The Effect Of Ventilating Conditions On The Sensory Quality And Taste-chemical Quality Of Yellow Tea In The Yellowing Process

In this study,10 samples of Chunyu No.2 experimental tea and 37 samples of zhenong 113 experimental tea were made to study the effects of rolling and non rolling,time of yellowing,types of ventilation and ventilation methods on the sensory,color and taste of yellow tea,and the contribution materials of characteristic taste of yellow tea.The results are as follows:(1)The degree of yellowness of the two groups of tea leaves was all the same as "oxygen through > air > seal > nitrogen > no stuffy yellow",which was consistent with the oxygen content in the environment.The degree of yellowness of tea samples after rolling was greater than that of tea without rolling process.The rolling technology and ventilation conditions have a significant impact on the quality of yellow tea.(2)In the range of 0-4.5h,the degree of yellowness increased with the increase of yellowing time under all ventilation conditions.The growth rate was: seal > ventilation,oxygen > air > nitrogen.After 4.5h,the degree of yellowness slowly;both the sealed environment and the increase of oxygen content in the environment could accelerate the rate of yellowing and reduce the time of yellowing;nitrogen could delay the process of yellowing.The sensory quality of the samples increased firstly and then decreased with the increase of the time of depressing yellow,and the quality of the samples was the best after 4.5 hours of depressing yellow.The total score,aroma score and taste score of the samples were higher than those of the sealed samples.Under the condition of nitrogen,air and oxygen for 4.5H,three kinds of high-quality yellow tea with different styles,fresh,sweet and sweet,were formed.The change trend of tea color was basically the same under different ventilation conditions.With the increase of the time of depressing yellow,the value of C * and B * of dry tea decreased,and the value of a * increased;the value of L * of tea soup decreased,and the value of C * and a * and B * increased;the speed of change was consistent with the degree of yellowness,the fastest under oxygen and the slowest under nitrogen.The degree of yellowness has a significant effect on distinguishing the whole sensory and color quality of tea samples.(3)The content of water extract decreased with the increase of the degree of draught;the gallic acid content of the air draught tea was 7.02% lower than that of the sealed draught tea;the gallic acid content of the tea in oxygen was 106.57% higher than that of the tea in nitrogen,and the degree of draught increased,gallic acid content increased gradually;catechin content,total catechins,total simple catechins and total ester catechins decreased with the increase of the time of depressing yellow;the amino acid content of tea samples in oxygen environment was lower than that in other two environments;the total flavone content of ventilating depressing yellow tea samples was 5.16% higher than that of dense depressing yellow tea samples;among the above changes,oxygen environment changed the fastest and nitrogen environment changed the least obvious.The time of depressing yellow and oxygen content of aeration gas were negatively correlated with catechins [except(-)-catechin gallate],water extracts,amino acids(except glycine),alkaloids and most flavonoids,and positively correlated with gallic acid,(-)-catechin gallate,kaempferol and kae-3-o-galrha.The degree of yellowness has a significant effect on distinguishing the chemical quality of the whole taste of tea.(4)The main contribution substances of characteristic taste of yellow tea are distributed in the "molecular weight > 5K" and "molecular weight < 1K",among which the contribution degree of "molecular weight > 5K" in tea soup to the sensory attributes of yellow tea style is greater.