甜菊红茶加工工艺及抗氧化研究

Study on the Processing and Antioxidant Activity of Stevia Black Tea

【目的】为提升甜菊茶口感,降低甜菊叶寒凉性,更好地发挥甜菊叶保健价值。【方法】以茶用甜菊品种‘甜侬6号’叶片为原料,对萎蔫、发酵、干燥等甜菊红茶制备工艺进行研究;分析发酵时长对甜菊红茶所含甜菊糖苷类、绿原酸类、异绿原酸类和黄酮类化合物含量的影响。【结果】室温萎蔫失水27%左右时,揉捻汁液渗出少、成型好;揉捻后室温保湿发酵4 h,阴干,所得甜菊红茶茶汤寒凉性降低、口感醇厚;在甜菊红茶发酵中,(异)绿原酸类化合物降解,瑞鲍迪苷(Rebaudioside,R)系列中RD、RN、RM、RI、RB,甜茶苷(Rubusoside,Rub)和双糖苷(Steviolbioside,SB)含量逐渐增大,RA和RF含量相对稳定,甜菊苷(Stevioside,STV)含量逐渐下降,咖啡酸、阿魏酸、槲皮苷检出量增高;相比晒干叶(甜菊绿茶),甜菊红茶抗氧化性变化不明显。【结论】通过发酵将甜菊叶制备为红茶,降低了其寒凉性。当其被制成红茶时,不仅有甜菊叶清香,入口回甘、温润醇厚,还能提高降血压、降血脂、抗氧化相关化合物含量,有效提升甜菊叶保健价值。

【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.