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Water temperature is very closely related to brewing and extraction. It not only affects the degree of extraction, but also affects the quality of extraction. Theoretically, throughout the brewing and extraction process, the temperature of the hot water in contact with the coffee grounds should remain at 91-94°C, the so-called The Best Water Temperature Throughout Extraction.

In daily life, many friends do not use a thermometer when brewing pour-over coffee; they brew a coffee bean with an approximate water temperature, and then, because the taste is different every time, they begin to question whether the coffee beans are stale or simply not good. How big a difference can different water temperatures make to a coffee's flavor performance? In this article, Front Street will talk about the influence of pour-over coffee water temperature on coffee extraction.

This time Front Street used a washed coffee bean from the Front Street Yirgacheffe Gedingding Cooperative for the comparative experiment. The generally recommended water temperature for pour-over coffee is 86-93°C, so this brewing was divided into 5 groups: 80°C, 86°C, 90°C, 93°C and 96°C to brew this coffee bean.
 

Front Street brewing parameters are as follows:
Dripper: Hario V60
Grind size: medium-fine grind (75% pass rate through a 0.85mm aperture sieve)
Dose: 15g
Coffee-to-water ratio: 1:15
Brewing water temperature: 80°C, 86°C, 90°C, 93°C, 96°C

Front Street staged extraction: This time staged brewing is used. First, pour in 30g of water and bloom for 30s; at this point the coffee swells into a “hamburger” shape. In the second stage, pour 125g of water in a small circle at the center. The pouring height is 4cm, and the force is gentle so as to minimize the tumbling of the coffee bed as much as possible; the water flow rate falls at 4g per second. Once the water level drops to 1/2 of the coffee bed, begin the third stage of pouring. This stage is also poured gently in circles from the center outward until 225g is reached, at which point pouring ends. Once all the coffee liquid in the dripper has finished dripping, the extraction ends, at a time of 2'01". After the coffee extraction is complete, gently swirl it, and wait until the coffee liquid is fully uniform before tasting.
 

Through 5 brews at different water temperatures, the results are respectively:
80℃: Slight astringency, lemon peel, obvious tea-like quality, with a tea sweetness as the main note.
86℃: Kumquat acidity, slightly sharp.
90℃: Bright citrus acidity, obvious fruity sweetness.
93℃: Bright citrus acidity, with a black tea note in the finish.
96℃: Fruit tea, with a tea astringency, concentrated flavor.
 

How does water temperature affect coffee extraction?

Data from past street brewing experiments reflect that: the higher the water temperature, the more coffee substances are extracted and the higher the concentration; the lower the water temperature, the fewer coffee substances are extracted and the lower the concentration.  In terms of flavor, with other parameters held constant (for light-roast coffee), the lower the water temperature, the more the extracted coffee tends toward acidity, and the higher the water temperature, the more the extracted coffee tends toward bitterness and sweetness. Coffee is not better the higher its concentration, nor is more extracted coffee substance better, so an appropriate water temperature can avoid over-extraction during brewing, which causes bitterness and astringency in coffee, and can also reduce the situation of under-extraction leading to a weak and thin coffee taste.
 

Why do different water temperatures produce different coffee flavor expressions?

During pour-over brewing, water and coffee undergo some complex chemical reactions, with different reactions occurring at different stages, and water temperature directly affects the extraction rate of different components in the coffee during brewing, extracting the quinic acid, amino acids and tannic acid, caffeine, oils and other substances contained in the coffee. 
 

Two-thirds of a coffee bean is made up of lignocellulose, and the other third consists of soluble aroma molecules, which, upon contact with water, are dissolved out in order according to molecular size. The first small molecules to be dissolved out include acidity and aroma, then the medium molecules of sweetness, and finally the large molecules of burnt bitterness. This is how the different layers of flavor in coffee come about.

Water temperature is the key to accelerating the release of aroma molecules. Too high a temperature will cause the aroma molecules to be released too quickly; when brewing within the same extraction time, the aroma molecules will already have been fully released before extraction is complete, and the remaining extraction time will then release the flavor of the lignocellulose, giving the coffee a woody taste, woody astringency, and so on; if the temperature is too low, the aroma molecules will be released too slowly, and when brewing within the same extraction time, the aroma molecules will not yet have been fully released after extraction is complete, so the resulting coffee will only have a sweet-and-sour sensation, lacking a full-bodied flavor, and will seem thin overall.

So what water temperature is appropriate for everyday brewing?

FrontStreet Coffee recommends a water temperature for pour-over coffee generally between 86 and 93 degrees Celsius. For lighter-roasted coffee beans (such as the washed Yirgacheffe coffee beans just brewed by FrontStreet), use between 90 and 93 degrees Celsius, while for darker-roasted coffee beans (for example FrontStreet's PWN Golden Mandheling coffee beans), use a lower water temperature between 86 and 88 degrees Celsius.

Best Value Everyday Pour-Over Coffee Bean Recommendations: Qianjie Ethiopia Yirgacheffe Gutingding, Qianjie Panama Hacienda La Esmeralda Green Label Geisha Coffee Beans

Espresso Coffee Bean Recommendations: Qianjie Classic Blend, Strawberry Candy Espresso Blend

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Qianjie Coffee store address: No. 315 Donghuadong Road, Yuexiu District, Guangzhou