How important is oxygen in Pu-erh's conversion?

We are all aware of the fact that the older a Pu-erh is, the better the quality. There are currently two options to acquire a well aged Pu-erh:

1. Buy it from a vendor, which is often expensive
2. Purchase young and store to age

The storage conditions are however crucial, they can make or break a tea. There are abundant theories out there speculating on the ideal conditions for a Pu-erh to age and convert: humidity, temperature and oxygen levels etc. There is however not so black and white when it comes to apply them in real life.

There has been an interesting article published recently about a an interesting experiment.

Method (www.puercn.com, Author: Yang Zhong Yue)

Four samples were created in 2013 using the same product, a fresh Jingmai (景迈) Gushu Pu-erh Maocha:

  • One vacuum sealed
  • One sealed, buy not vacuumed
  • One sealed, buy injected oxygen on a regular base
  • One natural open storage

All four samples were stored in a storage with a humidity machine for 4 years – the machine starts extracting extra humidity after it has exceeded 70%.

Results

  • The vacuum sealed Pu-erh sample: The colour has converted nicely into golden red, aroma strong in both dry leaf and tea brew. The downside is that it is very bitter, the most bitter one of the four samples.
  • The sealed but not vacuumed sample: good colour – golden red; Good aroma, but slightly less than the vacuum sealed sample; Significant reduction in bitterness and astringency.
  • Oxygen injected sample: Colour gold, less red than the previous two; Aroma OK, but not as strong as previous two. Bitterness and astringency reduced, more than the vacuumed one, but similar to the non-oxygen injected one.
  • Natural open stored sample: Colour gold, similar to the oxygen injected one; Very little aroma remained; There is some reduction in bitterness and astringency, but not as much as the sealed non-vacuumed one.

Summary

  1. Vacuuming is good to keep the Pu-erh teas in their original state, eg sample keeping, but not for consumption purpose ageing.
  2. Oxygen did not appear to have significant impact on the Pu-erh tea’s conversion, illustrated by the results of the oxygen injection and the natural open storage sample.
  3. There has been an active and ongoing internal conversions regulated by the internal enzymes of the tea leaves under the sealed conditions, result in rather satisfactory reduction of bitterness and astringency and colour conversion, without losing the aroma as the open stored sample. 
  4. The author acknowledged that this comparison was only conducted 4 years after the storage, longer term differences of the storage impacts on the Pu-erh teas are yet to be studied. 

Last modified onSunday, 13 January 2019 22:50
En Jie Rudd

The founder and owner of Valley Green Tea

I grew up in the Fu-Jian Province – the tea country of China. Tea drinking has been part of our daily life for as long as I can remember.

While I was working as a public health researcher a few years ago, I read many research reports conducted over the last 30 years about the health benefits of green tea in fighting certain life style related challenges such as cancer, obesity, cardio-vascular and inflammatory diseases etc.

From my research, I realised there is a significant gap between what people consume (i.e. commercial tea bags) for assumed health benefits and the actual benefits that have been enjoyed by the Chinese for a long history from the premium loose leaf teas.

As well as being potentially beneficial to health, the premium loose teas (green tea being the biggest group) are most enjoyable beverages with a fascinating history, colourful culture and holistically dynamic in every aspect.

It is my passion to share, not only the products, but also the whole culture dynamics around the premium teas with the tea enthusiasts, here in Australia and around the world.

Valley Green Tea currently supplis a diverse range of premium loose teas to the tea drinking community that suit all tastes and all cultures and to pass on a deep understanding of the history and benefits of this wonder beverage.

Website: https://www.valleygreentea.com.au
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