The chemical substances that contribute to the aromas of natural products — fruits, fruit juices and other foods — are varied. The Dutch TNO organisation regularly updates its Volatile Compounds in Food publication, which currently lists at least 7,000 different substances found in some 400 foodstuffs.

Individual foods can be used to provide sources of all the individual aroma substances, although these are often present in the food in very low concentrations. The more important sources of natural aroma chemicals are essential oils, simple plant extracts, fermentation products, fruit juices, plant exudates and dairy products. Well-established physical processes have been developed whereby such sources can provide concentrates from which individual chemical compounds — the basic aroma chemical building blocks — can be isolated.

Natural sources of aroma chemicals (or their precursors) where individual substances are present in economically significant quantities are invariably not actual foods (or beverages) but are materials used as ingredients. An example is vanilla beans, rich in vanillin, or pimento berries, which contain essential oils with a significant content of eugenol and isoeugenol. Ingredients such as these are widely used to provide the starting point for a wide range of natural aroma chemicals. Other true natural ingredients that can be obtained readily and affordably include a range of simple alcohols and fatty acids as well as aldehydes and ketones. Interaction between these components is the basis for the production of a huge range of further aroma chemicals.

Today, there is a very wide range of aroma chemicals available that enables flavourists to make natural flavours by simple compounding techniques that are directly analogous to the way nature-identical aroma chemicals have always been made. Nature-identical aroma chemicals are chemically identical (at least at the molecular level) to their natural analogies but made by chemical synthesis.