2014-02-19

Soft Water vs. Ristretto?

Theory of the day:

I. Malaysian water is too soft (pure)... lacking in metal+ ions.

II. This allows more protons (H+ ions, responsible for the sour taste) to dissolve, causing our coffees to err on the side of sour.

III. Pulling ristrettos (restricted flow rate) espressos helps to fix this problem by increasing the ratio of oils to water in the cup, thereby inhibiting the extraction of acids into the coffee. (The downside of course, is a higher waste of coffee, since you have to throw away more of the water-soluble good stuff, along with the extra acid.)

(My working knowledge of chemistry is quite rusty these days, and there's something here about electropositivity that I'm missing - but I'm close to the ballpark of standard theory on this, though not quite there, I guess...)

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1. So we got a $75 TDS meter today and confirmed that our water is around 50-65 ppm. This is below the 150 ppm target, and outside the 75-250 ppm acceptable range that is suggested by the SCAA.

2. Recently we've also noticed that longer extraction times benefit the flavour complexity of our espressos (using any methods to reduce flow rate, while keeping dose (g), yield (g), water temperature, and pressure curves, the same).

SO, hypothesis: I'm wondering if (1.) is part of the reason for (2.), since at any point during the extraction period, the water in the basket has already been hardened by the coffee that was dissolved earlier...

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Physically the closest way to model a smell is as a wave... like sound... but that's not standard theory SIC yet. Lol

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It's well documented that coffee made from very pure water tends to be more sour. This could be due to the higher solubility of H+, given a lesser amount of competing metal+ in the water to begin with.

(Moreover with regard to (2.), this would totally make sense that pulling ristrettos, where the oil:water ratio is higher than in normales, increases the pH of an inherently acidic espresso - if there's less water in espresso "very sour," becomes "not so sour," because sourness comes from stuff that only dissolves in water.)

It's important for us to be familiar with the hardware (well, wetware) of tongue taste receptors. Also to note that the 4/5/6/whatever taste model is just a model, and there are a lot of phenomena that are excluded by it. Good introduction here.

http://en.wikipedia.org/wiki/Taste#Further_sensations

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NAH GOT JOURNAL ARTICLE. lol

Na+ in solution with acids reduces the human perception of sourness. (Typically in harder (less pure) water, Ca+ and Mg+ are common... but are easily swapped out of solution by Na+ (because Na is the "more reactive metal")... have to check the math later, but this suggests that harder water inhibits our sour sense system, regardless of whatever else its doing to the solubility of H+.)

http://www.ncbi.nlm.nih.gov/m/pubmed/19490344/

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I guess one day, when we finally run out of toys, we could always attach a handle to the bypass valve on one of the espresso machine's pumps... and get a "manual pressure paddle" setup for free.

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