Identification of bitter compounds in whole wheat bread crumb

Consumer acceptability of whole wheat foods is challenged by negative bitter flavour attributes. In this study, bitter compounds in whole wheat bread crumb were investigated. Utilising sensory-guided multi-dimensional fractionation techniques, the compounds with the highest bitterness intensity in the crumb were purified and identified by LC-MS-ToF and NMR techniques. The main bitter compounds were reported to be L-tryptophan, Wessely-Moser isomers apigenin-6-C-galactoside-8-C-arabinoside & apigenin-6-C-arabinoside-8-C-galactoside, and 9,12,13-trihydroxy-trans-10-octadecenoic acid (pinellic acid). Sensory recombination experiments of the bitter compounds formulated at the concentrations determined in expectorated saliva after bread mastication indicated pinellic acid had the greatest contribution to the bitterness perception of the crumb. Quantitative analysis of pinellic acid in the raw flour was reported to be inherently low compared to bread; the concentration increased more than 30-fold after flour hydration and baking.