The history of attempts made using chemical structures to predict odor is strewn with bright ideas followed by puzzling disappointments. Perhaps no category of flavor chemicals highlights this better than the series of unsaturated octenones. Having used five members of this small family at various times over the years, this author finds the differences in odor between such closely related chemicals startling.
Oct-3-en-2-one (FEMA# 3416, CAS# 1669-44-9) is quintessentially nutty in character and is widely used in nut flavors to very good effect. Oct-4-en-2-one (CAS# 33665-27-9) has a good black tea aroma and has only been used, to this author’s knowledge, on an experimental basis. Oct-1-en-3-one (FEMA# 3515, CAS# 4312-99-6) is surprisingly characteristic of cooked mushrooms, with a slight earthy tinge in the background— therefore finding moderate use in mushroom and related flavors. Oct-4-en-3-one (FEMA# 4328, CAS# 14129-48-7) is basically berry-like in character and recently has found some use in raspberry flavors.