Two-step mass spectrometric approach for the identification of diketopiperazines in chicken essence
Diketopiperazines (DKPs) have been found in a variety of foods and beverages that impart a metallic bitter taste. The presence of DKPs in chicken essence (CE) was first postulated by a two-step monitoring technique, with mass precursor ion scanning from the immonium ion of a specific amino acid first, followed by mass matching with a DKP database. The postulated DKPs were further verified by tandem mass spectrometric (MS/MS) analysis. It was found that this technique performed well, with about 20 DKPs tentatively identified. Proline was an important constituent of the DKPs in CE, together with other non-polar amino acids, such as glycine, alanine, valine, leucine/isoleucine and phenylalanine, which also showed great magnitude. Some proline-based DKPs in CE were quantified before and after thermal treatment at 130 °C for 1 h. The concentrations of the DKPs were determined not only by the relative ease of formation and the stability of the DKPs, but also by past thermal processings.
KeywordsDiketopiperazine Cyclic dipeptide Chicken essence Protein hydrolysate Mass spectrometry
Financial support for this study from the Ministry of Economic Affairs (92-EC-17-A-18-R7-0332), Taiwan, the Republic of China, is highly appreciated.
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