... is being able to get my hands on prototype equipment...
As you're aware, Garage Roasters sells two fabulous coffee grinders:
Turin is considering bringing out a dual boiler coffee machine, and I've had the opportunity to bench test a very early prototype.
Just as a reminder, we'll touch on the basic architecture of coffee machines. There are three main formats which coffee machines adopt:
- Single boiler - a single boiler handles heating for both espresso extraction (at around 93*C) and milk steaming (temperatures in excess of 100*C within a pressurised tank at anywhere between 1.5 and 3.0 bar of pressure). Single boilers have the benefit of a small footprint because they only need space for one boiler, the downside to this design is that the user cannot extract coffee and steam milk simultaneously. It usually takes a long time for the boiler to move between espresso extraction and steaming temperatures because of the significant thermal capacity of the water in the boiler and the material which the boiler is made from.
- Heat exchanger - one boiler constantly runs at milk steaming temperature and pressure. A long tube (the heat exchanger) runs from the steam boiler to the brew chamber and if that tube is well calibrated then the water within the tube loses enough heat to enter the brew chamber at the correct temperature for espresso extraction. With this design the user can extract espresso and steam milk simultaneously. There is no waiting time required for the boiler to change temperature as it always operates at milk steaming temperature. The one downside to this design is that brew temperature may not be as precise as the user would want.
- Dual boiler - this design uses two separate boilers operating at different temperatures to handle both espresso extraction and milk steaming. The temperatures of both boilers can be managed extremely precisely. This is a no compromise architecture, the only downside is that these machines tend to occupy more bench space because they need to accommodate two boilers (the brew boiler is usually quite small though).
The prototype machine that I was testing was quite fascinating. It had a touch screen on the top of the group head which provided options for single shot, double shot, temperature settings, steam settings, and system settings. Single and double shots are highly customisable with settings for brew volume, pre-infusion volume, and pre-infusion time.
The machine heated up quickly from start up, taking only seven minutes to build steam pressure to 2.1 bar.
Coffee extraction was straightforward and excellent and steam pressure was strong. Both milk coffees and espressos tasted great.
I provided three suggestions for features that I would like to see incorporated into the production machines:
- An indicator light showing when the brew boiler is ready for espresso extraction
- A daily timer that switches on the machine in the morning early enough to be ready and warmed up for my first espresso
- A manual function which allows the user to drive the extraction pump for as long as they want