Food, just like humans, gradually deteriorates because of a natural aging process. However, there are a few things we can do that will have a positive effect on the shelf life and safety of our food. Some preservation is done at the food manufacturing level and some occurs naturally, but a better understanding of the processes may help you extend the shelf life. Preservation methods and storage conditions must be designed to reduce the rate of decomposition and protect the safety, appearance and taste of our food.

The causes of food spoilage - Once food is harvested or slaughtered, its plant or animal tissue soon starts to decay. Microorganisms, such as fungi (molds & yeasts), spoilage bacteria, and their enzymes usually cause the spoilage process. Not all these changes in food are undesirable. Some people like aged beef and cheeses or very ripe fruit. The production of wine and beer involves conversion of sugars to alcohol, while souring of milk is essential in the production of cheese.

However, it is important to remember that some of the conditions that accelerate spoilage, such as inappropriate temperature and moisture control, also encourage the growth of pathogenic microorganisms that cause foodborne illness. Consequently, spoiled food is not just an issue of quality, it is also often a question of food safety.

• Mold & Yeast: Corn, nuts, breads, meat, cheeses, fruits and vegetables are all affected by mold. Do not try to salvage cheese that shows visible mold by cutting it away, unless of course it is a natural part of the cheese (i.e. bleu cheese, Brie, or Camembert). Mold forms a network of microscopic strands that extend into the foods which could cause allergic reactions or illness, so discarding them is the safest option. Most cheeses do not improve with age. Deli meats are the same. Yeast can cause discoloration, slime, and odors on sweet, acidic refrigerated foods or jams/jellies.
• Bacteria: Some spoilage bacteria are also pathogenic (disease causing). For example, Clostridium perfringens (a common cause of spoilage in meat & poultry) and Bacillus cereus (spoils milk & cream) are also responsible for causing foodborne illness. Most foods are subject to bacterial growth.
• Enzymes: Enzymes are naturally present in the cells of microorganisms that break down animal and plant foods. Breakdown continues until blanching or cooking inactivates the enzymes.

Other causes of spoilage include: 1) the bruising or piercing of vegetables, fruits or vacuum packaged food by rough handling; 2) oxidation (changes the taste or texture when exposed to oxygen) or freezer burn; 3) pest infestation as a result of poor receiving control, storage, rotation or cleaning; 4) adulteration through addition of leftover, inferior or undesirable food or ingredients to fresh food.

Detecting spoilage relies on being aware of the typical indicators, such as appearance (discoloration or slime), texture, smell or taste (obviously not recommended if any of the others are present).

Bottom line prevention - When in doubt, throw it out. Food spoilage affects your bottom line in food waste dollars. Prevention includes good receiving inspection practices, following the manufacturer's instructions, unfailing temperature recording and control, being observant and of course good sanitation and personal hygiene by food handlers.