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meat Composition of meat muscle thà nh phần thịt heo, cơ thịt heo thành phần thịt mỡ gan heo đường muối tiêu và các loại gia vị khácthành phần thịt nạc heo mỡ heo đường muối và các loại gia vị khácthành phần thịt xẻthành phần sữa heothủy phân thịt heo nạc vaithành phần dinh dưỡng của thịt heobảng thành phần dinh dưỡng của thịt heothành phần dinh dưỡng trong 100g thịt heo1 1 thành phần dinh dưỡng
Composition of meat muscle and their properties and their changes during food processing and preservation Muscle types and structures a Muscle cell are very active cells and requires huge supply of energy b They use glycogen to produce glucose-GLYCOLYSIS c They also take up glucose and fatty acids from blood stream d Glycogen, glucose and fatty acid are converted to PYRUVIC ACID e PYRUVIC ACID enters MITOCHONDRIA and liberates ATP (Energy) - AEROBIC PATHWAY f The Mitochondria requires Oxygen supply for this conversion reaction g Absence of Oxygen would produce Lactic acid Changes in energy metabolism When the animal dies, the metabolism presented by the dotted lines immediately cease Oxygen supply to the mitochondria stops, stopping the ATP formation Pyruvate take anaerobic pathway and forms LACTIC ACID Glucose and fatty acid transport from blood stream into the cells stop Glycolysis continues but gradually ceases as enzymes are inactive at LOW PH As ATP is no more available, Ca and Na/K pumps also stops Change in muscle proteins Myofibrillar protein s get partially or completely degenerated by enzyme Photolytic enzymes, mainly campaigns are involved in this degradation Calcium ions released from the cell membrane activate captain enzymes present in the muscles Rigor mortis occurs, which is the Latin term used for 'stiffening of muscles after death' It has distinct phases The post-mortem developed muscle extensibility remains relatively constant for some time, called the delay phase Subsequently, the extensibility declines rapidly during the onset phase Finally, the muscle reaches a stage where there is no further decline in extensibility, referred to as the completion stage I The muscle contraction/shortening is associated with the chemical changes discussed before Rigor starts when ATP levels begins to deplete and continues till ATP is totally lost Actin and Myosin fibrils need ATP to remain separated When ATP is lost, myosin heads attach firmly to actin filaments making the muscle fibers very compact and short Mechanisms of Muscle pm Changes and Quality of Meat and Flesh: Modulation by Muscle Properties After slaughter, the meat is typically stored in a cold room at 4°C for to 30 days depending on species, subsequent processing methods, and packaging The longest storage periods are used for beef (a,b) Histological sections of bovine muscles were obtained from slaughter (a) and 12 days post-mortem (b) Light microscopy observation During storage (4°C in a cold room), the cell shrinks and the extracellular space increases (c, d) Histological longitudinal sections of bovine muscle taken from slaughter (c) and 12 days post-mortem (d) observed by transmission electron microscopy Connective tissue also undergoes morphological changes during meat aging, detectable as early as 12 p.m in chickens but as late as weeks in cattle This degradation facilitates collagen dissolution during cooking, thereby improving the tenderness of cooked meat In fact, during aging, reduction of the perimysium resistance is associated with decreasing amounts of PGs along with an increase in collagen solubility due to the increased activity of certain enzymes II Relations between Muscle Properties and Meat Quality Technology quality During storage, the internal structure of the muscle changes The muscle fibers contract horizontally while pushing the intracellular water out to the extracellular space, their size increases In terms of processing into cooked products, the technological quality is related to the water holding capacity of the meat, i.e is the ability of meat to hold water inside Water holding capacity is strongly influenced by the rate and extent of the decrease in pH The high rate associated with high muscle temperature (eg, due to stress or vigorous physical activity directly before slaughter) causes denaturation of muscle proteins, decreased water retention and increased secretion, and When cooked, pork and poultry are lost Nutritional Quality Meat and flesh are an important source of proteins, essential amino acids (AAs), essential fatty acids (FAs), minerals, and vitamins (A, E, and B), which determine nutritional quality The AA profile is relatively constant between muscles or between species However, collagen-rich muscles have a lower nutritional value because of their high glycine content, a nonessential AA Compared with white muscles, red muscles have larger myoglobin content and thereby provide higher amounts of hem iron, which is easily assimilated by the body Although IMF constitutes a small fraction of muscle mass, it is involved in human FA intake because the content and nature (i.e., the profile) of meat FA varies according to species, the anatomical origin of a given muscle, and animal diet Sensory quality Color and form: The composition of muscle fibers affects the color of meat through the amount and chemical state of myoglobin The high myoglobin content of type I and type IIA fibers leads to a positive relationship between the ratio of these fibers and the intensity of red color In deep muscle and meat stored under vacuum, myoglobin is in a reduced state and has a purple-red color When exposed to oxygen, myoglobin will be oxidized to oxi myoglobin, giving the meat its attractive bright red color During meat storage, myoglobin can be oxidized to met myoglobin, creating a brown color, unappealing, negatively perceived by consumers