| Green tea,without ferment in the process,produced in many parts of our country.Because of the manufacture process has retained benefit ingredients of fresh leaves at maximum possibility,green tea has more efficient pharmacology relatively,and highly popular with consumers.In this paper,the fried green tea in China was used as the research object,and the sensory properties were analyzed by modern sensory analysis technique.The sensory properties and taste compounds were connected by multivariate statistical analysis method.Using three-point test and curve fitting method detect the threshold of the main taste monomer,at the same time,the interaction effect between them was tested by the factorial experiment design.Finally,green tea extract and the main taste of the monomer material was used to establish a green tea taste standard regression model.1.Analysis of biochemical compositionThe regular components of the test samples were analyzed by spectrophotometry and high performance liquid chromatography（HPLC）,the results showed the average contents of water extract as follows,EGCG,caffeine,glutamic acid,theanine and total free amino acid in test sample were 43.34%,17.35%,3.53% 8.32%,2.79%,0.44%,2.11%,3.77%.2.The linear scale evaluation method was used to analyze the taste attribute15-point evaluation was applied to the experiment,The results showed that the umami and sweetness of the samples were lower,the variation range of umami was larger than sweetness,and the change of sweetness was slightly between 27.The bitterness and astringency were higher than others in total,which were in between 412 and 714.The average of umami,sweetness,astringency and bitterness strength of 16 samples were 4.60,4.17,9.62 and 9.93.Through the biochemical composition and the relevant points of taste points attribute,tea polyphenols / water extracts were significantly negative correlated with umami,EGCG/water extract had a significantly negative correlation to umami,extremely significant nagative correlation to sweetness and significantly positive correlated with bitterness.Caffeine / water extract is significantly negative correlated with umami and sweetness,the glutamic acid / water extract is significantly associated with the umami,and the total free amino acid / water extract is significantly negative correlated with astringency.in addition,Some derivative compounds also had a significant correlation to the taste of tea,the derivative effect of EGCG plus rutin was 13% higher than EGCG solo work for umami,tea polyphenols and amino acids have no correlation to sweetness,and the ratio of the two is negatively correlated with sweetness,EGCG and caffeine have a significant negative correlation for both flavor and sweetness,but their ratios have significant positive correlations,and（EGCG + rutin）/（rutin + caffeine）is higher than EGCG / caffeine.3.The threshold and interaction effect of the main taste substances of green teaThe thresholds of EGCG,caffeine,rutin,sucrose and glutamic acid were analyzed and calculated by three-point experiment and curve fitting method.the result showed thresholds as follows,Astringent taste was 47.86μg / ml and bitter taste was 153.60μg / ml（EGCG has two taste）.The thresholds of caffeine,rutin,sucrose and glutamic acis was 81.28μg / ml,15.85μg / ml,125.89μg / ml,60.26μg / ml,respectively.Fitting curve also shows that the correct recognition rate of sucrose and rutin is linearly related to the logarithm of its concentration,the correct recognition rate of glutamic acid,caffeine,EGCG bitterness and astringent taste were logarithmic related to logarithmic of its concentration.The interaction between the five monomers was tested by the modified factorial design,Bitter taste,astringency and umami strength were significantly increased with the increase of caffeine,EGCG and glutamic acid（p<0.01）,Sweetness increased significantly with sucrose concentration（p<0.05）,rutin can significantly increase the bitter strength of caffeine（p<0.05）,while the effect on EGCG is not significant,Caffeine significantly enhanced the astringent strength of EGCG（p <0.05）,and its low concentration had a significant effect on rutin（p<0.05）,while high concentrations did not,The effects of EGCG and rutin were not significant.Only high concentrations of glutamate can significantly reduce the bitter taste of EGCG（p<0.05 level）,but its effect on astringency is not significant.The weakening effect of caffeine on umami was stronger than EGCG,but neither of them was significant.the effect of glutamic acid on caffeine is less than caffeine,the sweetness of sucrose can be significantly reduced by caffeine bitterness（p<0.05）,sucrose can only reduce the bitterness（p<0.05）of EGCG with low concentration,but not obvious for its astringency,in addition,it can also reduce the gluten acid umami strength not significantly.While the low concentration of glutamic acid made sweetness of sucrose solution the change that first increase and then reduce.When sucrose and glutamic acid are present at high concentrations simultaneously,the bitterness strength of caffeine can be significantly reduced（p<0.05）.4.Construction of the standard model of taste attribute evaluationUniform experimental design and quadratic polynomial stepwise regression analysis were used to establish the effective regression equation of flavor,sweetness,bitterness and astringency,the results achieved in this research were as follow: Yumami=18.87593-0.01861 x1+0.31019 x4-0.00028 x2*x3+0.000454 x3*x5 Ysweetness=2.90098+0.06604 x5-0.000252 x1*x3-0.00002 x2* x5+0.00014 x4*x5 Ybitterness=-5.93637+0.13859 x1+0.03851 x2-0.00006 x1*x1-0.00001 x2*x2-0.000031 x2*x4+0.001911 x3*x4 YAstringency=34.19060-0.00347 x3*x3+0.00086 x4*x4+0.00002 x1*x2+0.00030 x1*x3+0.00045 x2*x3-0.00455 x3*x4.Using those equation,the maximum and minimum values of flavor,sweetness,bitterness and astringency respectively were 55.72 and 0.00,51.36 and 0.00,103.61 and 0.3,96.61 and 34.26,indicating the highest intensity and minimum strength achieved by the standard of the four equations. |
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