TLDR
Changing the water temperature when making drip coffee does not really change how it tastes, as long as the strength and amount of coffee extracted stay the same.
Summary
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1 Study Aim
The study set out to determine whether the temperature of the water used to brew drip coffee, when brew strength (total dissolved solids, TDS) and extraction yield (percent extraction, PE) are held constant, has a significant effect on the coffee's sensory qualities. The authors wanted to clarify if commonly recommended brewing temperatures are truly necessary for achieving the best flavor, or if other factors are more important. The researchers wanted to see if water temperature really changes the taste of drip coffee when other factors are kept the same.
2 Study Design
The researchers brewed coffee using a commercial drip machine at three different water temperatures: 87°C, 90°C, and 93°C. For each temperature, they adjusted grind size and brew time to achieve nine combinations of brew strength (TDS) and extraction yield (PE), covering the range of the Coffee Brewing Control Chart. This resulted in 27 unique coffee samples. A panel of 12 trained tasters evaluated each sample in triplicate, rating 31 sensory attributes (like bitterness, sourness, and aroma) using a standardized scale. All samples were served at the same drinking temperature to avoid bias from serving temperature differences. The team brewed coffee at three temperatures and had trained tasters rate the flavor, keeping coffee strength and extraction the same each time.
3 Findings
The study reveals that brew temperature, within the tested range (87–93°C), had almost no effect on the sensory profile of drip coffee when brew strength (TDS) and extraction yield (PE) were kept constant. Only one out of 31 sensory attributes (nutty flavor) showed a minor difference with temperature, and this difference was very small. In contrast, both TDS and PE had significant impacts on many sensory attributes, such as bitterness, sourness, and mouthfeel. The authors suggest that industry standards focusing on strict brew temperature requirements may not be justified, and that adjusting TDS and PE is more important for controlling coffee flavor. Lower brew temperatures could also improve safety and reduce energy use without sacrificing taste. The results show that water temperature does not change the taste of drip coffee much, but the amount of coffee dissolved and extracted does.