An aroma compound, also known as an odorant, aroma, fragrance or flavoring, is a chemical compound that has a smell or odor. For an individual chemical or class of chemical compounds to impart a smell or fragrance, it must be sufficiently volatile for transmission via the air to the olfactory system in the upper part of the nose. As examples, various fragrant fruits have diverse aroma compounds, particularly strawberries which are commercially cultivated to have appealing aromas, and contain several hundred aroma compounds. Generally, molecules meeting this specification have molecular weights of less than 310. Flavors affect both the sense of taste and smell, whereas fragrances affect only smell. Flavors tend to be naturally occurring, and the term fragrances may also apply to synthetic compounds, such as those used in cosmetics. Aroma compounds can naturally be found in various foods, such as fruits and their peels, wine, spices, floral scent, perfumes, fragrance oils, and essential oils. For example, many form biochemically during the ripening of fruits and other crops. Wines have more than 100 aromas that form as byproducts of fermentation. Also, many of the aroma compounds play a significant role in the production of compounds used in the food service industry to flavor, improve, and generally increase the appeal of their products. An odorizer may add a detectable odor to a dangerous odorless substance, like propane, natural gas, or hydrogen, as a safety measure. Aroma compounds classified by structure Esters Linear terpenes Cyclic terpenes Note: Carvone, depending on its chirality, offers two different smells. Aromatic Amines Other aroma compounds Alcohols Furaneol (strawberry) 1-Hexanol (herbaceous, woody) cis-3-Hexen-1-ol (fresh cut grass) Menthol (peppermint) Aldehydes High concentrations of aldehydes tend to be very pungent and overwhelming, but low concentrations can evoke a wide range of aromas. Acetaldehyde (ethereal) Hexanal (green, grassy) cis-3-Hexenal (green tomatoes) Furfural (burnt oats) Hexyl cinnamaldehyde Isovaleraldehyde – nutty, fruity, cocoa-like Anisic aldehyde – floral, sweet, hawthorn. It is a crucial component of chocolate, vanilla, strawberry, raspberry, apricot, and others. Cuminaldehyde (4-propan-2-ylbenzaldehyde) – Spicy, cumin-like, green Esters Fructone (fruity, apple-like) Ethyl methylphenylglycidate (Strawberry) alpha-Methylbenzyl acetate (Gardenia) Ketones Cyclopentadecanone (musk-ketone) Dihydrojasmone (fruity woody floral) Oct-1-en-3-one (blood, metallic, mushroom-like) 2-Acetyl-1-pyrroline (fresh bread, jasmine rice) 6-Acetyl-2,3,4,5-tetrahydropyridine (fresh bread, tortillas, popcorn) Lactones gamma-Decalactone intense peach flavor gamma-Nonalactone coconut odor, popular in suntan lotions delta-Octalactone creamy note Jasmine lactone powerful fatty-fruity peach and apricot Massoia lactone powerful creamy coconut Wine lactone sweet coconut odor