Green Blending Basics

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The mystery of blending

In a recent post about creating a great Holiday Blend, I mentioned a few strategies for blending greens. Blending helps roasters create something greater than the sum of its parts. Roasters often have questions about blending, and it’s a topic that we spend a lot of time discussing during our roasting classes. We wanted to share some of our best practices for coffee blending to help demystify the world of blends.

Pre-Blend vs. Post-Roast

There are a few approaches to blending, and people have a lot of opinions about which is the “right” way. Let’s start with some definitions. A pre-blend is a blend where green coffees are mixed together prior to roasting, then roasted together. With this method, all of the coffees spend the same amount of time in the roaster. In theory, this should result in the same roast level for each component. But we know that differences in bean density, moisture, and size will create some variety in the ways that the coffee takes on roast flavor. The argument against pre-blending is related to this variance. Many people feel that pre-blending sacrifices the quality of one or more components since you’re not applying the “ideal roast” to each individual bean.

Post-roast blending seeks to solve this problem. A post-roast blend is a blend of roasted coffees, all profiled to perfection. Those roasts get mixed together at the designated percentages then bagged up. The benefits of this approach are obvious; an ideal roast profile for every bean results in a better tasting blend. You also get more bang for your buck, since you can roast two coffees individually and end up with three retail bags (two single origins and the blend). What’s the drawback, if there is one? Post-roast blending requires additional labor hours. Coffees need to be mixed thoroughly after roasting instead of just mixing together in the drum, and that takes time. Fortunately, we’ve designed our cooling trays to be large enough to accommodate up to 3 full batches of roasted coffee, so mixing in the cooling tray is a nice option for post-roast blenders.

Our approach

At Mill City, all of the blends we roast as part of our Toll Roasting program are pre-blends. We like the efficiency of pre-blending. We also think the slight variances produced by different bean metrics add complexity to the flavor of the blend. What’s most important to us is that a blend is easy to brew, and we know that if all of the components spend the same amount of time in the roaster, they’ll be similarly easy to extract. The only time we don’t pre-blend is when green components have different sizes (like mixing a peaberry and a Pacamara). We also avoid pre-blending when a component is a delicate natural processed coffee that needs a different heat application.

Of course, there’s an in-between approach: the pre/post-roast blend. Roast the components that play well together as a pre-blend, then add in a post-roast component of something that needs its own unique profile. It’s the best of both worlds!

Don’t overcomplicate it

We see a lot of blends out there in the coffee world. The vast majority of them have three components. It’s a safe number. A three-bean blend is easy to design, easy to control, and easy to weigh out. The three components will each have a specific purpose: something for base flavor, something for sweetness, and something for acidity (or body). Two-bean blends are also quite common. We don’t recommend using more than four coffees in a blend. This is because blends with a high number of components become less consistent when dosing.

In class, we use the espresso shot as a good example. How many grams of coffee go into a double shot? Usually around 18g-20g. If your espresso blend has five components, what’s the likelihood that every 19 gram dose will have the correct amount of each of those components? Not likely. Who suffers in that situation? The barista, probably, because every shot will pull differently! The customer will also have a less consistent, and probably lower quality, beverage experience. Keep the components small and you’re able to execute a higher level of control and quality assurance in your blends.

What’s on the label

The nice thing about blends is that they can be offered year-round. Seasonal coffees can be swapped out for fresh crop offerings, as long as the flavor profile of the blend stays consistent. Give your blend a name that speaks to your company’s ethos, or your neighborhood vibe, or whatever else illustrates your brand. By keeping origin information off of your label, you have the freedom to replace components whenever you need to.

For companies who really want to provide some coffee information on their bag, consider keeping it general. I’ve seen blends use wording like “a combination of coffees from Africa and Latin America” or simply “coffees grown in South and Central America”. This phrasing leaves a lot of producing countries available to utilize, depending on what’s available and what fits the flavor profile.

Customers are comforted by consistency. Creating a blend that’s solid, reliable, and available year-round is a great way to foster trust and build brand loyalty. Seasonal blends during the holidays are great sellers, but carrying a year-round option for drip coffee, espresso, and cold brew is another great way to keep sales steady.

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