ABx wrote:Did you catch the article in The Art of Tea magazine? Apparently the oolong farmers started a rumor that puerh is dangerous, so they sent a bunch to a lab for testing.
No, I didn't read it. Do you know the results?
While there were some that have potential risks on poorly stored cakes, none of the molds made it into the brew. The age of the tea made no difference, it was about how they were stored. Some bacteria (in general) did, but it was only tested with water at 80C. Boiling water would probably kill most of the rest.
When it comes to the dry cakes, I think you have to keep in mind how relatively little there is and the fact that it would probably be pretty well clung to the cake.
Personally I tend to think that if there were a problem that it would have been discovered in the past 2000 years. It doesn't take much of a pattern for people to pick up on it, especially in modern times.
Anyway, the "white frost" is indeed harmless and some consider it desirable as it theoretically protects the leaves. It can be found on cakes stored in just about any conditions. It's the ones that are deceptively "speed aged" by spraying water on them that you'd want to watch out for, if anything.