June 9, 2015

Water Quality for Brewing

An espresso shot is basically 98.8 % water. Yes, the extracted coffee is only a very small percentage of the served beverage. Water is the main carrier of the coffee flavours; the exact amount contained in a beverage will vary depending on brewing method used.

Understanding the facts behind water quality in coffee brewing should be the starting point in all coffee service. However, over the last 10 years the industry’s focus has been primarily on barista training, procurement of quality green beans, roasting techniques and brewing equipment science. We have often overlooked the obvious. An espresso shot is basically 98.8 % water. Yes, the extracted coffee is only a very small percentage of the served beverage. Water is the main carrier of the coffee flavours; the exact amount contained in a beverage will vary depending on brewing method used.

Typically a drip filter coffee contains roughly 1.2% flavouring material and 98.8% water. Whereas, a typical espresso will contain on average 1.8 – 2.2% and approx. 98.2% water. When looked at on a macro scale, it’s clear that coffee is a potent flavouring material.

The emphasis on quality water in coffee making is probably more evident in simpler brew methods such as pour-over and filter brews, where you have a slower infusion of coffee and water. These methods, when testing different water qualities on the same coffee, brewed under identical scenarios will vary greatly when water elements like chlorine levels, PH, TDS, and hardness are modified.

Recently I attended the Pentair APAC conference in Thailand and sat in on a seminar with Ben Collins, the Technical Foodservice Manager for Pentair/Everpure – South East Asia. Ben’s presentation covered the numbers of measurement for the correct water quality in the perfect coffee brew. He explained that much of the science so far was around delivering perfect levels of water quality that protected expensive espresso equipment, but some of these modified waters affected the quality of the coffee tastes. In Scott Rao’s The Professional Barista Handbook, he quotes that espresso machine manufacturers routinely recommend water softeners to remove total hardness and so protect espresso equipment, but they don’t say that soft water may ruin your espresso taste. So what is the happy medium between high quality taste and full protection of expensive equipment?

As I explained, today we are spending a lot of time and money sourcing very high quality coffee from around the world, looking at growing conditions, farming practices, storage and handling, even before we start talking roasting science. So focusing on what is the perfect water quality for different brewing methods is vital. World champion baristas now take their own modified water for competitions, and it has been crucial in some winning performances.

Ben explained the different areas as coffee professionals that we should be looking at and how we can get the ultimate taste partner for coffee brewing. The SCAA has a standard for water in barista competitions which is (fig 1).

Water Terminology and Understanding the Jargon

TDS: Total Dissolved Solids.

pH: A measurement of acids and alkalis – water has a pH level of 7 – neutral

Total Hardness: The measurement of dissolved calcium and magnesium in water.

Carbonate Hardness: Refers to only the bicarbonate, and carbonate anions (- charge); it does not measure the sulfates and other anions.

Acid: A solution with a pH reading lower than #7.

Alkaline: A solution with a pH reading higher than #7.

Alkalinity: A solution able to buffer or neutralise acids.

RO: Reverse osmosis.

Parasite removal: Giardia and Cryptosporidium.

Water filters and water treatments

All water can be modified for the perfect coffee delivery by water filtration and treatment methods. In Australia, we have vast differences in water quality from state to state. Water supply authorities in Australia have guidelines that they must deliver for safe drinkable treated water to households. These guidelines, however, allow for large variations in water chemistry, and this is not always perfect for coffee and tea brewing.

There was a recent study carried out in the United Kingdom by the department of Chemistry at the University of Bath. They looked at the ratio of general hardness to its carbonate hardness. The testing showed that the most influential chemicals needed in brew water are magnesium and calcium and the buffer bicarbonate/alkalinity. Calcium and magnesium create binding energy that coffee will stick to in the brewing process. Basically, these minerals stop coffee dissolving in the brewing process. There is a fine line, however, as we know that many filtration systems remove calcium and magnesium from water to protect expensive equipment from the formation of scale, so where do you draw that line so as not to affect the quality of coffee brewing water that needs some of these minerals to enhance coffee taste?

The good thing about technology today and the work that the Pentair scientific and product development department has carried out is the production of filtration and treatment systems that can tick all the boxes to be totally flexible. For example, the user of this equipment can quickly adjust the carbonate levels they want delivered by turning an adjustment key on the filter housing, without changing filters. Water quality can change from the supply source, so with constant testing the filtration systems can be modified to suit those changes, which is crucial in perfect brewing methodology. With the introduction of the Claris Ultra, Pentair is now offering a new standard of water filtration technology providing previously unavailable accuracy for scale and acidity control.

Types of Filters and Treatments

Activated Carbon – is the most used filtration system in coffee making, which often removes chlorine which affects the taste of coffee (dissolves coffee molecules). Chlorine kills organics, and coffee is an organic.

Mechanical Filters – remove sediment such as silt and can also remove parasitic cysts (the filter must carry NSF standard 53 certification to be able to make cyst removal claims).

Water Softeners – used to soften hard water by removing (Ion exchange process) calcium and magnesium levels found in high levels in hard waters.

Reverse Osmosis (RO) – reverse osmosis system is one of the most effective means of removing hardness and TDS from water. These systems can even be used where water quality is very challenging. Straight RO water is likely to be too pure for coffee and tea brewing, because the systems remove high levels of TDS. An RO system suitable for coffee needs to have an adjustable blend valve to allow small levels of filtered water to mix with the pure RO water, to give the user control of the TDS output. Low TDS water can be corrosive and can affect the copper and brass components in espresso equipment.

Understanding how TDS can change the taste of brewed coffee

Many roasters are taking the time needed to test their coffee TDS and the acidity levels of the coffee. This is done with a portable TDS meter. Portable TDS or total dissolved solids meters are a great tool, as they are relatively cheap and can be used to not only test the coffee solution, but the water as well. For all practical purposes, a TDS meter is just a customised conductivity meter that relates the amount of coffee flavouring material based on its conductivity across a solution. For example, a reading of 1,800 ppm in TDS refers to corresponding flavouring material content of 0.18% and 99.82% water on the Brewing Control Chart. *1.8% will correspond to 18,000 ppm. Therefore, if using a TDS meter that has a maximum measurement range of less than 18,000 ppm, the reading can be extrapolated to determine the actual measurement.

In Conclusion

As you can probably tell through this article, water testing and tasting can be quite a challenging project when it comes to tuning in your coffee system. Blending of water seems to be the ideal way to get the best out of taste profiles and also to have the right protection for your precious coffee making equipment. Pentair do know and understand the difficulties of designing the right water system to suit your geographical location and the marriage of the water system to specific brands of coffee equipment. I had many conversations whilst researching this topic with David King from Pentair in Sydney, who has been involved in the technical side of water treatment most of his life. David helped me through the minefield of opinions that I was exposed to whilst trying to make sense of this technical process, staying impartial and not product/brand specific.

The main reason I became passionate about this subject is because I could see a really big gap in the coffee brewing process where most new age coffee businesses are pushing all the other elements of the science but still not quite getting their heads around the suitability of water for their setup. Water is the biggest part of the beverage and needs to be the starting point.

Pentair is a large international business and water is the life blood of everything they do and they are across all water technology in all industries. They have focused heavily of late on the Foodservice side of their business as they have predicted the issues that will arise when the growing population starts to strain this precious life source we know as water.


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