Mapping Taste-Relevant Food Peptidomes by Means of Sequential Window Acquisition of All Theoretical Fragment Ion-Mass Spectrometry.

During the last few years, key taste-active compounds have been isolated and identified by means of a combination of a time- and lab-consuming successive fractionation and sensory characterization. Because the peptidome of fermented, protein-rich food is very complex, new strategies are necessary to accelerate the identification of taste-active peptides. In this study, two advanced mass spectrometric approaches were developed to comprehensively map the bitter tasting peptidome of fermented foods by data-independent acquisition (DIA) using sequential window acquisition of all theoretical fragment ion-mass spectrometry (SWATH-MS) and an in silico-assisted triple quadrupole (QQQ)-based targeted proteomics approach, separately. Application of both techniques on two fresh cheese samples as well as on crude medium-pressure liquid chromatography fractions exhibiting intense bitter taste, followed by filtering the hydrophobic target peptides (Q value of ≥1200 cal/mol) showing a signal-to-noise ratio of ≥10 and a fold change of ≥3 when comparing the less bitter to the more bitter cheese sample, revealed the candidate bitter peptides, which were then validated by means of synthetic reference peptides and human sensory evaluation. The bitter peptides were then quantitated in the fresh cheese samples as well as in a series of dairy products by means of QQQ-MS and SWATH-MS, separately. Although the QQQ-MS method showed 2-80-fold lower limits of quantitation (LOQ), the SWATH-MS method could be shown for the first time to enable the comprehensive quantitation of all sensorially relevant key bitter peptides with LOQs far below the bitter taste recognition concentration of each peptide.