Composition of Muscle and Meat

Composition of Muscle and Meat - Composition of Muscle...

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Unformatted text preview: Composition of Muscle & Meat Meat Difference in Muscle & Meat Difference General •There is an alteration of muscle’s biochemical and physical properties •This improves the keeping quality and acceptability of the subsequent food product Composition of Meat Composition Lean meat of all species consists of approximately 72% water*, 20% protein, 7% fat* and 1% ash water*, protein and ash *water and fat are inversely related ( fat H2O) A) Water (72%) Juiciness, Flavor and Texture (lubricant) Key factor in meat processing (transport Key medium, solvent) medium, Composition of Meat cont’d B) Protein (20%) B) 1) Myofibrillar - salt-soluble proteins 1) Myofibrillar salt-soluble 11.5% of muscle wt. (> 1/2 total protein) Myosin and Actin -- most abundant 2) Sarcoplasmic - water-soluble proteins 2) Sarcoplasmic Glycolytic enzymes such as myoglobin Glycolytic myoglobin (O2 binding protein inside the muscle (O cell) and hemoglobin cell) Composition of Meat cont’d Protein cont’d Protein 3) Stromal - connective tissue proteins 3) Stromal Collagen - single most abundant protein found in mammalian species (provides strength and support) strength Elastin - found in arterial walls giving those tissues elasticity tissues Example: ligamentum nuchae (or backstrap) Example: ligamentum Composition of Meat cont’d C) Fat (7%) C) 1) Subcutaneous - beneath the skin 2) Intermuscular - between muscles 3) Intramuscular - between muscle bundles - in 3) the muscle - MARBLING MARBLING D) Ash (1%) Iron () Zinc () Potassium () Calcium () Sodium () Tissues in Meat Tissues 1) 2) 3) 4) 1) 2) Muscle Connective Tissue Adipose Tissue Nervous Tissue Blood Vessels Epithelial Tissue Muscle is a Specialized Tissue! • Muscle has the ability to CONTRACT. CONTRACT Muscle Tissue Types • Smooth Involuntary – – – – – Not striated Single nuclei Sympathetic nervous system Digestive, respiratory, & vascular tissues Extremely elastic & pliable Extremely Muscle Tissue Types • Striated Involuntary – – – – Cardiac muscle Branched structure Intercalated discs 1 to 2 nuclei/ cell Muscle Tissue Types • Voluntary Striated – Skeletal muscle – Multi-nucleated Skeletal Muscle Skeletal Drawing of a Skeletal Muscle Connective Tissue Organization Connective • Epimysium – Epi- = on, upon – around muscle body • Perimysium – Peri- = about, around, encircle – around muscle bundles Connective Tissue Organization Connective • Epimysium – Epi- = on, upon – around muscle body • Perimysium – Peri- = about, around, encircle – around muscle bundles • Endomysium – – Endo- = inside, within around myofibers (muscle cell) Muscle Bundle (a.k.a. fasciculi) • Contains 20-40 Contains myofibers myofibers • Encased by Encased perimysium perimysium • Number & size vary Number with muscle location & function location Myofiber (Muscle fiber) • Individual muscle cell • Multinucleated • Cell wall: sarcolemma • Encased by endomysium • Mucopolysaccharide basement membrane Mucopolysaccharide (or basal lamina) (or Myofibrils Myofibrils • Inner makings of a muscle cell • Embedded in sarcoplasm • Mitochondria located between myofibrils Myofibrils (continued) • Comprised of repeating units: sarcomeres Comprised sarcomeres – – – – – – A band I band Z disk M line H zone Pseudo-H zone The smallest (most basic) unit of muscle - sarcomere Sarcomere Sarcomere Myofilaments • Thick filament (below in red) – Myosin Contractile Myosin & Its Fragments S1 Papain/ Chymotrypsin ROD Alkali Alkali light chain light Regulatory light chain COOLMM COO- Actin binding Actin and ATPase activity activity HMM Trypsin Fig. 2.28 in book Myofilaments • Thin filament (below in blue) – Actin Contractile Molecular Structure of Actin • Globular (G-actin) – Monomeric unit • Filamentous (F-actin) – Strands of G-actin intertwined – 13 G-actin monomers / turn. – ~400 G-actin molecules in one F-actin double ~400 helix helix Regulatory Proteins • Serve to “regulate” contraction (speed Serve & spatial orientation) spatial – Tropomyosin – Troponin Regulatory Tropomyosin (Tm) • Thin filament protein Thin – component of F-actin. • Dimer (α-helix , coiled coil) • 7-aa repeat (a, b, c, d, e, f, g) b, • Molecules interact head to tail forming Molecules a long polymer long Regulatory Tropomyosin (Tm) • Binds F-actin near “groove” A A End view Regulatory Tropomyosin (Tm) • Binds F-actin near “groove” • Spans 7 G-actin molecules • Tm binds each of 7 G-actin molecules in 2 sites Regulatory Troponin (Tn) • 3 Subunits – TnT • Binds tropomyosin – TnI • Inhibitory subunit – TnC • Ca2+ binding subunit Regulatory Troponin T (TnT) • • Base subunit Bound to Tm & the other Tn molecules Regulatory Troponin I (TnI) • Inhibitory subunit • Inhibits actin-activated myosin ATPase Inhibits activity activity • Binds actin and likely blocks myosin Binds binding site on actin Regulatory Troponin C (TnC) • Ca2+ binding subunit Regulatory Front View +Ca2+ -Ca2+ Top View Structural/ Cytoskeletal Proteins • Ties f-actin together at Z-line – α- Actinin • Laterally attach sarcomere to Laterally sarcomere sarcomere – M-protein/skelemin at M line Structural/ Cytoskeletal Proteins • End to end attach sarcomere to End sarcomere sarcomere – Primary protein- Desmin • Maintain 3-D orientation of thick & Maintain thin filaments thin – Titan and Nebulin Structural/ Cytoskeletal Proteins • Attach outer most myofibrils to sarcolemma – Filamin, vinculin and talin PHOTOGRAPH OF SARCOMERE ...
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