We were talking with one of our suppliers about pu-erh tea when he mentioned that he had a few small lots of pu-erh that he bought in the late 1990s. He samples them occasionally to monitor the aging process. He remarked that one of the teas was beginning to turn more astringent, which begs the question: Is aging pu-erh tea similar to wine in that it eventually reaches a point of diminishing returns, and if so, how does one plan for this?
Some wines benefit more from aging than others. Generally reds are better candidates for aging than whites. Most wines reach their aging peak in three to seven years. Fifteen years is usually the maximum except for a few very expensive German Rieslings.
There seems to be a common misconception about pu-erh tea: that, unlike wine, the aging process is always beneficial and the longer the process goes on, the better. Unfortunately, just like some types of wine that age better than others, the same is true for the processed pu-erh tea leaf called mao cha. A number of factors go into determining which leaves benefit from aging. Mao cha can be either green or ripe (cooked), and of a wide range of grades in quality. The end product is divided between loose-leaf or pressed into a variety of shapes like tea cakes or beengchas. Better quality green mao cha pressed into cakes are usually the ideal candidate for a long aging process (up to 30+ years). It is a very rare cooked or ripe pu-erh that merits aging past ten years. Most ripe/cooked tea of average quality leaf is almost always consumed immediately after processing as aging is of little help to the taste. There is considerable controversy over the aging process surrounding ripe/cooked pu-erh.
After picking, pu-erh leaves are turned into mao cha by a short process referred to as “kill green.” The leaves can be artificially aged by a six-month to a year-long fermentation procedure called wo dui or pressed into cakes and stored for natural aging. Some green leaves will remain in loose form but generally the better quality leaves are pressed into cakes and aged in that form.
Virtually all mao cha can benefit from at least a short aging process. In the case of most ripe or cooked teas, this might just be for a few months to even out the adverse effects of the fermentation process. Some pu-erh aficionados feel that cooked pu-erh should not be aged over ten years. Raw green mao cha of good quality are usually pressed into cakes or beengchas and placed into storage for anywhere from five to 40 years before reaching a point of diminishing returns. Quality is judged by growing region, cultivation and leaf grade.
Environmental factors surrounding the tea’s storage will affect how quickly and successfully a tea ages. The tea must be stored away from any strong odors lest they acquire them, sometimes permanently. Air flow regulates the oxygen content surrounding the tea and removes odors from the aging tea. Humidity is a factor; the higher the humidity, the faster the tea will age. However, water accumulating on the tea causes the growth of mold or can dilute the flavor of the tea so is to be avoided. Humidity in the range of 60-85% is optimal for the aging process. Sunlight has an adverse effect on tea, causing it to become bitter and prematurely dries out the leaves. In addition, tea should not be subjected to high heat since undesirable flavors will develop. On the other hand at low temperatures, the aging of pu-erh tea will slow down dramatically. Some believe that tea quality is adversely affected if it is subjected to highly fluctuating temperatures or humidity.
Ultimately, one will have to sample the tea to determine how much a particular cake is benefiting from the aging process. To arrest the aging process, wrap the tea in shrink-wrap or plastic (some say tightly fitting glass is best), store it properly and enjoy drinking it at one’s leisure.