Synthetic flavors: efficiency and safety factors for sweaty and fishy odorants

Rat feeding trials were conducted with two pairs of food additives which exhibit similar odor qualities but vastly different odor intensities. The maximum no-adverse-effect dietary levels in a 90-day trial were as follows: isovaleric acid, 5% 2-ethylbutyric acid, 0.6% trimethylamine, 0.16% piperidine, 0.08%. In view of these no-effect levels, the concentrations of trimethylamine and piperidine used in human food sometimes infringe the Federal 100-fold practical safety factor. In the maximum concentrations used in food, purified 2-ethylbutyric acid and piperidine could be neither tasted nor smelled by human observers, and appear to serve no useful purpose as flavorings. Calculations are presented which suggest that, when their widely differing odor thresholds are taken into consideration, isovaleric acid has about 22,000 times greater theoretical safety factor than 2-ethylbutyric acid for producing a given intensity of a sweaty aroma. By similar considerations, trimethylamine has about 260,000 times greater theoretical safety factor than piperidine for generating a fishy odor.