Alpha-farnesene is a naturally occurring sesquiterpene hydrocarbon (C15H24) primarily found in the peel of apples and other fruits, where it contributes significantly to the characteristic green, fruity aroma. It exists as multiple stereoisomers, with the (3E,6E) form being predominant in nature. Biosynthesized via the mevalonate pathway from farnesyl pyrophosphate, it serves ecological roles as a plant defense compound and insect semiochemical. Industrially, it is used in flavor and fragrance formulations. Chemically, it features a conjugated triene system making it prone to oxidation. It is highly lipophilic and volatile at room temperature, evaporating readily to produce its sensory profile. In food science, concentrations in apple skin can reach several mg/kg, influencing post-harvest quality and storage disorders like superficial scald.