5-Methyl-2-phenyl-2-hexenal (FEMA# 3199, CAS# 21834-92- 4) is, in my opinion, the single component in cocoa beans that is most directly responsible for their characteristic aroma. Despite the fact that the ingredient seems to be so very product-specific, it is found quite widely in nature and can be used in a broad range of distinctly different flavor categories.
Other commonly used ingredients with a similar profile include 2-phenyl-2-butenal (FEMA# 3224, CAS# 224-567-0), which is predominantly cocoa in character but is distinctly more floral, and 4-methyl-2-phenyl-2-pentenal (FEMA# 3200, CAS# 247-869-4), which is strongly cocoa and works well when used in conjunction with 5-methyl-2- phenyl-2-hexenal, especially in cocoa and nut flavors. (+/-)-4-Methyl-2-phenyl- 2-hexenal (FEMA# 4194, CAS# 26643- 92-5) is an interesting variant with a similar character, but is perhaps slightly less effective in use. The dose rates given below are the levels to be used in flavors that are intended to be dosed at 0.05% in a ready-to-drink taster, beverage or bouillon. They all assume that the chemical is used alone, without other members of the same family