In line with this, there are many factors that roasters need to consider to best highlight a coffee’s flavours and aromas when extracted as espresso. Roasters ultimately need to account for these factors when sourcing their coffees, but the roasting process itself plays a huge role in influencing flavours and aromas.

To learn more about how to roast for espresso, I spoke to Kaapo Paavolainen, founder of One Day Coffee Co., and Ghilyon Welby-Watson, head roaster at Tate Coffee Roastery. Read on to find out what they had to say.

You may also like our article on roasting specialty coffee blends.

Why do certain coffees work better as espresso? 

Although the roasting process itself has a major impact on how espresso extracts, choosing which coffee to use is a crucial first step. Some considerations include:

• Origin
• Altitude
• Variety
• Processing method

Kaapo (who is also the 2021 Finnish Barista Champion) emphasises the importance of having a certain flavour profile in mind before sourcing green coffee to roast for espresso.

“It’s about the potency of flavour,” he says. “It needs to be strong enough for people to appreciate it on its own, but it also needs to cut through milk.

“The same coffee with different roast profiles will result in different flavours,” he adds.

He uses a washed Panama Gesha as an example.

“As filter coffee, Gesha has more floral notes, as well as flavours like jasmine, peach, apricot, bergamot, orange blossom, and citrus fruits,” he explains. “However, when prepared as espresso, it’s more challenging to balance all of the citrus qualities. 

“In turn, these flavours can’t be expressed in the best way possible,” Kaapo adds. “Even if you play around with the roast profile, you would have to roast it too dark or develop it for too long, so you would destroy most of the delicate tasting notes.”

Keeping consumer preferences in mind

Ultimately, it’s the roaster’s responsibility to make sure roast profiles allow a coffee’s inherent characteristics and qualities to shine through. However, at the same time, consumer taste preferences also inform a roaster’s decision to choose a particular coffee for espresso.

“We personally source coffee based on what we think appeals to the wider market, how the coffee will translate as espresso, and of course, quality and flavour,” Ghilyon says. “For us, we serve our coffees at all of Tate’s locations in London, which cater to a vast and diverse audience whether they drink specialty coffee or not, so why not source coffees that are both high-quality and all-round crowd pleasers?”

There are many different approaches that roasters can take to source their coffees. While some may need to appeal to a wider range of consumers, other coffees may be better suited to people who are looking for more unique and interesting sensory profiles, such as experimentally processed coffees.

“There is certainly a market for these coffees in the appropriate setting,” Ghilyon says. “We tend to focus less on variety, and more on flavour profile, origin, and processing method.”

How do you develop a roast profile for espresso?

Once a roaster has sourced their coffee to use as espresso, there is an element of trial and error involved in developing a specific roast profile. However, some of the main variables that roasters can experiment with are:

• Temperature
• Total roast time
• Colour of the beans (or Agtron measurements)
• Timing of “first crack”

“I monitor how the coffee behaves during the roasting process,” Ghilyon tells me. “I check the colour and temperature changes regularly, and also consider total roast time.

“Most importantly, however, you have to taste your coffee,” he adds. “If you don’t enjoy the coffee while cupping it or it doesn’t extract in the right way, what is it that you don’t like? And how can you improve it? You need to analyse the data and then continue to experiment with different roast profiles. 

“There are a number of factors to consider when developing a roast profile, but we are primarily looking for consistency, so we tend to keep things simple,” Ghilyon continues.

No matter their approach, roasters need to make sure their roast profiles result in the optimal level of solubility for espresso extraction. Essentially, more soluble coffees can be extracted more quickly. And given that most espresso is extracted between 25 and 45 seconds, a higher level of solubility is especially important.

To achieve this, you usually have to roast for longer to create a more developed (or “medium”) roast profile. When not managed correctly, however, Kaapo notes that the risk of creating unpleasant “roasty qualities” can increase. 

For more experienced and skilled roasters, he emphasises that using high-quality equipment helps to prolong roast profiles without sacrificing any of the coffee’s inherent flavour characteristics.

Do certain roast profiles work better for espresso?

Considering that solubility is key to extracting excellent espresso, it is recommended to use a more developed roast profile.

“I think there is a more preferred profile for espresso compared to filter coffee,” Ghilyon says. “Medium roast profiles result in more balanced acidity and allow you to extract more of the coffee’s flavours and aromas [in a shorter period of time].”

Kaapo explains how roasters can use Agron spectrophotometers to measure roast profiles, which use infrared light to determine roast profile. For instance, the higher the Agtron number, the lighter the roast profile.

“Using similar roast profiles, try to match Agtron numbers for one particular coffee,” he suggests.

However, while Agtron measurements help to ensure consistency, they don’t always indicate the optimal espresso roast profile for a specific coffee. To achieve the best results, roasters need to account for other variables, too.

Blends vs single origins

In recent years, single origins have become popular options for espresso. However, many roasters prefer to use blends – mostly because they result in more overall balance and well-rounded flavour profiles.

But does this make a difference to how you should roast these coffees? 

“It’s mostly a matter of mixing the different coffees to create the blend, [rather than using a different roast profile],” Kaapo says. 

Any blend contains at least two different types of coffee – such as origin, variety, or processing method, for instance. Roasters will usually blend each component separately to achieve the right solubility level, and then mix post-roasting.

“We roast coffee for maximum flavour,” Kaapo explains. “So if we have the best possible roast profiles for two specific coffees, we can blend them together using a certain ratio and find the ‘sweet spot’ where they complement one another.”

However, over the past few years, a growing number of roasters have started to use more developed roast profiles for milk-based espresso beverages. Essentially, these roast profiles ensure that the coffee’s flavours are expressed in a way which is complementary to the natural sweetness and creaminess of milk.

Furthermore, some roasters may wish to avoid using certain origins or processing methods for milk-based espresso beverages. For example, Ethiopian or Kenyan coffees tend to be brighter and have more floral and fruity flavours, and are therefore best when roasted to lighter profiles – which may not pair well with milk.

Tips for tweaking roast profiles for espresso

Ghilyon emphasises the importance of experimenting with different roast curves to achieve different results, and ultimately find what works best.

“You can change the charge temperature (the reading on the drum once the beans are added), develop the coffee for longer or shorter periods of time, or experiment with timings for the Maillard reaction,” he says. 

This term refers to a series of chemical reactions between amino acids and sugars in the beans, which causes them to “brown” and release flavours and aromas. In coffee roasting, the Maillard reaction is the time between when the beans start to turn yellow and when first crack takes place – the moment in which pressure builds up inside the beans and causes them to irreversibly expand.

All about taste

In the end, there is no one-size-fits-all approach to finding the best roast profile for espresso. However, Kaapo tells me that cupping and tasting coffees as much as possible is essential. 

“You need to taste different roast profiles for one particular coffee – as well as for many other coffees, too,” he explains.

For less experienced roasters, this can be challenging at first. However, with plenty of practice, the process can become more straightforward.

“It can be difficult to achieve consistent results every time, but if we continue to maintain quality across the supply chain, then we can provide a dependable and reliable experience for our customers,” Ghilyon concludes.

In roasteries and coffee shops the world over, developing roast profiles for espresso has been common for some time now. Not only do these roast profiles ensure a more balanced sensory profile, they also help to elevate overall beverage quality.

Every roaster will have their own approach, but one of the most important factors to keep in mind is the needs of their customers – and knowing how to cater to them accordingly.

Enjoyed this? Then read our article on what’s the future for espresso.

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The post A guide to roasting specialty coffee for espresso appeared first on Perfect Daily Grind.

In fact, its adaptability has led other companies and brands to design and create their own accessories for the AeroPress, including a number of different filters. 

However, the material of an AeroPress filter – usually either paper or metal – has a significant effect on extraction, and thereby the final cup profile.

To learn more about the differences between paper and metal filters, I spoke with Valerian Hrala, Campus Director at Boot Coffee, and Ben Jones, the 2016 US AeroPress Champion. Read on to find out more.

You may also like our article on how to brew coffee with the AeroPress using different grind sizes.

How do paper and metal filters affect extraction and flavour differently?

When it comes to the AeroPress, there are two main types of filter: paper and metal.

Paper filters are popular for many reasons, including their ability to absorb some of the oils present in coffee during extraction. This leads to a cleaner-tasting flavour profile with a less enhanced body.

However, in terms of performance and how they affect coffee flavour, there is a lot of variation between paper filters. This can depend on the type of material used to manufacture them, or whether they are bleached or unbleached.

Moreover, given the rising interest in sustainability in the coffee industry, more and more people are opting for reusable coffee filters, such as metal, which help to reduce waste.

For some years now, several brands have manufactured and sold metal filters which are designed to be used with the AeroPress. However, in 2022, AeroPress launched its own metal filter, which is made from premium grade 316 stainless steel. 

According to AeroPress, the main difference between its metal and paper filters is that “the reusable metal filter allows oils to pass through for a somewhat fuller-bodied cup of coffee, whereas the paper micro-filter keeps out those oils for a cleaner flavour profile”.

Testing the metal AeroPress filter

Valerian tells me that to test the differences between the AeroPress metal filter and the standard bleached paper AeroPress filter, he prepared two batches of coffee using each type of filter.

He explains he used a lot sourced from Gesha Village in Ethiopia, which was harvested in June 2022. For reference, Valerian says this coffee typically has notes of tropical fruit and cacao nibs, with aromas of pineapple. 

For his recipe, Valerian says he used 15g of medium ground coffee to 260g of water for both batches. He tells me he used around 104g of the brew water to pre-wet the grounds before stirring for ten seconds. He then added the remaining water and pushed down the plunger for approximately 30 seconds.

Both coffees were then decanted into separate thermal carafés and cupped alongside each other.

“I was very surprised by the performance of the metal filter,” he says. “I was expecting a much murkier beverage which contained microfines, but by using a medium grind size, I ended up with a coffee which was full bodied with a clean aftertaste.”

How can you create different flavour profiles using the metal AeroPress filter?

It’s clear that using a metal filter results in a fuller-bodied cup of coffee. But is there a way to experiment with metal filters to extract different sensory profiles?

Ben explains that changing the grind size when brewing with a metal filter allows you to achieve a variety of results.

“In terms of cup profile, metal filters allow you to extract a little bit of extra sediment,” he says. “This creates a sensory profile closer to a French press.”

Although coffee quality, roast level, and water quality all play an instrumental role in the extraction of flavours and aromas, grind size is key when using a metal filter.

Ben tells me that no matter which coffee you use, particle size distribution will inevitably have an effect on body and taste. This term refers to the variance in size of ground coffee particles, including the volume of “boulders” (larger-sized particles) and “fines” (smaller-sized particles).

The effects of grind size

If there is too much variance in particle size distribution, you can end up both underextracting and overextracting your coffee at the same time. This will taste both sour and bitter, meaning you aren’t able to experience the full range of the coffee’s flavours.

Ultimately, to achieve a more uniform particle size distribution, you need to invest in a high-quality grinder. However, when brewing with a metal filter, it is often preferable to have a slightly broader particle size distribution so that you can highlight different aspects of a coffee.

For example, Ben explains that if you grind some of your dose to a slightly different grind setting, you can accentuate acidity. He adds that this could be especially useful when brewing darker roasts, which tend to lack acidity. 

However, it’s important to note that using different grind sizes when brewing one coffee takes considerable skill, and may not always produce the best-tasting results.

Ben also tells me about “stacking”, which is a technique he used in his winning 2016 US AeroPress Championship routine.

This method is when you layer several filters in the AeroPress filter cap. Ben explains that you can use multiple paper or metal filters, or even a combination of both. 

“It increases resistance in the brew chamber,” he says. “Combining a metal filter with several paper filters helps to provide more structure.

“If you want to emphasise sweetness in the cup, you can add a couple of extra grams of coffee in your dose, stack the filters, and then use bypass brewing (when you add extra water once the coffee is extracted),” he adds.

Brewing different drinks with a metal filter

The versatility of the AeroPress means that you can prepare a variety of different drinks with it, including espresso-style beverages. 

“To make an espresso-style drink with the AeroPress, you should use a metal filter as it won’t absorb oils or change the texture,” Ben says. “You will also extract more fines with a metal filter.”

Ben shares his current favourite recipe for brewing espresso-style beverages with the AeroPress below. He uses Olympia Coffee’s medium-dark roasted Morning Sun coffee, which currently uses beans sourced from Los Milagros Organic in Chiapas, Mexico. 

Ben adds that the coffee has notes of chocolate, hazelnut, raisin, vanilla, and honey.

Ben’s espresso-style AeroPress recipe

• For this recipe, you need to use the inverted AeroPress method, as well as a metal filter
• Grind 20g of coffee slightly coarser than for espresso (Ben says he uses a conical burr grinder to do this)
• Add 75g water just off boil and stir vigorously
• At 00:45, secure the filter cap, flip the AeroPress, and push down on the plunger
• The press down should be around 30 seconds
• When you hear a hissing sound, push the plunger all the way to the bottom
• Ben explains that there won’t be any crema on the drink, but it will be a concentrated beverage with a thick texture

Ben recommends enjoying the espresso-style drink straight, or adding your preferred type of milk.

Tips and advice on using metal AeroPress filters

Although reusable metal AeroPress filters are certainly more sustainable, proper cleaning and maintenance is essential if you want to consistently extract high-quality coffee when you brew with them.

Ben says that to easily maintain a metal filter, you should treat it similarly to a screen in an espresso machine. This is the metal mesh filter which screws into the grouphead to prevent ground coffee from entering the machine.

Ben says that between brewing coffees, he rinses his metal AeroPress filter with hot water. He adds that once a week, he soaks the metal filter in water with a small amount of espresso machine cleaning powder. He explains that this helps to remove any buildups of oil or sediment.

Changing grind size and brew time

When it comes to using different grind sizes with metal filters, Ben adds that you generally need to compensate by changing the total brew time. 

For instance, he tells me that with a coarser grind size, you need a longer brew time. Ben recommends between two and a half minutes and three minutes, which can help to highlight the sweeter flavour notes.

Conversely, he says brewing with a metal filter for shorter periods of time, but with a finer grind size, can accentuate fruity flavours, as well as bringing out some cacao notes.

While paper filters continue to be popular, it’s clear that more and more people are pivoting to metal filters for their AeroPress for a number of reasons. Irrespective of the motivation, however, it’s clear that you can use them to brew a range of different beverage styles, as well as manipulating a coffee’s flavours and aromas.

Ultimately, whichever filter material you choose for your AeroPress, experimenting with different extraction variables is key if you want to find that “sweet spot” for your coffee.

Enjoyed this? Then read our article on how AeroPress recipes have changed in recent years.

Photo credits: AeroPress

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