Lecture 1- Animal QLT308 PDF

QUALITY MANAGEMENT - ‫ﺑرﻧﺎﻣﺞ إدارة اﻟﺟودة‬ Derived Substance Characteristics ‫ﺧﺻﺎﺋص اﻟﻣواد اﻟﻣﺷﺗﻘﺔ ﻣن اﻟﻧﺑﺎت واﻟﺣﯾوان‬ (QLT308) Lecture 1 Characteristics of substances of animal origin ‫ ﺳﻌﯾد ﻛﻣﺎل أﺑواﻟﻐﯾط‬/.‫د‬ Said Kamal Abolghait...

QUALITY MANAGEMENT - ‫ﺑرﻧﺎﻣﺞ إدارة اﻟﺟودة‬ Derived Substance Characteristics ‫ﺧﺻﺎﺋص اﻟﻣواد اﻟﻣﺷﺗﻘﺔ ﻣن اﻟﻧﺑﺎت واﻟﺣﯾوان‬ (QLT308) Lecture 1 Characteristics of substances of animal origin ‫ ﺳﻌﯾد ﻛﻣﺎل أﺑواﻟﻐﯾط‬/.‫د‬ Said Kamal Abolghait, PhD 1 Characteristics of substances of animal origin course contents:- A- Characteristics of meat:- 1. Muscle Composition and Conversion of Muscle into Meat 2. Meat Tenderness - Collagen and gelatin 3. Meat color - Myoglobin 4. Acidification - Lactic acid – Glycogen 5. Water holding capacity (WHC) - Myofibrils 6. Marbling – Lipid 7. Factors That Influence Meat Composition B- Toxicological chemical changes during heating and cooking. 1. Maillard Reaction Products 2. Hazards of Furan 3. Chloropropanols and Chloroesters 4. Heterocyclic Aromatic Amines 5. Acrolein 6. Nitrates, Nitrites, and Nitrosamines 7. General Aspect on Trans Fatty Acids C- Bioactive substances. 1. Omega-3 Fatty Acids 2. Conjugated Linoleic Acid 3. Milk Peptides 4. L-Carnitine 5. Choline 6. Coenzyme Q10 7. Glucosamine Academic Reference 8. Chondroitin 9. Melatonin 2  Definition Meat is generally defined as the flesh of certain animals used as food that is often widened to several edible tissues (mainly muscular tissue, but also associated adipose and connective tissues) and edible organs. 3  Muscle Composition and Conversion of Muscle into Meat Distinction between the terms ‘muscle’ and ‘meat’ The term meat, reflects the chemical and structural nature of the muscles after death of the animal. Where the post-mortem aspect, differs because initiation of series of biochemical and biophysical changes. 4 Chemical composition of typical adult mammalian muscle after rigor mortis but before degradative changes post-mortem 5 Chemical composition of typical adult mammalian muscle after rigor mortis but before degradative changes post-mortem 6 Skeletal muscle cells, called muscle fibers, are long, narrow, very specialized cells covered by the cell membrane (sarcolemma), whose cytoplasm (sarcoplasm) contains the organelles and the structures responsible of muscle contraction, the myofibrils. 7 8  Myofibrils are cylindrical structures made up of repeated units known as sarcomeres that cause the striated appearance of muscle when meat is observed by electron microscopy. Striations result from the complex organization of the myofibrillar proteins, responsible for the muscle contraction. The striations originate from alternating dense bands (A-bands) and less dense I-bands; the latter are divided in two parts by dark lines known as Z-lines. The space between two Z-lines is a 9 sarcomere. 10 Muscle fibers also contain proteins in the sarcoplasm (sarcoplasmic proteins) and enzymes in different cell structures or organelles. 11  Connective tissue structures define the organization of muscle. Muscle fibers are individually surrounded by a thin connective tissue sheath (the endomysium) and are bundled into groups or fascicles by connective tissue septa, the perimysium, associated to blood vessels and nerves; the muscle is completely 12 surrounded by the epimysium.  The main proteins in connective tissues are collagen and elastin. Collagen is the most abundant protein and includes several types of polypeptide chains. – Type I collagen is the major component of epimysium and perimysium, – while types III, IV, and V collagen are in the endomysium. 13  Collagen fibers are formed by long tropocollagen molecules. Each tropocollagen molecule consists of three polypeptide chains twisted together into a coiled triple α helix. 14 The polypeptide chains have the repeating sequence [– glycine–proline– hydroxyproline– glycine–(one of the other amino acids)…]. Proline and hydroxyproline are approximately 25 % and glycine 33 % of the total amino acid residues. 15  The N-terminals, non-helical regions of the α chains, are forming intermolecular cross-links that are important in collagen resistance in living animals and also in meat toughness. Cross-links are covalent bonds in which lysine and hydrolysine are involved. The cross-links increase with age and augment collagen insolubility 16 and hardness of matured animal meat. Under heating (60–65 °C) in moist conditions, collagen swells, its triple helix structure is destroyed at a great extent and transforms into random coils; then, it is called gelatin, becomes soluble, and can retain and immobilize high amounts of water and form gels after rapid cooling to 4 °C. 17 18 Elastin can be found in lower amounts and is located in capillaries, ligaments, tendons, and nerves. This protein contains about 40 % glycine, 40 % hydrophobic amino acids (18 % valine), and small amounts of proline and hydroxyproline and suffers cross-linking by lysyl oxidase action. Elastin becomes more insoluble with the increase of animal age. 19  Meat Tenderness Assessed as “force to chew” and/or the “time to chew.” The major and most variable eating quality (organoleptic ) attributes of meat depend on: 1. Muscle structure (size and types of muscle fibers and connective tissue distribution mainly present as collagen and to a lesser extent elastin), 2. The nature and extent of post-mortem biochemical changes (shortening and ageing) 3. Cooking procedures. Myofibrillar toughness is influenced by two processes: The development of rigor mortis. Tenderization arising from the ageing of meat. 20  Hydroxyproline (Tenderness indicator) Collagen is a fibrous protein consists of rope-like triple helix of α chains containing GXY repeats (G is glycine, X is proline and Y is usually hydroxyproline). Hydroxyproline is formed post-translationally by the action of proline hydroxylase and vit-C as cofactor. The hydrogen-bonding between the OH groups on hydroxyproline stabilises the triple 21 helix.  Colorimetric method for determination of Hydroxyproline content in meat - ISO 3496:1994. Briefly, the hydrolyzed meat sample is mixed with chloramine-T solution and measuring the developed color absorbance at 560 nm. Collagen = hydroxyproline x 8. Connective tissue = collagen x 37/8. 22 Muscle Hydroxyproline (µg/g) Psoas major 350 L. dorsi (lumbar) 520 Rectus femoris 550 L. dorsi (thoracic) 610 Sartorius 870 Triceps (lateral head) 1000 Extensor carpi radialis 1160 Superficial digital flexor 1430 Top five beef muscles in order of tenderness 1. Psoas major (Tenderloin) 2. Infraspinatus (Top Blade) 3. Gluteus medius (Top Sirloin) 4. Longissimus dorsi (Strip Steak) 5. Triceps brachii (Shoulder) 23  ‫وش اﻟﻔﺧده‬ ‫ظﮭراﻟﻔﺧده‬ ‫اﻟﺳﻣﺎﻧﺔ‬ ‫ﻋﻣود اﻟﺗﻠﺑﯾﺎﻧﻛو‬ ‫ﻋرق اﻟﻔﻠﺗو‬ ‫اﻟﻛوﻻطﺔ‬ ‫اﻟروزﺑﯾف )ﺑﯾت اﻟﻛﻼوي(‬ ‫ﻟﺣم اﻟﻛـﺗــف‬ ‫)ﺑﯾت اﻟﻠوح(‬ ‫اﻟﻛوﺳﺗﺎﻟﯾﺗﮫ )اﻻﻧﺗرﻛوت(‬ ‫اﻟرﯾش‬ ‫اﻟﺻدر‬ ‫)اﻟدوش(‬ ‫رﻗـﺑﺔ وﺑﯾن أﻛﺗﺎف‬ ‫‪24‬‬