| As the main quality ingredients, theaflavins play an important role in black tea’s color, smell andtaste, showing a significant positive correlation with the quality of black tea. Fermentation is a set ofcomplicated chemical reactions, including polyphenols oxidized to theaflavins by enzymes and furtheroxidation of theaflavins. To improve the content of theaflavins in black tea, the impacts of temperature,humidity, degree of withering and tenderness of fresh leaves on withering and formation of theaflavinsduring fermentation for congou black tea and CTC broken black tea were studied in this paper, hopingto provide theoretical basises for theaflavins improvement and the standardized production of black tea,the results were as the following:With controlled withering environment conditions, treatment with70%relative humidity got thehighest content of theaflavins in congou black tea. Results suggested that high relative humidity was notgood for withering, the degree of polyphenols oxidation was relatively higher in the treatment with90%relative humidity, while the contents of theaflavins and thearubigins were the least. There was asignificantly positive correlation between polyphenol oxidase activity and water content of leaves in theprocess of withering. The formation of pigment substances coming from polyphenols oxidation relatedclosely to polyphenol oxidase activity and peroxidase activity during fermentation. Contents oftheaflavins and thearubigins in made tea were negatively correlated to polyphenol oxidase activity ofwithering leaves.The effect of different withering degrees to process CTC black broken tea showed that: teapolyphenols content in the end of fermentation reduced with the withering time prolonged in differentwithering degree treatment, the effect of enzyme activity was that PPO and POD activities were reducedwith the withering time prolonged on the whole. it got the best quality of CTC broken black tea whenthe water content of withering leaves was69.4%, the score of liquor color showed a positive correlationwith theaflavins and thearubigins, correlation coefficient were0.98and0.79.With controlled fermentation environment conditions, the enzyme activities and characteristiccomponents in congou black tea showed similar changes during fermentation. The activity ofpolyphenol oxidase and peroxidase were getting lower, the contents of theaflavins and thearubigins firstgot high and later low, theabrowns was getting high all the way. Treatments with different temperature,humidity and tenderness of leaves showed that tenderness of leaves had the most significant impacts onthe fermentation of congou black tea. Compared with one bud and two to three leaves, one bud with oneleaf materials had the highest activity of enzyme and contents of polyphenols and catechins, and thecorresponding made black tea had the relatively higher contents of theaflavins, thearubigins andtheabrowns, meaning that such kind of materials were basically fit for making black tea. Under100%relative humidity, high temperature was good for the quick accumulation of theabrowns, but not so fortheaflavins and thearubigins, and low temperature had adverse effects for the accumulation oftheabrowns. The tea polyphenols and catechins’ oxidation rate of fermentation leaves changed in suchway:18℃>23℃>28℃, the highest theaflavins content arreared in23℃treatment, the thearubigins content changed in the sequence of18℃>23℃>28℃, theabrowns were:28℃>23℃>18℃. Treatmentof RH70%and RH100%showed that theaflavins content came to the highest point after low humiditytreatment for1.5hours, which suggest that the fermentation conditions should be of high humiditywhile oxygen is in abundant supply.The effects of temperature on CTC broken black tea fermentation suggested that contents oftheaflavins, thearubigins got to the highest and theabrowns the least under32℃fermentation treatment,and the activity of PPO, POD were higher under such a treatment while compared with34℃and36℃treatment. |
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