Contribution of Vicine, Convicine, and New Derivatives to the Bitter Off-Taste of Fava Bean Proteins

Abstract

This study employed activity-guided fractionation to identify the compounds that are responsible for the bitter off-taste of fava bean protein isolates and concentrates. UHPLC–ToF-MS and 1D/2D NMR experiments led to the identification of three known bitter compounds, vicine, convicine, and 3′-O-β-d-glucopyranosyl-L-DOPA. In addition, eight previously unknown vicine and convicine derivatives were identified. The bitter thresholds of the analytes were determined and found to be in the range of 0.10 to 1.44 mmol/L. To assess the taste contribution, the corresponding dose-overthreshold (DoT) factors were calculated, and it was shown that convicine with a DoT > 230 is playing a central role for the bitter off-taste. Furthermore, the analysis of fatty acids and their oxidation products suggests that linolenic-, linoleic-, and oleic acid directly contribute to the off-taste of fava bean protein. In addition, cell-based studies showed activation of bitter receptors TAS2R16 and TAS2R43 by vicine and convicine, respectively.