Light Roast Vs Dark Roast Coffee: The difference explained

By Shabbir
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The beauty of coffee is that a single bean can taste wildly different depending on how you roast it and how you brew it.

In this post, we’ll take a look at how roasting coffee beans to varying levels produces different characteristics: specifically light roast vs dark roast coffee beans.

Light roast and dark roast can taste like two totally different cups of coffee.

Before you have your delicious cup of heaven, the humble coffee cherry has to undergo a lot of transformations. One essential part of this transformation of course is the roasting process, during which it transitions from a green bean into the brown coffee bean we all know and love.

Varying levels of roasting will produce wildly different characteristics.

During the roasting process, the coffee beans absorb heat and undergo chemical changes. As the coffee bean absorbs more and more heat, the pressure inside it increases until it cracks. Once it cracks, it can start absorbing more energy until it cracks a second time.

The first crack is when a coffee bean is said to be light roast.

The second crack and beyond is dark roask, and in between the two is medium roast.

The cracks correlate with roasting temperatures.

Light Roast Vs Dark Roast Coffee Quick Comparison

Light roast

  • Highest level of caffeine by volume
  • Very flavorful
  • Fruity and floral flavors
  • Very mild
  • Can be acidic

Dark roast

  • Bittersweet and bold
  • Less caffeine by volume
  • Lower acidity
  • May be too bitter or strong for some people
light roast vs dark roast coffee, the beans have some stark differences

What’s a light roast?

Light roasts are coffee beans that have been roasted until they reach a temperature inside the bean of about 355-400 degrees F. Light roast coffee beans are generally a pale shade of brown and are roasted to a point where they just begin to crack.

Interestingly, light roasts contain the most caffeine(when you measure by volume), and the beans are not at all oily.

Moreover, light roasts are very acidic compared to other levels of roasts. Since you’re the closest to the actual green coffee bean(they’ve not been roasted long enough), a light roast will contain more acid and more complex flavors.

If you were wondering where to find the fruity and floral notes in coffee, lighter roasts are where you want to look. You should also keep in mind that the higher acidity may not sit well with you if you have a sensitive stomach.

When you next have a cup of light roast coffee, try and make the distinction between the acidity of the coffee and the reduced bitterness. You’ll be able to taste the sourness of the acid and notice how less bold the cup is.

The science behind the milder flavor and fruity flavors is that the shorter roasting time means there was less time for the sugar to caramelize. That’s why when you brew a light roast, more of the sugars will get infused in the water and you’ll be able to taste more actual sugar and less caramelization, which tends to be bitter.

What is a dark roast?

Dark roasts are coffee beans that have been roasted till they reach an internal temperature of over 450 degrees Fahrenheit. This temperature is when the first and second cracks have already finished.

Anything above 450 degrees F is considered a dark roast, though some roasters will go even higher to 465 degrees to 482 degrees. 482 is the top limit.

French and Turkish roasts are at the high end of the spectrum and they have nearly charred beans.

Dark roasts are exposed to so much heat that the oil from inside the bean comes to the outside and the bean develops an oily sheen.

Please bear in mind that you should not use oily beans in super automatic espresso machines as the oil will stick to the burrs in the grinder and start coating the inner pipes, too, eventually bringing your machine to a halt.

As for caffeine, there’s pretty much the same amount or at least a similar amount of caffeine as other roasts, except the beans are now smaller, so there will be a difference in the amount of coffee you’re using if you measure by volume vs if you measure by weight.

Instead of the floral flavors you experienced in the light road this time you will experience bold and earthy flavor notes like dark chocolate and nuts. These roasts are ideal for french press and espresso as the brewing process really brings these flavors out.

Another interesting taste brought out in dark roasting is a toasty flavor. The drinks also have a lot more texture – so it will feel much richer in your mouth than other roasts.

Medium roast vs Medium-dark roast vs dark roast vs light roast coffee

Medium roasts as the name suggests is a perfect goldilocks zone between light and dark roasts. It shares some qualities of the light roast and other qualities of the dark roast.

It is similar to light roast in the sense that there is no oil on the bean, and it is similar to the dark roast in its color – the bean is a darker shade of brown and closer to the dark roast.

Medium roasts reach a temperature of between 400 to 430 degrees F, and it is roasted until the second crack just begins.

Since this is a halfway bean between the light and dark roast, it will have some of the sweetness of the lighter roast but more aroma and body similar to the dark roast.

Medium roasts are a great middle ground and are very popular as they’re very versatile.

Between 430 degrees to 450 degrees F the medium-dark roast stage begins. Here, the beans start to darken a little more and this is in the start of or halfway through the second crack stage.

Higher temperatures will bring out some more oils, so there may be a very light, subtle oily sheen on the beans.

Medium dark roasts start to go easy on the sweetness, but have much smokier, heavier flavor and textures. You may also find spice aromas.

Other names for the medium dark roast are: Vienna roast, full city roast, or after-dinner roast.

Light roast vs dark roast: taste and acidity

Light roast coffee is the sweetest since it contains the most sugars. Medium roast will be a mix between sweet and intense, and dark roast will be very intense.

It’s interesting to note that light roasts will be sweet, but on the acidic side. In this context, acidity does not refer to chemical acidity, but a taste profile.

This means the coffee will have a very tart sweetness.

Is dark roast coffee more bitter?

To the uninitiated, dark roast coffee may seem quite bitter. However, once you develop a taste for it, there’s a hidden caramelly sweetness under the intensity. As long as you use fresh coffee beans, dark roasts will actually be quiet pleasing to the taste.

Bitter is a characteristic we’ve picked up from years of drinking cheap coffee!

Light roast vs dark roast: caffeine

There’s a common misconception with regards to light roast and dark roast caffeine levels. Interestingly, fans of light roast feel that light roast has more caffeine, whereas fans of dark roast say that it has more caffeine.

The truth is that caffeine is actually quite stable during the whole roasting process. The amount of caffeine actually burned off is quite minimal!

One way that there is indeed a difference is that dark roast beans tend to be smaller than light roast beans as they shrink more during the extended roasting process.

So if you measure by volume, light roast has more caffeine, as they’re denser than dark roast beans.

But if you measure by weight, dark roast will have more caffeine, as they have less mass, and you’ll more beans in total for a given weight!

Conclusion: Which is best?

For starting out, the best coffee roast is a medium roast since it balances the best of light roasts and dark roasts. It’s a good point to begin your coffee journey, and as you develop a taste, you can either increase the intensity by segueing to medium-dark and even dark roasts, or stepping back to light roasts.

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About Shabbir

Shab is the Chief Caffeine Officer at Coffee Brewster. When he's not weighing out coffee beans for his next brew, you can find him writing about his passion: coffee.