Picture the scene…
You’re standing in your favorite outlet, trying to choose the coffee for your perfect morning pick-me-up. You’ve decided on country of origin.
You know you want whole beans. You reach out to take a pack – but then you pause…
The coffee next to your outstretched fingers is light roasted. The one next to it on the shelf is dark. Dark roast vs light roast – what do you do? You’ve no idea what the difference is!
Never fear, we’re about to end your roast-related confusion! From flavor to caffeine content, we’ll give you the information you need to find the perfect roast for you.
To understand what effect roasting has on your coffee, it’s important to start with the process itself.
Coffee beans are actually the pips inside the fruit of the coffee tree, known as the cherry. When the pips are removed, they’re green in color and have a grassy fragrance.
If you try brewing with those green pips you’ll end up with a bitter drink that’s a million miles from the coffee we know and love.
It’s the process of roasting that puts that right. The basic principle is pretty simple, and you can take a look at how it’s done in this YouTube video.
The green beans are heated to an internal temperature of about 400 degrees Fahrenheit. This intense heat causes sugars and amino acids inside the bean to decrease while gases build up.
The bean hardens and turns from green to brown, and a fragrant oil called caffeol is released. It’s this caffeol that replaces the grassy aroma of green beans with the delicious coffee smell we know and love.
The longer the beans are roasted, the darker they become – just like baking a cake in the oven. It’s the natural sugar inside the bean that’s responsible for this color change, going from sweet to caramel to burnt, the longer it’s exposed to heat.
The light and dark roasts you see on packs of coffee reflect the visual appearance of the coffee bean. There are actually four categories: light, medium, medium-dark and dark. So if you pick a light roast, you’ll be choosing a bean that’s had less heat exposure than a dark roast.
So what does the roasting style mean for the way your coffee tastes?
Again, the basics are pretty simple. The longer the bean is roasted, the more its original flavor will be masked by flavors from the roasting process. That doesn’t mean that either light or dark roasts are better – it just means they’ll taste quite different.
Light roasted beans are, as you’d expect, light brown in color. They’re denser than darker roasts and can look dull as there’s no oil on the surface of the beans.
They will have been heated to an internal temperature of around 400 degrees Fahrenheit. At this temperature, the beans pop and expand, a process that is known as the “first crack”. Light roasts are not usually roasted beyond this stage, and in some cases, roasting ends even before the first crack.
The beans will have a toasted grain taste, a pronounced acidity and a bright flavor. They retain more of their original flavors than any other roast style, so you’ll be able to tell your Colombian from your Javan. Fruity and floral coffees are often light roasts.
It’s worth remembering, though, that roasting is an art as well as a science. If the heat hasn’t got through to the very center of the bean, you may be left with an unpleasant, grassy flavor.
Even a perfectly light roasted coffee won’t be to everyone’s taste. Some people simply find the favor too citrusy or floral. If that sounds like you, you’ll want to investigate a darker roast.
Medium roasts are a shade darker but still have no oil on the surface of the bean.
They will have been roasted to an internal temperature of between 410 and 428 degrees Fahrenheit. That’s between the end of the first crack and just before the beginning of the second crack.
They balance the original flavor of the bean with more of the flavors from the roasting process. Some of the brighter notes of lighter roasts may be lost, but there’ll be more caramel sweetness. As such, medium roasts offer a good compromise between acidity and body.
Medium-dark roasts are darker again, and may have some oil on the surface of the bean.
The flavors and aromas of the roasting process become more noticeable in these beans. The result is a coffee with more body and spice than lighter roasts.
The beans are roasted to the beginning or middle of the second crack, from 437 to 446 degrees Fahrenheit. If you’re looking for beans roasted to the beginning of the second crack try a “Full-City” roast. If you want to go darker still, Viennese roasts are roasted until the middle of the second crack.
Finally, dark roasts are almost chocolatey in appearance, with a sheen of oil on the beans.
With these roasts, the original flavor of the bean is hidden by the flavors from the roasting process. You’ll get bold, rich, full-bodied coffee as a result.
Dark roasts – like light roasts at the other end of the spectrum – are particularly vulnerable to unpleasant results if the beans are poor quality or the roaster unskilled. Instead of chocolatey darkness, you can find yourself with a charred or acrid flavor.
So in a nutshell, dark roast vs light is broadly the same issue as brightness vs body.
If you search online for whether dark or light roasts have more caffeine, you’ll find a confusing array of answers. Many people assume that darker roasted beans have more caffeine than their lighter counterparts. Others argue that the opposite is true.
So who’s right?
The surprising answer is: no-one – or at least, it depends on how you measure it.
Despite what some articles claim, caffeine is not lost during the roasting process. The amount of caffeine in each bean stays largely stable as it’s heated. That, however, is not the end of the story.
What does change during roasting is the density of the coffee bean? Broadly speaking, the longer it’s roasted the less dense – and the less heavy – it becomes.
That means the same amount of coffee by weight will contain a different number of beans, depending on whether it’s light or dark roasted.
One amateur coffee-loving scientist put this to the test by measuring out equal weights of light and dark roasted coffee. Then he counted the beans. In a ten gram sample, he found he had sixty-five light roast beans and sixty-seven dark roast beans.
In a nutshell, darker roasts weigh less. If you measure your coffee by weighing it out, you’ll get more dark roasted beans than you will light. With roughly the same amount of caffeine per bean, that means you’ll get slightly more caffeine with a darker roast.
Remember, though: in ten grams of coffee, there were only two more dark roast beans than there were light roast. The truth, then, is that the difference is so small you’ll probably struggle to notice it.
If you want to cut your caffeine consumption – or you’re looking for a cup to really wake you up in the morning – focus instead on the amount you’re drinking and the coffee variety. Robusta beans have more caffeine than Arabica, and even Arabica varies widely depending on the plant species.
We’ve seen that there’s precious little difference in caffeine levels between light and dark roasts. But there are lots of other ingredients that have an impact on the health benefits – or otherwise – of your favorite drink.
Top of the list is antioxidants. These neutralize reactive molecules called “free radicals” which can damage cell structures in the body. They are considered to be important to overall health and may have a role in protecting us from diseases such as cancer.
Coffee (and tea) are good sources of antioxidants - not least because most of us drink so much of it. But before you decide to double your dose, remember: there are other sources of antioxidants out there – fruit and vegetables, for example – that don’t come packaged along with addictive caffeine.
That said, if you want to know which coffee roast has the most antioxidants, recent research has provided the answer. A Korean study published in 2017 compared the amounts of chlorogenic acid, a well-known antioxidant, in coffees of different roast levels.
The researchers went on to expose extracts of each coffee to human cells to test their anti-inflammatory and antioxidant properties. They found that the lighter the roast, the more chlorogenic acid it contained.
Furthermore, higher levels of chlorogenic acid translated to greater protection of the human cells against damage and inflammation.
So far so good. A note of caution though: the lab tests were carried on cell cultures, not human beings. The results would need to be replicated in human trials to be sure that lighter roasts have greater anti-inflammatory properties.
And it’s also worth remembering that chlorogenic acid isn’t the only kind of antioxidant found in coffee. In 2010 a research division of the French Government published levels of overall antioxidant activity for three different coffee roasts.
This showed that the highest level of antioxidants was actually in medium roast, whilst light roasts had the lowest level. The difference between all three, though, was small – medium roasts had only 13% more antioxidants than light.
Until the evidence is clearer, we’d recommend choosing your roast style on the basis of taste.
So far, lighter roasts are scoring better in terms of health benefits – but we haven’t yet considered weight loss. Here dark roasts have the edge, with a 2011 study finding that their consumption was associated with weight loss.
Researchers gave either dark roast or light roast coffee to 30 study participants for 12 weeks. The same coffee bean was used for each group; the only difference was the roast time.
At the end of the study, the researchers noted that the dark roast coffee had led to what they called a “significant” weight reduction in overweight test subjects. The light roast had no such effect.
The question of whether light or dark roast coffee is stronger is tricky to answer. That’s because everyone has a different idea of what they mean by coffee strength.
Some coffee experts say that in their experience, what people often mean is the intensity of flavor. That makes it a very difficult thing to measure – is a strong fruity flavor as strong as a strong caramel one?
The simplest answer is that if by “strong” you mean “acidic” then choose a light roast. If you’re after a strong roasting flavor, go for a dark roast.
A better way of thinking about strength is to consider how much water and/or milk you’re adding to your coffee. The ratio of coffee to water is easily measured, so you can compare “strength” accurately.
This, of course, means that it’s the brewing method that affects strength, rather than the roast level of the bean. Taking that measure, an espresso will be stronger than a cappuccino, and a ristretto will be stronger again.
It’s clear that there are big differences in the tastes of light and dark roasted coffees. What’s not so clear is whether one or the other is better for your health.
For that reason, we’d recommend focusing on flavor to find your perfect roast level. To return to our imaginary coffee store – why not just pick both coffees and see which you prefer?
If you have any questions, please comment and let us know.
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