Black tea extracts are normally produced by a hot or boiling water extraction process, usually a countercurrent process. 红茶的提取物通常是用热水或沸水通过逆流萃取工艺来制取的。
Adesign calculation method has been proposed for the counterflow extraction process of partially miscible ternary systems. 针对部分互溶三元系逆流萃取过程提出了一种设计型精确计算方法。