Bitterness and Astringency of Sinapine and Its Components

Sinapine, choline chloride, and sinapic acid were evaluated for bitterness and astringency, at suprathreshold concentrations in water, by a trained sensory panel using magnitude estimation. Power functions (S = kCn) were established for the bitterness of each of the three chemicals and the reference caffeine; none of the exponents for bitterness was significantly different from caffeine (n = 0.98) suggesting that, for any of these taste precursors, a doubling of concentration would double the bitterness perceived. Equimolar solutions of caffeine and sinapine were considered similar in intensity and significantly more bitter than choline chloride; sinapic acid was intermediate in bitterness. The sum of the bitterness values calculated from the power functions for choline chloride and sinapic acid accounted for approximately 80% of the bitterness of sinapine, at equimolar concentrations. Fifty to 94% of the bitterness perceived from tasting water slurries of rapeseed flour and protein concentrate was explained by the bitterness expected from their content of sinapine and free choline. Reliable power functions could not be established for the astringency of sinapine, choline chloride, and sinapic acid at the concentrations used. However, a clear psychophysical function was established for the astringency of the reference alum.