It wasn’t until I was 29 years old, spending a year living in Costa Rica, that I had my first real cup of coffee. As an inner-city middle school teacher, the first six years of my professional life were fueled by an unhealthy Diet Coke habit. Little did I know that my first cup of coffee, enjoyed at El Toledo coffee farm, would ruin me once I returned stateside.

Upon moving back to the Midwest, I tried Starbucks and our local coffee chain, but I noticed a huge difference in taste. Sure, that probably made me a coffee snob. Still, I couldn’t help but balk at the bitter and burned taste that accompanied every cup.

The chemistry of coffee

As it turns out, there was a good reason for my sudden aversion to the beverage I had grown to love in Costa Rica. See, broadly speaking, there are three different types of roasts: light, medium, and dark.

In a dark roast, bitter is the predominant flavor. That’s because bitter is the flavor you get when things get burned.

Dark roast is far and away the most common in the United States. For many of us, it’s all we’ve ever tasted. We associate dark roast with a “strong coffee” that has lots of caffeine. In reality, light roast has more caffeine — but that’s another topic for another coffee teardown.

When we roast our coffee at El Toledo, we demonstrate to tourists how the beans change over the course of just a few minutes of cooking, and what those few minutes means for the taste that ends up in the cup. In the picture below, each group was taken out at one-minute intervals, beginning 15 minutes into the roasting process.

Here’s what you should know about roasting:

• In a light roast, the flavors are more fruity and acidic. That’s because the coffee cherries that the beans come from are fruity and acidic.
• In a medium roast, the coffee tastes more balanced and sweet. That’s primarily because the glucose has been heated up and activated, but it also hasn’t burned away yet.
• In a dark roast, bitter is the predominant flavor. That’s because bitter is the flavor you get when things get burned.

Dark roast is cheap

With a light roast, there’s a huge difference in the taste of high- and low-quality beans. High-quality beans are those grown with lots of shade, at high altitudes, and in diverse ecosystems that allow the beans to mature slowly. They have much more flavor.

Low-quality beans are usually from low-lying farms that have little shade or diversity. They mature very fast, and lack the opportunity to absorb the flavors of the fruit they come from. Abject sourness is usually the result.

But high-quality beans have lower yields, due to the time and diversity (space for other plants) necessary to grow them. Low-quality beans can be produced en masse.

It would be financially stupid for a large chain to buy high-quality coffee beans and use them for dark roast coffee.

As beans are roasted longer, the difference in taste between high and low quality disappears.

Think of it this way: You and a friend go to a steakhouse for dinner. You order the filet mignon, while your friend orders the shank. Obviously, if you order both extremely rare (light roast), there’ll be a huge difference in taste.

However, if you order both extremely well done (dark roast), they will start to taste much the same. Burned meat tastes like burned meat — no matter the quality.

The same is true for coffee.

Different elevations, farming practices, ecosystems, and even weather patterns can have huge effects on how coffee beans taste. In dark roasts, that’s no big deal — you’re burning all the flavor away.

It would be financially stupid for a large chain to buy high-quality coffee beans and use them for dark roast coffee. They can pay less for low-quality ones that will yield — more or less — the exact same taste. That means wider profit margins.

There’s a not-so-evil reason, too

I’m not a Starbucks-hater. While I don’t like their coffee, I think some of these challenges are just part and parcel of being a global corporation. On par, the company does very well by encouraging sustainable practices among its suppliers, and goes above and beyond for its employees.

Here’s the less insidious reason that bitter, burned coffee is favored by every major chain: It’s the only way to guarantee uniformity.

As my friend Morgan Housel put it:

Staying relevant in this world requires building a strong brand…But brand has to be earned through repetition, convincing people that what they experienced yesterday is what they can expect to experience tomorrow. It’s hard, and it can take a long time. But it’s sensationally powerful.

When you realize how much of a brand is just a tight distribution of outcomes, you see that powerful brands can be built on top of subpar products.

In essence, that’s what’s going on here. If we took a light roast from El Toledo, and compared it to the light roast from a farm just one mile away, the tastes could be enormously different. Different elevations, farming practices, ecosystems, and even weather patterns can have huge effects on how coffee beans taste. In dark roasts, however, that’s no big deal — you’re burning all the variability and flavor away. In light roasts, that flavor is the entire sell.

No multinational coffee company will ever make a killing on light roast coffee. I’d argue that even the light roasts offered by Starbucks and others are extremely low quality.

The next time you’re in Costa Rica — or any other coffee-producing country for that matter — get a cup of light roast. You’ll be shocked by just how flavorful it is.