Does total dissolved solids determine sour/bitter balance in espresso?

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#1: Post by iploya »

Can total dissolved solids (TDS) solely determine the sour/bitter balance in espresso?

TDS quantifies the amount of coffee extracted from the bean and dissolved into the water, right? And the sour/bitter balance is all about the factors (temperature, time, etc.) that affect how much coffee is extracted while pulling the espresso shot, right?

(I realize as I write this that there is the problem of uneven extraction (channeling, non-uniform particle distribution, etc.) that can cause some particles to extract too much (bitter) and other particles to under-extract (sour) so I guess my question should include the assumption of uniform distribution.)

Thanks. Random questions that occurred to me while making coffee this morning.

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#2: Post by russel »

russel at anacidicandbitterbeverage dot com

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iploya (original poster)
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#3: Post by iploya (original poster) »

Haha, OK. Let me try clarifying the question.

1) TDS quantifies the amount of coffee (solids) extracted from the bean. (Correct?)
2) The amount of coffee (solids) extracted from the bean determines where the espresso is on the sour-bitter spectrum. Increasing the amount of coffee extracted from the bean moves the espresso further along the sour-bitter spectrum.
--> Therefore, assuming an even extraction, the TDS should determine sour/bitter balance.

(Note, this is not to suggest you can tell solely by the value of the TDS whether the espresso is sour or bitter, just that the TDS determines, i.e., is directly related to.

Is this still not correct?? What am I missing?

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#4: Post by Nunas »

iploya wrote:Can total dissolved solids (TDS) solely determine the sour/bitter balance in espresso? <snip>
It's nowhere near that simple. I created a table to remind me what to do the 70+ year old brain is getting forgetful :lol: . Perhaps you already know this :wink:

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#5: Post by iploya (original poster) »

Thanks, so this table correlates parameters like grind size, brew time, and brew temperature. Each of these affects extraction from the bean, correct? For example, assuming all other variables held constant:
- the longer you brew the more coffee will extract
- the hotter you brew the more coffee will extract
- the finer you grind, the more coffee will extract
- and so forth. Right?

I guess my question also includes the unstated assumption of for a given coffee dose. If you increase any of the above (longer, hotter, finer), the more coffee you will extract from that dose, the more solids will dissolve in total, and the further along the sour-bitter spectrum your espresso will move (the sour stuff extracts first, followed by the bitter stuff).

The chart has a lot of info so if there's something else I am missing please let me know.


#6: Post by GDM528 »

I found this page in the How-Tos section of HB to be pretty handy, and sorta relates to navigating the final extraction:
/espresso-g ... tions.html


#7: Post by iyayy »

maybe yes and no?
if dissolving solids alone,
maybe 96c shot at 20s will have same tds as 88c shot at 30s, provided everything else is kept same?
maybe by theory yes, and by theory both should taste same...

but i have high doubt it would taste the same in reality.
its just like dialing in grinder to similar tds would still give different taste.

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#8: Post by mrgnomer »

There's also how the TDS is diluted. At high concentrations I believe our ability to taste character notes is distorted. I think of it like barrel concentration single malt Scotch. Have it straight and you could miss a lot of what's in there. Stretch the concentration by diluting it with a bit of water and the flavour notes become more apparent. You could pull a lot of solids out of a roast in a concentrated TDS shot and not be able to distinguish the character in there because the shot is overwhelming to the palate. Letting the shot go longer might not be the way to dilute it since solids continue to be extracted changing the flavour profile. Maybe dilute with some water to stretch out the flavors. I think I will try that today.
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#9: Post by Jeff »


"TDS" as measured with a refractometer is the refractive index of the sample, run through a formula, that gives a reasonable approximation of the total dissolved solids in the cup. It is a rough measure of the "strength" of the coffee. It does not say anything about how effectively the coffee was extracted. Those solids may be "tasty", "un-tasty", and usually a combination of both.

Extraction Yield (EY) is often estimated from TDS in the cup and knowledge of the dose, yield, and extraction technique. It can also be measured by trying the puck (or filter and grinds) and weighing what remains. It measures how effectively the coffee was extracted.

Neither determine taste.

TDS can be a good batch-to-batch or shot-to-shot control tool. EY can be a good tool to determine if your gear or technique have impacted your ability to extract what the coffee has to offer. Higher EY is sought after as it expands the range you can explore. The tastiest point may not be the highest EY, especially for coffees and roasting that are not high quality and free of defects.

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#10: Post by iploya (original poster) »

Thanks for entertaining the question everyone. I think this sheds some light on it for me. The way my brain works I am always searching for a way to reduce complex or abstract stuff to something simpler or more formulaic, even though that is not always possible.

Another point that occurred to me (which is probably just a different way to express some of the above points) is that the different compounds probably extract at different rates depending on how you reach a particular TDS. For example, suppose I experiment to find two grind settings, where the first grind setting at 200F produces the same TDS as the second grind setting at 195F. I imagine those two "recipes" would extract the various compounds in different ratios (and hence, taste different) even though the total dissolved solids is the same numerically.