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Is dark roast or light roast coffee stronger? Let's ask Lemonjello's Owner Matthew Scott

By: Matthew Scott

Dark roast coffees have been a staple for coffee drinkers for a long time. In the past decade, though, they have had a stigma attached to them because of the Third Wave coffee movement and a push towards lighter roasts and more traceability in the supply chain. However, dark roasts are seeing a resurgence.

Why? Well, some people just like them. Different roast levels exist, after all, so that you can find what you like best.

When choosing the coffee for you, there are several things to consider. Roast level, a blend or coffee from a single origin or region, how it’s ground, and how it’s brewed. In this article, we’re going to break down roast level.

Let’s look at some basics.

Does a light roast or a dark roast coffee have more caffeine?

This one is tricky. For years, folks thought dark roast coffee did because it tasted stronger. Then a camp came around that believed light roast coffee had more caffeine because the bean would clearly lose caffeine content as it was roasted longer and lost mass. Well, science has clearly proved that caffeine is extremely stable during the roasting process. So it comes down to brewing.

The majority of people probably still use scoops to measure coffee at home. But we know from science that weight is more accurate than volume, so weighing your beans is the best way to ensure a consistent brew time after time. And if you weigh the same weight in beans of a light roast and a dark roast, you’ll have more dark roast beans because they are lighter in weight. So with 2 cups, light & dark, brewed with the same weight of beans, the dark roast would have more caffeine because there are more beans used. There are a number of studies online, but this one at is a great summary.

That being the case, I think it supports drinking what you like over looking for more caffeine. Looks like you’ll be getting really close to 95 mg per 8oz cup no matter what you do.

What really is the difference, then, between a light and dark roasted coffee?

It has to do with first crack and second crack.

"What?" you ask.

I’m not a roaster, so in looking at a succinct way to describe this, I use this paragraph from Perfect Daily Grind, a pretty great coffee source.

“First crack" is the moment when coffee beans begin to approach edibility. Coffee goes through two “cracks” when roasting, and light to medium roasts will finish somewhere between them. Dark roasts will typically be roasted past second crack.”

A few things happen as a result of this. Mass decreases the longer you roast a coffee, so darker beans are lighter in weight (think like cooking a steak from medium rare to well done). Lighter roasted coffees usually have more “tasting notes” specific to the terroir and processing method. Darker roasted coffees might have notes like chocolate or tobacco or caramel, but generally they taste like a dark roast. Any coffee roasted dark will taste fairly similar whereas lighter roasted coffees have a wide range of tasting notes.

Dark roast coffees also have an oily surface that light roast coffees don’t. This is because later in the roasting process when the internal temperature of the bean raises to a certain point, the oils in the bean are forced out onto the surface due to a chemical reaction with oxygen.

This leads us again back to this: Drink what you like.

Let’s talk a bit about brewing. All coffees can be brewed well if you have the right amount of coffee to water ratio, it’s ground correctly for the brewing method, and the water is filtered right. (Reasonably filtered water will allow you to extract the right amount of coffee into it. You don’t want distilled water, for instance, because there is nothing in it and it will over-extract your coffee. But if there are too many dissolved solids in your water, it will under-extract your coffee.)

There are also brewing methods that lend themselves to different things. Batch brewing using a standard coffee maker is usually the most consistent. If you’re brewing by the cup, I recommend a French Press for darker coffees and a manual pour over like the Chemex or Hario V60 for a lighter roast. There are a lot of other manual brew methods on the market these days. They will all brew you good coffee, but many of them were created in this Third Wave and lend themselves to lighter coffee.

Final question. So what if I have a lighter coffee and want it to taste more bold like a dark roast?

There are a couple of options. If you increase the amount of coffee you use per cup (but the same amount of water), that will raise the strength of the cup. It will also increase the body, which may imitate the dark roast you’re used to.

You can also grind finer so that you slow down the brewing process and extract a little more from the coffee. This can work, but it might also increase the bitter flavors in the cup, depending on the coffee.

Since the stigma is changing about dark roasts, remember it’s up to you to decide what you like when it comes to your coffee. And that’s pretty exciting! There are so many options. And even many of your small specialty coffee roasters are starting to re-introduce darker roasts, meaning you don’t have to sacrifice quality when choosing a dark roast for you.

Whatever you choose, please enjoy!

Matthew Scott

Holland, MI

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