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Notes on Raw and Cooked Puerh Tea

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Version 0.5
Copyright © 2009 by Zack Smith.
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Some of the cooked Puerh tea:

Click to enlarge.

A chunk of a Puerh cake:

Click to enlarge.

Introduction

This is a page where I'm collecting information about Pu'erh tea, which is reknowned for its health-giving properties. It is a tea that is mostly unheard-of in North America however, which is where I'm based.

At right is a typical fermented Puerh tea. They are always reddish-brown. Raw Puerh tea is usually yellowish. Pu'erh comes from certain parts of the mountanous Yunnan province of China, including Puerh prefecture, Menghai etc.

Puerh often comes in the form of a disc-shaped "cake", which is compressed tea. At right is a chunk of one such cake.

Catechins

Catechins are polyphenols, meaning they have multiple benzene (phenyl) rings. These are connected to a ring that contains an oxygen atom in place of the usual carbon.

Catechins belong to the flavinoid family of compounds and are antioxidants. They are secondary metabolites of plants, meaning that they are present in a plant but their lack will not cause the plant to die.

Catechins have a healthful effect when consumed by humans due to the antioxidant aspect.

You can find catechins in white tea, green tea, Oolong tea, Pu'erh tea and black tea.

Epigallocatechin gallate (EGCG)

Epigallocatechin gallate is, as its name suggests, a catechin. It is found in green and Pu'erh tea but not in black tea.

There is more of it in green ("raw") Pu'erh than in fermented ("cooked") Pu'erh, because fermentation oxidizes the polyphenols. This table shows the difference:

Close-up of the cooked Puerh tea:

Click to enlarge.

Pu'erh cake in the disc shape:

Click to enlarge.

EGCG is known for its anti-cancer property and for lowering blood cholesterol.

It is also believed to reverse developing atherosclerotic plaques but it has no effect on established plaques.

Research sources

EGCG's effect on atherosclerosis:
Differential Effects of Green TeaDerived Catechin on Developing Versus Established Atherosclerosis in Apolipoprotein ENull Mice.

Cholesterol:
Polyphenol contents of Pu-Erh teas and their abilities to inhibit cholesterol biosynthesis in Hep G2 cell line.

Pu'erh sample found to have little catechins:
Survey of Catechins; Gallic Acid; and Methylxanthines in Green; Oolong; Pu-erh; and Black Teas.

Temperature and preparation method greatly affect catechin extraction:
Extractability of tea catechins as a function of manufacture procedure and temperature of infusion.

Catechins and obesity:
A Green Tea Extract High in Catechins Reduces Body Fat and Cardiovascular Risks in Humans.

Unknown results:
Characterization of pu-erh tea using chemical and metabolic profiling approaches.

Microbes

Cooked Pu'erh is fermented, i.e. chemically processed by microbes. Several species of bacteria and fungi are involved but the main one is a fungus called Aspergillus niger. Which species predominate in any given Puerh tea cake seems to depend on the tea source and the tea factory.

Pu'erh is well known for the fact that as it ages, its qualities improve. It is common in China to find Puerh cakes costing the equivalent of hundreds of dollars that are 10, 20 or more years old. This is because the fermentation process continues indefinitely, similar to wine. This occurs whether the Puerh is cooked or raw.

Sources

Some References on Puer and Aspergillus.

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