A new study by researchers at the UC Davis Coffee Center, titled ‘Brew temperature, at fixed brew strength and extraction, has little impact on the sensory profile of drip brew coffee’, was published on 5 October in the prestigious journal Scientific Reports.
The research found that, where brew strength and extraction yield were kept constant, temperature had a negligible impact on the perceptible sensory quality of the brewed coffee within the limited range measured.
“The water temperature definitely affects how quickly the coffee is extracted, but what our research indicates is that what really matters is the final brew strength and final extraction yield at the end of the brew,” saysprincipal investigator behind the paper, Professor William Ristenpart.
“If those metrics are the same in two different brews, it doesn’t matter what brew temperatures were used to achieve them because tasters can’t differentiate them: they taste the same. In other words, it’s the destination that matters, not the route you took to get there.”
Coffees were brewed to specific values of total dissolved solids (TDS) and per cent extraction (PE), spanning the range of the classic Coffee Brewing Control Chart. The study tested three separate brew temperatures of 87°C, 90°C, or 93°C, adjusting the grind size and overall brew time as necessary to achieve the target TDS and PE.
If TDS and PE were the same across two brews where the brewing temperature was different, tasters were unable to differentiate between them.
In contrast to tasters’ inability to distinguish between the three different brewing temperatures, results confirm that both the brew strength and the extraction yield had significant impacts on the sensory qualities of the brew.
Although the concepts of TDS and PE – and their effect on the sensory qualities of brewed coffee – date back to the 1950s, this work provides new insight as to how specific and important sensory attributes vary within brewing conditions.
The results indicate that TDS had the greatest impact on the sensory properties, with PE yielding a lesser, but noticeable, impact.
This research is published as a part of the three-year research project – Towards a deeper understanding of brewing fundamentals – supported by the Specialty Coffee Association’s Coffee Science Foundation and Breville Corporation.
A plain-language version of the work will be included in an upcoming issue of the SCA’s quarterly publication, 25.
View the paper HERE.
