Substances (natural or man-made) which have unintentionally contaminated food through the production process (eg. acrylamide) or from the environment (eg. heavy metals). They can enter the food chain and even bio-accumulate. The major concern related to their presence in foodstuffs is their genearlly negative impact on food quality and the potential risk to human health.
Certain toxic or undesirable compounds can be formed in foods during their processing; for example, during heating, baking, roasting, grilling, canning, hydrolysis or fermentation.
Naturally occuring substances, eg mycotoxins and marine biotoxins. Other examples of toxions in food include bacterial toxins or certain plant toxins such as potato glycoalkaloids. Whilst the bacterial/fungal contamination can be elimated with heat treatment, the toxins can remain in the food products as contaminants.
Food adulteration can happen accidentally when an unapproved or wrong additive is introduced to the food. This results in mislabelled food. Foods may also ne intentionally adulterated masking food spoilage or to sell a low-value food for gain (eg. melamine in milk and Sudan dyes in chilli powder).