How Should Roasters Handle an Espresso Blend Coffee Profile?
Roasting an espresso blend coffee comes down to balancing density, bean size and flavor tendencies across the components. A Front Street blend of Colombia Medellin and Ethiopia Yirgacheffe shows the problem: the Colombia lot mixes Caturra and Typica across 1,300 to 2,000 meters, so green bean density can vary noticeably from batch to batch.
A long, gentle early roast rhythm helps heat reach the center of dense, plump Supremo-grade beans. Because the Colombia base carries sweetness and body but weaker early aroma, the Ethiopia component adds lift. Pre-blending raw beans is common for stability and saves labor, and a development ratio near 25 percent suits espresso extraction.
The roasting of espresso blends is centered on balancing the density, size, and flavor tendencies of different bean types. Starting from the choice between pre-blending raw beans and post-blending roasted beans, this article uses the blend case of Front Street Colombia Medellin and Front Street Ethiopia Yirgacheffe as an example to break down in detail the logic of adjusting heat, airflow, and moisture during roasting, as well as how to handle combinations of green beans with large density differences through stages such as steaming, heat boosting, and coasting. The article also outlines an espresso blend roasting approach with development ratio controlled at around 25%, and includes measured espresso extraction parameters and flavor descriptions, making it suitable for enthusiasts who want to gain a deeper understanding of espresso blend roasting.
In the production of blended coffee beans, post-blending roasted beans is usually more stable than pre-blending raw beans. However, many roasters today choose pre-blending raw beans for espresso beans or single-origin blends, and some green bean suppliers have even completed the blending in advance, so roasters can simply roast what they receive. Based on conventional experience, pre-blending raw beans offers better stability and saves considerable labor time, so more roasting workshops tend to adopt the pre-blending raw bean method.
Take the "Procrastination" blend used in our shop as an example. It is composed of one Colombia bean and one Ethiopia bean. The base is a Colombia with outstanding sweetness, produced in the Sierra Nevada de Santa Marta within Medellin, at an altitude range of 1,300-2,000 meters. Before roasting, we noticed that this bean consists of two varieties, Caturra and Typica. A wide altitude span plus mixed cultivation of two varieties means the density of the green beans may differ noticeably. Fortunately, it is Supremo grade, with a rounder bean shape and good plumpness. Coffee beans of this form make it harder for heat to penetrate into the center during roasting, so from the start we set a relatively long roasting rhythm.
Although this Front Street Colombia Medellin has high sweetness and a good mouthfeel, its early-stage aroma and flavor are relatively weak, and its aftertaste only reaches a medium-short level. To make up for these shortcomings, we added another bean to enhance the aroma, flavor, and aftertaste, namely Front Street Ethiopia Yirgacheffe (YEKI) G2. This bean comes from the KAFA forest in Ethiopia, is washed processed, and dried on raised beds combined with mechanical drying. The green beans show a beautiful emerald green color and excellent appearance. It grows at an altitude of 1,600 meters, and the bean shape is overall slightly longer than Yirgacheffe, with a softer mouthfeel than Yirgacheffe. Observing the green bean form before roasting, you can see that the center line is slightly turned outward, and the bean shape is not large. Based on experience, this bean more easily allows heat to penetrate to the center.
Front Street Colombia Medellin
Front Street Ethiopia Yirgacheffe
Roasting these two beans with different heat tolerance together after pre-blending raw beans is actually equivalent to simultaneously handling three different varieties of green beans with different densities, sizes, and shapes, which is a considerable challenge for many beginners. If the relationship among water, heat, and airflow is not well coordinated, it is very easy to roast such pre-blended raw beans unevenly, or to make the flavor too flat.
At this point, trade-offs must be made. First, as an espresso bean, I believe mouthfeel is the most critical, and there absolutely must not be any underdeveloped flavor. This is the core requirement when roasting this blend. But the difficulty is that we not only want a good mouthfeel, but also a good early-stage aroma and a medium-long aftertaste. This is exactly why we added Front Street Ethiopia Yirgacheffe.
In testing, the average density of the Colombia reached 788 kg/m³, while the density of the Ethiopia was 723 kg/m³, a clear difference between the two. Therefore, in the early stage of roasting, we use medium-low heat with a small airflow opening and carry out a longer steaming stage, allowing the water molecules in the green beans to evaporate evenly. The purpose of using a small airflow opening is to keep the water molecules inside the drum, while the drum must continuously maintain a state close to equilibrium between positive and negative pressure in order to keep moisture stable. At this time, most of the coffee beans' heat energy comes from contact heat with the drum wall, and the thicker the drum of the roasting machine, the better the performance in this regard.
When the coffee beans turn completely white, switch to medium-high heat and increase the airflow opening to raise the proportion of hot air in the drum, allowing heat energy to pass quickly through the water molecules into the bean center. Note here that the airflow opening should not be opened too wide. The greater the hot airflow, the harder it is for the coffee beans' aroma and flavor to express themselves; but if there is too little hot airflow at this stage, heat energy cannot be quickly transferred through the water molecules to the bean center, making uneven roasting more likely. Therefore, the airflow opening needs to be used reasonably according to your own operation and understanding of the roasting machine.
At this point, you only need to observe whether the roasting machine curve deviates too much from your set first crack point. Generally, we enter first crack at around 10 minutes 20 seconds to 10 minutes 30 seconds. Because these are three different varieties of green beans with different densities, sizes, and shapes, the sound at the beginning of first crack is rather scattered. At this time, we carefully judge the point of rolling first crack. When the coffee beans enter rolling first crack, we boost with high heat for about 30 seconds. The heat at this stage is the highest in the entire roasting process. The greater the heat, the better the coffee beans' aroma and flavor development, but note that if the heat is too high, or the heat-boosting time is too long, it is very easy to scorch both ends of the coffee beans. Also, the better the aroma and flavor development, the shorter the flavor tasting window.
After this stage of high heat, the sound of rolling first crack is still very intense, but note that at this point it is already the end of first crack. At this time, we turn off all heat and open the airflow to the maximum, coasting for about one minute. During this time, judge the aroma performance of the roasted beans and choose to drop and cool immediately when the caramel aroma is at its best. Note here that throughout the entire maximum-airflow coasting process, the coffee beans should be in an exothermic stage, so the bean mass temperature must not fall. If the roasting machine's drum is relatively thin and poor insulation causes the bean temperature to drop, then you can try not turning off the heat after the heat boost, but instead reducing it to low heat so the coffee beans continue to develop.
We usually call the stage from the start of first crack to drop the development stage, and the proportion of this stage's duration in the total roasting time is called the development ratio. For example, in the curve below for roasting this blend, the development time is 3 minutes 35 seconds, accounting for about 27.3% of the total time, which is the development ratio. For espresso blends, we generally choose to control the development ratio at around 25%, so that even if the roast level is not dark, the crema and body are very suitable for espresso.
At the same time, because of the medium-long roasting time, the development of the two coffee beans is relatively close, making underdeveloped flavor less likely. Although Front Street Ethiopia Yirgacheffe loses a little flavor, it still retains very good floral and fruity notes for espresso, while Colombia as the base can make the coffee fuller in body and better in mouthfeel.
In such a medium-roast espresso blend, because of the relatively high development ratio, this blend has good crema and body. When we tested it in our own shop, we used a Slayer espresso machine, Mythosone grinder, IMS shower screen, VST 15g basket, took 14 grams of coffee powder, with a brew head water temperature of 91.6°C, pre-infusion for 3 seconds, pre-infusion water flow of 400ml/min, and a flow rate extracting 24 grams of coffee liquid in 25 seconds. The early stage has a faint wild ginger flower aroma, and the flavor includes not only caramel, roasted cocoa, and chocolate, but also bright and clear citrus-like acidity such as grapefruit and rum.
Of course, roasting methods vary from roasting machine to roasting machine, and all roasting curves and methods can only serve as references. In roasting, I believe the most important thing for a roaster is the roasting philosophy. Without a roasting philosophy of one's own, a roaster's roasting is like a walking corpse, just as the saying goes, so dramatically: "Be a roaster with a soul."
The above content is compiled by CoffeeHunters, a coffee news website.
