Microbiology of Red Meat

Red meat is made up of voluntary skeletal muscle tissue and comes from cattle, sheep, pigs, goats, deer, horses and camels. While these meats can be prepared in many different ways, common to all methods is the need to keep meats from spoiling, usually by keeping the microbial content as low as possible. This is typically done through proper slaughtering conditions, meat storage and cooking to a high enough temperature. In a recent article, Dr. Roy Betts gives an overview of red meat processing and his recommendations for proper handling.¹

The conditions in which an animal is slaughtered and butchered can make a huge difference in microbial content. Since dirt and feces often contaminates the animal hide, handling skin, hides, and leakage from parts of the digestive tract can contaminate the rest of the carcass. Likewise, dirty knives and captive bolts also pose a risk of contamination. For this reason, it is very important to avoid contamination of the carcass and keep working conditions clean.

After the meat is cut, it is stored. According to Dr. Betts, this stage is where most microbial growth occurs. A simple way to store meat is to overwrap it and pack it in air; however, the meat will have a shorter shelf-life. Under these conditions, the bacterial population is dominated by aerobic psychrotrophic bacteria such as Pseudomonas spp, Acinetobacter, Enterobacter and sometimes Brochothrix thermosphacta.

Storage in vacuum packs will help eliminate metmyoglobin formation (giving a brown coloration) and inhibit the aerobic organisms, however Lactobacillus, Carnobacterium and Leuconostoc are still able to grow. Even storage under modified atmospheric conditions of elevated levels of oxygen (70-80%) and carbon dioxide (20-25%) still won’t eliminate growth.

To decrease the risk of microbial growth further, meats are most often processed, cured, and cooked. Meats that are ground such as burgers or sausages will have microbial growth throughout, not just on the surface, so proper cooking of at minimum 70ºC for two minutes (or equivalent) at the slowest heating point, is necessary. After this point, the meat should be consumed immediately, kept at a temperature of >63ºC before consumption; or cooled quickly to <8ºC and stored at chilled temperatures (an absolute maximum of 8ºC, but lower will extend product life to a greater extent). Dr. Betts warns against cooking meats at very low temperatures, since this can actually invite microbial growth, rather than impede it.

In today’s market, red meats are widely popular and more often than not, are safe to consume. Dr. Betts maintains that the key to producing safe products is to be aware of the handling conditions and understand the risks involved.

For further support on microbiology testing of meat products and to read Dr Betts full article, visit our food and beverage community.

You might also enjoy the article – Where’s the Beef? E. coli O157:H7 Screening

Reference
1. Betts, Roy “Microbial Update: Red Meat Products”