龙井茶冲泡下沉特征及加工工艺对外形品质和下沉速度的影响

Sinking Characteristics in Longjing Tea Brewing and the Effects of Processing-related Factors on Appearance Quality and Sinking Speed

为解决目前市场上部分龙井茶冲泡后下沉慢的问题,文章研究了龙井茶冲泡后下沉规律、影响茶叶下沉的物理因素及加工工艺对其外形品质和下沉速度的影响。结果表明,龙井茶沸水冲泡后静置过程中,芽叶集中下沉时间点能够作为茶叶下沉速度的衡量标准。茶条宽度及长宽比是影响龙井茶下沉的重要物理因素,手工龙井茶外形较窄、下沉快,芽叶集中下沉时间点在90~200 s间;机制龙井茶外形相对宽扁,茶条最宽幅度宜控制在0.55 cm以内,长宽比控制在4.0~6.0之间的龙井茶,其下沉速度较快,芽叶集中下沉时间点小于290 s;茶条最宽幅度大于0.6 cm,长宽比小于4.0的产品下沉速度慢。加工过程中青锅及精制能够显著影响茶条规格,其中青锅工序中注重压力控制,轻压杀青后逐步加压做形,控制好压力差,适当延长做形时间,可以形成龙井茶扁平、挺直、光滑、嫩绿油润的良好风格;精制能明显提高外形的美观度,加快冲泡过程中的下沉速度。

In order to solve the problem of slow sinking in tea brewing of some market Longjing teas,the sinking characteristics and physical-related factors in Longjing tea brewing were studied in this research.In addition,we explored the effects of processing technology on the sinking characteristics in tea brewing.The results show the point-in-time that lots of buds and leaves were sinking(sinking time of most buds and leaves)could be used as sinking speed criterion in Longjing tea brewing.Tea width and length-width ratio are important physical factors that influence sinking speed in Longjing tea brewing.Manual making Longjing tea shows good sinking quality in brewing because of its narrow shape,with sinking time of most buds and leaves ranging from 90 to 200 seconds.Machine making Longjing tea shows wider flat shape compared to manual making tea.Machine making Longjing tea,with width at most less than 0.55 cm and length-width ratio range from 4.0-6.0,shows good appearance characteristic of Longjing tea and good sinking quality with sinking time of most buds and leaves less than 260 s.The tea product with width more than 0.6 cm and length-width ratio less than 4.0,exhibits little Longjing tea appearance characteristic and sinks slowly.Fixing technology and fining technology play important roles in the Longjing tea shape characteristics.Pressure control is the key to develop shape characteristics during fixing processing.The fixing processes start by less pressure,and then gradually increasing pressure for flat-shape forming.The increased pressure difference and suitable shaping time should be controlled during fixing processing,which were beneficial to the formation of typical Longjing tea with appearance characteristic of flat,straight,smooth,pale green and glossy.The fining technology obviously improved the appearance of Longjing tea,with sinking faster in Longjing tea brewing.