Bitter off-taste in stored cold-pressed linseed oil obtained from different varieties

Freshly pressed linseed oil shows a delicate nutty flavor. However, after only 1 day of storage, a bitter off-taste develops. It is caused mainly by the formation of a cyclic octa-peptide named cyclolinopeptide E (CLE) containing the oxidized amino acid methionine. A simple and fast determination by solid-phase extraction and high-performance liquid chromatography with UV detection has been developed in order to measure the formation of this cyclic peptide during storage in correlation with the increasing bitter off-taste of the oil, which was determined by a sensory panel. The development of this bitter off-taste was analyzed in several oils prepared from linseed of a single variety from seeds obtained during a growing test. Highest bitterness was perceived in oil from the variety Eurodor, corresponding to CLE contents of 925 mg/kg, and lowest bitterness was perceived in oil from the variety Baladin, corresponding to a CLE content of 485 mg/kg. In some varieties, additional bitter compounds might be present in significant amounts.