Ever wonder why sometimes there’s a bit of sediment in your tea cup? Or speculate as to what exactly it is?
Since customers evidently prefer that their tea beverages be clear rather than murky, manufacturers of ready-to-drink tea beverages have long looked into tea sediment, which forms simply from the binding of polyphenols to proteins (assuming you’ve filtered out any bits of actual leaf).
A brief foray into research studies shows that this issue can be countered in various ways, including adjusting the amounts of tannins in the tea or calcium in the water, or by using additives.
Sediment can be reduced by limiting how much strictinin is in the tea.
Strictinin is an ellagitannin, with ellagitannins comprising the largest group of tannins. Under the high temps used in making tea beverages, strictinin reacts with water to break down into ellagic acid. Then, when ellagic acid combines with proteins, it forms sediment, according to a study on green tea (Niino et al. 2005).
However, you sort of want that ellagic acid because whether ellagic acid, strictinin, or tannin, they’re polyphenols—those plant compounds that offer a plethora of health benefits!
A recent study measured the amount of ellagitannins in various teas and found that brewing 4 g (0.14 oz) of tea leaves yields enough ellagic acid to be significant.
Urolithins, the gut microbiota metabolites produced in vivo from ellagic acid and ellagitannins, were detected in human urine after dietary tea beverage intake. . . . These results suggest that the daily intake of ellagitannins from tea can have a role in tea health effects. (Yang, X. and F. Tomás-Barberán 2019)
Therefore, although less strictinin would mean less sediment, it would also mean fewer polyphenols.
Another study looked to reduce sediment in green tea concentrates.
One way to do this? Add sugar.
Sucrose and fructose both work, but fructosyl is especially efficient at reducing sediment. Researchers demonstrated that (a) the addition of sugar reduced sediment by some 30–86%, and (b) the composition of the sediment that remained contained fewer polyphenols (a decrease of ~24–50%), less caffeine (a decrease of ~2–6%), and, of course, more sugar (an increase of~21–57%) (Xu et al. 2017).
They concluded that “sugars competitively participated in sediment formation with polyphenols/caffeine” (Xu et al. 2017).
Hmmm, but then the sugar offsets the health benefits of tea, right?
The calcium ion is essential for neuronal and muscle cell function. It also affects sediment in green tea.
Scientists looked at how calcium in water impacted turbidity, organic acid levels, and sediment of green tea infusions. The more calcium, the cloudier the tea as the calcium reacted with organic acids (Xu et al. 2013).
You can readily see this if you brew tea with hard water, water that contains too much calcium and magnesium (and water is a terrific solvent for these alkaline earth metals). Although, conversely, you don’t want water that’s entirely soft either.
All the dissolved solids that are in water—minerals, metals, salts, and so on—will affect your tea infusion, so your target is somewhere in the higher end of “soft” to the lower end of “moderately hard,” according to David Beeman of GC Water, as quoted in an article by R. Kroesen.
As a reference, the USGS classifies water as:
- soft: 0–60 ppm calcium carbonate
- moderately hard: 61–120 ppm
- hard: 121–180 ppm
- very hard: >180 ppm
Beeman believes that the best range for brewing tea is between 17 and 68 ppm (with 150 ppm of total dissolved solids) (Kroesen 2017).
This is why many tea houses and restaurants have filtering systems—and why you often can’t replicate that superior taste of tea in your own home.
Many people like to squeeze a little lemon into their tea, and because Ceylon teas are especially amenable to additives, I experimented with Ceylon OP Nuwara Eliya (available from TeaHaus).
When you add lemon to tea, you immediately see a chemical reaction, demonstrated by a change in color, which can be quite dramatic. But when I squeezed some lemon juice into a cup of brewed Nuwara Eliya, only the color altered; the amount of sediment didn’t budge.
However, when I added fresh lemon juice to Nuwara Eliya loose tea leaves before brewing, there was appreciably less sediment. (I used the same type of filter for all brews.)
On the downside, however, the lemon flavor was overpowering. Good if you want lemon tea, not so great if you want to actually taste the Ceylon itself.
Tea or Spice Particulates
Of course, there are times when you want your tea to be opaque, such as with chai and other spice-heavy blends.
And because matcha is literally powdered green tea, the point is to have a great deal of turbidity!
At the End of the Day
Sediment might be unappealing to some, and I can understand why food companies would prefer crystal clear beverages, but the sediment just naturally occurs with some teas. Really not a big deal.
–Kroesen, R., “A closer look at water for tea,” Fresh Cup Magazine, 1/12/17.
–Niino, H., et al., “Determination of mechanism of flock sediment formation in tea beverages,” J. Agric. Food Chem. 53(10):3995–99. 2005.
–Xu, Y.-Q., et al., “Effect of saccharides on sediment formation in green tea concentrate,” LWT 78:352–60. May 2017.
–Xu, Y.-Q., et al., “The impact of Ca2+ combination with organic acids on green tea infusions,” Food Chemistry 139(1–4):944–48. August 2013.
–Yang, X. and F. A. Tomás-Barberán, “Tea is a significant dietary source of ellagitannins and ellagic acid,” J. Agric. Food Chem. 67(19):5394–404. 2019.
All teas shown are available at TeaHaus.