Session: Parallel session 9 - Complex mixtures - polymers - microplastics

Untargeted characterization of short peptides in complex food matrices

Food products are complex mixtures with a diverse macromolecular composition, as polyphenols, carbohydrates, lipids and proteins, in addition to their hydrolysis-derived structural entities as phenols, oligosaccharides, fatty acids and short peptides composed of up to four amino acids. Short peptides are growingly gaining interest and their analysis in complex food matrices is crucial, knowing their exceptional nutritional value, organoleptic properties and health-promoting features. If the analysis of free amino acid is well established, the analysis of short peptides is challenging due to their small size and extreme physico-chemical features, making it hard to separate them adequately by LC and to detect them by MS. Moreover, they are not covered by classical omics workflows. Herein, we present our developed workflow dedicated to the identification and quantification of short peptides in fermentation-derived food matrices. Our developed method consists of an amino-group labeling of short peptides in lyophilized food matrices with dansyl chloride at basic pH. Following reaction quench, the neutralized reaction medium is filtered and analyzed by nanoESI nanoLC-MS/MS. The raw data was processed and treated with our in house-developed program in python language, Short_pept, which allows the reliable identification of dansyl-labeled short peptides sequences based on MS/MS spectra and specific fragments and reporter ions mapping. In a first phase the program extracts ion signal intensity, retention time and scan number informations for all fragmented ions including reporter ions. A second verification phase allows the accurate separation of isobaric structures based on chromatography peak detection. Thanks to this workflow, we were able to characterize short peptides in various food matrices derived from fermentation-related hydrolysis. In commercial yeast extract, we were able to identify 545 short peptides. Other chemical modifications were successfully detected.