Brewing = “Selective solvent extraction process”

Ben BicknellI am so happy I was able to attend the event tonight at Five Senses “a love affair – H2o & Coffee”. Over the last few months I have been lucky enough to do many different styles of cupping, but this one was special. The coffee was the same across the board, a freshly roasted Ethiopian washed Yirgacheffe, but each of the 8 cups used different water… but more about that later. Below I have listed my basic understanding from the event based off of what I can recall and my notes.

For the first portion of the night we were lucky enough to have Ben Bicknell, the Five Senses Strategic Project Manager and World Barista Championship judge, walk us through an informative presentation about the impact that different water can have on the coffee we drink.

The conversation started questioning the status quo, with the realisation that while in most cafes we have some level of filtration, the potential benefit or harm is likely quite accidental. This lack of understanding is most obvious when we travel to different areas and notice significant differences in the brew even if the recipe, equipment, person making the coffee and the coffee all remain a constant.

“Though if it really is that important, what is the right solution? More filters, or getting the water straight from the tap?”

slide1-01While it has often been described as “an ingredient”, water is actually better described as a solvent, and thus brewing coffee is actually  a “selective solvent extraction process”. It is selective because depending on what is in the solvent, it will react with and pull out different elements from the coffee.

We already change the solvent (water) in different ways to get what we want from the coffee, and leave what we don’t, by changing the temperature.  Sometimes when the solvent is too efficient (when it is too hot) it over extracts the coffee, and sometimes it is not efficient enough (when it is too cold).

There are other ways of effecting the solvent by adding something like alcohol, which enhances the extraction of certain elements, or soap (though not recommended for coffee) in the extraction of oils.

So, what is in our water already?

Most people in the coffee industry should already be aware of what total dissolved solids (TDS) are, though in this case the “major players” are:

  • Metal cations like calcium or magnesium
  • Acidity
  • Alkalinity like carbonate buffering

Calcium and magnesium

  • Depending on the region the quality and compounds in water will be effected. For example, in some areas limestone aquifers will result in more calcium leeching into the water as limestone is composed mostly of calcium carbonate (CaCO3). This can cause things like soap lathering more poorly.
  • Calcium and magnesium exist as positively charged ions and so are well suited to drawing out the negatively charged flavour particles (where positive attracts negative).
  • While the attraction of flavour particles will increase to some point thanks to the increased solubility, if you add too much, as there are only a certain amount of charged ion slots, there is a point where it can no longer draw any more (and will start to flat line).

Acids and Bases

  • In this case acids are seen as sour (lemony + vinegary) but they are positively charged (with a pH<7). N.B. There is a difference between the acidity and the perceived acidity
  • By comparison bases are bitter but are negatively charged (with a pH>7)
  • When mixed, the acid and base balance and neutralise each other.

Buffers

Water Quality - BuffersIf you go half way to neutralising the acid and base, you get a buffer. Buffers will neutralise whatever is then added to prevent change. The most important buffer in drinking water is bicarbonate.

If you look at the wave as the peak of the acid (high) and the base (low), the buffer is the point where that wave in normalised. As the acid and base are effectively cut off, the resulting perception of flavours is muted.

Designer Water

So…. what is the solution? Should we now have to bring our own water if we expect to be able to replicate the same flavours/extraction in different locations? It is not practical. So what can we do?

Step 1: start with mains water…
Step 2: filter it (but by which method?)

Filtering Methods

  • Reverse osmosis is a water purification technology that uses a semipermeable membrane to remove larger particles from drinking water. The result is a TDS as close to 0 as you can get, however at 0, with out the particles to attract the flavour particles, the extraction will be quite different.
  • With remineralisation, where you reintroduce some of the compounds/minerals back to the water, you can add a buffer. This is often done more so to protect the machinery than anything else, but the result will also be a better soluble solution.
  • You could also use carbon filters to modify the water or water softeners with different reactions from each.

Final Conclusions

Given the relatively small amount water used by an espresso machine, and the difficulty in modifying the water that is used by the machines, this sort of conceptual altering of the water is more likely to effect filter coffee, as it is easier to modify the water in this method.

That said, recommendations for future standardised water at competitions might be required to ensure that the extraction of coffee is able to be replicated by competitors in areas where the makeup of water otherwise impacts on the results.

So… what would you add if you could?

And then the fun began

At this point, we grabbed a cup, a spoon and set to slurping our way through 8 different samples of coffee made with spiked water. And here is what I noted down. What would you expect the result to be? Click to find out what I experienced.

For me this sample seemed to have a high level of acidity and high level of florals

I found it bland. Very low acidity.

It seemed to have a medium acidity, more balance and better sweetness

Um… is this coffee? Tastes like…. chewy.. chalky water. Tastes of the absence of coffee.

This one had a nice level of sweetness and a good balance

Hmmm… chewy. Not as dead as 4, but quite muted.

??? Um… this is strange. It is not bad. Has a high level of acidity and a strange spicy floral to it.

This one is my favourite. The balance of sweet juicy notes with medium acidity is quite nice. Hard to believe it is the same coffee.

All of my comments were made before the reveal (it was a blind tasting) and as an experience it was rally enlightening. Doesn’t mean I am going to go out and start adding calcium, magnesium or bicarbonate to my water before I brew coffee, but it fantastic to have been able to compare and contrast them.

Thanks again to Five Senses for a fantastic night.

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