Ethyl cis-4-octenoate (FEMA# 3344, CAS# 34495-71-1) is an unusually attractive unsaturated aliphatic ester. The character is fresh and typical of tropical fruits, generally fruity with a hint of pineapple. The effect of this ingredient in flavors, usually at a relatively modest level, is to add freshness, rather than to be highly specific to a particular fruit type. It is found in nature in relatively few natural fruits, but the serendipitous combination of an especially fresh character and relative heat stability make it potentially far more useful than its natural abundance would suggest.
Ethyl trans-4-octenoate (CAS# 78989-37-4) has a similar character but is slightly less attractive because of hints of fatty and melon notes. It is more widely used in fragrances than flavors, but where it is permitted it is almost as useful as the cis ester in flavors.
Many other similar esters can claim a rightful place in a flavorist’s palette, but ethyl cis-4-octenoate has a cleaner and more widely usable profile in most types of fruit flavors, with the possible exception of melon.