关键词: 北京油鸡, 炖煮鸡汤, 滋味, 鲜味, 游离氨基酸, 核苷酸, 呈味肽

Abstract: In order to understand taste components in the stewed chicken broth of Beijing Youji, the compositions of free amino acids and nucleotides were analyzed by high performance liquid chromatography (HPLC) and the taste active values (TAVs) of the nucleotide compounds were calculated. The results showed that amino acids with umami and sweet taste together accounted for 54.52% of the total amino acids, much higher than the percentage of bitter taste amino acids (34.47%). Among the free amino acids determined, alanine and glutamic acid, with umami and sweet taste, were more abundant and had higher TAVs, indicating that they contribute highly to the umami taste of the chicken broth. The concentration and TAV of inosine 5’-monophosphate (5’-IMP) were much higher than those of adenosine 5’-monophosphate (5’-AMP) and guanosine 5’-monophosphate (5’-GMP), indicating 5’-IMP to be the major nucleotide contributing to the umami taste of the broth. Furthermore, chromatographic separation of the broth was performed with Sephadex G-15, yielding three taste-active fractions. Fraction 2 exhibited obviously stronger umami taste than that of the chicken broth. High performance gel liquid chromatography analysis showed that the fraction was mainly composed of oligopeptides (accounting for 84.29% of the total peak area) with molecular mass < 3 kDa. Then this fraction was subjected to matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS) analysis, and peaks with higher intensity were selected for tandem MS analysis. As a result, four peptides were identified, Leu-Val-Gln-Tyr, Val-His-Ala-His-Ser, Ala-Gln-Asn-Ser-Tyr-Pro-His-Ala, and Ala-Glu-Gln-Tyr-Arg-Leu-Val-Gly. These peptides, mainly composed of umami and sweet amino acids like Gln, Ala and Ser, may contribute to the delicious taste of chicken broth.

Key words: Beijing Youji, stewed chicken broth, taste, umami, free amino acid, nucleotide, taste-active peptide