus muscles from eight carcasses (n=8) were fabricated into 2.54-cm thick color-labile inside (ISM) and color-stable outside (OSM) steaks. One steak for sarcoplasmic proteome analysis was immediately frozen, whereas other steaks were allotted to retail display under aerobic packaging. Color attributes were evaluated instrumentally and biochemically on 0, 2, and 4days. Sarcoplasmic proteome was analyzed using two-dimensional electrophoresis and tandem mass spectrometry. ISM steaks demonstrated greater (P<0.01) abundance of glycolytic enzymes (fructose-bisphosphate aldolase A, phosphoglycerate mutase 2, and beta-enolase) and phosphatidylethanolamine-binding protein 1 than their OSM counterparts. Possible rapid post-mortem glycolysis in ISM, insinuated by over-abundance of glycolytic enzymes, could lead to rapid pH decline during early post-mortem, which in turn could potentially compromise its color stability. These results indicated that differential abundance of sarcoplasmic proteome contributes to intramuscular variations in beef color stability.

Myoglobin chemistry and meat color.

Consumers rely heavily on fresh meat color as an indicator of wholesomeness at the point of sale, whereas cooked color is exploited as an indicator of doneness at the point of consumption. Deviations from the bright cherry-red color of fresh meat lead to product rejection and revenue loss. Myoglobin is the sarcoplasmic heme protein primarily responsible for the meat color, and the chemistry of myoglobin is species specific. The mechanistic interactions between myoglobin and multiple extrinsic and intrinsic factors govern the color of raw as well as cooked meats. The objective of this review is to provide an overview of the current research in meat color and how the findings are applied in the meat industry. Characterizing the fundamental basis of myoglobin's interactions with biomolecules in postmortem skeletal muscles is necessary to interpret the chemistry of meat color phenomena and to engineer innovative processing strategies to minimize meat discoloration-induced revenue loss to the agricultural economy.

Amino acid sequence of myoglobin from white-tailed deer (Odocoileus virginianus).

Our objective was to determine the primary structure of white-tailed deer myoglobin (Mb). White-tailed deer Mb was isolated from cardiac muscles employing ammonium sulfate precipitation and gel-filtration chromatography. The amino acid sequence was determined by Edman degradation. Sequence analyses of intact Mb as well as tryptic- and cyanogen bromide-peptides yielded the complete primary structure of white-tailed deer Mb, which shared 100% similarity with red deer Mb. White-tailed deer Mb consists of 153 amino acid residues and shares more than 96% sequence similarity with myoglobins from meat-producing ruminants, such as cattle, buffalo, sheep, and goat. Similar to sheep and goat myoglobins, white-tailed deer Mb contains 12 histidine residues. Proximal (position 93) and distal (position 64) histidine residues responsible for maintaining the stability of heme are conserved in white-tailed deer Mb.

Proteomics of muscle-specific beef color stability.

The objective of the present study was to differentiate the sarcoplasmic proteome of color-stable (Longissimus lumborum; LL) and color-labile (Psoas major; PM) beef muscles. LL and PM muscles from seven beef carcasses (24 h post-mortem) were fabricated into 2.54 cm steaks, aerobically packaged, and assigned to refrigerated retail display for 9 days. LL steaks demonstrated greater (P < 0.05) color stability and lower (P < 0.05) lipid oxidation than PM steaks. Proteome analyses identified 16 differentially abundant proteins in LL and PM, including antioxidant proteins and chaperones. Proteins demonstrating positive correlation with redness (aldose reductase, creatine kinase, and ß-enolase) and color stability (peroxiredoxin-2, peptide methionine sulfoxide reductase, and heat shock protein-27 kDa) were overabundant in LL, whereas the protein overabundant in PM (mitochondrial aconitase) exhibited negative correlation with redness. The color stability of LL could be attributed to the overabundance of antioxidant proteins and chaperones, and this finding suggests the necessity of developing muscle-specific processing strategies to improve beef color.

Species-specific myoglobin oxidation.

The effect of the lipid oxidation product, 4-hydroxy-2-nonenal (HNE), on oxidation of oxymyoglobin (OxyMb) from seven different meat-producing species was investigated. Relative to controls, HNE increased OxyMb oxidation within all species (p < 0.05) at both 25 and 4 °C, pH 5.6. The relative effect of HNE was greater for myoglobins (Mbs) that contained 12 ± 1 histidine (His) residues than for those that contained 9 His residues (p < 0.05); HNE efficacy in all species except chicken and turkey decreased with time. Mono-HNE adducts were detected in all species except chicken and turkey. In general, HNE alkylation increased the Mbs' ability to accelerate lipid oxidation in a microsome model. However, neither an HNE nor a Mb species dependent effect was observed. Results suggested that microsome model system associated lipid oxidation overshadowed HNE and species effects on OxyMb oxidation observed in lipid-free systems.