Study on the Processing and Antioxidant Activity of Stevia Black Tea
[Objective]To improve the taste of stevia tea,reduce the'coldness'of stevia leaves,and enhance the health benefits of stevia,[Methods]the preparation processes of stevia black tea,including wilting,fermentation,and drying,was studied using the leaves of the stevia variety'Tiannong 6';The effect of fermentation duration on the content of steviol glycosides,chlorogenic acids,isochlorogenic acids,and flavonoids in stevia black tea was analyzed.[Results]Wilting at room temperature with a water loss of approximately 27%resulted in less juice leakage and better molding;After rolling,moisturizing and fermenting at room temperature for 4 hours,drying in the shade,the stevia black tea soup had reduced'coldness',and had a mellow taste;During the fermentation of stevia black tea,(iso)chlorogenic acid compounds degraded,contents of rebaudioside(R)series RD,RN,RM,RI,RB,rubusoside(Rub)and steviolbioside(SB)gradually increased,contents of RA and RF remained relatively stable,content of stevioside(STV)gradually decreased,and amount of caffeic acid,ferulic acid and quercitrin increased;Compared to sun-dried leaves(stevia green tea),the antioxidant activity of stevia black tea did not show significant changes.[Conclusion]By fermenting stevia leaves into black tea,its'coldness'is reduced.After it was made into black tea,it not only had the fragrance of stevia,sweet and mellow,but also improved the content of compounds related to lowering blood pressure,lowering blood lipids and antioxidants,thus effectively enhancing its health value.
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