From the Lab

Tuesday, December 8, 2020

Water Filtration & Extraction Quality

Water may be ubiquitous, but it’s not uniform. Water is filled with naturally occurring minerals and salts that vary from location to location. The mineral content in your water also has a significant effect on coffee extraction and taste. Mineral content has the power to make the difference between a cup that’s dull, earthy and chalky and one that’s rounded, balanced and lively.

Due to this variability, we often turn to water filtration systems to achieve consistency in cupping and calibration. As the Quality Control & Admin support in Australia, I’m constantly communicating with my counterparts in our QC labs that support our wide range of origin and destination operations. I’ve seen firsthand how water filtration and mineral content can affect cupping.

A solid understanding of our local water filtration and mineral contents enables us to stay calibrated across all our labs.  A carefully calibrated and monitored water system enables us to make better buying decisions and more accurately match quality expectations for our customers.

Understanding Water Filtration Systems

While there are a wide range of water filtration systems, the majority focus on controlling and improving the amount and composition of total dissolved solids (TDS) in water. In turn, the mineral content impacts water alkalinity, hardness and pH, which, in turn, impacts extraction and taste.

And this is where water filtration gets complicated, and fascinating! It’s not simply a matter of removing all minerals because dissolved solids actually play a big role in extracting flavor compounds from coffee. Coffee brewed with completely demineralized water tastes unpleasant and flat because demineralized water doesn’t draw out the full range of flavor notes – acidic, fruity, floral, sweet and chocolatey – that we find (and love) in coffee.

Research has found that different minerals are particularly good at drawing out specific kinds of flavor compounds. While there’s no one-size-fits-all perfect water composition, science gives us a pretty good blueprint of which minerals impact which flavor or texture. With this information, we can adjust mineral content to help extract the best cup.

The Main Players

Magnesium (Mg) - Binds to and extracts fruity, acidic and sweet flavor compounds. Magnesium-rich water leads to a sweeter, brighter & stronger cup, with more body to boot. But, since it’s such an effective extractor, too much magnesium often leads to over-extracted, bitter and harsh flavors.   

Calcium (Ca) - Helps emphasize rounder, sweeter and heavier notes. Too much calcium can lead to a chalky, unpleasant mouthfeel. Calcium is also a strong contributor to scaling and mineral build up on machinery.

pH – Measure of acidity. Water that’s too alkaline is too good at extraction and creates an over-extracted and unpleasant cup that’s bitter and tannic. Water that’s too acidic will under-extract flavor, the cup won’t be too bitter or tannic, but it won’t have many other flavors either. Acidic water will also corrode your equipment.

Alkalinity – Measure of the quantity of bicarbonates in water. Bicarbonates help keep pH stable, aiding a balanced extraction.

Hardness – Measure of the quantity of dissolved minerals in water.

There are several industry standards for mineral content. Interestingly, there seems to be a pretty clear consensus on ideal alkalinity range but a much wider range of ideal hardness across standards. This is especially nuanced when you consider that mineral content impacts extraction, alkalinity impacts pH, and pH impacts how effective extraction is.

Improving Sucafina’s Filtration Set Up

As a global company, it’s imperative that our QC labs can easily communicate about cup quality. To complement our work on calibration across our labs, we recently performed a small experiment in our Sydney lab where we evaluated the nuances between our current and previous water filtration systems.

We created an exercise to test how the mineral content in water from both our current and previous water filtration systems impacted cup scores for 5 different coffees. Following SCA protocol, we cupped all 5 coffees using 3 different waters (our previous system, current system and local tap water). To ensure as much objectivity as possible, our team of 3 cuppers did not know which water was which during cupping. 

Water Quality Now and Later

Our experiment gave us a better understanding of how our new water behaved with a range of origins and processing methods. It also enabled us to pinpoint the specific ways in which our water technician can help us further hone our mineral composition to suit our needs.

The field of how mineral content affects coffee extraction and cup quality is growing. I’m very excited to see what coffee and sensory professionals discover in the coming years. Sign up for our newsletter(link) to keep an eye out for new articles and studies about sensory science, origin updates and more. In the meantime, I recommend Water for Coffee: Science Story Manual by Maxwell Colonna-Dashwood & Christopher H. Hendon as an excellent source for coffee professionals interested in learning more about water quality and coffee.

About the Author

Before joining the Sucafina family in November 2019, Celine Nguyen completed a bachelor's degree in food science and agribusiness at the University of Sydney. She published her honor’s thesis on the sensory properties of abalone on alternative diet in a collaborative project with South Australian Research and Development Institute. She has always been interested in sensorial analysis and food chemistry.