How to Control Water Temperature in Pour-Over Coffee? Does a 1°C Difference Really Matter?

Introduction

Water temperature is one of the four essential elements of coffee brewing, playing a crucial role in determining the flavor profile of a cup of coffee. So how do we determine the appropriate water temperature for brewing?

Water Temperature

We generally recommend brewing pour-over coffee with water temperatures between 86-93°C. Specifically, we suggest using 90-93°C for light to medium roast coffees and 86-89°C for medium to dark roast coffees. How was this temperature range determined?

First, let's discuss water extraction efficiency. When water temperature is higher, coffee extraction efficiency increases, making it easier to extract compounds from coffee beans, resulting in higher coffee concentration. However, this also makes it easier to extract undesirable flavor compounds, leading to over-extraction. Conversely, lower water temperature reduces extraction efficiency, making it more difficult to extract compounds from coffee beans, resulting in lower coffee concentration, but potentially causing under-extraction. Therefore, we know that both room temperature water and boiling water are unsuitable for brewing coffee.

Secondly, thanks to coffee associations like SCAA and SCAE that establish data-driven scientific standards, along with technological advancements, we can easily build upon this established knowledge. The extraction efficiency of water temperatures between 86-93°C easily achieves extraction rates between 18-22%. Through multiple tests, FrontStreet Coffee has found that controlling water temperature at 90-91°C consistently yields optimal flavor when brewing most light to medium roast coffees.

Does a 1°C Difference in Water Temperature Matter?

A 1°C difference in water temperature certainly has an impact, but is this impact significant? FrontStreet Coffee conducted a comparative experiment using 89°C, 90°C, and 91°C to brew Yirgacheffe coffee (recommended temperature: 90°C), keeping all other parameters as consistent as possible. The results showed differences, but they were not very obvious and would be difficult to distinguish without side-by-side comparison. The measured coffee concentrations were 1.26%, 1.27%, and 1.30% respectively.

Of course, a 1°C difference in water temperature within the kettle doesn't have a major impact on pour-over coffee, but this doesn't vindicate a "close enough" approach (as the "butterfly effect" suggests, small differences can lead to different outcomes). This is because many factors affect water temperature, and the effective temperature that participates in coffee extraction is the temperature within the filter cup, not necessarily the temperature inside the kettle. This raises an important point: if we want to determine the precise water temperature, we should measure the temperature when it contacts the coffee grounds in the filter cup. However, since the temperature in the filter cup is difficult to determine, we can only use the kettle temperature as a reference.

Other Factors Affecting Water Temperature

If we rely solely on kettle temperature as the basis for water temperature, there are indeed too many uncertain factors.

1. Kettle insulation properties. It's important to understand that coffee brewing is an extraction process, and kettles made of different materials have different insulation properties. For example, copper kettles retain heat better than stainless steel kettles. When starting brewing at 90°C, the water temperature in a copper kettle drops to 86.4°C after 1 minute and 30 seconds, while the water temperature in a stainless steel kettle drops to 83.6°C after the same time. The amount of water in the kettle also affects its cooling rate.

2. Pour height. FrontStreet Coffee conducted an experiment in a previous session showing why high-pour brewing results in lower concentration compared to low-pour brewing. A significant reason is that when the water column enters the filter cup, the larger surface area exposed to air causes faster cooling.

3. Filter cup insulation properties. The actual coffee extraction temperature is certainly lower than the kettle temperature. For example, when brewing with a ceramic filter cup, the maximum temperature during extraction reaches 87.7°C (with initial kettle temperature of 91°C). If the ceramic filter cup is not preheated, the extraction temperature will be even lower (measured maximum temperature of 86.9°C).

Water temperature is a very important parameter, but when we refer to water temperature, we're not just talking about the initial kettle temperature. The temperature changes after the water leaves the spout also deserve careful consideration, as the true water temperature is essentially the temperature during coffee extraction.

Important Notice :

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