Study On Umami Peptides And Taste Characteristics Of Boletus

Leccinum extremioientale and Boletus edulis are two common wild edible fungi in Yunnan.They both have a delicious and unique taste,and rich in nutrition.In this paper,fresh Leccinum extremioientale and Boletus edulis were used as materials to isolate and purify the small molecular peptides with umami taste,and the amino acid sequence and molecular weight of these peptides were identified.After ethanol extraction,combined with sensory evaluation,gel filtration chromatography,anion exchange adsorption and reversed-phase high-performance liquid chromatography were used to separate and purify the small umami peptides from the Leccinum extremioientale and Boletus edulis.The amino acid sequence of the peptides was determined by Nanoupgrade ultrahigh performance liquid chromatography-tandem mass spectrometry.The results are as follows:Atotal of three umami peptides sequences were obtained by gel filtration chromatography and reversed-phase high performance liquid chromatography from Leccinum extremioientale.They were Asp-Gln-Glu-Asp-Leu-Asp-Glu-Ser-Leu-Ile-Gly-Val-Lys(DQEDLDESLIGVK,1459.704Da),Tyr-Asn-Glu-Tyr-Pro-Pro-Leu-Gly-Arg(YNEYPPLGR,1107.535 Da)and Phe-Asn-Glu-Ile-Ile-Lys-Glu-Thr-Ser-Thr(FNEIIKETST,992.517 Da),and their umami thresholds were 0.10 mmol / L,0.26 mmol / Land 0.14 mmol / L,respectively.In the process of optimization of ethanol extraction conditions,the optimal ethanol extraction conditions were obtained as follows: 30:1 liquid to solid ratio,40 % ethanol concentration,2 hours extraction time.Under these conditions,the highest extraction efficiency of Leccinum extremioientale was obtained.The components were further separated and purified by anion exchange resin,two umami peptides sequences were obtained:Glu-Pro-Lys-Glu-Glu-Gly-Ala-Glu-Ala-Glu(EPKEEGAEAE,1088.474 Da),Phe-Glu-Gly-Val-Glu(FEGVE,580.261 Da),their umami thresholds were 0.08 mmol / L and 0.17 mmol / L,respectively.Boletus edulis was purified by gel filtration chromatography and reversed-phase high performance liquid chromatography,two umami peptides sequences were obtained.They were Leu-Glu-Phe-Lys-Gln-Ile-Ala-Gly-Ser-Phe(LEFKQIAGSF,1138.6023 Da),Thr-Val-Ile-Asp-Ala-Pro-Gly-His-Arg-Asp(TVIDAPGHRD,1079.536 Da)respectively,and their umami thresholds were 0.35 mmol/Land 0.27 mmol/Lrespectively.In the process of optimization of ethanol extraction conditions,the optimal ethanol extraction conditions were obtained as follows: 20:1 liquid to solid ratio,50% ethanol concentration,1 hour extraction time.Under these conditions,Boletus edulis obtain the highest extraction efficiency.The components were further separated and purified by anion exchange resin,three taste sequences were obtained,Thr-Lys-Glu-Val-Tyr-Glu-Gly-Glu-Val(TKEVYEGEV,1053.510Da),Ile-Val-Pro-Arg-Phe-Glu(IVPRFE,760.435 Da)and Phe-Gly-Leu-Asp-Phe(FGLDF,598.290 Da),with umami thresholds of 0.29 mmol / L,0.45 mmol / L and 0.34 mmol / L,respectively.According to the analysis of the obtained umami peptides,there are many umami amino acids and sweet amino acids in the isolated umami peptides,which have an important impact on the umami threshold of the umami peptides.Therefore,the spatial structure and amino acid composition,sequence and terminal amino acids of delicious peptides also affect the taste threshold of delicious peptides.