Among the sources involved in the food contamination processes the following ones can be highlighted: a) External raw food contamination due to environmental contamination; b) Transport of raw materials to the factory where they will be processed; c) Food conditioning, which involves the storage of raw materials, preheating, disinfection, cleaning and sterilization steps; d) Heating steps either by boiling, cooking, baking, frying or combining with other ingredients at high temperature in an oven or in a reactor; e) Food packaging; f) Transport of packaged food and g) Storage and distribution of packaged food. The problems related to each step as well as the resulting contaminants for the food are shown and discussed.