What is flow rate and why is it a hot topic of conversation? BeanScene speaks with Dalla Corte Australasian Business Development Manager Tristan Creswick to explore Dalla Corte’s latest addition, the Zero.
The science
Water flows through the coffee puck in an espresso machine at a particular rate: slow at first because of resistance, but as the extraction continues and the puck erodes, there is less resistance and the water flow rate increases, and increases further as the puck continues to erode.
“The constant eight to nine bars of pressurised water that most machines operate with, however, is always seeking the path of least resistance, so once the puck has eroded, the result is channelling,” Dalla Corte Australasian Business Development Manager Tristan Creswick explains.
The reason a specialty barista focuses so much on puck preparation, Tristan says, is because they aim to evenly distribute the ground coffee particles, remove any clumps and/or air pockets, then complete the routine with a firm level tamp. Ideally, this will cause water to flow evenly through the coffee puck.
“We need water to flow past each particle of ground coffee if we’re going to evenly extract from each particle. The opposite of which, being uneven extraction, results in a lower total extraction percentage and increased bitterness and/or astringency,” Tristan says.
He adds that even the best puck preparation will struggle to completely eradicate channeling.
“If we seriously contemplate the way pressurised water behaves when forced through oily particles of different sizes and shapes, we arrive to the conclusion that there will always be, at minimum, some micro-channeling that occurs,” Tristan says.
It is difficult to eradicate channelling completely when there is a constant eight to nine bars of pressure throughout the shot. However, if water flow rate can be controlled, causing it to slowly start saturating the coffee puck (pre-infuse), increase (ramp up), and then slowly decrease (ramp down) as the puck erodes, there is a better chance of reducing channelling. This process, Tristan says, is commonly referred to as “flow profiling”, and is essentially, the amount of water that enters the puck per second, such as seven grams per second.
“By controlling the speed and the amount of water that enters the puck, moment by moment throughout the espresso shot, a barista can more easily reduce channelling, increase overall extraction, and fix common sensory issues like excessive sourness and or bitterness, consistently,” Tristan says.
Meet the Zero:
Back in 2015, Dalla Corte introduced the Digital Flow Regulator in its single group machine, the Mina. This technology allows a barista to control the flow of water throughout the whole espresso extraction, making channelling a thing of the past.
Now, as Dalla Corte’s latest machine Zero makes its debut, also featuring the Digital Flow Regulator, it is possible to control water flow and reduce channelling in a cafe on a two or three-group machine.
“Consistency is key here, because what good is having one exquisite cup of coffee if your next cup is just ‘OK’. For a business, it’s not good. Customers come into cafés expecting to order and receive a familiar beverage every time they enter,” Tristan says.
The Digital Flow Regulator also allows baristas to brew filter coffee on an espresso machine.
“By reducing the water flow rate to be three grams per second, for example, we’re creating something very close to a hand-brewing style of a pour over coffee. No more moving away from the espresso machine every time a customer orders a filter brew coffee. We can hear the sighs of collective relief from baristas everywhere,” Tristan says.
“Thanks to the ability to control flow rate, a barista can combat common difficulties in various grind sizes, allowing them to get light fruity flavours without sourness, or bold chocolate notes without bitterness. Then, once they’ve found the perfect recipe, they can easily modulate the Flow Profile to recreate that same brew with digital precision.”
Using Zero, a lead barista can create a flow profile for each blend a café serves, and rest assured that other baristas can recreate the same flavour profile with little effort. In terms of consumer satisfaction, Dalla Corte says this is “a major leap forward”.
The Zero is coming to major cities throughout Australia, starting with Brisbane from 24 May.
Demonstrations will be available for baristas to try their hand at flow profiling and experience the device first hand. Dalla Corte is also set to host a flow profiling barista competition.
To book a spot at the Brisbane demonstration, click here: https://l.linklyhq.com/l/RmH4
For more information on the Dalla Corte Zero, contact Tristan directly on 0449955136, or visit au.dallacorte.com