Activation Spectra of Human Bitter Taste Receptors Stimulated with Cyclolinopeptides Corresponding to Fresh and Aged Linseed Oil

Linseed oil is rich in unsaturated fatty acids, and its increased consumption could aid in health-promoting nutrition.However, rapid oxidation of linseed oil and concomitant development of bitterness impair consumers'acceptance. Previous researchrevealed that cyclolinopeptides, a group of cyclic peptides inherent to linseed oil, dominantly contribute to the observed bitterness.In the present study, fresh and stored linseed oil andflaxseed were analyzed for the presence of cyclolinopeptides using preparativehigh-performance liquid chromatography combined with mass spectrometry- and nuclear magnetic resonance-based identificationand quantification. The purified compounds were tested for the activation of all 25 human bitter taste receptors of which only tworesponded exclusively to methionine-oxidized cyclolinopeptides. Of those, the methionine sulfoxide-containing cyclolinopeptide-4elicited responses at relevant concentrations. We conclude that this compound is the main determinant of linseed oil's bitterness andpropose strategies to reduce the development of bitterness

Automated summary

Cyclolinopeptides in linseed oil are responsible for its bitterness, and a specific compound called methionine sulfoxide-containing cyclolinopeptide-4 is the main determinant of this bitterness.