Meat Spoilage

Meat is considered to be spoiled when it is unfit for human consumption. A variety of factors can cause meat to spoil including micro-organisms, exposure to air, and improper freezing techniques. Spoiled meat may be inedible due to unpleasant tastes and odors or may be unsafe for consumption especially when micro-organisms have caused the meat to spoil.

Meat Spoilage by Bacteria, Yeasts, and Molds

Although a number of factors may contribute to meat spoilage, the most common cause of meat spoilage is the deterioration of meat caused by micro-organisms (bacteria, yeasts, and molds). Beware! Foods can contain dangerous bacteria and microorganisms but still have a normal appearance. Food which has not been handled or stored properly should not be eaten even if it has no apparent indications of spoilage. See Food-borne Illnesses for more information.

The table below shows some of the common indications that meat has spoiled.

Indication of Spoilage	Cause

Ammonia or sulfur smell, bad odor, tallow or chalky taste.	Degradation of proteins, lipids (fats) and carbohydrates caused by bacteria and/or enzymes naturally present in meat.
Slime formation, bad odor and rancid flavor, color change (such as grey, brown, or green)	Bacterial and yeast spoilage
Sticky meat surface	Mold spoilage
"Whiskers"	Mold spoilage
Surface colorations such as creamy, black or green	Growth of mold colonies
Tainting, souring, and putrefacation	Anaerobic bacterial spoilage of meat interiors, vacuum packed products, and sealed containers

Other Types of Spoilage

There are factors other than micro-organisms which can cause meat to spoil. They results from improper handling of meat.

Indication of Spoilage	Cause

Oxidative Rancidity (rancid flavor and odor)	Oxidation of meat fats due to improperly wrapped meat.
Brown or grey discoloration	Protein denaturation caused by heat, salts, ultraviolet light, low pH, and surface dehydration
Dehydration and discoloration during freezing resulting in dryness of cooked meat, nutrient loss, and sometimes a bitter flavor.	Freezer burn and drip which occurs during slow freezing.
Absorption of Off-Flavors	Storage of meat next to foods such as apples and onions which give off strong odors