Austin here, R&D Specialist at Uel Zing Coffee Lab. I recently heard a talk by UK Barista Champion, Maxwell Collonna-Dashwood, about how the water you use to brew coffee has an incredibly large effect on the actual flavor of your cup of coffee. He even has a new book on it, Water for Coffee. Turns out, using fancy artisanal and/or filtered waters doesn’t guarantee that you are using the best water to make your coffee. I already tend to be a bit skeptical of those pricey artisan waters from Europe or some tropical Island, and I figured my filtered water at home suited my coffee and me just fine. But after hearing Collonna-Dashwood's talk, I decided set up a little experiment at the Lab to see just how big of a difference water makes! This is the video that got me excited about water. It's 16 minutes but really interesting!
1 control water source for a baseline (Uel Zing triple-filtered Bloomington city water)
3 different water sources (Fiji, San Benedetto, Voss)
~80g of single origin coffee (Kenya AB Hanuguma, 5 days out from roast—by me)
Grinder (Breville Dose Control Pro)
Kettle (Bonavita temp control)
V60 + filters
Record the mineral composition and pH for each water used in the test. According to Collonna-Dashwood, the minerals to pay attention to are Calcium (Ca), Magnesium (Mg), and Bicarbonate (NCO3). This will help to analyze and make sense of the results and to feed future experimenting.
Now it’s time to brew. Start with the control water to get a good base line and dial in the coffee grind size for ideal extraction on the brewing device (a Hario V60). The number one thing here is to keep all variables the same except the water. Keep the dose and the yield consistent. I would even suggest weighing how much water is used to rinse the filter. This will ensure the only difference from cup to cup is the water used to brew. Once you have the coffee dialed in, use the exact same grind and mass for all water trials. Keep track of the tasting notes as you move from one cup to the other. How does the coffee feel? Does it have a transparent and thin consistency, or is it more heavily bodied? How does the coffee taste? Do the acids come out, or is it more muted and dull?
Here are all of the control numbers I used to throughout the lab:
Dose = 15.6g
Grind = 42 (on Breville Dose Control Pro grinder)
Water temperature = 198° F
Water mass = 240g for pour + 50g for rinse (this means the same amount of water passed through each filter)
Brew ratio, coffee mass to water mass = 1:15.38
Uel Zing water (Control)Ca: 28mg/L Mg: 3.9mg/L NOC3: 30 pH: 8
Coffee had balanced honey sweetness with a nutty after taste. It was smooth and pleasant. Not extreme in any direction but it tasted nice. Milky texture. Overall Rank: 2nd
Fiji Water [from the Island of Fiji]Ca: 18mg/L Mg: 15 mg/L NOC3: 152 pH: 7.7
Coffee texture felt similar to the control. The same general flavor profile remained but the sweetness seemed to fade a bit faster than before. Sweet at the front but more nutty on the finish. Overall Rank: 3rd
San Benedetto [Northern Italy]Ca: 50.3mg/L Mg: 30.8 mg/L NOC3: 313 pH: 7.52
Coffee was a lot more heavily bodied than the previous cups. The sweetness is completely gone and the overall taste is dull and bland. The coffee tastes stale with a dry finish. Overall Rank: 4th
Voss [Norway]Ca: 5mg/L Mg: 1mg/L NOC3: 20 pH: 6
This cup had more complexity and acidity. The sweetness was strong and had some hints of spice. The nuttiness was less but the total cup was well rounded. There was a nice bite to it. Overall Rank: 1st
Given your average cup of coffee is 98% water, water is a major factor in the final product. Water is more than an ingredient needed to brew—it is the vehicle for the coffee to the cup. It is the water's job to extract the solubles into the solution that we will enjoy. Clearly, not all waters are the same. Water alone doesn’t extract the necessary solubles for coffee; it is the minerals within the water that are doing the extracting, and if you change the minerals you change the extraction. When thought about on this level it all makes since.
The coffee made with the San Benedetto water had the heaviest mouth feel. This is because it had the heighest levels of the extracting minerals, Calcium and Magnesium. Calcium and Magnesium are “binders” meaning they like to bind to other particles. This is great for extracting coffee. Calcium likes to bind to heavier, creamier particles, while Magnesium likes to bind to acidic particles. Together, these two minerals extract the things we like most in coffee. But why did the coffee taste bland and not amazing? The third mineral we recorded was NCO3, Bicarbonate. This is a buffer. That means its job is to maintain the liquid’s pH as best as it can. To do this it will turn any acidic compounds it comes in contact with into its conjugate partner, or alkaline form. Long story short, it counteracts the work Magnesium did to pull out those good acidic and sweet tastes. The more buffer that is present in your water the harder it is to taste these flavors in the cup.
The best tasting cup, Voss, is interesting too. While it tasted the best out of the tests it had the least amounts of all minerals. This tells us that the binders, magnesium in particular, are very good at doing what they do, and a little can go a long way. Also, Voss had the least buffer and this can explain why it had the most complex and pleasing taste.
Following this experiment I used the Voss water to brew a light roasted Indonesian Java coffee. I wanted to know if the water that extracted a high acidity and sweet coffee like the Kenyan would preform well on a more earthy, sweet, and heavier bodied coffee. The results were drastically different. We preferred the shop water over the Voss in this case. The Voss gave the cup a more sharp metallic start and roasty finish. This could be due to the effectiveness of Voss's extraction because it almost tasted like an over-extracted coffee. The Voss does a really great job at extracting the acids from the coffee but the Java has completely different acids than the Kenyan, and in the Java's case, we don't necessarily want lots of acidity. I think this is where the metallic taste came from. Perhaps we would need a higher concentration of the buffer in order to help round the acidity and bring the earthy flavors to the front. It's a theory worth testing!
- Austin Patterson 12.14.15