Surendranath P. Suman

Myoglobin and lipid oxidation interactions: mechanistic bases and control.

Lipid oxidation and myoglobin oxidation in meat lead to off-flavor development and discoloration, respectively. These processes often appear to be linked and the oxidation of one of these leads to the formation of chemical species that can exacerbate oxidation of the other. Several investigators have reported preservation of fresh meat color following the inclusion of antioxidant ingredients. An understanding of the complementary oxidation interaction provides a basis for explaining quality deterioration in meat and also for developing strategies to maintain optimal sensory qualities.

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 myoglobins 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.

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 β-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.

Proteomics of lipid oxidation-induced oxidation of porcine and bovine oxymyoglobins.

Myoglobin (Mb) redox state affects meat color and is destabilized by lipid oxidation products such as 4‐hydroxy‐2‐nonenal (HNE). Our objective was to investigate lipid oxidation‐induced oxymyoglobin (OxyMb) oxidation in Mb from two major meat‐producing livestock species utilizing MS and proteomics tools. Porcine OxyMb was incubated with HNE and analyzed for metmyoglobin (MetMb) formation. MetMb formation was greater in the presence of HNE than controls at pH 7.4 and 37°C (p <0.05). MALDI‐TOF MS was used to identify adduct formation; only mono‐adducts of HNE (via Michael addition) with porcine Mb were detected. LC‐ESI‐MS/MS identified three histidine (HIS) residues in porcine Mb that were readily adducted by HNE (HIS 24, 36 and 119), whereas in bovine Mb seven histidine residues (HIS 24, 36, 81, 88, 93, 119 and 152) were adducted. Quantitation of HNE‐adducted peptides using isotope‐labeled phenyl isocyanate indicated that, initially, HIS 36 was preferentially adducted in porcine Mb whereas HIS 81, 88 and 93 were the predominant sites of early HNE adduction in bovine Mb. Preferential HNE adduction at the proximal histidine (HIS 93) was observed exclusively in bovine OxyMb and may explain why lipid oxidation‐induced OxyMb oxidation appears more extensive in beef, than in pork.

Improving beef color stability: practical strategies and underlying mechanisms.

This paper overviewed the current literature on strategies to improve beef color and attempted to logically explain the fundamental mechanisms involved. Surface color and its stability are critical traits governing the marketability of fresh beef when sold, whereas internal cooked color is utilized as an indicator for doneness at the point of consumption. A multitude of exogenous and endogenous factors interact with the redox biochemistry of myoglobin in post-mortem skeletal muscles. The scientific principles of these biomolecular interactions are applied by the meat industry as interventions for pre-harvest (i.e. diet, animal management) and post-harvest (i.e. packaging, aging, antioxidants) strategies to improve color stability in fresh and cooked beef. Current research suggests that the effects of several of these strategies are specific to type of animal, feeding regimen, packaging system, and muscle source. Meat scientists should explore novel ways to manipulate these factors using a biosystems approach to achieve improved beef color stability, satisfy consumer perception, and increase market profitability.

Effect of grind size and fat levels on the physico-chemical and sensory characteristics of low-fat ground buffalo meat patties.

Two experiments were carried out to investigate the influence of grind size (3, 4 or 6 mm) and fat levels (6, 8, 10 or 20%) on the physico-chemical and sensory characteristics of low-fat ground buffalo meat patties prepared using a combination of carrageenan (0.5%) and sodium alginate (0.1%). At a constant fat level of nearly 8%, there was no significant difference (P>0.05) in the cooking yield, pH, proximate composition and dimensional changes of patties prepared at different grind sizes. However, shear force value increased significantly (P<0.05) with an increase in grind size. The sensory scores were significantly (P<0.05) higher for patties prepared using 3 mm grind size as compared to those prepared at 4 and 6 mm grind sizes and hence it was adopted as the optimum grind size for low-fat ground buffalo meat patties. At a constant grind size of 3mm, cooking yield, moisture, protein and gain in height were significantly (P<0.05) higher and shear force values were significantly (P<0.05) lower for patties at all low-fat levels as compared to the control with 20% fat. Based on its significantly higher (P<0.05) sensory scores, 10% fat level was selected as optimum for low-fat ground buffalo meat patties, although even at 8% fat level sensory rating remained between good to very good.

Packaging-specific influence of chitosan on color stability and lipid oxidation in refrigerated ground beef.

We examined the influence of chitosan on lipid oxidation and color stability of ground beef stored in different modified atmosphere packaging (MAP) systems. Ground beef patties with chitosan (1%) or without chitosan (control) were packaged either in high-oxygen MAP (HIOX; 80% O(2)+20% CO(2)), carbon monoxide MAP (CO; 0.4% CO+19.6% CO(2)+80% N(2)), vacuum (VP), or aerobic packaging (PVC) and stored at 1 °C. Chitosan increased (P<0.05) redness of patties stored in PVC and CO, whereas it had no effect (P>0.05) in HIOX. Chitosan patties demonstrated lower (P<0.05) lipid oxidation than controls in all packaging. Control patties in PVC and HIOX exhibited greater (P<0.05) lipid oxidation than those in VP and CO, whereas chitosan patties in different packaging systems were not different (P>0.05) from each other. Our findings suggested that antioxidant effects of chitosan on ground beef are packaging-specific.

Differential abundance of sarcoplasmic proteome explains animal effect on beef Longissimus lumborum color stability

The sarcoplasmic proteome of beef Longissimus lumborum demonstrating animal-to-animal variation in color stability was examined to correlate proteome profile with color. Longissimus lumborum (36 h post-mortem) muscles were obtained from 73 beef carcasses, aged for 13 days, and fabricated to 2.5-cm steaks. One steak was allotted to retail display, and another was immediately vacuum packaged and frozen at -80°C. Aerobically packaged steaks were stored under display, and color was evaluated on days 0 and 11. The steaks were ranked based on redness and color stability on day 11, and ten color-stable and ten color-labile carcasses were identified. Sarcoplasmic proteome of frozen steaks from the selected carcasses was analyzed. Nine proteins were differentially abundant in color-stable and color-labile steaks. Three glycolytic enzymes (phosphoglucomutase-1, glyceraldehyde-3-phosphate dehydrogenase, and pyruvate kinase M2) were over-abundant in color-stable steaks and positively correlated (P<0.05) to redness and color stability. These results indicated that animal variations in proteome contribute to differences in beef color.

Effect of carbon monoxide packaging and lactate enhancement on the color stability of beef steaks stored at 1°C for 9 days.

Our objective was to assess the effects of lactate enhancement in combination with different packaging systems on beef longissimus lumborum and psoas major steak color. Strip loins and tenderloins (n=16) were assigned to one of four injection treatments (non-injected control, water-injected control, 1.25%, and 2.5% lactate in the finished product). Steaks were individually packaged in either vacuum, high-oxygen (80% O(2)/20% CO(2)), or 0.4% CO (30% CO(2)/69.6% N(2)) and stored for either 0, 5, or 9 days at 1°C. The L(∗) and a(∗) values of both the longissimus and psoas responded similarly to lactate, which at 2.5% darkened steaks (P<0.05) packaged in all atmospheres and improved (P<0.05) the redness of steaks packaged in high-oxygen. Packaging steaks in CO did not counteract the darkening effects of lactate. Nevertheless, CO improved (P<0.05) color stability compared with high-oxygen packaging.

Characterization of bison (Bison bison) myoglobin.

Bison is an alternate meat species gaining increased popularity in North America. Although previous investigations reported that bison meat discolors faster than beef, the molecular basis of this observation has not been investigated. Therefore, the objective of the present study was to determine the redox stability, thermostability, and primary structure of bison myoglobin (Mb), in comparison with beef Mb. Purified bison and beef myoglobins were analyzed for autoxidation, lipid oxidation-induced oxidation, and thermostability. Matrix Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry was utilized for determining the exact molecular mass of bison Mb, whereas Edman degradation was employed to determine the amino acid sequence. Bison and beef myoglobins behaved similarly in autoxidation, lipid oxidation-induced oxidation, and thermostability. The observed molecular mass of bison and beef myoglobins was 16,949 Da, and the primary structure of bison Mb shared 100% similarity with beef and yak myoglobins. Noticeably, the amino acid sequence of bison Mb was different from other ruminant myoglobins, such as water-buffalo, sheep, goat, and red-deer. The present study is the first to report the primary structure of bison Mb. Same primary structure and similar biochemical attributes of bison and beef myoglobins suggested that the observed rapid discoloration in bison meat could not be attributed to biochemistry of bison Mb.