All plants and animals have a natural microflora associated with them. For example, the plants have a natural microflora associated with the surface of roots, stems, leaves etc. The animals have a natural microflora associated with the skin, the gut content and external openings e.g. the mouth. These microflora are one of the sources of micfoorganisms associated with spoilage.

Equipment can be a source ofcontamination. It can be contaminated during production and also while it is not being used and most important, if not cleaned regularly and thoroughly. Other than the foreign objects, the most common source of microbial contamination in food are the employees i.e. the humans. The hand, hair, nose and mouth carry microorganisms that can be transferred to the food during processing, preparation, packaging and service by touching, breathing coughing etc. Further, water used for cleaning and as an ingredient in many processed food, if not clean/ pure can contaminate food. Microorganisms in air can also contaminate food during processing, preparation etc. Insects and rodents such as mice, cockroaches etc. carry dirt and disease with their feet, fur and faeces. They transfer dirt from garbage dumps and sewers to food or food processing and food service area, thus being a source of contamination. Finally, raw untreated sewage carries high microbial load and may contaminate water, food or equipment through faulty plumbing or otherwise.