Odorants

An aroma-compound, also known as an odorant, aroma, fragrance, or flavor, is a chemical compound that has a smell or odor. A chemical-compound has a smell or odor when it is sufficiently volatile to be transported to the olfactory system in the upper-part of the nose.

Generally molecules meeting this specification have molecular weights of <300. Flavors affect both the sense of taste and smell, whereas fragrances affect only smell. Flavors tend to be naturally occurring, and fragrances tend to be synthetic.

Aroma-compounds can be found in food, wine, spices, floral scent, perfumes, fragrance oils, and essential oils. For example, many form biochemically during the ripening of fruits and other crops. In wines, most form as byproducts of fermentation. Also, many of the aroma-compounds play a significant role in the production of flavorants, which are used in the food-service industry to flavor, improve, and generally increase the appeal of their products.

An odorizer may add an odorant to a dangerous odorless substance, like propane, natural gas, or hydrogen, as a safety measure.

Note: Carvone, depending on its chirality, offers two different smells.

High concentrations of aldehydes tend to be very pungent and overwhelming, but low concentrations can evoke a wide range of aromas.

Animals that are capable of smell detect aroma-compounds with their olfactory receptors. Olfactory-receptors are cell-membrane receptors on the surface of sensory neurons in the olfactory system that detect air-borne, aroma-compounds.

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Wikipedia