Food spoilage means the nutritional value, flavor, or texture of a food becomes damaged and/or the food is unsuitable or harmful to consume.” Several factors can cause food to become spoiled, all of which can be classified into two main categories: natural decay and microorganism contamination.

The majority of natural foods have a limited life or “shelf life.” Foods that are perishable — bread, milk, meat, fish, etc. — have a shorter shelf life than non-perishable foods. The deterioration of food begins once it is harvested, gathered, or slaughtered. The process is known as decay, which is the time period before actual spoilage occurs.

Natural Food Spoilage

A few factors that affect how food naturally decays include oxidation, enzymes, temperature, and physical damage. Each factor can contribute to natural food spoilage, as can the interaction between two or more factors.
When air interacts with food components, the chemical process of oxidation occurs. Oxidation can produce both physical and chemical effects, including changes in flavor, color, and nutritional value. Certain types of packaging exist that can slow the process of oxidation.

Enzymes are natural substances found in every type of food. When food ages, its chemical composition — including its enzymatic structure — changes in response. An example of this involves the ripening process of fruits and vegetables. When a fruit ripens, for instance, its color and flavor will change as a result of natural chemical changes to enzymes.

Physical damage often results in broken surface areas of food, which increase the risk of bacterial presence and growth. Foods that haven’t been packaged correctly are also subject to this type of risk, as are foods that haven’t been handled with the necessary care.

Storing food at appropriate temperatures is vital to slowing food spoilage. Each location in which food is stored requires a different temperature range. In cupboards and pantries, the recommended range is between 50 to 70 degrees Fahrenheit. In refrigerators, it’s between 34 and 40 degrees, and in freezers it’s zero degrees or below. At higher temperatures, food will deteriorate much quickly and the growth of microorganism is more likely.

Microorganism Spoilage

Microorganism (or microbial) spoilage occurs from three sources: molds, yeasts, and bacteria. This type of spoilage dramatically increases the risk of foodborne illness, also known as food poisoning. Bacteria-based spoilage is the most common cause of foodborne illness.

Yeast-based spoilage results from the chemical breakdown of yeast metabolism. Two types of yeast exist: true yeast and false yeast. True yeast, also known as fermentation, metabolizes sugar alcohol and carbon dioxide gas. False yeast materializes in foods with a high sugar content and in those that are highly acidic, producing a filmy substance on the surface.

Most forms of mold are microscopic, threadlike organisms that contain fungi. The fungi are transported by air, insects, and water, which can often be seen with the unaided eye because of spores. Molds can produce potentially dangerous side effects, including allergic reactions and respiratory problems. In some conditions, certain types of mold can produce poisonous chemicals called mycotoxins, which can make someone ill.

Highly acidic food, including fruit, jams, jellies and pickles, are more prone to spoilage from yeast or mold. Yeast and mold can be eliminated by applying heat of over 100 degrees Celsius (212 degrees Fahrenheit).

Many types of bacteria can cause food spoilage. As bacteria break down a food’s composition, they leave behind waste products that may be harmful to one’s health. Meat and vegetables have a higher likelihood of bacterial formation, as do other foods of low acidity. Consuming food that contains bacteria often results in food poisoning, a potentially serious condition that can cause nausea, vomiting, diarrhea, abdominal pain and fever.

Signs of Food Spoilage


Often times, it is possible to see, feel or taste the presence of food spoilage. When food deteriorates, it will usually give off an unpleasant odor and flavor if one bites into it. Further, the texture of certain foods, especially fruits and vegetables, will become noticeably different. Textural changes are generally evident by sight or by feeling around the food’s surface.

The appearance of food spoilage is often the result of microbial growth in the food. The growth is visible on the surface of foods and in a liquid’s contents. For example, meat will have a “slimy” appearance, often accompanied by an odor. Liquids will often become discolored and cloudy.

Texturally, spoiled food can become softened or discolored. Soft rot — the evident softness, mushiness, and discoloration of certain vegetables — is the byproduct of enzymatic deterioration. Tissue degradation and microbial buildup can alter the texture of food, as well.

Various measures can be taken to reduce the risk of food spoilage and slow down the natural process of food deterioration. Foods and beverages that require a certain temperature to maintain freshness should be refrigerated or frozen accordingly. All leftover food should be sealed in fresh bags and/or Tupperware.

Separating foods according to type is another important element of food preservation. Meats, cheeses, fruits, and vegetables should be compartmentalized during refrigeration. The separation efforts should be maintained throughout the foods’ duration.

Other preventive efforts, such as proper dehydration and canning practices, can also help to reduce the risk of food spoilage.