<P> Certain processes during normal production might help to decrease the caffeine content directly, or simply lower the rate at which it is released throughout each infusion . Several instances in China where this is evident is in many cooked pu - erh teas, as well as more heavily fired Wuyi Mountain oolongs; commonly referred to as' zhonghuo' (mid-fired) or' zuhuo' (high - fired). </P> <P> A generally accepted statistic is that a cup of normal black (or red) tea contains 40--50 mg of caffeine, roughly half the content of a cup of coffee . </P> <P> Although a common technique of discarding a short (30 - to 60 - second) steep is believed to much reduce caffeine content of a subsequent brew at the cost of some loss of flavor, research suggests that a five - minute steep yields up to 70% of the caffeine, and a second steep has one - third the caffeine of the first (about 23% of the total caffeine in the leaves). </P>

What is the swiss water method of decaffeination