There’s a convenience afforded to the roaster with pre-blending green coffee, allowing them to roast a single batch of blended coffees as opposed to managing several small batches of each component (especially convenient for those using larger roasters). Having this type of blend on hand and ‘ready to go’ gives the roaster ease of access as well as flexibility with batch size. One concern is that this type of blend might compromise roast evenness due to varied bean sizes, densities, moisture, etc. In most cases I haven’t found this to be much of a problem, and that a certain degree of averaging occurs between ingredients, in particular with drum roasting chambers. Roast technique also plays a large role in attaining an even roast, which I’ll talk about later.

Post-roast blending means mixing the coffees after roasting each individually. One reason to do this is to retain control of the roast level of each component. Roast, of course, also adds a whole other element to the flavor possibilities, and is used to pull out or obfuscate particular notes in the profile. With this you have the ability to control roast flavors as well as sweetness, fruited notes, and acidity. Slight roast variances will do fine as espresso or drip coffee.

Great Coffees Make Great Blends

I have a saying: “GIGO”, which means, “garbage in=garbage out”. There’s a lot of truth in that saying, because no matter what we do as roasters we can only make the end product as good as the initial ingredient(s). It’s no secret that some roasters use blending as a way to funnel off waning coffees – but no matter how much good, fresh coffee you throw on top of a ‘tired’ one, you can’t change it (would you throw three good apples and one rotten one through your juicer?). Sure, with some roast development you might be able to mask signs of age or baggy flavors, but the ‘garbage’ coffee will only get worse with time, never better. So that’s why it’s always best to approach a blend with solid ingredients. Not only will fresh coffees bring their respective profiles at their ‘peak’, but they also have staying power and store the longest – meaning, you’ll have the opportunity to offer the blend longer

There are many approaches to choosing blend ingredients and one thing to consider is having an idea of what kind of a profile you’re trying to achieve. For instance, if “classic” espresso is what you desire, try starting with a low acid, big bodied South or Central American coffee as nearly half the base, and then make up the difference with coffee(s) that you’d like to use as highlights. If you like to shoot from the hip, try roasting up a few different coffees you know work well as single-origin espresso, and then play around with ratios until you find one that fits. One thing to keep in mind is that to blend efficiently, it helps to have a basic idea of what characteristics are associated with various origins and processing methods, and it really helps to have a thorough knowledge of how the coffees you currently have function as both espresso and brewed coffee.

With espresso in mind, I put together a general list of espresso attributes and the roasts, processing methods and regions that are generally associated with them. These are fairly gross generalizations, and there are always exceptions to the rule. Not all Brazils are going to be bodied, nutty and low acidity, and likewise, not every African coffee is floral, complex, or citric. But this list will give you an idea of where to start – a base, if you will – when considering a blend profile that works.

Body:

Roasting for body can be tricky. To really develop mouthfeel in the roast requires stretching out the 1st Crack. During this stage, the cellular structure of the bean is at its most elastic and the breaking down of cellulose into non-sugar carbohydrates lends to a thicker mouthfeel. What makes this tricky is that you have to be careful not to stall the caramelization that is occurring at this same time. To do that would bake the coffee which will develop harsh flavors that can be medicinal, to oaty, to popcorn-like.
Natural and Pulp Natural coffees are great for this, especially those from Brazil and Yemen. They often bring with them layered chocolate, and nut flavors – try using as a base, or equally blended with other bodied coffees. With Yemeni coffees factor in the possibility of rustic sweetness and sometimes rougher flavors – you might use sparingly at first, like %25.

Colombian coffees can fit the bill. Washed coffee from Huila or Cauca often have great body and honeyed sweetness. Defined acidity may come with it so play with portions for balance.

Indonesian coffees often have heavy and sometimes syrupy mouthfeel and for this reason are historically popular espresso blend components. With Sumatra you don’t need a lot, as anything more that even 20% tends to overwhelm all other components. The herbaceous notes common in these coffees also add sharpness in an espresso. Javas can add really sturdy body, refined sweetness, and a sweet nuttiness to the finish.

Robustas are also commonly used to add body to a coffee. They definitely do that (lots of crema), but come with a flavor profile that is uniquely, well, “Robusta” – wood, paper, and bitterness.

Chocolate:

Roast level has more of an impact on cocoa flavors coming out of the blend, and roasting closer to Full City will produce those chocolate notes in coffees. Avoid toasty, roasty, and carbonized flavors by not taking the roast too far into 2nd Crack (and by not pushing the roast too fast!). Stretching out the drying phase can also help develop the sweeter side of chocolate flavors.

Dry Processed coffees are known for their overt fruitedness, but at deeper roast levels they can also have intense syrupy chocolate notes. Brazil coffees are great for syrupy chocolate flavors in the middle cup profile as well as nice cocoa powder notes in the finish.

Central and South American coffees are also a nice addition to a chocolaty espresso. I often use washed coffee and pulped natural (semi-washed) coffees from Brasil and El Salvador, adding chocolate flavors as well as a nice viscosity. Guatemala, Mexico, Colombia, Peru and Panama coffees can also work, often adding nuttiness, caramel and vanilla notes as well.

Acidity:

Roast level and development have a large impact on acidity as well. Lighter roasts will maintain more of the perceived acidity, and the development will determine where you experience that on the palate. Shorter development will promote that perceived acidity to the front of the palate. Roast development moves perceived acidity across the palate, and too much (or too long) will diminish it altogether.

Wet-Processed coffees are much better for applying acidity to a blend. You’ll get a cleaner, prominent, more sustained and confident acidity, whereas with a dry-processed coffee roasted lightly you’ll get a much more muddled acidity (not to mention more prominent earthy notes).

African coffees are well known for their vividly bright citric acidity. Washed Ethiopians will add lemon and bergamot brightness, while Rwandans have a mandarin orange character. If you want a Sauvignon Blanc type of acidity, a Kenya might do the trick.

Central American coffees roasted to lighter levels add citric and brassy/punchy acidity. Cleaner, simpler Centrals are best for this purpose as more complex coffee can add unwanted tactility or even muddled flavors into the blend.

Fruit:

Roasting for fruit notes is really determined by what type of fruit you’re trying to promote. If you’re looking for something citrusy than you’ll want to keep it light. But if you want cherry, berry and stone fruit flavors then you’ll actually want to roast a little deeper into City+ and even early Full City in some cases. The development of sweetness in the roast generally moves from cereal and malty, to candy-like, to fruited, and then into vanilla, caramel and cocoa, and beyond that into more bittering.

Natural and Pulped Natural coffees of course have a very distinct fruitiness that plays well in blends. This is also a function though of what kind of fruit you’re looking for. If you want more clean citrus like fruits, then washed coffees are a better component here.

African Coffees offer winey fruit notes, from the bright lemon and orange to more perfumed bergamot and even the raisin and blueberry of dry processed Ethiopias. A Kenya can give you anything from grapefruit to cherry to peach and apricot, but can also be overwhelming. When blending with Kenyas, finding the complimentary coffees and flavors can be tricky. A blend that I think is interesting is a Kenya and a dry processed Ethiopia, emphasizing the Kenya and using the DP Ethiopia as more of an accent.

Central/South American regions have many options for fruited characteristics. Colombia coffees can have intensely bright cherry notes offering brilliant highlights in blends. They are very sympathetic to a wide array of coffees as well. I always think of a Colombia in a blend as a big red balloon that you can fill with other accents. Guatemalan coffees from Antigua and Huehuetenango often lend flavors of dark berry, stone fruits and rhubarb tartness.

Managing your Blends

Try having two different types of blends: “Standard Blends”, ones you try to keep in stock as close to year round as possible (as long as fresh components allow), and a rotating list of “Seasonal or experimental blends” that highlight specific new crop coffees, often outside the realm of a classic espresso profile.

Try something like a seasonal blend, built around new crop coffees that inspire in the espresso machine. This is where you can take liberties with using components that aren’t necessarily what you’d find in a “classic” espresso profile. Wild and rustic Sulawesis, floral Ethiopians, and ultra-fruity naturals, all have a place here as long as we find a pleasurable shot in the aggregate sum. I enjoy putting these together, and they’re an opportunity to add an espresso offering to your list that is out of the ordinary and an alternative to the more ‘standard’ espresso profile. But when these are gone, they’re gone, and eventually replaced with a new seasonal offering.

So how do they roast?

An area of concern is about the evenness of roast for pre-blended coffees. It’s a valid concern as not all coffees are the same size, density, etc. First off, I take this into account when putting a blend together and roast to both light and dark ends of the roast spectrum in order to check the consistency of roast development between the individual coffees. One thing I’ve found is there’s a sort of equilibrium that is reached when roasting these blends in most drum roasters. I do my best to take these factors into consideration when blending, and include roast recommendations based off of my roasting experience.

Evenness in the roast for a green blend can have a lot to do with the thickness of your roasting drum, the intensity of the burners, or at the very least how you react to these particulars with your roasting technique. Because of this, infra-red burners or lower flame work really well to produce evenly roasted, green-blended blends. Not having an active flame licking the underside of the drum allows for a slightly more gentle conductive transfer, as well as makes it easier to add a little extra time to the drying phase. It’s also important not to use too much airflow on these roasts, especially during 1st Crack and after, as this could lead to tipping in some of the lower density coffees.

Adding a little extra time to your drying phase is truly the key to roasting a pre-blended coffee. The extra time allows you to better “normalize” all the components so that when you enter into 1st Crack they’re all start cracking together. You definitely don’t want to try to extend the time during 1st Crack itself, this could easily lead to the stalling of caramelization and baked flavors. I’m also not talking about a lot of time here, more like 30 seconds to a minute or so depending on how much brightness you want to see in the coffee. If this is for an espresso, then even a little more time on the drying phase can really help push the sweetness of the blend.

And in the End

Ultimately, in addition to there being a demand for blends, I blend because I love the coffee that comes out of it. It’s rewarding to put together a variety of beans based on their “best” aspects, and obtain a flavor profile that no one of the components could produce on its own. My approach is pre-blending the green beans, and my experience shows that this type of blend actually roasts quite evenly when taking a “slow and low” approach in the roaster. There’s certainly many ways to blend coffees, and I encourage you to try your hand at it – and why not start with the ingredients you currently have in stock? That’s always been the ideal starting point for me.