Introduction to Meat: Types, Importance, Composition

Introduction to Meat

• Meat refers to the edible flesh of animals.
• It is animal flesh that is eaten as food.

Types of Meat

• Common meats include beef, lamb, rabbit, poultry, and pork.
• Other types are veal, venison, seafood, wild game, and ostrich.

Edible By-Products

• Edible by-products include the brain, liver, and lungs.
• Other edible parts are cheek meat, ears, snout, spleen, and pancreas.
• Additional by-products are head meat, heart, intestines, kidney, lips, tongue, stomach, and tail/oxtail.

Why Meat is Important

• It is a source of high-quality protein.
• Provides zinc, iron, and Vitamin B12.
• Contains fat, including omega-3 fatty acids.

Composition of Meat

• Muscle tissue is made up of bundles of cells (fibers).
• Connective tissue contains collagen and elastin.
• Moisture accounts for 75% of muscle composition.
• Fat content varies: pork fillet (5-10%), pork belly (50%). Fat can be external or intramuscular (marbling).
• Other components include bone, nerve tissue, and blood vessels.

Cuts of Meat

• Board Bia (Ireland) describes 12 different cuts of beef.

Quality of Meat

• The suitability of meat for consumption depends on color, texture, and odour.
• Bacterial load, water activity (Aw), and water holding capacity (WHC) are also factors.

Water Activity (aw)

• Water activity is the ratio between the vapor pressure of the food itself, when in a completely undisturbed balance, and the vapor pressure of distilled water under identical conditions.
• Water Activity is the amount of free, unbound water available for use by microorganisms for growth.
• Fresh meat has the highest water activity (aw > 0.99) while processing decreases water activity.

Water Holding Capacity (WHC)

• WHC is the ability of food to hold its own or added water during force, pressure, centrifugation, or heating.
• WHC determines visual acceptability, weight loss, cook yield, and sensory traits.
• Factors affecting WHC include handling/processing, pH (lowest at isoelectric point of meat proteins (pH 5.2)), and heat treatments.

Changes to Meat Composition During Cooking

• Protein denaturation leads to a firmer texture by forming new bonds.
• Moisture loss depends on the cooking method.
• Fat rendering enhances flavour and juiciness.
• Collagen conversion converts to gelatin.
• Maillard Reaction enhances flavour and aroma.

Cooking Methods in Meat

• Dry heat: grilling, pan-frying with high heat for a short time are suitable for tender cuts like sirloin, rib-eye.
• Moist heat: braising, and stewing for tougher cuts like shoulder, shank with stiff collagen converting to soluble gelatin.

Color of Meat

• Myoglobin is the protein responsible for meat color, storing oxygen in muscle cells, and concentration dictates color with presence or absence of oxygen.
• After slaughter, deoxymyoglobin gives a purple color.
• Cut surfaces display oxymyoglobin resulting in a red color.
• After 5 days of storage, metmyoglobin displays a brown color.
• Above 60°C, myoglobin loses its ability to bind oxygen, forming tan-colored hemichrome.
• Nitrates/nitrites help stabilise the meat colour.

Nitrates and Nitrites

• Impart a cured flavour to meat products and reduces lipid oxidation.
• Controls pathogenic microorganisms like Listeria monocytogenes and Clostridium botulinum.
• Stabilises the red colour of fresh meat and gives a characteristic pink colour to cured meat.
• May link to higher risks of some cancers; vegetable sources (celery) can be used to cure meats.

Safety Considerations

• Wear safety glasses when using Sodium Nitrite, proper PPE, a mask and gloves when handling this chemical to avoid exposure to the skin.
• Discard into the appropriate waste chemical beakers.
• Treat Ascorbic acid similarly to sodium nitrite even though it is not inherently harmful.