The Impact of Water Variables on Coffee Flavour: Why Water Hardness Matters
Baristas use key variables such as grind size, water temperature, coffee-to-water ratio, and extraction time to modulate the flavour of the coffee in the cup. The barista begins by identifying the coffee’s flavour potential, informed either by their own knowledge or descriptions from the coffee roaster. Once a brewing method is chosen, the barista makes adjustments to optimise sweetness, acidity, aromatics, and body. After tasting the coffee, further refinements may be made to address over-extraction (leading to bitterness) or under-extraction (leading to acidity).
Several key variables influence the final coffee brew:
Water quality affects the sensory result, with the hardness and mineral content directly impacting flavour and crema in espresso.
Water quantity and ratio play a crucial role in extracting the right balance of compounds. Stronger coffee is often a result of a higher coffee-to-water ratio.
Water temperature affects extraction efficiency, with higher temperatures increasing the extraction of less polar, bitter compounds, and lower temperatures leaving sweetness and acidity unaffected.
Extraction pressure, particularly in espresso, determines the crema formation, while grind size and the coffee bed shape affect flow rate and extraction consistency.
Finally, the barista’s skill in managing these variables can create a cup of coffee that is balanced and optimised, whether for espresso, filter, or immersion brewing methods.
When we think about brewing the perfect cup of coffee, we often focus on the quality of the beans, the grind size, and brewing method. However, there’s an often-overlooked element that plays a crucial role in shaping the flavour of your coffee: water. As it makes up around 98% of your cup, the quality of the water used can dramatically affect the final taste, aroma, and texture of your brew.
One of the most important factors when it comes to water quality is hardness. Let’s explore how the hardness of water impacts your coffee and why it’s essential to understand its role in the brewing process.
What Is Water Hardness?
Water hardness refers to the mineral content of the water, specifically the concentration of calcium and magnesium ions. Hard water has high mineral content, while soft water has low mineral content. The hardness of your water is typically measured in parts per million (ppm) or milligrams per litre (mg/L), and it can directly influence the flavour of your coffee by affecting the extraction process.
How Water Hardness Affects Coffee Flavour
The minerals present in hard water, especially calcium and magnesium, interact with the coffee grounds during brewing. These minerals can influence how easily flavour compounds are extracted from the coffee beans, leading to a range of effects on your final cup:
Flavour Clarity and Balance
Softer water, with lower levels of calcium and magnesium, allows for a cleaner, more balanced cup. The lower mineral content enables the coffee’s natural acidity and sweetness to shine through, highlighting delicate flavours. In contrast, hard water can overwhelm these finer notes, often resulting in a flat or muted taste.Enhanced Body and Mouthfeel
Hard water tends to extract more compounds from the coffee beans, which can enhance the body and mouthfeel of your brew. However, this comes at a cost: the additional extraction can bring out bitter and astringent flavours associated with over-extraction. A delicate balance needs to be struck, as too much hardness can lead to an unpleasant, harsh aftertaste.Crema Formation in Espresso
In espresso, water hardness also affects the formation of crema, the foamy layer on top of the shot. Studies have shown that water with high hardness levels can lead to a destabilised crema, reducing the sensory experience. This is due to the way minerals interact with the proteins and polysaccharides responsible for crema formation.
The Role of Calcium and Magnesium in Extraction
Calcium and magnesium, the key players in water hardness, don’t just influence the flavour of your coffee—they play a direct role in the extraction process.
Calcium helps to extract certain flavour compounds more effectively, but it can also bring out bitter and astringent notes if overdone.
Magnesium, on the other hand, tends to enhance the extraction of fruity and acidic compounds, often associated with brighter and more vibrant coffees.
For baristas and coffee enthusiasts, understanding the balance between these minerals is key to fine-tuning extraction and ensuring that the resulting cup reflects the best qualities of the coffee beans.
Optimising Water Hardness for Coffee Brewing
To brew the best possible coffee, it’s important to manage the hardness of your water. Ideally, water should have a balanced mineral content—not too hard, but not completely soft either. The Specialty Coffee Association (SCA) recommends a water hardness level of around 50-175 ppm for optimal coffee extraction.
In practical terms, this means:
If you’re using hard water, consider investing in a water filter or a water softener to reduce mineral content.
For those using water that’s too soft, adding a small amount of filtered, mineral-rich water can help to improve extraction and bring out a fuller body and more balanced flavour.
Conclusion
Water is more than just the medium through which coffee is brewed—it’s a critical ingredient that can enhance or diminish the flavour and texture of your coffee. Understanding the impact of water hardness, in particular, can help you achieve more consistent and enjoyable brews, whether you’re preparing espresso, pour-over, or French press.
By optimising your water quality, you’ll not only taste the nuanced differences in your coffee but also appreciate the delicate balance of flavours that each cup can offer. So next time you brew a cup, consider the role your water is playing in the experience and experiment with the hardness to unlock your coffee’s full potential.
