Meat Science Quiz

Muscle to Meat Conversion

• Muscle is the main component of meat and meat products.
• After an animal dies, its systems shut down causing changes in muscle.
• The conversion of muscle to meat is a gradual process.
• Homeostasis is the maintenance of a balanced internal state.
• The nervous system and endocrine glands control homeostasis.

Exsanguination

• Exsanguination is the first step in conventional animal slaughter.
• It involves removing as much blood as possible.
• Thorough bleeding is important to prevent spoilage and improve consumer appeal.

Circulatory Failure and Lactic Acid Accumulation

• Exsanguination stops oxygen delivery to muscle tissue.
• Aerobic metabolism stops, causing a shift to anaerobic glycolysis.
• Anaerobic glycolysis produces lactic acid, which accumulates in the muscle.
• Lactic acid accumulation lowers muscle pH.

Glycogenolysis

• After slaughter, muscle converts glycogen to lactic acid.
• Glycogen breakdown affects meat quality by changing pH.
• The enzymes glycogen phosphorylase and debranching enzyme break down glycogen.
• Stress before slaughter can deplete glycogen and influence pH.

pH Decline and Meat Quality

• The ultimate pH of meat depends on the glycogen level at slaughter.
• Lowering pH is crucial for meat conversion as it affects protein denaturation.
• High temperature and low pH denature proteins.
• Denaturation affects water-holding capacity, pigment intensity, and texture.
• Rapid pH decline leads to pale, soft, and exudative (PSE) meat.
• Slow pH decline leads to dark, firm, and dry (DFD) meat.

Rigor Mortis

• Rigor mortis is the stiffening of muscle after death.
• It occurs due to the depletion of ATP and the binding of actin and myosin.
• Muscle glycogen levels at slaughter influence rigor mortis onset.
• Rapid pH decline (PSE) accelerates rigor onset.
• High muscle temperature during rigor exacerbates protein denaturation.

Postmortem Changes in Muscle

• Muscle loses its protective barriers against microorganisms.
• Structural integrity of muscle is disrupted, affecting texture and tenderness.
• Proteolytic enzymes, called cathepsins, are released and degrade muscle proteins.

Cold Shortening

• Cold shortening occurs when carcasses are chilled rapidly before glycogen is depleted.
• Rapid cooling induces irreversible muscle contraction.
• Cold shortening makes meat tougher, particularly in lean beef and lamb.

Tenderness of Meat

• Meat tenderness is influenced by grain, connective tissue, and fat.
• Finer-grained meat is more tender.
• Collagen in connective tissue affects toughness.
• Fat content adds lubrication during cooking, improving tenderness.

Meat Ripening or Aging

• Meat becomes more tender, juicy, and flavorful over time.
• Ripening occurs faster at room temperature than in a refrigerator.
• Aging increases free amino acid nitrogen.

Changes in Cooking

• Cooking involves protein denaturation, collagen hydrolysis, color change, drip formation, flavor development, and nutrient loss.
• Cooking denatures proteins, altering their properties.
• Collagen breaks down into gelatin, increasing tenderness.
• Meat color changes due to oxidation of iron in heme molecules.
• Drip is the loss of water and other compounds during cooking.
• Cooking enhances flavor and aroma through the formation of volatile compounds.