| Xuanwei ham is one of the three major hams in China,named because it is produced in Xuanwei.It is the representative of Yunnan ham and is often called"cloud leg".It is a traditional Yunnan famous and excellent product.The flavor characteristics of Xuanwei ham were studied in this paper.The umami components were optimized by using water temperature extraction,ultrafiltration,gel chromatography and reverse phase HPLC,and combined with sensory evaluation.Nanoliter HPLC-tandem mass spectrometry(Nano-LC-MS/MS)was used to determine the amino acid sequence of umami peptides.The activity of synthetic peptides was estimated using peptide information database,and the taste characteristics of synthetic peptides were detected by sensory evaluation using solid phase synthesis method.Finally,the homology model of umami receptors T1R1/T1R3 was constructed to obtain more accurate umami evaluation results.Molecular docking was used to study the interaction between umami peptide and umami receptor T1R1/T1R31,and to further explore the freshness mechanism of umami peptide.At the same time,nuclear magnetic resonance(NMR)technology and metabolomics technology were used to study Xuanwei ham in different years,and the changes of water soluble components during the fermentation process of Xuanwei ham were studied,and the results were combined with sensory evaluation results to better understand the flavor characteristics of Xuanwei ham.Key findings were as follows:Study on flavor peptide of Xuanwei ham(1)In this study,Xuanwei ham was taken as the research object,and the warm water method was used to extract it.Various separation and purification techniques such as ultrafiltration,gel chromatography,reverse phase HPLC were used to separate and purify its components,and Nano-LC-MS/MS was used to analyze its structure.Five peptides RKYEEVAR(RR-8),IVGRPRHQG(IG-8),MDAIKKKMQ(MQ-9),YVGDEAQSKRG(YG-11)and VNVDEVGGEALGR(VR-13)were obtained.Their molecular weights were 1050.57,1019.59,1134.60,1209.59 and 1314.67Da,respectively.According to the peptide activity database BIOPEP-UWM,all five identified peptides were predicted to have potential umami activity.(2)The synthesized small molecular peptides were evaluated for their flavor and umami characteristics.The results showed that all the four peptides showed umami with different intensities,and the critical point for umami identification was 0.25 mg/ml-0.80 mg/ml.The flavor enhancement was:VR-13(16)﹥YG-11=RR-8(8)﹥MQ-8(4),whereas IG-9 showed a strong bitter overtaste.The results of molecular docking showed that the four umami-taste peptides could successfully bind to the T1R3 subunit,and Asp219,Asn150 and Thr179 were the key binding sites.This result provides an important contribution to further study of the interaction between umami peptide and the umami receptor T1R1/T1R3.Based on ~1H-NMR,30 chemical components in Xuanwei ham extract were detected,including amino acids,organic acids,sugars,bases,and small peptides.PCA and orthogonal partial least squares methods were used to compare Xuanwei ham,and the differences of three different fermentation years were found,and a preliminary comparison was made:There are 16types,including 9 amino acids(glycine,taurine,valine,tyrosine,proline,alanine,proline,aspartic acid,tryptophan),1 type of sugar(β-glucose),The analysis of one base(choline),four acids(lactic acid,acetic acid,creatine,succinic acid)and one alcohol(glycerol)showed that the content of glycine,valine,taurine and tyrosine increased,while the content ofβ-glucose decreased in two years fermentation compared with one year fermentation.The contents of lactic acid,glycine,alanine,taurine,acetate,creatine,proline,succinic acid,choline,aspartic acid and tryptophan increased after three years fermentation compared with one year fermentation.The contents of lactic acid,alanine,proline,creatine,acetate choline,aspartate,glycerol andβ-glucose in the three-year fermentation were higher than those in the two-year fermentation. |
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