How to unlock the full potential of light roast espresso shots
Barista trainer Alex Slater shares how light roasted coffees require a fine-tuned approach to espresso brewing – and how good espresso machines can make all the difference.
Coffee’s journey begins on the farm, where the green, moist seeds of the coffee cherry develop all their complex, desirable qualities until ripe – far removed from the coffee beans most consumers know. That’s because before it can be brewed and enjoyed, it must be roasted.
The majority of coffee on the market is roasted until it’s dark brown, or in the case of some Italian and French espresso blends, closer to black. As such, many consumers are familiar with the bitter, syrupy nature of this type of espresso and have never been exposed to anything lighter.
Some commercial brands do offer medium roasts, but genuinely light roasted coffees are few and far between – or at least that was the case until the advent of specialty coffee.
In recent years, there’s been a gradual lightening of specialty espresso roasts. Experts are discovering that new roast profiles and fine adjustments to espresso brewing can result in better quality coffee.
In fact, even when it comes to espresso, many professionals and home baristas are now experimenting with light roasted coffees. This presents something of a challenge, but it’s one that has the potential to reap incredible rewards.
When brewed perfectly, light roasts express the flavours inherent in a coffee, highlighting the work put in at each stage of the coffee’s journey. Many coffee professionals, including regional barista trainer for 200 Degrees Coffee, Alex Slater, favour light roasted coffees for this reason.
“I absolutely love them,” he says. “Particularly that intense acidity that verges on the citrusy, coupled with fruit-forward sweetness and floral notes.”
The trick to unlocking their potential, he says, is balancing that acidity out with good extraction.
What role can good equipment play in brewing light roasted espresso?
Entry-level espresso machines are notoriously frustrating when it comes to brewing light roasts. Generally, these machines are designed to grind and brew darker beans, which are typically softer and less dense.
Conversely, lighter beans are harder to grind, requiring adjustments to both equipment and brewing variables. As such, virtually all coffee professionals agree that a decent grinder is the first port of call.
Alex also recommends considering variances in grind between conical burrs and flat burrs. Espresso enthusiasts are often divided over the clarity of flavour offered by flat burrs and the improved body afforded by conical burrs.
He explains that when compared with medium to dark roasts, light roasts require the home barista to really “pay attention to what they’re doing”.
“The challenge is mainly to do with solubility,” Alex explains. “The longer you roast your coffee, the less dense it is and the more soluble it’s getting. That makes it easier to extract.”
Coffee solubility is effectively the extraction potential of the bean. Both weak and over-extraction are undesirable in any coffee brew. Naturally, because lighter coffees are less developed than dark roasts, they require a different approach to extraction.
Some of the variables that affect extraction are grind size, water temperature, pump pressure, and equipment quality.
The importance of these variables was recently underscored by barista and YouTuber James Hoffman. In a recent product review, he expressed concerns that a high pump pressure coupled with low brew temperatures will frustrate extractions on lightly roasted coffee.
However, the best modern prosumer machines – such as those from Bellezza – are equipped with a proportional integral derivative (PID) controller. Using feedback from sensors, this device can regulate temperature, pressure, and water flow.
Ultimately, this is an invaluable mechanical aid for home baristas, allowing them to fully understand how their light roasted coffee is being extracted.
Some machines – like the Bellezza Bellona – also employ timers and pre-infusion technology to further optimise brewing. There are also superautomatic home machines like the Carimali C250 that feature adjustable pump pressure.
When it comes to traditional automatic espresso machines, Hoffman also stresses the importance of using a good basket in your portafilter. In his opinion, many of the baskets included with some home espresso machines lack the precision machining of professional baskets, negatively impacting the flow rate.
Fine-tuning the process
What really helps to ensure an even extraction, says Alex, is to analyse every single step of the brewing process. This begins with the coffee itself, with origin, variety and process all influencing its final density.
Equally important to consider is the water you’re brewing with. Thanks to pioneering research from the University of Bath and Maxwell Colonna-Dashwood, professionals now know that the mineral content of the brewing water has significant implications for extraction.
If the water is too hard, the coffee can over-extract. Too soft, however, and the coffee may taste flat. Furthermore, water with high alkalinity will result in an overly acidic cup.
Like many UK baristas, Alex uses specific, consistent water with a pH and mineral content ideal for light roast extractions.
Because we have to work harder to extract a lightly roasted coffee, Alex advises brewing at “around the 95 to 96˚C mark”, which is hotter than usual.
Alex further observes that problems often occur when working with dense coffees where the grind has been pushed as fine as it can go. However, a fine grind is essential when brewing light roasts as espresso, as the increased surface area allows for faster extraction.
He says that one potential solution is puck prep, which involves using tools like a Weiss distribution tool (WDT) and tamper to optimise the nature of the coffee grounds in the portafilter.
“That can play havoc with how your shot is going to pull,” Alex explains. “A WDT tool will make a world of difference.”
He adds that another way to optimise light roast espresso brewing is to change the typical coffee-to-water ratio used.
“I remember this video I watched from Alternative Brewing,” he says, referring to a video that recommends extracting 50g espresso from 20g of a light roasted Kenyan coffee in around 18 – 20 seconds.
“That blows my mind,” he remarks. “The theory behind such shots involves extracting the fruit-forward and acidic notes, really pushing those out, getting the sweetness in there, too, and then cutting off the shot before any bitter or astringent notes begin to come through.”
In his own experience, Alex has experimented with a light roasted, natural Nicaraguan coffee. He extracted a 25g yield from an 18g dose over 25 seconds – closer to the parameters one might use for a ristretto.
He says that the coffee “tasted phenomenal”. It was a key moment for Alex, helping him to realise that thinking beyond the typical espresso school of thought might be the key to unlocking the potential of light roasted coffees at home.
Ultimately, however, home baristas need to invest in top-quality equipment and coffee. Once that’s out of the way, it’s up to them to play around with variables until they brew the perfect espresso – and change the status quo.