Rancilio Specialty RS1 FOCUS: Temperature Profiling
While a flat temperature profile can definitely produce some tasty espressos, having the ability to brew espresso on a profile opens it up to many more flavor profiles and taste possibilities. Temperature profiling can even open up a coffee and show it in its best light, similar to the way a well extracted pour over can. This is because temperature is the most influential variable to extraction quality and determines the rate at which flavor compounds extract from the coffee and enter the espresso. Simply put, temperature determines what your coffee tastes like. And just like every other variable with coffee, small movements create big changes in the cup quality.
To describe how the technology works, let’s talk about a few areas where temperature profiling has produced a higher quality extraction across many different coffees. Oftentimes when brewing a coffee as espresso, it has a sweet spot of 10 to 14 days off roast where it tastes the best. This is because the sugar browning in the roasting process produces CO2 as a byproduct, and this is released when the ground coffee touches water. The fresher the coffee, the more CO2, and this off-gassing can impede the extraction process, hence why aging for several days can produce sweeter results.With temperature profiling, however, we’ve found that we can pull fantastic shots of espresso at just a couple days off roast using a ramp down profile. Let’s say for instance that you have a coffee from Burundi that is tasting delicious at 93°C. By starting the profile a couple degrees higher, say to 95°C (close up shot of temp change) the higher temperature at the beginning of the extraction facilitates the offgassing, allowing the solubles in the coffee to extract more readily. The temperature lowers gradually throughout the extraction to the ending temperature, preventing more bitter compounds from being over-extracted beyond what we want in the cup. (pull shots at flat temp, then ramp down).
Another tried and true tactic for temperature profiling is a long ramp-down for natural processed coffee. This allows the coffee to begin extracting at a high temperature to facilitate the extraction of all the sweet, fruity aromatics before profiling down throughout the shot to reduce the extraction of the fermenty, funky notes that are typically present with a high temperature extraction of a natural. A long ramp down will also mimic a lever espresso extraction, since a lever drops temperature in the espresso throughout the brewing process and also because the RS1’s preinfusion chamber allows for about a 10 second ramp up to pressure, similar to the pressure ramp up in a lever.
While dynamically changing temperature throughout the extraction can yield higher quality results in the cup, the most important aspect is that the brewing process is consistent and repeatable. See at Rancilio we have been working with temperature profiling technology for around 7 years now, and this latest version in the RS1 is the most accurate. It utilizes a stainless steel boiler and group rather than brass because brass has more thermal inertia. In other words, stainless steel is more nimble when it comes to temperature.
And to control the temperature delivery even more, we’ve added a heating element band to the grouphead to work with the group boiler and heat exchanger to control the temperature of the water from 3 points.
With our experiments using temperature profiling, we’ve found a few things that affect the extraction temperature of espresso: boiler water temperature, group temperature, and flowrate