Barista Magazine

DEC 2017-JAN 2018

Serving People Serving Coffee Since 2005

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F O A M : N E W S + T R E N D S TEMPERATURE PROFILING WITH ESPRESSO In recent years, many new approaches to extracting espresso have sprung up on the market. With variations in method everywhere from Kees van der Westen's new Idro-Matic preinfusion system to Decent Espresso's Flow Profi ling technology, the options available for brewing espresso vary almost as much as the plethora of manual-brew methods that exist for coffee. The ability to manipulate and adjust the amount and rate of increase of pressure in espresso has opened many discussions about how to coax the most delicious version of the perplexing liquid into a cup. It seems that now an increasingly large number of baristas, prosumers, and enthusiasts are engaging in the fi ne and enigmatic pursuit of extracting the nuances of espresso. As far as we've come with technology, we seem to be only scratching the surface of espresso's possibilities. Much effort in pressure ramping, profi ling, and control all manipulate one side of coffee's variables during extraction: turbulence. However, when it comes to extracting chemical compounds into the cup, one variable greatly affects the change in rate of extraction for these compounds, thus affecting the fl avor profi le: temperature. Many experienced baristas have spent countless hours fi ne-tuning espresso utilizing temperature as a controlling variable, and it is easy to see how much a small change creates drastically different results in the cup. But what about a temperature profi le? How would that affect the extraction of espresso? Before diving into how a temperature profi le affects espresso, I wanted to measure exactly what coffee experiences in the grouphead of an espresso machine. At Rancilio's North American headquarters just outside Chicago, I had the opportunity to examine precisely what the coffee experienced as hot water saturated it and began extracting. First, it is important to notice the temperature gradient. Even in a fl at, standard extraction, a puck of coffee experiences a swing in temperature. Even the most capable espresso machines will produce a temperature gradient as the coffee, basket, and portafi lter absorb the heat from the water until the brewing environment reaches equilibri- um. In response to this data, the approach to temperature must not be whether we want our coffee to experience a temperature gradient or not, but rather how much we want to control that. For a standard, fl at profi le (what most PID-equipped machines are designed to do), many things can reduce the gradient that the coffee experiences. The two most helpful tips are keeping the portafi lter in the grouphead as much as possible (the longer it is out of the grouphead, the more the temperature drops and the more heat the portafi lter will draw from the water before it reaches equilibrium), and purging right before a shot (2–3 seconds is likely suffi cient, and wiping the dispersion screen as well is good practice). This will help ensure repeatability of your temperature gradient and consistency in taste. For those trying to reduce temperature gradient as much as possible, my theory is that utilizing a temperature profi le that ramps down slightly will provide the quickest ramp-up in temperature. The idea is that by starting a few degrees above the target temperature (for my test, I started 3.5°F above the target), the higher initial heat jump-starts the warming process, with the rising temperature gradient meeting the declining profi le and maintaining target temperature. A preliminary ex- periment conducted using Rancilio's Temperature Profi ling technology supports this theory. On average, within the fi rst few seconds of water saturation (as indicated by a rise in temperature), the slight ramp-down profi le experienced a gradient that heated the coffee quicker. Extractions are refl ected in the graph based on when the temperature reading in the coff ee bed rose by more than 1° F, as to indicate when water began to touch the probe. The fi rst few seconds (between 3–5 seconds) that it takes to fi ll the preinfusion chamber and begin saturating the puck is susceptible to tamping and grooming inconsistencies and was omi ed, along with time a er reaching temperature. For each temperature profi le, 10 extractions were produced. For temperature readings, a J-type bead probe was mounted into a drilled portafi lter basket so that the temperature gradient of the actual tamped coff ee bed for each extraction could be measured. A Fluke 51 ii was used for temperature readings, and a Rancilio Classe 11 Xcelsius and Kryo OD grinder were used to prepare the espresso. The average of the six most similar extractions was taken and the data were logged in Plotly. Details about the experiment procedure can be found at the end of the article. 26 barista magazine

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