Integrated targeted and untargeted analysis of polar peptides in foods using hydrophilic interaction liquid chromatography-data-independent acquisition-mass spectrometry.

Abstract

A hydrophilic interaction liquid chromatography-data-independent acquisition mass spectrometry (HILIC-DIA-MS) workflow was developed for simultaneous targeted semi-quantification of polar peptides and untargeted profiling of both peptides and other polar compounds in complex food matrices. The method uses a zwitterionic HILIC column optimized for separation of short polar peptides that are challenging to retain on reversed-phase columns. Many of these peptides contain charged amino acids and contribute to basic taste modalities such as umami and saltiness. Both targeted peptide analysis and comprehensive untargeted profiling were achieved by applying DIA-MS detection. This data acquisition mode was shown to be reproducible and sensitive while enabling retrospective data processing. High-resolution MS1 scans (60.000 FWHM), combined with fast MS2 scans and DIA mass windows of 15 m/z yielded highly repeatable and selective LC-MS profiles, allowing differentiation of structural isomers (e.g., alpha-glutamyl (umami) and gamma-glutamyl (kokumi)). The method was validated using taste-relevant dipeptides, demonstrating low detection limits (0.1-0.9 µM), good intra-day and inter-day precision, and high recovery (96%) in commercial soy sauce and yeast extract matrices. The workflow was further applied to the relative quantification of peptides and the untargeted profiling of characteristic molecular features in cheese, ham, and extracts from dried food ingredients. The integration of targeted and untargeted analyses demonstrates the suitability of HILIC-DIA-MS for comprehensive characterization of polar compounds in food systems.