Separation And Identification Of Taste Peptides In Fermented Bean Curd And Shrimp Paste

Fermented food like white fermented bean curd and shrimp paste has been recognized as strong flavor food. Studying the flavor enhancing peptides in these kinds of food as the representatives of the plant and animal sources is important to the fermented food industry. In this paper, peptides from white fermented bean curd and shrimp paste as were prepared and analyzed through extraction, ultrafiltration, gel chromatography, reversed phase high performance liquid and mass spectrum identification. The molecular weight, amino acid composition, amino sequence and taste were explored. Chemical synthesis and sensory evaluation was also carried out to confirm the characteristics of peptides:(1) Peptides in raw materials were extracted by deionized water. The materials were homogenized at 40 ℃ water bath condition and extracted 1h. Grease and insoluble subjects were removed by centrifugation and filtration. Membrane ultrafiltration of white fermented bean curd with molecular weight less than 5000 Da was collected and stored below-20℃.(2) Using the Sephadex G-15 chromatographic column, components of white fermented bean curd were separated as F1-1, F1-2, and F1-3; components of shrimp paste were separated as F2-1, F2-2, and F2-3. F1-1 and F2-2 were chosen as the key components through sensory evaluation. The key components were separated by highperformance liquid chromatography. F1-1-1, F1-1-2, F1-1-3 from white bean curd, and F2-2-1, F2-2-2, F2-2-3, F2-2-4 from shrimp paste were identified by mass spectrometry.(3) F1-1-3 and F2-2-2 were selected according to the result of MS1, and identified by MS2. Mass spectrums were analyzed using Denovo software so the amino acid sequences were identified. Peptides were separated from F1-1-3, their sequence were identified to be Asp-Phe-Lys-Arg-Glu-Pro(A), Asp-Arg-Glu-Lys-Phe-Asp-Glu(B),Asp-Glu-Asp-Phe-Lys-Arg-Glu-Pro(C); Another peptide was also separated from shrimp paste, which is Asp-Gly(D).(4) The 4 peptides were synthesized and analyzed by sensory evaluation test. Taste profile, taste threshold value and taste enhancing effect results were obtained through sensory evaluation analysis. Peptide A and C exhibited umami taste. Peptide C also showed sour taste. Peptide B didn‘t show apparent flavor, but it showed enhancing ability of umami, sweet and salty. Peptide D exhibited tender sour taste but nonumami taste, but it has umami enhancing effect.