Bitter Taste?

[hooksie]

For herbal tea takes only 6–7 minutes using freshly boiled water.

Herbals tend to be much more forgiving in my experience.

For example, I steep my Rooibos for 10 minutes minimum.


And welcome Xerxes.

[Intuit]

That was a thumbnail sketch of tea chemistry.

An important determinant of raw leaf chemistry is controlled by the genes actively expressed in each cultivar. That's what distinguishes thousands of varieties from one another. This variable gene expression is called 'epigenetic regulation', an adapative response to environmental (growing, climate, soils/nutrients, pathogens and root microbial community) conditions of the parent strain(s).

It takes a few generations of plants to stabilize gene expression.

Sal noted:

" For some reason, subsequent infusions start the clock over again! "

The reason is this: the bruised leaf oils accumulate at the break surface. The more porous the leaf through processing, the deeper the water penetrates.

Thats why Eastern technique controls elution, beause the leaves are either not as broken, or they are tightly rolled in between oxidation steps, in China oolong and black teas. This extends the duration of extraction by several solvent volumes (steep number) and controls water creep into the depths of the leaf.

So you have layers of flavor combinations 'dissolving', one after the other, and each steep also has its own character because each chemical species has a different solubility in hot water.

Change the steep time, duration in steeps, and you can fiddle with the characteristic flavors extracted with each subsequent volume of water used.

That's what makes Eastern tea brewing very interesting and it's why you'll see tea lovers comparing elution sequence details against the perceived taste and odor eluted.

When leaves are rolled in-between oxidation steps, (I'm fairly certain that) it not only re-tightens the rolled form and controls heat penetration that catalyzes secondary reactions, it also controls the degree of oxidation within the rolled leaf layers. The way tea is rolled also determines it's unfurling rate in water and that controls the rate of water ingress/egress in the leaf and subsequent release of flavors and odors.

There is a wonderful Swiss Institute dedicated to tea quality control - those chemists surely could elaborate, expand and correct this explanation of the physico-chemistry of tea processing and brewing.

[sheila77551]

Great info, thanks!