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MDM (Mechanically Deboned Meat)

MDM (Mechanically Deboned Meat). Small bit left on carcass bones: is removed from bone by machine. 1978 USDA limits amount of bones (based on calcium content) Higher pH rather than conventional (marrow)

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MDM (Mechanically Deboned Meat)

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  1. MDM (Mechanically Deboned Meat) • Small bit left on carcass bones: is removed from bone by machine. • 1978 USDA limits amount of bones (based on calcium content) • Higher pH rather than conventional (marrow) • Bone marrow (or medulla ossea) is the soft tissue found in the hollow interior of bones. In adults, marrow in large bones produces new blood cells.

  2. Conventional (cold boning): carcasses are chilled after slaughter for 24 h and processes in chilled state (post rigor). • Hot boning :1-2h after slaughter (prerigor) hot.

  3. Following of animal’s slaughter: • its circulation ceases; the ability to re synthesize of ATP is lost; lack of ATP cause actin and myosin to combine to form actomyosin, which leads to a stiffing of muscle. • The oxygen supply falls, resulting in reduction of the O/R potential. • The supply of vitamins and antioxidants ceases , resulting in a slow development of rancidity.

  4. Nervous and hormonal regulation cease , thereby causing the temperature of the animal to fall and fat to solidify. • Respiration ceases, which stops ATP synthesis.

  5. Glycolysis begins , resulting in the conversion of most glycogen to lactic acid, which depresses pH from 7.4 to 5.6. this pH depression initiates protein denaturation, liberate and activatescathepsin, and completes rigor mortis. Protein denaturation is accompanied by an exchange of divalent and monovalent cations on the muscle proteins. • The reticuloendothelial system ceases to scavenge , thus allowing M.O. to grow unchecked. • Various metabolites accumulate that also aid protein denaturation. • (24-36 h , 2-5C)

  6. Spoilage of beef meat • Early sign of spoilage of ground beef is the development of off odor, followed by tackiness. (bacterial slime) • Sliminess is due to both masses of bacterial growth and softening or loosening of meat structural proteins.

  7. Some methods for detecting microbial spoilage in meats Chemical • Measurement of H2S production • Measurement of mercaptane produced • Determination of di- and trimethylamines • ATP measurement • Radiometric measurement of CO2 • Ethanol production (fish)

  8. Physical methods • Measurement of pH changes • R.I of muscle juice • Determination of alternation of E.C. • Measurement of surface tension • Measurement of UV illumination • Impedance changes • microcalorimetry

  9. Physiochemical methods • Determination of ERV • Determination of WHC • Determination of meat swelling capacity

  10. Mechanism of meat spoilage • Spoilage indicators of meat: • Lysin cadaverine (H2N(CH2)5 NH2) Enterobacteriaceae (increased more than putrescine in vacuum packaged meat) • Ornithine or Arginine putrescine (H2N(CH2)4 NH2) ( pseudomonas) decarboxylase decarboxylase

  11. ERV • First described 1964 • Determining incipient spoilage in meats , predicting shelf life • Volume of aqueous extract released by a homogenated beef when allowed to pass through filter paper for a given period of time.

  12. ERV • Good organoleptic and microbial quality: large volume of extract • Poor microbial quality: smaller volume of extract or none.

  13. ERV • Two aspect of meat spoilage: • Low temperature meat spoilage occurs in the absence of any significant break down . • Meat undergoes microbial spoilage : increase in hydration capacity meat protein

  14. Off odor • Amino acid begin to be utilized. • H2S (sulfur containing A.A) • NH3 (many A.A) • Indole (tryptophane)

  15. DFD meats • Dark- firm- Dry meats (ultimate pH>6, considerably lower supply of simple carbohydrate. • Spoilage is more rapid. (primary proteins are not attacked until supply of simpler constitute has been exhausted.)

  16. Spoilage of meat • Rise in pH (putrid meat 8.5) • Increase in bacterial number • Increase in hydration capacity of meat proteins.

  17. Spoilage of fresh liver: High carbohydrate , mean pH 6.41 (fermentative spoilage). Spoilage of sausage: Slimy spoilage (out side of casing): early stage discrete colonies (may be later coalescence to form uniform layer of gray slime). Favored by moist surface and confined outer casing. Souring: underneath of casing (usual source M.O.processed meat : milk solids). lactose : L.A. Greening: H2O2 (upon exposure to air , H2O2 : greenish oxidized porphyrine) H2S: sulfomyoglobin

  18. Fish • High levels of proteins and other nitrogenous compound • Carbohydrate content of fish is nil. • Nature of nitrogenous compounds. • Detecting fish spoilage : reduction of TMAO :TMA • TMAO : normal constitute of sea fish , no TMA in fresh fish. • Histamine (fish spoilage indicator) is produced by histidine

  19. Total volatile compound • TVB: ammonia, DMA, TMA. • TVN: TVB+ other N compound that are obtained by steam distillation • TVS: aerated from product and reduce alkaline permangenate solutions • TVA: acetic , propionic, related organic acids

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