The Effect Of The Interaction Of Taste Nucleotide With EGCG And Its Protein Complex On Taste

Taste is an important factor affecting the quality of tea,and is the result of the interaction of water-soluble substances in tea.Among them,astringency and umami have the greatest impact on the overall taste.It is generally believed that the astringency of tea is mainly derived from EGCG,and the umami taste is mainly derived from amino acids.However,in actual research,there is a certain contradiction between the content of biochemical components and the results of sensory evaluation.There is no obvious astringency,and the free amino acid content is relatively high and strong but there is no obvious umami taste.Studies have shown that the content of taste-presenting nucleotides in white tea withering greatly increases and participates in the presentation of white tea’s umami taste,but its taste mechanism is rarely reported.This article aims to explore the interaction between taste-producing nucleotides and EGCG and its protein complexes,in order to clarify the taste-producing mechanism of tea soup.Provide theoretical support for tea processing technology improvement and tea beverage processing.This study uses a variety of methods to study the interaction between flavored nucleotides in tea and EGCG and its protein complexes,explore the mechanism of their interaction,and further understand the source of umami and astringency in tea soup,so as to fully explain The taste of tea provides a new perspective,provides theoretical support and new development ideas for tea processing,and provides a new method for concealing the astringency of EGCG in the development of tea-flavored foods and beverages.First,SDS-PAGE was used to explore the precipitation effect of IMP,GMP,and EGCG on salivary proteins.On this basis,nuclear magnetic resonance technology was used to determine that IMP and GMP would be complexed with EGCG,and the flavoring nucleotides were explored by particle size analysis.The stability of the mixed solution with EGCG and its protein complexes and the effect on the diameter of the main particles.At the same time,the interaction type of IMP,GMP and EGCG was analyzed by spectroscopy,and the type of fluorescence quenching of EGCG-BSA,binding constant and The number of binding sites,and finally,the effects of IMP and GMP on EGCG astringent signal and sensory evaluation were combined to judge the effect of IMP and GMP on EGCG taste.The main results are as follows:Taste is an important factor affecting the quality of tea,and is the result of the interaction of water-soluble substances in tea.Among them,astringency and umami have the greatest impact on the overall taste.Previous studies believe that there is a certain contradiction between the astringency,umami biochemical content of tea and the sensory evaluation results.Although it has been found that the taste nucleotides(IMP,GMP)are up-regulated during the withering process of white tea,it is still in the tea taste.The contribution in China is rarely reported.This article aims to explore the interaction between flavoring nucleotides and EGCG and its protein complexes,in order to clarify the flavoring mechanism of tea soup umami and astringency,enrich the interaction mechanism of flavor substances in tea soup,and provide information for subsequent research on flavor substances in tea soup Theoretical support provides theoretical basis for the improvement of tea primary processing and deep processing technology.The results are as follows:1.First select six sample solutions of EGCG,IMP,GMP,EGCG-IMP,EGCG-GMP and EGCG-IMP-GMP to react with saliva samples to simulate the interaction of EGCG,flavored nucleotides and saliva in human oral cavity in vitro effect.The results confirmed that EGCG can complex with salivary protein to form a precipitate,and single IMP and GMP do not precipitate salivary protein.SDS-PAGE method to explore the precipitation effect of IMP,GMP,EGCG on saliva protein The test results show that EGCG,IMP,GMP have different precipitation effects on saliva protein.A single IMP and GMP can promote the complex reaction between EGCG and salivary protein.When IMP and GMP are present at the same time,the promotion of EGCG and salivary protein is stronger.2.In order to analyze the influence of flavoring nucleotide IMP and GMP on the complexation of EGCG,the test fixes the concentration of EGCG to 2×10-5 mol/L,adds different IMP and GMP concentrations as test samples,and uses laser nanoparticle size analyzer The particle size analysis of IMP,GMP and EGCG mixture was carried out.The particle size analysis method is used to explore the stability of the mixed solution of taste nucleotides and EGCG and its protein complexes and its influence on the main particle diameter.As the concentration of IMP and GMP increases,it will complex with EGCG and BSA-EGCG.The combined reaction increases the particle diameter in the solution,and can make the EGCG-IMP,EGCG-GMP,and EGCG-IMP-GMP solutions more stable.Based on the above results,it is inferred that flavoring nucleotides are also an important contributor to the mellowness of tea soup.3.Use nuclear magnetic resonance technology to determine,qualitatively and quantitatively analyze the structure(including configuration and conformation)of IMP,GMP and EGCG single components and mixtures.It is further confirmed that IMP and GMP will be complexed with EGCG.There is no interaction between IMP and GMP,but they can change the NMR spectrum of EGCG,resulting in a certain degree of displacement and tensile vibration.When IMP and GMP are present at the same time,it will interact with EGCG.The combination effect is stronger.4.In order to explore the binding type,binding constant,and number of binding sites of the interaction between IMP,GMP and EGCG,the spectrum of IMP,GMP,EGCG,EGCG-BSA and their mixed solutions was measured by spectroscopy.The UV absorption spectrum results of the interaction between IMP,GMP and EGCG are calculated and analyzed.There is only one interaction between IMP,GMP and EGCG.It is speculated that the non-covalent bonding may be hydrogen bonding.The binding constant of EGCG-IMP is0.01086,the binding constant of EGCG-GMP is 0.10835,and the binding constant of EGCG-IMP-GMP is 0.03915.The results of fluorescence emission spectroscopy can be calculated and analyzed.The flavoring nucleotide IMP and GMP cannot react with BSA alone,but when the two exist at the same time,it will reduce the fluorescence intensity of BSA;GMP will be the first to combine with EGCG in BSA-EGCG to recover The fluorescence intensity of BSA;when IMP and GMP exist at the same time,the static fluorescence of BSA and BSA-EGCG will be quenched.The binding constants are 0.6639 and 1.4932 respectively,and the number of binding sites were 1 and 1.5.5.With the 0.05 mg/m L EGCG standard solution as the test level,three mixed solution samples with significant spectral response differences were selected for electronic tongue detection,and the impact of IMP and GMP on the astringency signal of EGCG was collected and analyzed by electronic tongue technology.At the test level,with the increase of taste nucleotide concentration,both bitterness and astringency increased.The degree of increase of astringency was significantly greater than that of bitterness,but the aftertaste value of astringency tended to decrease.IMP has the largest increase in astringency of EGCG,and IMP-GMP blending has the smallest increase in astringency of EGCG,but as a whole,IMP has the smallest increase in astringency,followed by GMP,and IMP-GMP has the largest increase.Therefore,it is speculated that the effect of flavoring nucleotides on the umami taste of tea is mainly derived from the synergistic effect of sodium glutamate.6.The sensory evaluation of the three flavor compounds showed that EGCG was astringent,slightly bitter at high concentration and returning to sweet quickly;the human tongue was sensitive to the sweet taste of IMP,but its duration was short;GMP produced astringency at low concentration and sweet taste at high concentration,regan appeared more slowly and increased with time.Three groups of mixed solutions with different concentrations were set up for sensory evaluation to understand the effect of flavor nucleotides on the taste of EGCG.It was found that the addition of IMP and GMP could reduce the astringency of EGCG,the acerbity taste weakens,returns the Gan,the Sheng Jin effect is good。...