Mechanism Of The Interaction Between Meat Essence And Umami Compounds On Umami Perception

The interaction between various flavor substances in complex food systems has an important influence on flavor perception.Odor-induced changes in taste perception(OICTP)play significant role in flavor perception,which could be utilized to enhance flavor quality.One of the research hotspots is the impact of flavor interaction on the umami perception.In this dissertation,the effects of meat essences on the flavor characteristics of monosodium glutamate(MSG)and soy protein isolated hydrolysate(SPIH)were investigated by sensory evaluation with or without nose clip.Moreover,gas chromatography-mass spectrometry,liquid chromatography-mass spectrometry and multivariate statistical analysis were used to identify the key flavor substances that affect the aroma-taste interaction.Subsequently,based on the construction of taste receptor model,molecular dynamics simulation was used to estimate the effect of aroma substances on the binding between taste substances and umami receptors T1R1/T1R3,thereby clarifing the internal mechanism of aroma substances on umami intensity enhancement.Finally,guided by the capacity on flavor intensity enhancement through the interaction with meat essence,protein regulation enzymolysis technology was executed to achieve the targeted preparation of the soybean peptide flavor materials,providing technical support for the industrialized preparation of peptide flavor materials,and suppling a theoretical basis for improving the flavor quality of condiments.The main results of this dissertationare as follows:(1)Results of the influence of different meat essences on the umami characteristics of MSG showed that the umami enhancement induced by seafood essence S1 was the strongest,indicating that the interaction between S1 and MSG had significant impact on the flavor perception.Different concentrations of essence and MSG substrate had different OICTP results.When MSG at low and medium concentration,accompanying with the increase of essence concentration,the umami enhancement induced by S1 on MSG was stronger,while no significant differences were observed at high MSG concentration.In the medium concentration essence system,the umami intensity of MSG at different concentrations was significantly improved,especially S1 having more obvious effect on the high concentrations of MSG.Fiftynine aroma compounds were detected in seafood essence S1,among which,3-methylthiopropionaldehyde(Methional),methyl sulfide(DMS),D-limonene(DLE),2,3-dimethylpyrazine,and dimethyl trisulfide could significantly enhance the umami perception of MSG.The umami enhancement induced by DMS,DLE,and dimethyl trisulfide in sensory results with the nose clip were relatively strong as well.Notably,sulfur-containing compounds had a significant enhancing effect on MSG umami perception whether with the nose clip or not.(2)Molecular docking and molecular dynamics simulations were used to investigate the effect of Methional,DMS,and DLE on the molecular recognition of MSG and umami receptor T1R1/T1R3,respectively.The umami receptor T1R1/T1R3 model was homologously constructed by using crystal structure of the active form of human calcium-sensing receptor extracellular domain 5K5 S as the template.For each aroma substance(X),T1R1/T1R3-MSG,T1R1/T1R3-X and T1R1/T1R3-MSG-X systems were established,and 50 ns MD simulation was carried out respectively.The hydrogen bonding effect and binding energy of MSG in different systems were analyzed.It was found that Methional,DMS and DLE molecules could enhance the hydrogen bonding between MSG and umami receptor T1R1/T1R3,thereby enhancing their affinity.(3)Seven enzymes were occupied to hydrolysing soybean protein isolate(SPI)for obtaining the corresponding SPIH.Results of enzymatic hydrolysis characteristics showed that pancreatic had the highest hydrolysis efficiency,with protein recovery and hydrolysis degree of 64.71% and 9.55%,respectively,followed by alkaline protease and papain.The molecular weight distribution of peptides from papain hydrolysate was concentrated in 3-6 k Da,accounting for 41.02%.Besides the enzymatic hydrolysis efficiency of acid protease and flavor protease was relatively low.Overall,the taste characteristics of SPIH were dominant in umami and bitterness,with slight sour,sweetness and saltness.Meat essences had different effects on taste perception of SPIH obtained from different enzymes,even on different peptide molecular weight distribution in the same SPIH.Seafood essence S1 exhibited excellent effects on increasing umami and reducing bitterness for different SPIHs,although the change of the taste characteristics induced by S1 of each SPIH was different,resulted by the composition difference of hydrolysates.The effect of the aroma-taste interaction was not determined by the umami intensity of the original hydrolysate or specific peptide molecular weight distribution.After preprocessing the SPIH liquid quality data,multiple statistical analysis was conducted to identifying and analyzing peptides,where TTTTL,FGQL,ELL,LWLK,FSKHF,NNNPF,YGSL,NSLP,YFRF and RLDLN,with VIP values above 1.70,were determined,indicating a significant correlation between peptides and OICTP in umami perception with nose clip.(4)Ten aroma-taste interaction related peptides in SPIH above were synthesized by solid-phase.The synthesized peptides had different taste features.Among them,FSKHF had a plentiful taste,as well as a salty,bitter,and slightly umami peculiarity.Sensory experiments with and without nose clip showed that seafood essence S1 could induce the enhancement of taste perception of soybean peptides like FSKHF,TTTTL,NSLP,RLDLN,ELL and NNNPF.Methional,DMS,and DLE had significant umami enhancing effects on FSKHF.Results of molecular dynamics simulation showed that FSKHF and aroma substances like DLE,DMS and Methional could mutually enhance the binding between umami receptor,prolong the duration of conjugation,and be conducive to stability.DMS had a relatively strong role in enhancing the binding energy between the peptide and umami receptor.(5)The regulation enzymolysis was explored to increase the content of target peptides with significant OICTP effects in SPIH.It was found that the hydrolysis factors affect the peptide composition and content in the hydrolysate.The OICUP results were correlated with the target peptide content,when their variation was similar to those of the target peptide content.The single factor hydrolysis experiment of papain and acid protease along with the optimization experiment of two enzymes combination were carried out.The results showed that papain and acid protease with the addition ratio 2:1 were used to enzymolysis soy protein isolate synchronously,the hydrolysate had gorgeous enzymolysis characteristics,containing a high concentration of target peptides,also its umami and bitterness perception could be modified by interaction with seafood essence S1.Results based on the sensory evaluation with nose clip as the main criterion showed that the optimal enzymatic hydrolysis conditions were as follows:p H3.0,55 °C,12 hours,and enzyme addition 0.8%.