Sunday, November 8, 2009

Oxidizing Herbs like Black or Oolong Tea

This post and its follow-up have inspired a new post on Teacology: Oxidizing Herbs Like Black Tea or Oolong Tea.

I've read a lot about the tea production process in the course of researching tea for writing the material on RateTea. One basic thing that people learn when they start learning about tea is that black tea is oxidized whereas green and white tea is not. Oolong tea is "partially oxidized", placing it somewhere between green and black teas.

One thing that comes out when you start researching teas and herbal teas is that the process of oxidizing leaves before brewing tea is not something limited to the tea plant (Camellia sinensis). A similar process is also used to process Rooibos and Honeybush tea. The process doesn't exactly work the same way (rooibos and honeybush is collected and placed to oxidize in heaps, from what I've read, whereas the tea plant is oxidized in a more controlled environment, indoors).

The New Idea:

I thought...why not try a similar process with herbs? My family and I already grow and dry a variety of herbs for tea, including spearmint, peppermint, lemon balm, sage, orange mint, and wild bergamot/bee-balm/oswego tea, to name a few. We have already experimented extensively with different blends, times of harvesting, and ways of drying.

A couple months ago, I began some trial runs, experimenting with different ways of oxidizing the leaves, using several different kinds of herbs. The processes are similar but can be summarized:

Gather Leaves -> (optional and variable) Let them wither/dry partially --> Crush / Bruise the leaves --> Place them in a cool, moist place and let them sit --> heat to stop the oxidation

I placed the teas on ceramic plates to oxidize, covered by a moist cloth. The leaves generally turn a black color, much like black tea. I heated them in a toaster oven at a low temperature, just above boiling point. I tried varying the time of oxidation, the moisture, and the time and temperature of heating.


The results were mixed...some were definitely better than others, but overall they were surprisingly good. Most of the teas resembled oolongs more than black teas in their level of oxidation, suggesting that perhaps I need more thorough bruising of the leaves or a longer oxidation time. The best result by far, and the one that most resembled black tea was one I obtained by gathering lemon balm, rolling the leaves to bruise them heavily, and then placing them overnight in a cool, moist place.

The flavor of this new tea was complex and hard to describe. Surprisingly, the brewed tea had a more vegetal aroma than tea made from normal dried lemon balm. The aroma also had a few floral tones totally absent from normal lemon balm, and a hint of toastiness. The lemon aroma was diminished slightly but remained fairly strong. The leaf infused more quickly, and brewed a much darker color (but not as dark as black tea).

I look forward in continuing my adventures in oxidized herbal teas. I also had decent results using apple mint and wild bergamot. I'm currently working on some sage and I'm going to see how that comes out and will post updates here! I would encourage others to experiment with oxidizing herbs for tea too!

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