Volatile Compounds Generated from the Maillard Reaction of Dipeptides Asn–Pro and Pro–Asn and a Mixture of Asparagine and Proline with Glucose

Dipeptide-derived Maillard volatiles make a significant contribution to flavor chemistry. Their formation is related to many factors such as Maillard reaction parameters and dipeptides’ sequence. In order to understand Maillard compound formation characteristics in specific dipeptide systems, volatile compounds were first identified in the dipeptide Maillard system of Asn–Pro and Pro–Asn with glucose under three temperature gradients (130, 150, and 170 °C). Eight classes of O- and N-containing compounds were identified by GC-MS analysis, mainly providing sweet, roasted, and bakery-type notes. Among them, proline-derived compounds, pyrrolizines and azepines, were produced in the highest amount, followed by pyrazines. In addition, oxazoles, furans, pyrroles, pyridines, and quinoxalines were detected far more in the dipeptide system than in the mixture of single asparagine and proline, especially when they reacted at lower temperatures (130 and 150 °C). Aroma formation characteristics of the dipeptide Maillard system of Asn–Pro and Pro–Asn indicated that amino acids bound in the peptide form may direct the Maillard reaction toward specific types of aroma compounds. Potential modifications of dipeptides were proposed, revealing the ability of Asn and Pro as terminus amino acids of dipeptides for the formation of Maillard aroma products.