Rheology is Brewed: The Battle of the Coffees – Colombia vs. Brazil

Grab your favorite mug and get ready for a caffeinated clash of titans! We all know that coffees produced in different regions are distinct; like wine, the taste will vary with soil, climate, and altitude. Some of our lab members are partial to the distinct flavors from Colombia and Brazil when it comes to their cups of coffee. But, being rheologists, we had to ask: are there other differences when it comes to their flow properties?

Ever wonder why some espresso shots taste rich and balanced, while others feel flat or watery? It’s not just the beans — it’s science! When coffee powders make their way through a machine, things like flow energy, wall friction, cohesion, and flow function all come into play. Take confined flow energy: it’s a measure of how much effort it takes to move or compress the coffee powders when they’re packed tightly together — just like during tamping. Wall friction tells us how easily the powders flow through chutes and into the portafilter. Then there’s the flow function, which measures how well the coffee powder flows under pressure — similar to how water moves through a sponge. In brewing, a good flow function indicates that the coffee powder can maintain its structure and allow water to pass through evenly, which is essential for consistent extraction and flavor. Cohesion, on the other hand, refers to the internal stickiness that keeps the puck intact during brewing, helping water flow evenly through the bed. Get all these working in harmony, and you’re rewarded with a beautifully balanced, flavorful cup. Behind that magic morning shot is a whole lot of coffee powder rheology!

Fortunately, these can all be measured on our Discovery™ HR Rheometer with the Powder Accessory. Will we see any differences in our Brazilian and Colombian coffee powders?

Colombian and Brazilian coffees each bring something special to the table. Colombian coffee, which thrives at higher altitudes, bursts with bright flavors. Brazilian coffee grows at lower altitudes and offers a heavier body and lower acidity.

But wait, there’s more! These coffees are also processed differently. Colombian coffee often gets the washed treatment for a clean profile, while Brazilian coffee uses natural or honey processing for extra sweetness and body.

And here’s where rheology steps in: beyond just taste and flavor, rheology uncovers fascinating differences in texture and mechanical properties that can impact your coffee preparation — think dosing, tamping, and brewing. It’s important to note that while both beans used in this study are medium roasted, the roasting methods may vary slightly, leading to differences in the degree of roast. But that’s all part of the fun! So, whether you’re a coffee connoisseur or just someone who loves a good brew, join us as we explore the fascinating world of coffee powders and conduct some of the best smelling experiments the lab has seen!

Confined Flow Energy: We observed that confined flow energy across various tip speeds is higher for Brazilian coarse ground coffee compared to Colombian coarse ground coffee (See figure 1). This could stem from the more irregular shapes of Brazilian ground coffee. The higher confined flow energy indicates that Brazilian coarse grounds require more force to be tamped effectively.

For fine ground coffee powders, the confined flow energy of Brazilian and Colombian ones is quite similar. This similarity arises because the smaller particles in fine grounds pack more densely, reducing void spaces and diminishing the impact of shape irregularities on overall flow behavior (See figure 2).

Recognizing these subtle differences is key to fine-tuning your tamping technique and promoting a more even extraction during brewing.

Flow Function (ffc) and Cohesion: For both fine and coarse ground coffee powders, Brazilian coffee has a slightly lower flow function and slightly higher cohesion than Colombian coffee. However, this difference is less pronounced in finer grounds (see Figures 3 and 4). The higher surface oil content of Brazilian coffee powders, under consolidation stress, tends to increase cohesion, which reduces the flow function. The oils act as binding agents between particles, promoting clumping and making flow more resistant under stress. In contrast, at controlled moisture levels, it seems that the higher degree of caramelization in this Colombian coffee, which is easily noticeable by smell compared to the Brazilian coffee, might enhance powder flowability by smoothing particle surfaces, reducing inter-particle friction, and limiting mechanical interlocking. This typically results in a higher flow function in shear cell testing, especially under moderate consolidation stresses.

This slight difference in flow function can influence the brewing process — Colombian coffee allows water to pass through a bit more readily than Brazilian coffee. As a result, the variation in extraction efficiency can subtly impact the final flavor profile.

Wall Friction: These joint factors are also mirrored in angle of wall friction measurements, which show that for both fine and coarse ground, wall friction for stainless steel is slightly higher for Brazilian coffee (See figure 5). This means that Brazilian coffee might resist movement more strongly during flow from the hopper to the doser or against the portafilter walls during tamping.

In this epic battle of coffee powders, both Colombian and Brazilian beans bring unique characteristics to the table. Colombian coffee tends to flow better under controlled conditions. Meanwhile, Brazilian coffee, with its higher surface oil content and quirky particle shapes, puts up more resistance to flow but rewards you with a rich, velvety texture that’s hard to beat.

Whether you prefer the bright, complex flavors of Colombian coffee or the robust, aromatic profile of Brazilian coffee, there’s no denying that each has its own special charm. It’s like a dance-off where both styles have their own unique moves! So, the next time you brew a cup, take a moment to appreciate the intricate science behind your favorite beans. Happy brewing!