Introduction:Delve into the roasting techniques of Italian-style blends, from green blending strategies and density difference management to precise development rate control. This article uses hands-on experience to analyze how to balance the characteristics of beans from different regions and varieties, creating a rich and well-balanced blend. Ideal for professionals and advanced enthusiasts aiming to enhance their roasting skills and master espresso flavors.
The key to roasting Italian-style blends lies in harmonizing the density, bean size, and flavor profiles of different beans. This is not only a technical challenge but also a test of the roaster’s judgment and experience. This article will start with a discussion on choosing between green blending and roasted blending, and through practical blending examples, explain how to adjust firepower, air vents, and moisture management during the drying, ramp-up, and development phases based on differences in green bean density, while mastering an ideal development rate to produce an espresso-friendly blend.
In the market, many roasters prefer using pre-blended roasted beans to ensure batch consistency and time efficiency. However, an increasing number of roasters are opting for green blending—combining beans from different regions and varieties themselves to create more distinctive flavor profiles. For roasteries, green blending allows flexible recipe adjustments and saves time waiting for suppliers to blend, making it the preferred choice for many small-scale roasting workshops.
Taking a common “blending practice bean” as an example, its base bean comes from the Medellín region of Colombia, grown in the Sierra Nevada de Santa Marta at altitudes between 1300 and 2000 meters, cultivated from a mix of Caturra and Typica varieties. Due to the large altitude variation and complex variety mix, there is a noticeable density difference among the green beans. Additionally, the Supremo-grade beans have a round and plump shape, which affects heat penetration speed. It is recommended to use a longer roasting profile to allow heat to uniformly penetrate the core of the beans.
While this Colombian base bean offers good sweetness and body, its early-stage aroma is relatively subdued, and the aftertaste is only moderately short. Therefore, we chose to add a washed bean from Ethiopia’s KAFA Forest as a complement. This bean variety is grown at 1600 meters altitude, with vibrant green appearance, and employs a drying method combining raised bed sun-drying and mechanical drying. The beans are slightly longer than typical Yirgacheffe beans, feel soft to the touch, and according to observation, their center line is slightly turned outward, indicating efficient heat conduction that aids in aroma release.
Blending these two green beans with significantly different heat absorption capacities essentially presents a challenge akin to handling three or more distinct materials at once. If the balance between firepower, air vents, and moisture is not achieved, it can easily result in underdeveloped beans or an overall dull flavor. Thus, roasters must make clear trade-offs: for Italian-style blends, the primary goal is to ensure a solid mouthfeel without underdevelopment, while also maintaining aromatic complexity and a moderate aftertaste extension.
According to measured data, the average density of the Colombian bean is 788 kg/m³, while the Ethiopian bean is only 723 kg/m³—a difference of over 60 kg. This makes the initial drying phase particularly critical. It is recommended to use medium to low heat along with a small air vent, extending the drying time to allow internal water molecules to release evenly. Using a small air vent at this stage helps prevent rapid moisture loss while maintaining pressure balance inside the drum, facilitating stable evaporation of moisture. Heat during this phase mainly comes from contact conduction via the drum wall, so using a roaster with a thicker drum is more advantageous.
Once the surface of the green beans turns whitish, switch to medium-high heat and increase the air vent proportion to enhance hot air circulation and drive heat rapidly into the bean core. However, be cautious not to open the air vent too wide, as excessive airflow can destroy aromatic compounds due to high temperatures, resulting in a flat flavor profile. On the other hand, insufficient hot air can prevent effective heat transfer to the bean core, leading to localized underdevelopment. Adjust the air vent opening according to the specific roaster’s characteristics, and continuously monitor the curve trend to ensure that first crack begins between 10 minutes 20 seconds and 10 minutes 30 seconds.
Since the blend contains beans of varying densities and sizes, the sounds during the initial stage of first crack are often scattered. At this point, patiently determine the onset of dense first crack. When entering the dense first crack phase, it is recommended to apply approximately 30 seconds of intense heat pushing—this is also the stage with the strongest heat output throughout the roast and helps fully develop flavors and aromas. However, carefully control the duration and intensity, as excessive heat pushing may cause scorching of the bean surface and tips, and shorten the optimal flavor window.
After the heat pushing ends, if the first crack continues but has slowed down, immediately turn off all heat and set the air vent to maximum for about one minute of cooling—or “coasting.” During this phase, the bean mass is releasing heat, and it is important to ensure there is no significant drop in bean temperature. If a temperature decline is observed, consider not ending the roast by turning off the heat completely, but instead maintaining a low flame to preserve heat, ensuring the roasted beans achieve optimal caramel aroma before cooling.
Generally, the phase from the beginning of first crack to dropping the beans is considered the “development phase,” and the proportion of its duration relative to total roast time is the development rate. For this blend, the development phase lasted 3 minutes and 35 seconds, accounting for about 27.3% of total roast time, i.e., a development rate of around 27%. For Italian-style blends, it is recommended to keep the development rate around 25%. This way, even with a medium roast level, you can retain good crema and a rich mouthfeel, making it very suitable for espresso preparation.
Under this roasting strategy, although some of the flavor characteristics of the Ethiopian washed bean may be slightly diminished, it still delivers clear floral and fruity notes in the espresso. The Colombian base provides intense richness and stable sweetness. In actual shop extraction tests, using a Slayer machine, Mythosone grinder, IMS shower screen, and VST 15g portafilter basket, 14g of coffee was dosed, with a water temperature set at 91.6°C, a 3-second pre-infusion, and an output flow rate of 400ml/min, yielding 24g of coffee in 25 seconds. The final cup exhibited delicate wild ginger flower notes, accompanied by caramel, cocoa, and chocolate undertones, along with bright citrus acidity reminiscent of grapefruit and rum tones, all balanced with clear layering.
It should be especially noted that the thermal efficiency and reaction curves vary for each roaster model. The roasting profiles and parameters provided in this article are for reference only. For a roaster, the most valuable asset is not a single roasting technique, but the ability to establish a unique roasting philosophy tailored to bean characteristics and target flavors. Only with a clear flavor direction and firm technical conviction can one truly roast Italian-style blends with soul.
The above content is compiled by CoffeeHunters, a coffee news website.
