Effects of Water Content on Volatile Generation and Peptide Degradation in the Maillard Reaction of Glycine, Diglycine, and Triglycine

Peptides abundant in food and protein hydrolysates are known to be important to process flavors. The present study reports the volatile profile of the Maillard reactions of glycine, diglycine, and triglycine. The reaction with glucose was conducted at 0−100% water content in glycerol medium at 160 °C for 1 h. Volatile compounds were quantified by stir bar sorptive extraction−gas chromatography−mass spectrometry, and nonvolatile compounds were quantified by high-performance liquid chromatography−tandem mass spectrometry. The major volatiles produced from each of the reaction systems were trimethylpyrazine and 2,5-dimethylpyrazine. Volatile generation increased as water decreased, and the overall reactivity of the glycine and glycine peptides in volatile formation was glycine ≈ triglycine > diglycine. Triglycine was very unstable and mainly degraded into cyclic Gly-Gly and glycine, whereas diglycine had a higher stability than triglycine toward hydrolytic cleavage of the peptide bond. The amounts of glycine, diglycine, cyclic (Gly-Gly), and triglycine in the peptide−glucose reaction mixtures at different water content were reported. Keywords: Peptide; volatiles; SBSE; glycine; water content; diketopiperazine; LC−tandem MS