Abstract
At present, most investigations involving the Maillard reaction models have focused on free amino acids (FAAs), whereas the effects of peptides on volatile products are poorly understood. In our study, the formation mechanism of pyrazines, which were detected as characteristic volatiles in sunflower seed oil, from the reaction system of glucose and lysine-containing dipeptides and tripeptides was studied. The effect of the amino acid sequences of the dipeptides and tripeptides on pyrazine formation was further highlighted. Four different dipeptides and six tripeptides were selected. The results showed that the production of pyrazines in the lysine-containing dipeptide models was higher than that in the tripeptide and control models. Compounds 2,5(6)-Dimethylpyrazine and 2,3,5-trimethylpyrazine were the main pyrazine compounds in the dipeptide models. Furthermore, the C- or N-terminal amino acids of lysine-containing dipeptides can exert an important effect on the formation of pyrazines. In dipeptide models with lysine at the C-terminus, the content of total pyrazines followed the order of Arg−Lys > His−Lys; the order of the total pyrazine content was Lys−His > Lys−Arg in dipeptide models with N-terminal lysine. Additionally, for the tripeptide models with different amino acid sequences, more pyrazines and a greater variety of pyrazines were detected in the tripeptide models with N-terminal lysine/arginine than in the tripeptide models with N-terminal histidine. However, the total pyrazine content and the percentage of pyrazines in the total volatiles were similar in the tripeptide models with the same amino acids at the N-terminus. This study clearly illustrates the ability of dipeptides and tripeptides containing lysine, arginine and histidine to form pyrazines, improving volatile formation during sunflower seed oil processing.
Highlights
The Maillard reaction is a complex chemical reaction between a carbonyl compound and an amino group under heating conditions [1]
The peptides were mixed with glucose and reacted at pH 8.0 and 140 ◦ C for
Arg/His−Lys dipeptides and glucose using their corresponding free amino acids (FAAs) as controls, which were designated Control (Arg + Lys) and Control (His + Lys), respectively
Summary
The Maillard reaction is a complex chemical reaction between a carbonyl compound and an amino group (e.g., amine, amino acid, peptide, or protein) under heating conditions [1]. In the past few decades, researchers have established numerous Maillard model systems to understand the reaction process and products. In these models, free amino acids (FAAs) and carbonyl compounds are the most studied candidates [1,3,4,5,6]. Maillard model systems consisting of peptides and carbonyl compounds [10,11,12]. Compared with the FAA-containing Maillard models, the specific volatile products from the peptide-containing Maillard models were higher [13]. Pyrrolizines were detected in the proline-containing dipeptide model and considered proline-specific volatile compounds [14]. The 2(lH)-pyrazinones were only detected in the Gly-containing peptide
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