Microbial spoilage of meat and meat products

Meat is a term that refers to the edible parts of animals, such as muscles, fat, organs, and bones. Meat and its products are highly nutritious foods that provide protein, iron, zinc, vitamins, and minerals to humans. Meat can be obtained from various sources, such as poultry (chicken, turkey, duck), red meat (beef, pork, lamb, goat), game (deer, rabbit, wild boar), and seafood (fish, shellfish). Meat can also be processed into various products, such as ham, bacon, sausage, salami, jerky, canned meat, and meatballs.

However, meat and its products are also highly perishable and prone to microbial spoilage. Microbial spoilage is the deterioration of food quality and safety caused by the growth and activity of microorganisms. Microorganisms can cause changes in the appearance, odor, flavor, texture, and nutritional value of meat. They can also produce toxins or cause infections that can harm human health. Microbial spoilage can occur at any stage of the meat production chain, from the farm to the fork.

The susceptibility of meat and its products to microbial spoilage depends on several factors, such as:

  • The intrinsic properties of meat: Meat has a high water activity (aw), which is a measure of the availability of water for microbial growth. Meat also has a neutral or slightly acidic pH (5.5-6.5), which is favorable for most microorganisms. Meat contains nutrients that microorganisms can use as energy sources, such as sugars, amino acids, vitamins, and minerals. Meat also has enzymes that can catalyze biochemical reactions that affect its quality and stability.
  • The extrinsic properties of meat: These include the environmental conditions that affect meat during handling, processing, storage, and distribution. Temperature is one of the most important factors that influence microbial spoilage. High temperatures can accelerate microbial growth and activity, while low temperatures can slow them down or inhibit them. Other factors include oxygen availability (aerobic or anaerobic), relative humidity (moist or dry), light exposure (visible or UV), and packaging methods (vacuum or modified atmosphere).
  • The microbial load and diversity of meat: This refers to the number and types of microorganisms that are present on or in meat. The microbial load and diversity depend on the source and health status of the animal, the hygiene and sanitation practices during slaughtering and processing, the contamination from equipment and personnel during handling and distribution, and the cross-contamination from other foods or surfaces during storage and preparation.

Some of the common microorganisms that cause spoilage of meat and its products are bacteria (such as Pseudomonas spp., Acinetobacter spp., Brochothrix thermosphacta, Lactobacillus spp., Enterobacteriaceae spp., Staphylococcus spp., Clostridium spp.), molds (such as Penicillium spp., Aspergillus spp., Cladosporium spp.), yeasts (such as Candida spp., Rhodotorula spp.), and parasites (such as Trichinella spp., Toxoplasma gondii). Some of these microorganisms can also be pathogenic to humans (such as Salmonella spp., Campylobacter spp., Escherichia coli O157:H7, Listeria monocytogenes).

Therefore, it is important to understand the factors that affect the microbial spoilage of meat and its products and to apply appropriate methods to prevent or control it. Some of these methods include:

  • Good hygiene practices: These include washing hands and utensils before and after handling meat; cleaning and sanitizing equipment and surfaces; avoiding cross-contamination; using potable water; wearing protective clothing; following personal hygiene rules; inspecting raw materials; separating raw and cooked foods; disposing waste properly; training staff on food safety.
  • Good manufacturing practices: These include following standard operating procedures; monitoring critical control points; applying hazard analysis and critical control point (HACCP) principles; using approved additives and preservatives; maintaining proper temperature and humidity; using appropriate packaging materials; labeling products correctly; tracing products throughout the supply chain.
  • Good storage practices: These include storing meat at refrigeration (4°C) or freezing (-18°C) temperatures; using first-in first-out (FIFO) system; checking expiration dates; rotating stock; avoiding temperature abuse; protecting products from light exposure; preventing insect or rodent infestation.
  • Good preparation practices: These include thawing frozen meat in the refrigerator or under cold running water; cooking meat to a safe internal temperature (71°C for poultry, 63°C for pork, 71°C for ground meat, 63°C for whole cuts of beef or lamb); using a clean thermometer to check the doneness; resting meat before serving; reheating leftovers to 74°C; discarding spoiled or suspicious products.

By following these practices, we can ensure the quality and safety of meat and its products and prevent microbial spoilage. In the next sections, we will discuss the sources and causes of microbial contamination of meat, the events that take place during rigor mortis after the slaughter of the animal, the spoilage of fresh meat by enzymes and microbial action, the types of spoilage of meat under aerobic and anaerobic conditions, the defects caused by microorganisms on fresh meat, the spoilage of refrigerated meat by psychrophilic organisms, and the spoilage of cured meat and its long shelf-life compared to fresh and raw meat.