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Possible role of muscle protein in flavor and tenderness of meat
Journal of Food Biochemistry
Abstract
Evidence suggests that both the myofibrillar proteins and collagen play important roles in meat flavor and tenderness. The probable contributions of the purified proteins to flavor are reviewed in terms of their amino acid composition, especially the sulfur containing and certain other amino acids that have been implicated in meat flavor development. Myofibrils solubilized in sodium dodecylsulfate (SDS) undergoproteolysis on warming to room temperature overnight or on storing for several days at 0–4°C as demonstrated by extra protein bands. The extra proteins appear to be due to the presence of indigenous muscle proteases. The implications of some indigenous muscle proteases are reviewed in terms of their probable role in tenderization of postmortem meat.
... The flavor of dry-cured products, Coppa Piacentina PDO included, is based on a pool of different volatile and non-volatile compounds which are produced also during the ripening step (Sforza et al., 2006). Non-volatile molecules include peptides and free amino acids, which are released from the muscle proteins by the action of endopeptidases, mainly calpains and cathepsins, and exopeptidases (Pearson et al., 1983). The pool of these proteinaceous compounds directly contributes to the final taste, and indirectly to certain aroma compounds (Toldrá, 2006). ...
Coppa Piacentina is an Italian protected designation of origin (PDO) dry-cured product obtained from the muscle of pork neck and ripened for at least six months. Metabolomics- and volatilomics-based strategies, combined with a chemical characterization of free amino acids were applied to identify biomarkers of long-ripened Coppa Piacentina PDO. Long ripening induced a significantly increase of total free amino acids, mainly represented by glutamic acid, involved in the umami taste perception. Untargeted metabolomics, performed using UHPLC-HRMS, allowed to identify 32 putative gamma-glutamyl-peptides, known as main contributors to the kokumi taste. Unsupervised and supervised multivariate statistics observed a clear modification of these peptides over the ripening, with gamma-glutamyl-peptides which significantly increased in long-ripened samples. A volatilomics-based strategy, conducted with GCxGC-MS, was then performed, and 93 different compounds were identified, with aldehyde and ketones deriving from the lipid auto-oxidation which increased according to ripening.
... One of the factors affecting the rate of oxidation is the degree of un saturation of the fatty acids, polyunsaturated fatty acids are much more susceptible 56 to oxidation than monounsaturated or saturated fatty acids. Unsaturated fatty acids are prime targets for oxidation reactions and oxidation of unsaturated fatty acids adversely affect the colour, texture, nutritive value (Pearson et al., 1983b), and safety of meats (Addis, 1986). Oxidation in meat is also reported to be initiated in the phospholipid rich cell-membranes . ...
Association between lipid composition, shelf life and sensory quality in ruminant meats
https://www.slideshare.net/esrakurtkont/esra-thesis-british-library
... In dry-cured ham, proteolysis affects the final texture (hardness, cohesiveness…) of the product and is considered essential to obtain acceptable-quality taste and flavor characteristics (Arnau et al. 1998; García-Garrido et al. 2000;Toldra 1998;Zhao et al. 2008). Many authors have found that besides the proteolytic enzymes discussed above, proteolysis rate is also impacted by the convergence of pH and processing parameters such as salt concentration, water content, ageing temperature and time (Arnau et al. 2003;Pearson et al. 1983; Ruiz-Ramirez et al. 2006;Toldra et al. 1997). Andres et al. (2005) showed that temperature promotes lipase activities and lipid oxidation leading to the generation of volatile and nonvolatile compounds responsible for flavor in dry-cured ham. ...
Because of public health problems, the food industry must lower sodium content in all food products, therefore in cured meat products. During the dry-cured ham elaboration process, decreasing salt content may induce microbial safety problems and texture defects due to an excessive proteolysis that could affect later the industrial stage of slicing. On account of that, this work of thesis aims at (1) studying the relationship between proteolysis, structure and texture during the various stages of dry-cured ham manufacture, and (2) building a “numerical ham” model to predict spatially the time course of water and salt content, and thus water activity (a w ), and to couple these variations with proteolysis. This work combines experimental studies and numerical modelling and simulation. Firstly, a new and powerful technique for quantifying proteolysis that uses “Fluorescamine” was developed and validated on pork meat samples and samples extracted from industrial dry-cured hams; a new proteolysis index (PI) was defined. Based on an experimental design, the time course of proteolysis was quantified in laboratory-salted and dried pork meat samples prepared from five different types of pork muscle. Applying multiple linear regression enabled us to build phenomenological models relating, for each pork muscle, PI velocity to temperature, and to water and salt content. Using Comsol ® Multiphysics software, these phenomenological models were then combined with heat and mass transfer models and associated with calculation of a w , thus constituting the “numerical ham” model. In addition, the time course of PI, five textural parameters (hardness, fragility, cohesiveness, springiness and adhesiveness), and four structural parameters (fiber number, extracellular spaces, cross section area, and connective tissue area) was quantified on samples extracted from two different muscles of industrial dry-cured hams removed from the process at five different processing times. Multiple polynomial regression was applied to build phenomenological models relating PI, salt and water content to some textural and structural parameters investigated. These last models could be rapidly incorporated in the “numerical ham” model to constitute a real process simulator. In the future, the “numerical ham” model should be improved in order to take into account (1) the strong decrease in ham volume due to drying and also (2) the decrease in proteolysis velocity with time as a result of the reduction in the amount of protein that can be hydrolysed in the ham. Once completed and improved, the process simulator will be available to professionals to test scenarios allowing sodium content to be reduced in dry-cured hams without altering their final quality.
... One of the most important processes taking place during ham ageing is the proteolysis of muscle proteins. Endogenous exo-and endopeptidase activities, together with processing parameters (salt amount, ageing temperature and length of the ageing phase), greatly influence the proteolysis degree, yielding different amounts and patterns of free amino acids (FAAs) and peptides (Pearson, Wolzak, & Gray, 1983). ...
Sixteen Parma hams were manufactured following regular standard procedures up to the 13th month of processing and then divided into two groups according to established levels of cathepsin B activity in fresh hams. Each group was selected in order to include the same number of hams with low or high cathepsin B activity. The two groups were further split to be kept for an additional month at two different temperatures (18 and 26 °C) and then analysed for proximate composition, free amino acids and oligopeptides (MW
... These enzymes have acidic pH optima and, therefore, if involved in postmortem tenderization, they are most involved once muscle approaches its ultimate pH. To explain a basis for meat tenderization during postmortem storage, it has been postulated that one class of these proteases or the synergistic action of both classes of proteases (CDP's and lysosomal enzymes) is responsible for postmortem changes (Dutson, 1983;Goll et al., 1983;Pearson et al., 1983). It is logical to assume that the class of proteases responsible for postmortem aging should have higher activity in the carcasses with a high aging response and vice versa (Koohmaraie et al., 1988). ...
ABSTRACT: The objective of this study was to determine the aging patterns of nine selected muscles from the chuck and round from two quality grades of beef: United States Department of Agriculture (USDA) Select and the upper 2/3 of USDA Choice grade. The International Meat Purchase Specifications (IMPS) (NAMP, 1988) 115 2-piece chuck was separated and the following muscles were selected for study: infraspinatus, triceps brachii? lateral head, triceps brachii? long head, serratus ventralis, complexus, splenius, and rhomboideus. The IMPS 167A knuckle was also separated and the vastus lateralis and rectus femoris were evaluated. ABSTRACT: These muscles were selected because of the possibility of being used as cuts where tenderness is critical due to the probability that they would be cooked with a dry cooking method, based on results from the Muscle Profiling Study conducted by the University of Florida and University of Nebraska in conjunction with the National Cattleman's Beef Association. Each muscle was divided into four portions, progressing from anterior to posterior or dorsal to ventral orientation to the carcass. One steak was removed from each portion for evaluation. Aging was conducted at 7, 14, 21, or 28 days. After achieving their appropriate aging treatment, Warner-Bratzler Shear (WBS) force analyses were conducted on an Instron (Canton, MA) universal testing machine. Aging affected all of the muscles evaluated in this study in a similar fashion; therefore, consistent recommendations can be given for these muscles. ABSTRACT: This study revealed that USDA grade had an effect on aging, in that it would not be necessary to hold muscles from the upper 2/3 of USDA Choice grade beyond 7 days of age. For USDA Choice grade, there was in increase in thaw loss from 14 to 28 days of aging, but aging up to 7 days had no effect. Muscles from lower marbled grades (i.e., USDA Select), should be aged a minimum of 14 days postmortem. As USDA Select grade was aged from 7 to 21 days, there was an increased percentage of thaw loss. However, after 14 to 21 days of age, it seems that there is no further increase in thaw loss percentages. The muscles respond differently depending on grade; USDA Select generally had higher cooking losses than USDA Choice. Location within a muscle had an effect on WBS values in four of the nine muscles evaluated. This indicated that muscles would have to be treated on an individual basis when fabricating and merchandising individual retail cuts from these muscles. ABSTRACT: For some muscles, location within the cut can be ignored, and for others location must be considered for tenderness enhancement or product utilization. Text (Electronic thesis) in PDF format. System requirements: World Wide Web browser and PDF reader. Mode of access: World Wide Web. Title from title page of source document. Document formatted into pages; contains 77 pages. Thesis (M.S.)--University of Florida, 2004. Includes vita. Includes bibliographical references.
Pastırma is a traditional dry‐cured meat product. Proteolytic changes play an important role on pastırma quality. In the present study, proteolytic changes of “sırt” pastırma (Longissimus thoracis et lumborum) and “şekerpare” pastırma (Semitendinosus) types were investigated during production. While the average total free amino acid (FAA) amount was 311.24 ± 21.76 mg/100 g dry matter in raw material, it was 825.26 ± 103.90 mg/100 g dry matter in the pastırma. Proteolytic changes were more evident after the first drying stage. Alanine, leucine, glutamic acid, arginine, and lysine amino acids in both pastırma types were predominant. The average total FAA amount was high in sırt‐pastırma. Arginine (for children), methionine, isoleucine, leucine, and lysine, essential amino acids, were also high in “sırt” pastırma. On the contrary, SDS‐PAGE profiles of the both pastırma types were generally similar and there was no significant difference between the average nonprotein nitrogenous substances (NPN‐S) amount of the pastırma types.
Practical applications
Although it is possible to produce many types of pastırma depending on the muscle used as raw material, the “sırt‐pastırma” and “şekerpare‐pastırma” are the widely produced types. According to the results of this research, the first drying in pastırma production is an important stage in terms of proteolytic changes. In the “sırt pastırma,” the amount of total free amino acid was higher compared to the “şekerpare pastırma.” This result could have a positive effect on the sensory properties of the “sırt pastırma.” Moreover, some essential amino acids were high in this type of pastırma.
Background
The final characteristics of processed meats depend on many factors but one of the most important is the intense proteolysis occurred in muscle proteins due to the action of endogenous enzymes in dry-cured ham, and also microbial peptidases in the case of dry-fermented meats, that not only affects taste and flavour but also the generation of bioactive peptides.
Scope and approach
In this review main difficulties in the identification of bioactive peptides in processed meats have been described. This study highlights the novel strategies used during the last years to identify naturally generated peptides, and emphasises the need of robust quantitative methodologies for the adequate characterisation of their bioavailability. In fact, the most common and well established quantitation approaches using proteomics are not adapted for peptidomics analysis, so alternative strategies need to be considered.
Key findings and conclusions
The progress in the identification and characterisation of the activity of natural bioactive peptides is highly dependent on modern instruments and bioinformatics tools as well as updated protein databases. In fact, the use of in silico approaches and proteomics can be complementary tools in the identification of peptides from meat protein sources as the empirical experimental design can be simplified by using bioinformatics for computer simulation in most of the steps. Finally, Multiple Reaction Monitoring mass spectrometry methodology previously used in the quantitation of therapeutic peptides and biomarkers arises as a powerful tool for absolute quantitation or semi-quantitation of bioactive peptides.
Dry-cured hams are appreciated products in many European countries. One of the most important processes taking place during ham processing and responsible for its unique taste and flavour is the proteolysis of muscle proteins. Muscle peptidases play an important role in breaking down muscle proteins and generating small peptides and free amino acids. It is known that changes in genetics and processing conditions can result in differences in the action of endopeptidases and exopeptidases.
In this study, the peptides generated in Spanish Teruel, Italian Parma and Belgian dry-cured hams have been identified and quantified using a label-free methodology to assess main differences in proteolysis between the 3 types of hams. The identification of the peptides resulted in differential peptide sequences according to the type of ham. On the other hand, an aqueous peptide extract fractionated by size-exclusion chromatography was assayed for Angiotensin-Converting Enzyme (ACE) inhibitory and antioxidant activity. Peptide fractions of Teruel ham exhibited 93% ACE inhibition while those from Parma and Belgian hams had ACE inhibitory activity of 70% and 76%, respectively. The investigated peptide fractions exhibited similar values of DPPH scavenging activity whereas an important Fe2 + reducing power was also detected in the same fractions, suggesting the important presence of peptides with antioxidant activity in the three studied types of dry-cured hams.
Intrinsic characteristicsPost-mortem changesPreservationHandling for live salesPractical processing techniques
Peptides are critical to the taste of dry-cured ham. To isolate and identify umami peptide fractions from the water-soluble extractions (WSEs) of Jinhua and Parma hams, separation procedures utilizing Sephadex G-25 and reversed-phase high-performance liquid chromatography (RP-HPLC) were combined with sensory evaluations (taste dilution analysis and an electronic tongue). The amino acid sequences of the umami peptides, Cys-Cys-Asn-Lys-Ser-Val (CCNKSV) from Jinhua ham and Ala-His-Ser-Val-Arg-Phe-Tyr (AHSVRFY) from Parma ham, were identified by MALDI-TOF-MS; subsequently, both were synthesized, and their umami taste properties were evaluated. The results indicate that the tastes of the umami peptides were similar to those of the hams' WSEs.
Samples were obtained from bovine Longissimus dorsi (L), Biceps femoris (BF) and Psoas major (PM) muscles at different times of postmortem storage at 1.2°C. At day 1 postmortem, PM was the most tender muscle followed by BF then L; PM muscle also had the smallest fiber area and longest sarcomere followed by BF and L. After postmortem storage, shear force values decreased greatly for L, and only slightly for PM. There were no differences in activities of cathepsins, B, H, and L for any of the muscles. However, L muscle had the highest Ca++-dependent protease activity followed by BF and PM. Thus results suggested that Ca++-dependent protease activity was best determinant of tenderization resulting from postmortem storage at refrigerated temperatures.
Within a project aimed at studying the peptide fraction in dry-cured Parma hams, a peptide was purified by means of reversed phase-high performance liquid chromatography (RP-HPLC) and identified by its molecular mass and amino acid sequence analysis. The peptide showed a very high degree of homology with the N-terminal part of different mammalian pyruvate kinases reported in databases and was accordingly identified as the N-terminal part of swine pyruvate kinase, whose sequence had never been reported before. The peptide was determined quantitatively by comparison with a suitable internal standard (Phe-Phe) in commercial ham samples with different age degrees. The peptide was found to be ubiquitous in Parma ham and its amount to increase during ageing even if a large variability was found within each assayed maturing time. The correlation found with the ham proteolysis degree (P<0.01) suggests that this peptide is related to the endopeptidasic activity. The peptide did not show a significant relationship with bitterness perception in assayed dry-cured ham, in agreement with the hypothesis that this taste is more related to free amino acids and low molecular weight peptides.
Procedures have been developed for purification of three of the four protein components usually found in skeletal muscle troponin
preparations. These three components are the ones required for troponin activity, and an apparent functional property of each
has been defined. TN-I with a molecular weight of 24,000 inhibits actomyosin ATPase activity both in the presence and absence
of Ca++. TN-T, with a molecular weight of 37,000, interacts with tropomyosin as evidenced by the appearance of a new hypersharp peak
when mixtures of the two proteins are examined in the analytical ultracentrifuge. TN-C, with a molecular weight of 20,000,
was the only component which possesses high affinity Ca++ binding activity. The sulfhydryl groups of troponin are found only in TN-I and TN-C. TN-I and TN-T require salt for full
solubility and both proteins show a strong tendency to aggregate. An attempt has been made to interpret results on troponin
fractionation obtained in other laboratories in the light of the properties of our purified components.
β-Actinin, a minor regulatory protein of muscle, was purified from skeletal muscles of rabbit and chicken by DEAE-Sephadex chromatography. β-Actinin consisted of two subunits, βI and βII, with chain weights of 37,000 and 34,000 daltons, respectively. The amino acid compositions were similar, though not identical. It appears that each of the two subunits is associated in solution. β-Actinin had the following effects on actin: (1) inhibition of reassociation of F-actin fragments; (2) inhibition of network formation of F-actin; (3) inhibition of growth of F-actin fragments; (4) retardation of depolymerization of F-actin and (5) acceleration of polymerization of G-actin. All these actions of β-actinin can be explained in terms of action as an “endiDg factor.” Experimental evidence favored the view that β-actinin is bound to one end of the F-actin filament, namely to the end opposite to the direction of polymerization. Fluorescence-labeled anti-β-actinin stained the middle portion of the A band of myofibrils. Based on the finding that the statn was unchanged on removal of myosin, it is suggested that β-actinin is located at the free ends of the I filaments of myofibrils. Thus is seems likely that β-actinin functions as an ending factor for actin filaments.
This chapter focuses on Ca2+-activated muscle protease in myofibrillar protein turnover. SDS-polyacrylamide gel electrophoresis shows that, when incubated with individual, purified myofibrillar proteins, the protease degrades C-protein, tropomyosin, troponin-T, and troponin-I but has no effect on either the heavy or light chains of myosin, a-actinin, actin, or troponin-C. Degradation of C-protein by the protease produces two fragments of approximately 10,000 and 130,000 daltons. Degradation of tropomyosin, troponin-T, and troponin-I by the protease results in fragments of approximately 10,000–14,000 daltons. Because the Ca2+-activated protease has free access to myofibrils in the muscle cell, its activity must be under close regulation to prevent continuous and indiscriminate degradation of functioning fibrils.
This chapter attempts to clarify the chemical changes that are responsible for the physical change in the muscle of meat. All skeletal muscles are striated in appearance and make up more than 50% of the weight of the animal. The chapter discusses the nature of these striations and the color of the muscle that is dependent on its myoglobin content. It presents the chemical changes associated with contraction and with onset of rigor mortis and changes associated with relaxation and with resolution of rigor mortis. Five experimental models for contraction and relaxation have been mentioned. The chapter discusses the use of enzymes for tenderizing meats along with some disadvantages. The enzymes that have been investigated for use in tenderizing meats are proteolytic in nature and are divided into three groups depending upon their source. The effect of tenderization in meat is difficult to treat quantitatively because adequate criteria of what constitutes tenderness is lacking.
The odor responses, and the chemical compounds isolated, from the volatile pyrolysis products of lyophilized cold water extracts of lean beef and lean pork were found to be similar. The flavor precursors in lean meat are low molecular weight compounds present in the dialyzable portion of the cold water extracts of the raw lean meats. Beef and pork fat when heated produced dissimilar aromas. Free fatty acids and carbonyls were determined in these fats before and after heating. The results suggest that, on heating, the lean portions of pork and beef contribute an identical meaty flavor to these meats, while the characteristic flavor differences in pork and beef reside in the fat.
Purification and properties of a new alkaline protease of rat skeletal muscle have been reported. The purification procedure of the enzyme is as follows: skeletal muscle tissue was extracted successively with Hasselbach-Schneider solution, 5M urea solution and 2% sodium deoxycholate solution. After then, the enzyme was extracted from the residue with 1.1M potassium iodide solution. This enzyme solution was treated with n-butanol, and dialyzed against water. The enzyme precipitated during dialysis was collected and dissolved in 1.1M potassium iodide solution. The enzyme solution was fractionated with acetone, and chromatographed on Sephadex G-200. The final preparation showed over 20000 times of purity.
The optimum pH range of the enzyme activity is 9.5_??_10.5, and the maximum reaction rate occurs at 47_??_57°C. The enzyme is stable below 47°C at pH 7.3. At 37°C, the enzyme is stable during 30min at least, in the pH range of 5.5-10.0. Below pH 5.0, it is relatively labile. Hg²⁺, Ca²⁺, Mg²⁺, Mn²⁺, C0²⁺, and Zn²⁺ scarcely affect the enzyme activity at the concentration of 1mM. Ethylenediaminetetraacetate shows little effect on the activity at the concentration of 10mM, and iodoacetamide, 2, 4-dinitrophenol, p-chloro-mercuribenzoate show the similar effect at the concentration of 1mM. Diisopropyl-fluro-phosphate inhibits the enzyme activity. From the results obtained, this enzyme is presumed to be responsible for the activity of autolytic breakdown of rat skeletal muscle proteins in the alkaline pH range.
The purified Ca2+-activated protease (CAF) isolated from porcine skeletal muscle and capable of removing Z-disks from intact myofibrils is optimally active on either myofibril or casein substrates at pH 7.5 and in the presence of 1 mM Ca2+ and at least 2 mM 2-mercaptoethanol. No CAF activity is detected when 1 mM Mg2+, Mn2+, Ba2+, Co2+, Ni2+, and Fe2+ are added singly. When added with 1 mM Ca2+, Co2+, Cu2+, Ni2+, and Fe2+ inhibit, whereas Mg2+, Mn2+, and Ba2+ have no effect on CAF activity. CAF is irreversibly inhibited by iodoacetate but is unaffected by soybean trypsin inhibitor. S0/20,W=5.90 S, and sedimentation equilibrium molecular weight - 112 000 for purified CAF. Because purified CAF migrates as two polypeptide chains with molecular weights of 80 000 and 30 000 in sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the CAF molecule must consist of one each of these two polypeptide chains. Approximate molecular dimensions of 38 X 220 A can be calculated for CAF from calibrated gel permeation column data or from S0/20,W and the molecular weight. Amino acid composition and physical properties of purified CAF distinguish it from the known catheptic enzymes and from other proteases found in blood or in granulocytes. Purified CAF removes Z-disks the 400-A periodicity associated with troponin in the I band and partly degrades M lines but causes no other ultrastructurally detectable effects when incubated with myofibrils. These results agree with the earlier finding that purified CAF degrades troponin, tropomyosin, and C-protein but has no effect on myosin, actin, or alpha-actinin, and suggest that CAF may have a physiological role in disassembly of intact myofibrils during metabolic turnover of myofibrillar proteins.
1.1. In samples representing 60–70 per cent of the total collagen from bovine semimembranosus muscle, the yields of salt- and acid-soluble collagen were 0.3 and 0.48 per cent, respectively.2.2. Collagen from muscle differed significantly from that of skin and tendon in solubility and distribution of cross-linked components.3.3. The component ratio of β12 to β11 was approximately 2: 1, indicating random crosslinking among the ai and α2-chains.4.4. The amino-acid composition of muscle collagen showed both similarities and différences when compared with either reticulin or skin and tendon collagens.
Cathepsins A and D were separated and partially purified from extracts of chicken breast muscle. The properties of muscle cathepsin D are similar to those of cathepsin D from other sources: optimal activity with hemoglobin substrate at pH 2.8, lack of requirement for cysteine or ferrous ions, and failure to hydrolyze the synthetic peptides acted upon by cathepsins A, B, or C. Muscle cathepsin A showed a greater affinity for CBZ-α-l-glutamyl-l-phenylalanine than for CBZ-α-l-glutamyl-l-tyrosine, was optimally active at pH 5–5.4, and did not require cysteine activation. Cathepsin A alone showed little or no activity on hemoglobin unless cathepsin D also was present. This demonstrates that cathepsin A is restricted in its activity to breakdown products of proteins resulting from the prior action of cathepsin D or, presumably, other proteinases. When isolated from breast muscle of genetically dystrophic chickens, both cathepsins A and D showed the same enzymic properties as those of normal muscle and differed from the latter only in quantity.
Seventeen compounds produced from the reaction of furfural, hydrogen sulfide, and ammonia in aqueous solution under cooking conditions were identified by a GC-MS technique. Major reaction products were cyclic methylene polysulfides and furan derivatives. The formation of oxazole and pyrazine derivatives indicated that furfural produced a smaller number of carbon units. The formation of thiophene and pyrrole derivatives indicated that the oxygen atom in the furan ring exchanged with the sulfur and nitrogen atoms. In addition to those compounds, two self-condensation products of furfural, difurylethylene and furil, were obtained in large amounts from this reaction.
The compounds produced by heating a D-glucose-hydrogen sulfide-ammonia-water model system were extracted with methylene chloride using a liquid-liquid continuous extractor. Fifty-one compounds were identified by a combination of gas chromatographic and mass spectrometric techniques. The main constituents of the reaction mixtures were thiophenes, furans, pyrazines, and thiazoles. With small amounts of ammonia in the starting mixture, the reaction products consisted mainly of thiophenes and furans and possessed a somewhat sulfury aroma which was also akin to that of rare cooked meat. When the amount of ammonia was increased, however, the reaction mixture contained a large proportion of pyrazines, a smaller proportion of thiazoles, thiophenes, and furans and the mixture possessed a nutty or burnt aroma.
Using a modified Likens and Nickerson extraction procedure followed by low temperature/high vacuum distillation, representative samples of aroma volatiles were obtained from beef while cooking by microwave radiation and by conventional means. Separation of the components of the isolates was achieved by gas chromatography and the majority of the components were identified by combined gas chromatography/mass spectrometry. A comparative study was undertaken of the effect of cooking variations on the volatile components liberated. Such variations included heating in the presence and in the absence of water and for different periods of time for both conventional and microwave heating methods. Results indicated that certain carbonyl compounds, sulfides, pyrroles, and pyridines are probably important contributors to roasted notes as opposed to boiled or brothy qualities of heated beef aroma.
The volatile compounds produced by heating a model system of D-glucose-hydrogen sulfide-ammonia were entrained on Porapak Q and subsequently desorbed and transferred to a glass capillary column for separation and identification. Gas chromatographic and mass spectrometric methods were used to identify 34 of the major components. The compounds identified included a thiol, sulfides, thiophenes, thiazoles, and furans. Thiophene and furan derivatives were the major volatile constituents of this reaction mixture which gave roast beef-like aroma.
The following two model meat systems were heated: hydrolyzed vegetable protein (HVP)-L-cysteine-HCl-D-xylose-water and L-cysteine-HCl-D-xylose-water. The flavor concentrates were isolated by atmospheric steam distillation, followed by continuous solvent extraction of the distillate. Isolation and identification were accomplished by gas chromatography and coupled gc-mass spectrometry. Identifications were based on I E values and mass spectra. A total of 24 sulfur compounds were identified in the HVP-L-cysteine-HCl-D-xylose system and 15 were identified in the L-cysteine-HCl-D-xylose system, of which 10 were not present in the former model system.
Some precursors of beef flavor have been investigated. Those dealt with here appear to be relatively simple water-soluble components of beef muscle tissue. Inosinic acid or inosine and inorganic phosphate have been identified as one of the compounds involved. A glycoprotein of unknown structure is another component. Glucose has been identified as the sugar moiety of the glycoprotein. The amino acid composition is also discussed.
Eight tender and eight tough bovine longissimus samples were selected on the basis of significant differences in sensory tenderness score, Warner-Bratzler shear force value and myofibril fragmentation index. Longissimus samples were removed from carcasses at 1 day postmortem storage (2°C). These samples were subsequently analyzed for sarcomere length, sarcoplasmic and myofibrillar protein concentration, collagen concentration, pH values, fat and moisture content. SDS-polyacrylamide gel electrophoresis was used to further characterize the KC1 soluble myofibrillar proteins. No significant differences between groups were found for sarcomere length and chemical properties. A major difference, however, was detected between tough and tender muscle with SDS-polyacrylamide gels. That is, the 30,000-dalton component was present in tender longissimus, but it was absent in tough longissimus muscle. These results show that (1) the 30,000-dalton component is closely associated with tender steak and high myofibril fragmentation; (2) tenderness can be objectively detected early during postmortem aging; and (3) the presence, or absence, of the 30,000-dalton component offers the potential, after further investigations, of being useful as an index of tender or tough longissimus muscle.
ABSTRACTA synthetic model meat flavor system was developed by panel testing of various meat flavor precursors at different levels by predicting optimum concentrations using surface response methodology. The final flavor system consisted of an autoclaved mixture of simple sugars, amino acids, 5-nucleotides, glycoprotein, monosodium glutamate, and salt with fat as an optional component. Results demonstrated that the sulfur-containing ammo acids and simple sugars played an important role in flavor development, whereas, the other components either masked the harsh sulfury taste or enhanced the meaty flavor. The surface response method was shown to be a good technique for predicting the optimal level of components in the formulation, although panelists were not able to differentiate between small differences in the levels of components in the mixture. Subjection of the final formulation to the panel in comparison to five commercial meat flavor extracts and an authentic beef extract showed it to be equal or superior to all of the commercial samples and nearly equal to authentic beef extract.
Das Spektrum ausgewählter Aminosäuren ist hinsichtlich der Ausbildung eines fleischartigen Geschmackseindruckes bei der thermischen Reaktion mit Glucose untersucht worden. Die reinen Aminosäuren reagierten — wäßrigen Milieu einzeln und in Mischungen, die nach statistischen Versuchsplänen zusammengestellt waren, zu Produkten, die sensorisch und instrumentalanalytisch charakterisiert wurden. Zielgröße der Optimierung der Aminosäuren nach Art und Menge war der sensorische Eindruck.
Im Ergebnis konnten die Einflüsse der einzelnen Aminosäuren, optimale Versuchsparameter und eine optimale Zusammensetzung ermittelt werden. Das optimierte Modell ist durch sehr hohen Anteil an Glutaminsäure und durch hohe Anteile an Asparaginsäure, Arginin und Prolin gekennzeichnet. Bereits mit der Hälfte der getesteten 18 Aminosäuren resultierte ein im Aroma optimiertes Produkt, das sich im fleischähnlichen Qualitätseindruck nicht verbessern ließ.
The control (C) side of 23 animals was placed in a 2°C chill room at 1 hr postmortem, while the other side was high temperature cdnditioned (HT) at approximately 22°C for 4 hr postmortem, at 12°C for an additional 8 hr and was then placed in the 2°C chill room. The activity of cathepsin C and β-glucuronidase was measured on the nuclear, micro somal, and unsedimentable fractions at 12, 18 and 24 hr postmortem in order to determine the amount of sedimentable and free enzyme activity at these postmortem times. High temperature conditioning enhances the disruption of the lysosomal membrane as evidenced by a significant increase in percent of free enzyme activity at 12 hr postmortem for both cathepsin C and β-glucuronidase. There was also a significant decrease in total activity for both enzymes of the HT group at 12 hr postmortem due to autolysis of the free enzyme. These differences were not present at 18 and 24 hr postmortem (except for decreased total activity of cathepsin C at 18 hr), indicating that differences caused by high temperature conditioning take place very early postmortem and that the differences in enzyme activities are not detectable at later postmortem times. These results indicate that some of the differences in tenderness produced by HT treatments are possibly associated with the increased level of free lysosomal enzymes during the first 12 hr postmortem.
Considerable research has been done on model systems in which possible meat components have been heated. Many aroma components have been identified including carbonyls, pyrazines, thiols, thiazoles and other nitrogenous and sulfur-containing compounds. Some of these have been identified in the aroma of meat products. Some of the effects of processing on several beef aroma components were assessed. The relationship of concentration of a number of compounds in the aroma and their threshold of detection are discussed, as well as the “GRAS” concentrations permitted. Patents covering the development of meat aroma products are reviewed.
The influence of postmortem time and incubation temperature on the release of lysosomal enzyme activity and their effect on the muscle connective tissue have been investigated. Semimembranosus muscles from nine steers were restrained and held at 2°C (C) for 60 hr; five portions of each muscle were elevated to 37°C (HT) for different 12-hr sequences of the 60 hr. It was found that HT incubated samples showed a greater release of lysosomal enzymes (β-galactosidase and β-glucuronidase), regardless of the time postmortem when high temperature conditioning occurred. The inclusion of hyaluronidase or β-galactosidase in the sample incubation solution resulted in an increase in the dissolution of collagen fibers by collagenase, which indicates that lysosomal glycosidases may also participate in the dissolution of collagen fibers during postmortem aging.
Samples were removed from 6 veal, 35 A-maturity and 12 C-maturity bovine longissimus (L) muscles at 1 and 7 days postmortem. Myofibril fragmentation index (MFI), Warner-Bratzler (W-B) shear-force, sensory panel evaluation and sodium dodecyl sulfate (SDS) polyacrylamide gels of myofibrils were determined on muscle samples and steaks. Correlation coefficients between MFI and W-B shear-force were -0.95, -0.73 and -0.65 and, between MFI and sensory tenderness, were 0.97, 0.75 and 0.72 for steaks postmortem aged for 7 days at 2°C from veal, A-maturity and C-maturity carcasses, respectively. SDS-polyacrylamide gels showed that the intensity of the 30,000-dalton component corresponded to the tenderness level of the steaks. These results demonstrate that MFI accounts for about 50% of the variation in tenderness and that myofibril fragmentation and the intensity of the 30,000-dalton component offer potential usefulness as indices of tenderness.
Cooking resulted in significant increases in adenylic acid, total purine nucleosides and bases of 80 beef roasts of eight different cuts. It decreased the contents of inosinic acid, guanylic acid and sum of individual nucleotides (adenylic, cytidylic, uridylic, inosinic and guanylic acids) in these samples. Significant differences were also found between the various constituents of raw and cooked samples of the beef cuts.
Studies were made of the influence of heating on nucleotides and total purine nucleosides and bases of beef, pork and lamb muscle. lnosinic acid was the predominant nucleotide in all three species and it was degraded by heating. Adenylic acid increased during cooking in meat from all three species. Cytidylic, uridylic and guanylic acids were present in relatively low concentrations in meat from all three species and changed little during cooking. A rapid method for estimating total nucleotides resulted in greater variation than a specific method for measuring individual nucleotides.
The contribution to beef aroma of some compounds previously identified in the flavor volatiles from cooked beef was estimated by surface response methodology. In general, heterocyclic compounds containing oxygen, nitrogen and/or sulfur and unsaturated alcohols gave higher predicted scores and had lower optimum concentrations than ketones, aldehydes, alkanes or saturated alcohols. It was further demonstrated that hydrophilic compounds are more likely to contribute to meat aroma than hydrophobic compounds, thus, verifying a more important role for water-soluble compounds in contributing to meat flavor. On testing mixtures of compounds, the optimum concentrations were generally lower, but there was a greater range in maximum scores. Special significance is given to the fact that highest scoring two-component mixture (2-acetyl-3-methylpyrazine and H2S) resulted from combining the two single compounds that scored highest alone. Furthermore, the reaction mixture of H2S with 4-hydroxy-5-methyl-3(2H)-furanone gave the highest predicted score in the entire study. Thus, results indicate that the surface response method offers promise for unraveling the complexity of the meat flavor system.
Water-soluble extracts of beef contain flavor precursors of compounds responsible for a characteristic broiled steak aroma. Dialysis separated the extract into a nondialyzable high-molecular-weight fraction having a brothy odor during boiling, and a low-molecular-weight fraction having a broiled-steak odor when pyrolyzed. The fraction responsible for the broiled-steak aroma was separated on ion-exchange resins. An aromatic fraction was obtained containing amino acids and peptides. Although sugars have been found in previously described flavor fractions, no sugars were found in this material.
The method of N-terminal analysis has been applied to the protein fractions of beef to detect proteolysis on storage at low or high temperature. Parallel studies have been made on the histology, non-protein nitrogen and free amino-acids, and on the extractability and electrophoresis of the structural proteins. While definite small increases in free amino-acids occur, increases in N-terminal groups were negligible. Other results give no evidence of proteolysis. It is concluded that proteolysis is not a significant factor in the tenderising of beef by ageing.
A partially purified fraction of bovine muscle cathepsins prepared from a crude extract by precipitation with ammonium sulfate between 45 and 55% saturation was assayed for activity on 18 peptides and other synthetic substrates, and on preparations of four natural substrates isolated from beef. Three of the synthetic substrates were partially hydrolyzed by the enzyme preparation. The hydrolysis of carbobenzoxy-L-glutamyl-L-tyrosine indicated endopeptidase activity. Dipeptidase and/or endopeptidase activity was evidenced by the hydrolysis of glycyl-L-tyrosine and L-leucyl-L-tyrosine. When using either of these two peptides as the substrate, a chromatographically distinct compound was detected which was absent in the enzyme and substrate blanks.
The fraction had no detectable enzymatic action on crude preparations of actin, myosin, and actomyosin. Commercially purified serum albumin was hydrolyzed, but at a much slower rate than denatured hemoglobin, which has been widely used for assaying catheptic activity. Sarcoplasmic proteins indigenous to the crude extract appeared to be readily hydrolyzed by the cathepsins.
Six lamb carcasses were split, the left side (ES) was electrically stimulated (25 pulses, 0.5–1 set each at 440V) while the right side (C) served as an unstimulated control. Samples were removed at 1 hr post-stimulation and assayed for total, free, and specific activities of the lysosomal enzymes β-glucuronidase and cathepsin-C. A significant (P < 0.05) increase in percent free activity and a significant decrease in specific sedimentable activity and total activity of both enzymes was found for the ES samples. This indicates that the lysosomal membranes are disrupted due to electrical stimulation. The possible effects of the free lysosomal enzymes on muscle proteins and meat tenderness is discussed.
Paper and ion-exchange chromatography were used to determine qualitatively certain constituents in lyophilized diffusates from cold-water extracts of beef, lamb, and pork muscles. The qualitative contents of low-molecular-weight diffusible organic constituents in tissue from these three species were remarkably similar. Involvement of constituents studied as flavor and odor precursors is discussed.
Quantitative analyses were made of water-extractable amino nitrogen and carbohydrate constituents of beef, lamb, and pork before and after heating. In all three species, taurine, anserine-carnosine, and alanine were present in relatively large quantities, and losses of these were large during heating. Other important amino acids degraded during heating were: glutamic acid, glycine, lysine, serine, cystine, methionine, leucine, isoleucine, and methyl histidine. Heating caused marked increases of phosphoethanolamine in samples from the three animal species studied. Ribose was the carbohydrate most labile to heating, and glucose was the most stable. The importance of these constituents as odor and/or flavor precursors of meat is discussed.