Barista Magazine

DEC 2014 - JAN 2015

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And so began a project and collaboration that has taken us to some really exciting places since that fateful day when my coffee tasted so mysteriously bad. We have even had a scientific paper on the subject published. [Editor's note: Maxwell's explorations into water science were the basis of his 2014 U.K. Barista Championship performance, which earned him the national title, and a rank of fifth at the World Barista Championship in Rimini, Italy, in June.] Together, we approached the problem by looking at water chemis - try first, and then at coffee. This was followed by the combination of the two. What do they mean to each other? We discussed current water recommendations and the different reasonings exchanged within the coffee industry. This allowed us to focus on answering the right questions and write off the irrelevant and misleading inquiries. Our first port of call was to look at the varying minerals in water and to discern the impact they may have on the coffee. With the help of a large and obscenely powerful supercomputer, we ran computa - tional calculations to assess the different binding energy that the different minerals would have on different compounds in coffee. It is this aspect of our work that has been published in the American Journal of Agricultural and Food Chemistry. It has long been documented that really soft water isn't able to pull enough flavor out of coffee, and here we were study - ing this process in detail. Binding energy is simply the mineral's likelihood of sticking to other com - pounds and pulling them into the brew. We could quickly eliminate many of the miner - als from our realm of interest as they dis- played low binding energy. In the case of something like sodium, the binding ener - gy result was negligibly different to that of water itself. It would therefore take up numbers (within our TDS reading) without impacting on the extraction (in large quan - tities it will of course start to display itself independently as a taste). This alone is a particularly interesting notion. It's easy to focus on the flavor of the water itself, sur - mising that the flavor of the water plus the flavor of the cof- fee equals the final beverage. This is a misleading and ultimately incorrect way to consider the two ingredients. Water is a solvent and a coffee bean a collection of complex organic compounds. When these two come together, we get a beverage that is unique to their combination, and the flavor of the water itself is lost. Eighty parts of magnesium, for example, is completely wiped out by the intense and comparatively huge amounts of coffee compounds that have en - tered the solution. It's therefore the magnesium (or other minerals) binding energy altering what's being extracted into the drink. This ability is far greater than their inherent flavor. For the test, we picked several common compounds that are tast - ed in coffee, such as citric acid and quinic acid. The computational results showed that on all accounts, magnesium and calcium were the ones to watch. Magnesium displayed a higher overall pulling power than calcium, but calcium still showed significant pulling pow - er in its own right. It was interesting, however, to note that they had slight differenc - es in preference. For example, the results for magnesium suggested that it would extract a slightly higher percentage of the brighter and fruity-tasting acids such as malic and citric, whereas calcium showed a slightly higher preference toward chlorogenic and quinic acid. This would then suggest that coffee made with different ratios of magnesium and calcium, but to the same overall amount (TDS), would result in different tasting cups of coffee. However, there was a curious and substantial question to answer at this point. Most of the water concepts and theories I had heard previously stipulat - ed that a higher TDS would saturate the water and leave no room for coffee extraction. The thing is though, if minerals increase ex - traction, would a high TDS really lower it? After all, a high TDS for coffee-brewing water is still a very dilute solution. From a chemistry and physics point of view, this just doesn't hold up. You would need a TDS reading in excess of 1,000 parts per million to even begin to see this saturation issue. This con - fuses things further, though, as it means a high TDS water should create a full, flavorsome coffee—but it really doesn't. High TDS waters tend to produce dull, flat, and bitter brews with lowered acidity. Conjugate partners: The evil twin. Answering this question is really where our theory on water and coffee turned a corner and a cohesive concept took place. To solve this problem, we needed to look at the role bicar - bonate plays in the process. Bicarbonate is a base (al- kaline) but it also acts as a buffering system for the water. So what's a buffering system? It's pretty damned cool, that's what. Buffering systems in liquids are extremely important to a lot of things in a lot of ways. A good example of a buffering system is human blood, which needs to keep itself between 7.25 and 7.45 on the pH scale in order to keep us alive. It does this by managing the amount of compounds that are acidic and those that are alkaline. Let's take citric acid, for example. This is a weak acid. What this means is that it can easily be turned into a base/alkaline. It is still citric acid, but the proton has been knocked off and now it is something called a conjugate partner. I describe it as the evil twin of citric acid. This is not citric acid's natural state, but it's one that it can inhabit. Most compounds have this dual nature. What does it mean for coffee? Well a lot of what we taste in cof - fee is acidic compounds. And we, of course, really value positive acidity in coffee (not all acids taste typically acidic, nor pleasantly acidic). A high buffer or bicarbonate content then acts as a buffer to try and neutralize the cup of coffee—but we don't want it to be neutralized. It doesn't have the same needs as our blood. In doing so, the buffer makes a lot of the pleasant tasting acids taste dull, flat, bitter and alkaline. Hard waters tend to have a good amount of calcium and magne - sium, but the bicarbonate content also tends to go up disproportion- ately, and a TDS meter doesn't tend to give a reading that is fully informative of the bicarbonate content. For example, you can have a water with a 300ppm TDS reading and a bicarbonate content in excess of that very total. This means that a harder water will actually extract well or even in excess, but that the buffer will undo all of this and reverse a huge chunk of the flavor compounds. It then becomes apparent that a balance between the binding minerals and the bicarbonate is 76 barista magazine

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