How Does Different Water Quality Affect Cold Brew Coffee Flavor? What Water Makes the Best Tasting Coffee?

A freshly brewed pot of black coffee consists of a small amount of flavor compounds and mostly water. To make coffee taste delicious, besides water temperature, water quality also plays a crucial role. Experienced coffee enthusiasts should know that different brands of drinking water contain varying components, with differences in hardness and pH levels, which inevitably create distinctions in the taste of brewed coffee.

So one afternoon, FrontStreet Coffee conceived a small experiment, selecting four common bottled drinking waters from the market: Baishuishan Mineral Water, Nongfu Spring Natural Water, Jing Tian Natural Spring Water, and Yibao Purified Water. We made cold brew with the same coffee beans for comparison, hoping to explore how different waters affect the taste of cold brew coffee.

Parameters to Measure and Record

TDS value of each water, cold brew coffee concentration, coffee flavor, and mouthfeel.

Introduction to TDS

TDS (Total Dissolved Solids) indicates the amount of dissolved substances in water, including minerals, salts, metals, or other solids. The main components of these dissolved substances include ions such as calcium, magnesium, potassium, and sodium. These substances in water affect its hardness, and generally, hard water is not suitable for brewing coffee.

Scientific research shows that water containing appropriate amounts of calcium ions can better dissolve the acidity in coffee, but water with high calcium content easily forms scale. Water containing small amounts of magnesium ions can enhance the sweetness and aroma of coffee. Therefore, water containing appropriate amounts of calcium and magnesium ions is ideal for brewing coffee.

The measurement unit for TDS is mg/L, and the concentration unit is ppm. The larger the ppm value, the greater the amount of dissolved substances. For example, when water TDS is 50ppm, it means the total dissolved solid content in water is 50mg/L. At this point, FrontStreet Coffee would like to add that TDS can only detect the content of dissolved solids and cannot specifically identify the exact content of magnesium, calcium, and other trace elements.

Starting the Practical Experiment

For this experiment, FrontStreet Coffee selected Costa Rica Mozart coffee beans. The raisin honey processing method gives it osmanthus floral aroma and high sweetness reminiscent of ripe fruits and preserved fruits, making it very suitable for making iced coffee.

Water Quality Measurement Before Brewing

Baishuishan Mineral Water TDS: 58ppm Nongfu Spring Natural Water TDS: 37ppm Jing Tian Natural Spring Water TDS: 18ppm Yibao Purified Water TDS: 0ppm

Cold Brew Parameters

Coffee powder amount for each sample: 15 grams Grind size: 83% passing through #20 sieve (EK43s setting 9.0) Coffee-to-water ratio: 1:10 Steeping duration: 15 hours (filtered, then refrigerated for 2 hours)

Coffee Concentration Measurement and Tasting

Baishuishan Mineral Water - Cold Brew Concentration: 2.0% Mouthfeel: Berry, black tea, monotonous and heavy flavor, slight powdery texture in the mouth

Nongfu Spring Natural Water - Cold Brew Concentration: 2.15% Mouthfeel: Raisins, tropical fruits, light floral notes, obvious fermented wine aroma, full flavor

Jing Tian Natural Spring Water - Cold Brew Concentration: 1.98% Mouthfeel: Blueberries, dried fruits, slight fermentation, weak sweetness, unremarkable flavor, average aroma

Yibao Purified Water - Cold Brew Concentration: 2.09% Mouthfeel: Bright fruit acidity, sweet oranges, spices, highest clarity, overall uplifting and refreshing

Cold brew has relatively stable extraction conditions, with concentration directly determined by coffee-to-water ratio, grind size, and steeping time. Therefore, under the premise of only changing water quality, even the difference between Jing Tian with the lowest concentration and Nongfu Spring with the highest concentration is not significant.

Since cold brew is conducted in a low-temperature environment, the extraction power of water is relatively weak, typically only extracting small molecular substances such as floral aromas and fruit acids. Coffee is unlikely to develop the bitterness associated with light to medium roasts, so none of the four cups showed obvious negative mouthfeel. The flavor differences in each cup of coffee are due to the varying trace components (calcium and magnesium ions) in the four drinking waters, which affect the extraction amounts of various flavor substances in the coffee.

Based on FrontStreet Coffee's experience in making cold brew and combined with the results of this experiment comparison, if you want your coffee to consistently deliver its flavor profile while maintaining good fermentation characteristics, FrontStreet Coffee recommends using Nongfu Spring with a medium ppm value. If you prefer cold brew coffee with brighter acidity and fresher fruit flavors, why not try using purified water like Yibao to steep your coffee grounds.

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FrontStreet Coffee (FrontStreet Coffee)
No. 10, Bao'an Front Street, Yandun Road, Dongshankou, Yuexiu District, Guangzhou City, Guangdong Province

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Tel:020 38364473