How the food is produced and prepared can cause food contamination.

Animals

There are many foodborne microbes that are present in healthy animals, particularly in their intestines, nursed for food. Meat and poultry can be contaminated during the slaughter when even with small contact with the contents of the intestines.

Fresh fruits and vegetables can also be contaminated if they are washed with water which is already contaminated by animal manure or human sewage.

Food Handling

During the food processing, foodborne microbes are hosted by infected human handling the food or by cross contamination with other raw agricultural products.  For instance, Shigella, a bacterium, and Norwalk virus or Norovirus are introduced by infected food handler’s unwashed hands.

Food Preparation

In the kitchen, the microbes can be transmitted to the other with the use of the same knife, uncleaned cutting board, or other utensils without washing them in between the use. While fully cooked foods can also be contaminated again if they make contact with the raw foods that have pathogens.

Food Storage

There are many bacterial microbes that will multiply to bigger numbers in foods and cause disease. Under the warm and moist conditions, the slightly contaminated food that is left the night can be highly infectious because bacterial microbes will multiple fast. Immediate refrigeration or freezing will prevent the bacteria on food from multiplying. Some substances such as salt, sugar, or acid levels can keep bacteria from growing in numbers.

Heating the Food

The microbes are easily killed by the heat. When the food is heated to a temperature above 160 degrees Fahrenheit or 78 degrees Centigrade, even for several seconds, it can kill most of the bacteria, viruses, or parasites. Toxins are produced by bacteria differ in their sensitivity to heat. For example, the toxin that can cause botulism is made dormant by boiling while the staphylococcal toxin cannot.