Odor Thresholds of Various Unsaturated Branched Esters

A series of unsaturated branched esters were purified by preparative gas chromatography and their odor thresholds were determined using sensory panel methods. In general, unsaturated branched esters had higher odor thresholds than their saturated counterparts. Double bond position and configuration had marked influences on the odor threshold. In most cases, the addition of a double bond in the C-2 position of the acid resulted in significantly higher odor thresholds while the addition of a double bond in positions further away from the acid carbonyl had a smaller effect on the odor threshold. Ethyl 2-methyl-4-pentenoate had the lowest odor threshold (0.01 μL/10 3 L) of the esters tested while methyl (E)-2-methyl-2-butenoate (methyl tiglate; 130 μL/10 3 L) had the highest odor threshold.