[[EDITOR'S NOTE: Our own Geraldo is, despite his modest disclaimers, one of the nation's foremost authorities on pu'er tea. And he is as generous as he is learned: when I wrote asking him to expatiate a bit on the difference between the flavors of these two famous Menghai pu'er recipes, he offered a good bit more -- which, with his express permission, I now share, gentle reader, with you.]]
The Menghai Factory in Yunnan province is, of course, one of the best known and most highly esteemed of all commercial pu'er makers. Their tea cakes, like those of a number of other pu'er tea manufacturers, are routinely designated by numerical codes; while these may seem obscure to the casual onlooker, they actually tell a specific tale about the history and profile of each tea. Each part of the code signifies something specific.
As (comparative) cases in point, let us consider Menghai's famous recipes #7542 and #7532. The first two digits of each number tells us that both of these recipes were first developed in 1975. The final "2" in each signifies Menghai Factory itself. The penultimate digits -- 4 & 3 -- denote leaf grade, which can be a confusing term to the uninitiated; "leaf size" is, I think, more accurate here than "leaf grade." That is to say, in theory there could be a wonderful Grade 8 and an awful Grade 2. But the average size of the leaf in 7542 is a little larger than the size of the leaf in 7532.
Both of these cakes are mass-produced, blended bing chas. Both are inexpensive in their first year of existence, and then quickly increase in value. Because these bing chas are common and inexpensive in their earliest years, non-Asians often disregard the cakes as collectible pu'ers. But they both have proven track records over the years. #7532 is a little more expensive than #7542.
These days, much is made of the virtues of single-mountain pu'er cakes. But I most love the complexity in aged pu'er, and I believe blended leaf contributes to that complexity. I would have to check the actuality of this, but I think most of the famous aged Menghai bings from the seventies and eighties are #7542. These rare, often nicknamed cakes may differ because of the particular environment in which each was stored, and they have different names given by collectors.
Because pu'er cakes are agricultural products, the productions will vary from year to year, based upon all sorts of variables in nature. Moreover, some pu'er enthusiasts believe there has been a slow migration away from the original 1975 flavor -- reflecting a supposed industry change from a 'drink-later' to a 'drink-now' marketing approach, even for sheng pu'er. As a huge understatement, one can suggest that not many people writing in English tasted a #7542 or #7532 bing cha back in 1975. In fact, I do not think many people writing in any language tasted those cakes in 1975. Thus, it would be difficult to ascertain whether there is veracity in the flavor-migration opinion. I do worry, however, that the quality of the water used in pu'er production has changed much for the worse; but this would be true for almost all pu'er, not just for these two Menghai recipes.
Taste is a matter of taste, and here is my idiosyncratic opinion. Properly aged, Menghai #7542 evolves into a woody, spicy pu'er with strength in the lower notes. #7532 might be a tad more pronounced than #7542 in the upper notes. I love them both, but I might love #7532 just a little bit more.