Quantification and Bitter Taste Contribution of Lipids and Their Oxidation Products in Pea-Protein Isolates (<i>Pisum sativum</i> L.)

Abstract

An ultra-high-performance liquid chromatography-differential ion mobility (DMS)-tandem mass spectrometry method was developed to quantify 14 bitter-tasting lipids in 17 commercial pea-protein isolates (<i>Pisum sativum</i> L.). The DMS technology enabled the simultaneous quantification of four hydroxyoctadecadienoic acid isomers, namely, (10<i>E</i>,12<i>Z</i>)-9-hydroxyoctadeca-10,12-dienoic acid (<b>5</b>), (10<i>E</i>,12<i>E</i>)-9-hydroxyoctadeca-10,12-dienoic acid (<b>6</b>), (9<i>Z</i>,11<i>E</i>)-13-hydroxyoctadeca-9,11-dienoic acid (<b>7</b>), and (9<i>E</i>,11<i>E</i>)-13-hydroxyoctadeca-9,11-dienoic acid (<b>8</b>). Based on quantitative data and human bitter taste recognition thresholds, dose-over-threshold factors were determined to evaluate the individual lipids' bitter impact and compound classes. The free fatty acids α-linolenic acid (<b>10</b>) and linoleic acid (<b>13</b>), as well as the trihydroxyoctadecenoic acids, especially 9,10,11-trihydroxyoctadec-12-enoic (<b>3</b>), and 11,12,13-trihydroxyoctadec-9-enoic acids (<b>4</b>), were shown to be key inducers to bitterness in the isolates. Additionally, the impact of 1-linoleoyl glycerol (<b>9</b>) on the bitter taste could be shown for 14 of the 17 tested pea-protein isolates.