The flavour of a food is the combined effects of taste, smell and mouth feel. The taste is the combination of sensations perceived by the tongue and these are limited to sweet, sour, salty and bitter. The smell is the sense by which certain properties of volatile substances can be perceived on the sensitive membranes in the nose. The mouth feel is the tactile sensation created in the mouth when a food is chewed or dissolved combined with the tasting and smelling sensations.

The acceptability of a flavour is also complex. The human brain has an amazing memory for tastes and smells and can recall not only what, but often even where and when, it was previously exposed to them. For example, there are some wine tasters that claim they can identify a wine to a particular vineyard! Thus, when a consumer is tasting a biscuit it is important that their identification of the flavour is a "satisfactory" experience.

Sources and types of flavours

The largest group of flavours originate from plant materials. Usually the fruits or leaves of plants. Others come from cooking and these include the crust flavours (associated with the Maillard reaction between amino acids and reducing sugars), burnt flavours and roast flavours which include those from meats.

For biscuit manufacturing it is important that flavour ingredients are convenient to use and of standard strengths and qualities. To provide such substances is the challenge for the flavour ingredient industry.