Denaturation Of Myoglobin Research Articles

Evaluation of meat and meat product oxidation and off-flavor formation: Managing oxidative changes

One of the primary issues with processed foods during heat treatment and freezing storage is fat oxidation, which causes significant changes in fats due to their interaction with reactive oxygen species (ROS). This interaction leads to the creation of various aldehydes that have a high affinity for large molecules, such as proteins, leading to the formation of final products of advanced oxidation processes that contribute to food spoilage. Co-oxidation can also result in extensive damage. Another problem affecting the quality and nutritional value of meat products is protein oxidation, which can occur during storage via freezing and thawing or as a result of heat treatment. Heat treatment can cause physical and chemical changes, such as the loss of some essential amino acids and the transformation of certain amino acids into carbonyl compounds via various mechanisms. Protein oxidation is indicated by the accumulation of these carbonyl compounds, and the heat treatment can lead to the denaturation of myoglobin, which is responsible for the brown color of cooked meat and is influenced by several factors. Active protein aggregates can interact with the oxidation products of polyunsaturated fatty acids and with carbohydrate glycation or glycoxidation to produce Maillard products. It is critical to understand the oxidative changes that occur in fats and proteins in food, particularly in meat products, since these components are among the primary constituents of food.

Optimization of beef heat treatment using CFD simulation: Modeling of protein denaturation degree

AbstractBeef meat is most often eaten after heat treatment, but the quality of the final product is not always satisfactory. In this study, based on CFD modeling and simulation, optimization of the heat treatment process of beef was performed using RSM. The aim of the research was to select the parameters of thermal treatment in order to achieve the highest degree of denaturation of myosin and collagen proteins, and the lowest degree of actin denaturation and weight loss of the final product. The obtained results were verified by experimental studies, which showed statistically significant similarities with those predicted. Depending on the composition of the basic beef meat, heat treatment parameters should be selected individually in order to obtain a product characterized by the highest quality and, consequently, the highest acceptance among consumers. CFD modeling and RSM forecasting was a useful approach to study the unstable heat transfer in the combi steamer and also mapped the temperature distribution over the whole beef load, thus, optimizing the roasting process.Practical ApplicationThe use of CFD simulations and the RSM model in the meat industry will optimize the process of heat treatment of beef. This innovative method of predicting protein denaturation and thermal leakage will reduce mass losses caused by heat treatment. The consequence of using this model will be the delivery of an optimal dose of heat to the raw material, which will ensure the denaturation of myoglobin and collagen, and the actin will be left undenatured. As a result, the product will be characterized by the highest quality and acceptance of sensory features among consumers. As a result, energy consumption in the production of roast beef will be reduced and the demand for these products among demanding customers will increase.

Protein dynamics implications of the low- and high-temperature denaturation of myoglobin

We reinvestigate a simple model used in the literature concerning the thermodynamic analysis of protein cold denaturation. We derive an exact thermodynamic expression for cold denaturation and give a better approximation than exists in the literature for predicting cold denaturation temperatures in the two-state model. We discuss the "dark-side" implications of this work for previous temperature-dependent protein dynamics experiments and discuss microfluidic experimental technologies, which could explore the thermal stability range of proteins below the bulk freezing point of water.

Synergistic interactions of ionic liquids and antimicrobials improve drug efficacy.

SummaryCombinations of ionic liquids (ILs) with antimicrobial compounds have been shown to produce synergistic activities in model liposomes. In this study, imidazolium chloride-based ILs with alkyl tail length variations are combined with commercially available, small-molecule antimicrobials to examine the potential for combinatorial and synergistic antimicrobial effects on P. aeruginosa, E. coli, S. aureus, and S. cerevisiae. The effects of these treatments in a human cell culture model indicate the cytotoxic limits of ILs paired with antimicrobials. The analysis of these ILs demonstrates that the length of the alkyl chain on the IL molecule is proportional to both antimicrobial activity and cytotoxicity. Moreover, the ILs which exhibit synergy with small-molecule antibiotics appear to be acting in a membrane permeabilizing manner. Collectively, results from these experiments demonstrate an increase in antimicrobial efficacy with specific IL + antimicrobial combinations on microbial cultures while maintaining low cytotoxicity in a mammalian cell culture model.

Understanding the Thermal Denaturation of Myoglobin with IMS-MS: Evidence for Multiple Stable Structures and Trapped Pre-equilibrium States.

Thermal denaturation of holomyoglobin (hMb) in solution (10 mM ammonium acetate at pH = 4.5, 6.8, and 9.0) was monitored by ion mobility spectrometry (IMS) and mass spectrometry (MS) techniques to characterize the stability and investigate structural changes involved in unfolding. We utilize two experimental approaches to induce thermal denaturation: a variable-temperature electrospray ionization (vT-ESI) source that heats the bulk solution in the ESI emitter, and a variable-power 10.6 μm CO2 laser that rapidly heats nanodroplets produced by ESI. These two approaches sample different time scales of the denaturation process; long time scales (seconds to minutes) where the system is at equilibrium using the vT-ESI approach and shorter time scales (μs) by rapid droplet heating in which the system is in a pre-equilibrium state. Increasing the solution temperature (from 28 to 95 °C in the vT-ESI experiments) shifts the charge state distribution from low charge states ([M + 7H]7+ to [M + 9H]9+) to more highly charged species. This is accompanied by loss of the heme group to yield the apomyoglobin (aMb) species, indicating that the protein has unfolded. Monitoring the formation of aMb and the shift in average charge states of aMb and hMb with solution temperature allows for relative quantitation of their individual stabilities, highlighting the stabilizing effects of heme binding. We compare the degree of unfolding induced by heating the bulk solution (using vT-ESI) to the laser droplet heating approach and find that the rapid nature of the laser heating approach allows for transient pre-equilibrium states to be sampled.

Interactions Under Crowding Milieu: Chemical-Induced Denaturation of Myoglobin is Determined by the Extent of Heme Dissociation on Interaction with Crowders.

Generally, in vivo function and structural changes are studied by probing proteins in a dilute solution under in vitro conditions, which is believed to be mimicking proteins in intracellular milieu. Earlier, thermal-induced denaturation of myoglobin, in the milieu of crowder molecule showed destabilization of the metal protein. Destabilization of protein by thermal-induced denaturation involves a large extrapolation, so, the reliability is questionable. This led us to measure the effects of macromolecular crowding on its stability by chemical-induced denaturation of the protein using probes like circular dichroism and absorption spectroscopy in the presence of dextran 70 and ficoll 70 at various pHs (acidic: 6.0, almost neutral: 7.0 and basic: 8.0). Observations showed that the degree of destabilization of myoglobin was greater due to ficoll 70 as compared to that of dextran 70 so it can be understood that the nature of the crowder or the shape of the crowder has an important role towards the stability of proteins. Additionally, the degree of destabilization was observed as pH dependent, however the pH dependence is different for different crowders. Furthermore, isothermal titration calorimetry and molecular docking studies confirmed that both the crowders (ficoll and dextran) bind to heme moiety of myoglobin and a single binding site was observed for each.

Thermal Stability of Beef Myoglobin is Compromised by Reactive Lipid Oxidation Products

ObjectivesBrown color of cooked meat is the result of heat-induced denaturation of myoglobin (Mb). The denaturation temperature of Mb is governed by its redox state in raw meat; metmyoglobin (MMb) undergoes denaturation at a lower temperature than oxymyoglobin (OMb) and deoxymyoglobin (DMb). The secondary products of lipid oxidation, such as the 4-hydroxy-2-nonenal (HNE), compromise Mb redox stability and can thus impact cooked meat color. While previous investigations extensively studied lipid oxidation-induced Mb redox instability, studies are yet to be undertaken to examine the relationship between lipid oxidation and Mb thermal stability. Therefore, the objective of the present study was to investigate the direct influence of lipid oxidation (using HNE as a model aldehyde) on thermal stability of beef Mb at typical meat conditions.Materials and MethodsBeef Mb was purified, and OMb was incubated with HNE (0.15 mM Mb + 1.0 mM HNE) at pH 5.6 and 4°C for 21 d. The controls consisted of OMb plus a volume of ethanol used to deliver HNE to treatments. The samples were scanned spectrophotometrically from 650 to 500 nm on d 0, 7, 14, and 21, and MMb formation was calculated. The Mb samples were removed on d 0, 7, 14, and 21, and were digested with trypsin. The tryptic peptides were analyzed using liquid chromatography tandem-mass spectrometry (LC-MS/MS) for detecting HNE adduction sites. The thermal stability of Mb in the presence of HNE was assessed on d 0, 7, 14, and 21 by determining the percentage myoglobin denaturation (PMD) at 71°C in a water bath for 10 min. The experiment was replicated three times (n = 3). The effects of HNE on Mb redox and thermal stabilities during incubation were evaluated using the mixed procedure of SAS. The differences among means were detected at the 5% level using the least significant difference (LSD) test.ResultsWhile MMb formation increased (P < 0.05) during the storage in both control and HNE-treated samples, the oxidation was higher (P < 0.05) in HNE-treated samples. The PMD values increased (P < 0.05) in both treatments during the storage, and the HNE-treated samples exhibited greater (P < 0.05) PMD than the controls throughout the storage. Additionally, the PMD difference between HNE-treated and control samples increased over time. The LC-MS/MS analyses indicated that the number of histidines adducted by HNE increased with storage. HNE adducted four histidines (positions 24, 36, 93, and 152) on d 7, whereas five (positions 24, 36, 64, 93, and 152) and six (positions 24, 36, 64, 93, 113, and 152) residues were adducted on d 14 and 21, respectively.ConclusionThe mass spectrometric data indicated that thermal stability of beef Mb was compromised by reactive lipid oxidation products. The HNE adduction at the distal histidine (position 64), which is critical to heme stability, observed on d 14 and 21 as well as the increased number of histidines adducted by HNE on d 14 and 21 could be the possible reasons for the increased PMD on these time points. The adduction of HNE to histidines can alter the heme protein’s tertiary structure and thus exposes the heme to oxidation, thereby accelerating the formation of MMb, which is more susceptible to thermal denaturation than the ferrous Mb redox forms.

Endpoint Temperature Influences Sarcoplasmic Proteome Profile of Cooked Beef Longissimus Lumborum

ObjectivesCooking ensures safety and enhances the palatability attributes of meat. Denaturation of myoglobin results in the dull-brown color of cooked meats. The denaturation of sarcoplasmic proteins is influenced by the degree of heat treatment, and their solubility is decreased with an increase in the endpoint cooking temperature. While previous studies examined the relationship between myoglobin denaturation, cooked color, and internal temperature in beef, investigations are yet to be undertaken to characterize the association between endpoint temperature, sarcoplasmic proteome, and color attributes in cooked steaks. Therefore, the objective of the present study was to examine the influence of endpoint cooking temperature (60 and 71°C) on sarcoplasmic proteome and internal color of beef longissimus lumborum (LL) steaks.Materials and MethodsEight (n = 8) beef LL muscles (14 d postmortem; USDA Choice) were obtained from a commercial packing plant. Two 2.5-cm thick steaks were fabricated from the center of the muscles and were cooked to internal endpoint temperature of 60°C (C-60) or 71°C (C-71) in a clam-shell grill. Cooked steaks were immediately cooled in slushed ice, sliced parallel to the grilled surface, and internal redness (a* value) and color stability (R630/580) were evaluated instrumentally. Sarcoplasmic proteome from the interiors of the cooked steaks was analyzed using 2-dimensional electrophoresis, and the gel images were digitally analyzed. The protein spots exhibiting more than 2.5-fold intensity differences (P < 0.05) between C-60 and C-71 were subjected to in-gel tryptic digestion and were identified by tandem mass spectrometry.ResultsThe C-60 steaks demonstrated greater (P < 0.05) a* and R630/580 than their C-71 counterparts. Seven differentially abundant proteins were identified and were over-abundant (P < 0.05) in C-60 compared to C-71. The differentially abundant proteins belong to 6 functional groups, i.e., transport proteins (serum albumin and hemoglobin), energy metabolism (adenylate kinase isoenzyme 1), chaperones (heat shock protein β-1), antioxidant (thioredoxin-dependent peroxide reductase), glycolytic enzymes (fructose-bisphosphate aldolase B), and protease (cytosol aminopeptidase).ConclusionThe findings indicated that the endpoint cooking temperature influences the internal cooked color and the sarcoplasmic proteome profile of beef LL steaks. The overabundant proteins in steaks cooked to 60°C may be utilized as potential biomarkers for undercooked beef, which is a source for foodborne infections.

Effects of Ionic Liquid Alkyl Chain Length on Denaturation of Myoglobin by Anionic, Cationic, and Zwitterionic Detergents

The unique electrochemical properties of ionic liquids (ILs) have motivated their use as solvents for organic synthesis and green energy applications. More recently, their potential in pharmaceutical chemistry has prompted investigation into their effects on biomolecules. There is evidence that some ILs can destabilize proteins via a detergent-like manner; however, the mechanism still remains unknown. Our hypothesis is that if ILs are denaturing proteins via a detergent-like mechanism, detergent-mediated protein unfolding should be enhanced in the presence of ILs. The properties of myoglobin was examined in the presence of a zwitterionic (N,N-dimethyl-N-dodecylglycine betaine (Empigen BB®, EBB)), cationic (tetradecyltrimethylammonium bromide (TTAB)), and anionic (sodium dodecyl sulfate (SDS)) detergent as well as ILs based on alkylated imidazolium chlorides. Protein structure was measured through a combination of absorbance, fluorescence, and circular dichroism (CD) spectroscopy: absorbance and CD were used to monitor heme complexation to myoglobin, and tryptophan fluorescence quenching was used as an indicator for heme dissociation. Notably, the detergents tested did not fully denature the protein but instead resulted in loss of the heme group. At low IL concentrations, heme dissociation remained a traditional, cooperative process; at high concentrations, ILs with increased detergent-like character exhibited a more complex pattern, which is most likely attributable to micellization of the ionic liquids or direct denaturation or heme dissociation induced by the ILs. These trends were consistent across all species of detergents. 1,6-diphenyl-1,3,5-hexatriene (DPH) fluorescence was further used to characterize micelle formation in aqueous solutions containing detergent and ionic liquid. The dissociation thermodynamics show that EBB- and TTAB-induced dissociation of heme is not significantly impacted by room temperature ionic liquids (RTILs), whereas SDS-induced dissociation is more dramatically impacted by all RTILs examined. Together, these results indicate a complex interaction of detergents, likely based on headgroup charge, and the active component of RTILs to influence heme dissociation and potentially protein denaturation.

Endpoint Temperature Influences Sarcoplasmic Proteome Profile of Cooked Beef Longissimus Lumborum

ObjectivesCooking ensures safety and enhances the palatability attributes of meat. Denaturation of myoglobin results in the dull-brown color of cooked meats. The denaturation of sarcoplasmic proteins is influenced by the degree of heat treatment, and their solubility is decreased with an increase in the endpoint cooking temperature. While previous studies examined the relationship between myoglobin denaturation, cooked color, and internal temperature in beef, investigations are yet to be undertaken to characterize the association between endpoint temperature, sarcoplasmic proteome, and color attributes in cooked steaks. Therefore, the objective of the present study was to examine the influence of endpoint cooking temperature (60 and 71°C) on sarcoplasmic proteome and internal color of beef longissimus lumborum (LL) steaks.Materials and MethodsEight (n = 8) beef LL muscles (14 d postmortem; USDA Choice) were obtained from a commercial packing plant. Two 2.5-cm thick steaks were fabricated from the center of the muscles and were cooked to internal endpoint temperature of 60°C (C-60) or 71°C (C-71) in a clam-shell grill. Cooked steaks were immediately cooled in slushed ice, sliced parallel to the grilled surface, and internal redness (a* value) and color stability (R630/580) were evaluated instrumentally. Sarcoplasmic proteome from the interiors of the cooked steaks was analyzed using 2-dimensional electrophoresis, and the gel images were digitally analyzed. The protein spots exhibiting more than 2.5-fold intensity differences (P < 0.05) between C-60 and C-71 were subjected to in-gel tryptic digestion and were identified by tandem mass spectrometry.ResultsThe C-60 steaks demonstrated greater (P < 0.05) a* and R630/580 than their C-71 counterparts. Seven differentially abundant proteins were identified and were over-abundant (P < 0.05) in C-60 compared to C-71. The differentially abundant proteins belong to 6 functional groups, i.e., transport proteins (serum albumin and hemoglobin), energy metabolism (adenylate kinase isoenzyme 1), chaperones (heat shock protein β-1), antioxidant (thioredoxin-dependent peroxide reductase), glycolytic enzymes (fructose-bisphosphate aldolase B), and protease (cytosol aminopeptidase).ConclusionThe findings indicated that the endpoint cooking temperature influences the internal cooked color and the sarcoplasmic proteome profile of beef LL steaks. The overabundant proteins in steaks cooked to 60°C may be utilized as potential biomarkers for undercooked beef, which is a source for foodborne infections.

Sugar-Mediated Stabilization of Protein against Chemical or Thermal Denaturation.

The protective action of sugars against the denaturation of myoglobin was clarified by X-ray and neutron scattering methods. Different types of sugars such as disaccharides (trehalose, sucrose) and monosaccharides (glucose, fructose) were used. Experimental data and theoretical simulation based on three different solvation models (preferential solvation model, nonpreferential solvation model, and preferential exclusion (hydration) model) indicated that sugar molecules were preferentially or weakly excluded from the protein surface and preserved the native protein hydration shell. This trend was more evident for disaccharides. The preferential exclusion shifted gradually to the nonpreferential solvation at higher sugar concentrations. On the protective actions of the sugars against the guanidinium-chloride-mediated denaturation, all sugars, starting from the low concentration of 5% w/v, showed the protective trend toward the protein native structure, especially for the secondary structure. The thermal structural transition temperature of myoglobin was raised by about 4-5 °C, accompanied by amyloid formation, for all hierarchical structural levels. In particular, the oligomer formation of the amyloid aggregates was more suppressed. The above protective action was sugar-dependent. The present results clearly suggest that sugars intrinsically protect the native structure of proteins against chemical and thermal denaturation through the preservative action of the hydration shell.

Spectral computer graphics simulation of meat color based on heat denaturation of myoglobin

<b>Spectral computer graphics simulation of meat color </b><b>based on heat denaturation of myoglobin</b>

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.

Thermodynamic analysis of partially folded states of myoglobin in presence of 2,2,2-trifluoroethanol

The thermal denaturation of myoglobin was studied in the presence of 2,2,2-trifluoroethanol (TFE) at various pH values using differential scanning calorimetry and UV–visible spectroscopy. The most obvious effect of TFE was lowering the transition temperature up to 1.5mol·kg−1, beyond which no thermal transitions were observed. The protein conformation was analysed by fluorescence and circular dichroism measurements. Quantitative binding of ANS to the TFE induced molten globule state of myoglobin was studied by using isothermal titration calorimetry. The results enable quantitative estimation of the binding strength of ANS with the molten globule state of myoglobin along with the enthalpic and entropic contributions to the binding process. The results suggest occurrence of common structural features of the molten globule states of proteins offering two types of binding sites to ANS molecules which are a widely used fluorescence probe to characterise partially folded states of proteins.

Denaturation of α-lactalbumin and myoglobin by the anionic biosurfactant rhamnolipid

Glycolipid biosurfactants (GBS) are promising environmentally friendly alternatives to chemical surfactants. Surfactants interact with proteins in many applications, often leading to significant changes in protein properties. Given GBS' marked difference in structure compared to traditional chemical surfactants, it is of interest to investigate their impact on protein structure and stability. Here we combine spectroscopic and calorimetric studies to analyze the interactions between the anionic GBS rhamnolipid (RL) and two model proteins α-lactalbumin in the Ca2+-free apo-form (αLA) and myoglobin (Mb), whose interactions with traditional surfactants are well known. RL denatures αLA at sub-cmc concentrations (0.1–1mM) while Mb is only denatured above the cmc, i.e. in the presence of RL micelles. Denaturation leads to increased α-helicity, similar to the effect of SDS. The proteins bind approximately the same amount of RL by weight as SDS. However, RL employs a denaturation mechanism which combines features from non-ionic surfactants (very slow unfolding kinetics and few unfolding steps) with those of SDS (unfolding below the cmc in the case of αLA and the ability to unfold stable proteins in the case of Mb). We ascribe these features to RL's weakly acidic carboxylic head group and complex hydrophobic tail, which lead to a low cmc and low protein affinity. These features restrict the concentration range where RL monomers can bind and denature proteins while still allowing micelles to bind and denature to a significant extent.

Quantitative Evaluation of Myoglobin Unfolding in the Presence of Guanidinium Hydrochloride and Ionic Liquids in Solution

The use of ionic liquids in biochemical and biophysical applications has increased dramatically in recent years due to their interesting properties. We report results of a thermodynamic characterization of the chaotrope-induced denaturation of equine myoglobin in two different ionic liquid aqueous environments using a combined absorption/fluorescence spectroscopic approach. Denaturation by guanidinium hydrochloride was monitored by loss of heme absorptivity and limited unfolding structural information was obtained from Förster resonance energy transfer experiments. Results show that myoglobin unfolding is generally unchanged in the presence of ethylmethylimidazolium acetate (EMIAc) in aqueous solution up to 150 mM concentration but is facilitated by butylmethylimidazolium boron tetrafluoride (BMIBF4) in solution. The presence of 150 mM BMIBF4 alone does not induce unfolding but destabilizes the structure as observed by a decrease in threshold denaturant concentration for unfolding and an 80% decrease in the magnitude of ΔGunfolding from 44 kJ/mol in the absence of BMIBF4 to 8 kJ/mol in the presence of 150 mM BMIBF4. Thus, the BMIBF4 significantly destabilizes the myoglobin structure while the EMIAc does not, likely due to differences in anion interaction capabilities. This is confirmed with control studies using NaAc and LiBF4 solutions. EMIAc may be chosen as cosolvent additive with minimal effects on protein structure while BMIBF4 may be used as a supplement in protein folding experiments, potentially allowing access to proteins which have been traditionally difficult to denature as well as designing ionic liquids to match protein characteristics.

Femtosecond Coherence Spectroscopic Study of the Onset of Chemical Denaturation of Myoglobin upon Addition of Minor Amounts of Urea

AbstractThe interaction of urea with myoglobin, as a benchmark system for heme-containing proteins, is studiedviafemtosecond coherence spectroscopy. The work focuses on the effect of urea on the appearance of low-wavenumber oscillations, which are a measure of the geometrical structure of the heme group and its interaction with the polypeptide chain. Pursuing this approach, structural alterations (i.e.changes in the vibrational dynamics of the heme group) are detected at denaturant concentrations below the full denaturation limit of 6 M urea for myoglobin. In particular, the low-wavenumber oscillation associated with the heme-doming (i.e.the out-off-plane vibration of the propyrin macrocycle) is found to appear spectrally shifted with a concentration of only 3 M urea. These results suggest that the local environment around the heme is already altered despite the fact that macroscopic unfolding as manifested in the thermodynamic properties of the polypeptide chain is not complete at these urea concentrations.

Assessment of interactions between four proteins and benzothiazole derivatives by DSC and CD

The thermal denaturation of ovalbumin, lysozyme, myoglobin and fibrinogen at different BTS concentrations have been investigated using differential scanning calorimetry (DSC) and circular dichroism (CD) spectroscopy. Thermodynamic parameters: melting temperatures ( T m ), calorimetric enthalpy (Δ H), van’t Hoff enthalpy (Δ H v ) were obtained for all the systems under study. Thermal denaturation of the four proteins was completely irreversible. Changes in the protein conformation due to the adsorption of BTS molecules have been monitored by using UV-CD spectra. Greater changes in α-helical contents correspond with the BTS higher concentrations. The lysozyme denaturation temperature increases at low concentrations BTS indicating that BTS acts as a structure stabilizer; meanwhile it acts as a destabilizer at higher concentrations in all the proteins studied. The major effect is observed in the case of myoglobin, the protein with the highest α-helical secondary structure (75%).

Effects of L- or D-lactate-enhancement on the internal cooked colour development and biochemical characteristics of beef steaks in high-oxygen modified atmosphere

Abstract The effects of L- or D-lactate on internal cooked colour development of steaks packaged in high-oxygen (80% O2/20% CO2) modified atmosphere packaging (MAP) was investigated. Ten USDA Select beef strip loins were divided individually into 4 equal-width sections, and one of four treatments (control, 0.3% sodium tripolyphosphate, 2.5% L-lactate + 0.3% sodium tripolyphosphate, and 2.5% D-lactate + 0.3% sodium tripolyphosphate) was assigned randomly to the loin sections. Loin sections were injected to approximately 10% of their raw weight. Steaks packaged in high-oxygen MAP were stored in the dark at 1 °C for 10 days. Instrumental internal colour of raw and cooked steaks (70 °C), total reducing activity (TRA), NADH concentration, and percent myoglobin denaturation (PMD) were measured. Cooked steaks enhanced with 2.5% L-lactate/phosphate maintained higher a*/b* ratios, lower hue values, higher TRA and NADH concentration, and lower PMD than the control and D-lactate-injected steaks, whereas enhancement with 2.5% D-lactate did not affect cooked colour, TRA, NADH, or PMD. Thus, inclusion of an L-lactate/alkaline phosphate blend increased the reducing activity of muscle tissues by replenishing NADH and subsequently decreased the thermal denaturation of myoglobin by maintaining the reduced state of myoglobin in the high-oxygen package.

Thermal Denaturation of Myoglobin in Water−Disaccharide Matrixes: Relation with the Glass Transition of the System

Proteins embedded in glassy saccharide systems are protected against adverse environmental conditions [Crowe et al. Annu. Rev. Physiol. 1998, 60, 73-103]. To further characterize this process, we studied the relationship between the glass transition temperature of the protein-containing saccharide system (T(g)) and the temperature of thermal denaturation of the embedded protein (T(den)). To this end, we studied by differential scanning calorimetry the thermal denaturation of ferric myoglobin in water/disaccharide mixtures containing nonreducing (trehalose, sucrose) or reducing (maltose, lactose) disaccharides. All the samples studied are, at room temperature, liquid systems whose viscosity varies from very low to very large values, depending on the water content. At a high water/saccharide mole ratio, homogeneous glass formation does not occur; regions of glass form, whose T(g) does not vary by varying the saccharide content, and the disaccharide barely affects the myoglobin denaturation temperature. At a suitably low water/saccharide mole ratio, by lowering the temperature, the systems undergo transition to the glassy state whose T(g) is determined by the water content; the Gordon-Taylor relationship between T(g) and the water/disaccharide mole ratio is obeyed; and T(den) increases by decreasing the hydration regardless of the disaccharide, such effect being entropy-driven. The presence of the protein was found to lower the T(g). Furthermore, for nonreducing disaccharides, plots of T(den) vs T(g) give linear correlations, whereas for reducing disaccharides, data exhibit an erratic behavior below a critical water/disaccharide ratio. We ascribe this behavior to the likelihood that in the latter samples, proteins have undergone Maillard reaction before thermal denaturation.