Meat Science: Composition, Quality, and Safety
MEAT SCIENCE
Composition
Several factors influence the fat content and composition of meat:
- Kind: A clear difference exists between beef (high fat content) and pork (lower fat content).
- Race: Breed has a significant impact on fat content, especially in pigs.
- Age and Sex: In cattle, younger animals have more water and less fat than adults, and females tend to have more fat.
- Feed: Feed significantly influences fat content in pork but has less impact on beef.
- Preservation Treatment: Refrigeration leads to rapid loss of extracellular water, while freezing has little effect on overall composition.
Sensory Properties
- Color: Depends on the chemical form of myoglobin. The natural form has a dark red color.
- Juiciness: Related to the meat’s ability to retain water, which is influenced by factors such as the total or partial water content and any water added during processing. Excessive water addition can lead to swelling.
- Texture: Depends on the size of muscle fibers and the quantity of connective tissue. Heat treatment usually improves the texture of raw meat.
- Flavor and Aroma: Raw meat has little aroma and a flavor reminiscent of blood. Cooking develops the characteristic flavors and aromas valued by consumers.
Sanitary Aspects
Meat plays a crucial role in the human diet. While changes in eating habits led to a decrease in red meat consumption, it has regained popularity as part of a healthy diet when consumed in moderation. Lean meat is an important source of protein, vitamins, and minerals. Animal fats contribute saturated fatty acids in amounts similar to those found in vegetable fats. Some fats can help control obesity and slow stomach emptying, promoting a feeling of satiety.
The meat industry now produces processed meat products with lower fat levels than traditional options, responding to the demand for low-calorie products. However, it’s incorrect to assume that low-fat meat can be consumed without limits. There is a misconception that animal fats are a risk factor for high cholesterol and cardiovascular disease, and some studies have linked them to cancer development. However, there is no clear evidence of a direct relationship between meat consumption and the incidence of cancer.
Quality Criteria
Meat flavor quality is determined by various factors before and after slaughter. Phospholipid oxidation is a key process responsible for flavor alterations. Cooking methods and final internal temperature significantly impact the formation and stability of volatile and non-volatile compounds.
- Volatile Compounds: Present in low concentrations and responsible for a variety of odor sensations. The aroma of cooked meat products develops differently depending on the presence of water and whether the temperature exceeds 100°C. Roasted flavors are released when the temperature surpasses 100°C. Meat flavor derives from Maillard reactions and lipid oxidation.
- Non-Volatile Compounds: Contribute to the savory properties of meat. Some amino acids contribute sweetness, while others impart bitterness.
Inspection
Inspection procedures help identify and remove unfit carcasses from the food chain and prevent fraud in production.
- Antemortem Inspection: Involves examining live animals, although it can be challenging to detect sick animals before slaughter. This inspection relies on clinical signs, with particular attention to the skin, mucous membranes, genital tract (in females), and udder.
- Postmortem Inspection: Performed immediately after slaughter, without separating any parts of the carcass. It involves examining the blood, viscera, and carcass for any abnormalities. A long bone is sectioned to observe the bone marrow, and samples are taken for laboratory analysis and trichinoscopy (in pigs).
Anomalous Postmortem Processes
- Pork: High incidence of PSE (pale, soft, exudative) meat, characterized by a very fast postmortem glycolysis due to low pH while the temperature is still high. This leads to precipitation of sarcoplasmic proteins and reduced water-holding capacity. Reducing stress during transport and slaughter can help minimize PSE.
- Veal: DFD (dark, firm, dry) meat is characterized by a less pronounced pH decline due to low muscle glycogen levels. DFD meat is more susceptible to microbial spoilage. Good management practices during transport and slaughter can help limit DFD.
Alteration Processes
Bacteria that contaminate meat can cause spoilage if they grow. Microorganisms use carbohydrates as an energy source, either aerobically (molds, yeasts) or anaerobically (fermentation), resulting in various byproducts. Some bacteria can also break down proteins, leading to the accumulation of metabolic byproducts. Additionally, some bacteria attack fats directly through lipolytic enzymes. The type of initial bacterial contamination influences the type of meat degradation. Spoilage can occur on the surface or deep within the meat.
- Surface Spoilage: Caused by aerobic bacteria and involves changes in viscosity, discoloration, pigmentation, and rancidity.
- Deep Spoilage: The primary alterations are souring and putrefaction.
Pathogenic Microorganisms in Meat
If meat carcasses are exposed to temperatures above 20°C, anaerobic bacteria can develop. Among the pathogens and foodborne illness-causing microorganisms, Clostridium perfringens, Salmonella, Staphylococcus aureus, and Escherichia coli are noteworthy.
Alterations Before Obtaining Meat
- Zoonoses: Diseases caused by bacteria or parasites that can be transmitted from animals to humans, resulting in similar symptoms.
- Animal Toxins: Meat from animals that have been accidentally poisoned or medicated.
- Dangerous Fatigue: Meat from animals that have undergone excessive physical exertion.
- Hemorrhagic Conditions: Meat with a bloody appearance.
- Disgusting Conditions: Meat with an off-putting smell, taste, or color (pigmented or depigmented).
- Degenerative Conditions: Meat affected by fat degeneration, albuminoid degeneration, waxy degeneration, calcareous degeneration, or scleroderma.
- Indigestible and Less Nutritious: Meat from neonates or very young animals, or meat affected by hydrohemic conditions.
Alterations After Obtaining Meat
- Dirty: Meat contaminated with environmental dust, secretions, or other substances.
- Parasitized: Meat infested with parasites, primarily flies, moths, and mites.
- Rusty: Meat stored in damp conditions.
- Rotten: Meat that has undergone spoilage due to bacterial invasion.