A Study On Technology Of Decreasing Caffeine Content In Black Tea And Oolong Tea

In order to decrease the content of caffeine in black tea and Oolong tea,microwave pretreatment with soaking in hot water,magnesium oxide solution,organic solvent and spraying the pollution-free exogenous induction material were used respectively for processing decaffeinated black tea and decaffeinated Oolong tea in this study.The decreasing percent of caffeine in different tea cultivars and the effect of spraying the pollution-free exogenous induction material were also investgated,the results showed as follows:1.Microwave pretreatment with soaking in hot water was applied to this study to decrease the content of caffeine in Oolong tea and black tea.The results showed that,after shaking the fresh leaves of Oolong tea were treated by microwave with the power of 900W for 4 minutes,after then soaked for 5 minutes in hot water.The content of caffeine,tea polyphenols,amino acids and water extraction material reduced to 0.53%,13.68%,1.59%and 30.64%repectively.Black tea leaves after fermenting were treated in microwave with the power of 900W for 8 minutes,and soaked for 8 minutes in hot water,in which content of caffeine,tea polyphenols,amino acids and water extraction material reduced to 0.56%,5.59%,0.44%and 12.49%respectively.2.In this study,the effect of tea leaves from different cultivars on decaffeine technique was investigated.The results showed that:Meizhan and Maoxie were appropriate for decaffeine technique.3.The effect of microwave treatment with different time and power,as well as different soaking time of magnesium oxide solution on the rate of removal of several biochemical components were researched in this study.The results showed that:the content of caffeine,tea polyphenols,amino acids and water extraction material in Oolong tea reduced to 0.44%,10.65%,0.66%and 20%respectively with the treatment of microwave,magnesium oxide and hot water.While content of caffeine in black tea was down to 0.47%after the same treatment.It was indicated that this technology was appropriate for the producing of decaffeinated Oolong tea and black tea.4.In order to provide the raw material for decaffeinated instant tea,black tea were soaked with chloroform,ethanol mixed solvent at room temperature for processing decaffeinated black tea.The results showed that:after soaked with 3L mixed solvent under room temperature for 15 hours,the content of caffeine,tea polyphenols,amino acids and water extraction material in black tea decreased to 0.53%,10.49%,1.81%and 26.61%respectively.5.The pollution-free exogenous induction material was applied to tea plant in order to investigate the effect on the content of caffeine in tea shoot.The results show that after spraying ZMZ,the content of caffeine in tea shoots can be decreased significantly compared with control.