Kaempferol 3-O-(2′-O-Sinapoyl-β-sophoroside) Causes the Undesired Bitter Taste of Canola/Rapeseed Protein Isolates

By means of activity-guided fractionation using taste dilution analysis, liquid chromatography-tandem mass spectrometry (LC-MS/MS), liquid chromatography-time-of-flight mass spectrometry, one-/two-dimensional nuclear magnetic resonance spectroscopy, LC-MS/MS quantitation, dose-over-threshold considerations, and sensory spiking experiments, kaempferol 3-O-(2'-O-sinapoyl-beta-sophoroside), exhibiting a bitter taste above the low threshold concentration of 3.4 mu mol/L, was found for the first time as the key molecule contributing to the unpleasant bitter taste of rapeseed (canola) protein isolates. This finding opens new avenues for a biorefinery approach targeting an off-taste removal.