Pu-erh white frost vs mould

I was again approached by a customer today to say there was some ‘mould’ discovered on an aged Pu-erh tea cake received, which is actually the 'white frost'. I thought it is time to write a clarification. 

What is the white frost

A ‘white frost’ can develop on the surface of a cake (especially the ripened cakes) that not only a naive tea drinker, even some experienced tea drinkers can confuse it with mould, which could also develop over time if a tea is not stored probably.

The ‘white frost’ is the crystal product of the interaction between the natural probiotics of a Pu-erh tea and certain Pu-erh tea compounds. They are beneficial to health including being anti-inflammatory, anti-bacterial and enhances the gut balance. The mould on the other hand is harmful and should be avoided. 

The differences between the white frost and mould

Following are the differences between the two. 

• The appearance: the white frost is dry, crystal and flat on the leaves; A mould is sticky, fluffy, sometimes in various colours and grows above the surface.
• The taste: The Pu-erh tea with the white frost tastes like a normal Pu-erh, aromatic and clean, in the flavor of woody/earthy or date depending on the variety; A mouldy Pu-erh tastes mouldy, sour and unpleasant with a foul smell. 

How to avoid mould growing on a Pu-erh tea

Store Pu-erh tea under the condition of temperature 20-30^oC and humidity less than 75%, well ventilated space (eg home office).

Nei-Fei (内飞) paper

Most of the Pu-erh tea cakes and tea brick or Tuo Cha also have a traditional Nei-Fei, a piece of paper compressed on the surface of a cake/Tuo Cha/brick to provide information about the cake/Tuo Cha/brick in the case of outer wrapping paper is displaced and no longer associated with the tea. When a cake is broken up, some residuals of the Nei Fei on the tea leaves sometimes can be mistakenly thought to be mould. Careful inspection will differentiate the two as paper is dry and will strip off easily once the tea is in contact with hot water. The mould on the other hand will stick on and being marshy.