| Takifugu obscurus is popular among consumers for its delicious taste, and taste-activepeptides are the important compounds contributed to its palatable taste such as"mellowness" and "tenderness". So far no report was found about taste peptide of Takifuguobscurus. It has important scientific and practical significance to processing, utilizationand development of the simulation seasonings of the Takifugu obscurus to investigate itskey flavor peptides. Cultured Takifugu obscurus after heat processing are as samples.Modern separation and purification technology including membrane separation, gelfiltration chromatography and reversed-phase high performance liquid chromatography(HPLC) were used to obtain high purity of the oligopeptides. Matrix-assisted laserdesorption ionization-time of flight mass spectrometry/mass spectrometry(MALDI-TOF/TOF MS/MS), taste dilution analysis combined with the electronic tonguewere used to identify the taste-active peptides contributed to the puffer fish characteristicstaste.(1) The thin layer chromatography (TLC) combined with HPLC method wasestablished for identification the carnosine and glutathione from Takifugu obscurus muscle.And the contents of carnosine and glutathione were determination by the HPLC. The TLCused the silicon sheet with the developing solvents n-butanol, acetic acid and water (4:2:1).The samples were separated on Kromail C18column at30℃. An isocratic elution of90%acetonitrile and10%Mili-Q water containing0.05%trifluoroacetic acid was used. Theresults showed that the carnosine and GSH existed in Takifugu obscurus muscle. Thecontent of carnosine and glutathione (GSH) in Takifugu obscurus muscle was213μg/g(fresh weight) and211μg/g (fresh weight), respectively. This method was very simple,convenient and operated without derivant. It was suitable for the determination ofcarnosine and GSH.(2) To clarify the key flavour peptides that account for the cooked taste of puffer fish,flavour peptides were extracted from the flesh of Takifugu obscurus. Peptides fractions (P1,P2, P3, P4and P5) were purified from an aqueous extract of T. obscurus muscle byultrafiltration and Sephadex G-15gel filtration chromatography. P2was furtherfractionated into P2a, P2b, and P2c by RP-HPLC. Fraction P2b elicited umami and sweettaste. The amino acid sequence of P2b subfraction was identified asTyr-Gly-Gly-Thr-Pro-Pro-Phe-Val (836.4Da) by MALDI-TOF/TOF MS/MS. Hydrophilic amino acids residues Tyr, Gly, Gly, Thr, and Phe are likely to contribute to the umami andsweet taste of this octapeptide. The results of this study suggest this peptide is one ofimportant components of the ‘mellowness’ and ‘tenderness’ taste of the T. obscurus.(3) Using peptide solid phase synthesis synthesize Takifugu obscurus flavorpeptide(PFFP). The changes of umami and sweetness in PFFP under different temperatureand pH conditions and the analysis of the interaction between PFFP and sodium glutamate(MSG), sodium chloride (NaCl) and the mixture of MSG and NaCl are determined usingelectronic tongue. The results showed that heating the PFFP at100oC for30min canincrease its umami and sweetness. It can also increase the umami flavor of PFFP at pH4.0and lower its sweetness. However, it has no influence on the umami flavor and sweetnessfor PFFP at pH6.0and9.0. For the flavor characteristics of PFFP at different pH levels,within the range of pH4.0and pH9.0, there would be a decrease in the umami flavor withany change of the pH value. The strongest umami flavor comes from PFFP-100o C with ascore of8.84determined by the electronic tongue. The increasing of pH value of PFFPwould reduce its sweetness and vice versa. The heating of PFFP with different pH valueschanges its pH values and reduces its sweetness. PFFP at pH4.0has the highest sweetnessscore of8.75. MSG, NaCl and the mixture of MSG and NaCl helps to increase the umamiflavor and reduces the sweetness of PFFP, with NaCl having the most evident effect. It canincrease the sweetness score of PFFP from2.19to7.45. |
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