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The Color of Coffee Roast

It's very easy to distinguish a light coffee roast from a dark one. But these are two extremes. Often, the color of the roast differs by one or two tones and you can hardly see it visually. But the taste will be different. The degree of roast (or its color) is one of the main characteristics that affect the taste of coffee. In this article, you will learn what determines the color of the roast, what it affects, and how precisely to measure it.
How coffee roast color affects taste

The darker the roast, the less acidic and the more bitter coffee is. To ensure that the taste of our coffee is always stable, we carefully select and control the color of the roast. Taste descriptors such as berries, fruits and flowers are shifting towards others. Those are descriptors from the caramelization or dry distillation group: dark chocolate, nuts, caramel and smoke.

Let’s take as examples espresso and other types of coffee. Espresso is different from other brewing methods: its extraction takes 25-30 seconds, and the drink itself is more concentrated. In alternative methods, the extraction lasts 2-4 minutes, and the drink is less concentrated. In espresso, the ratio of coffee to water is most often 1/2, and the alternative is 1/16.

For espresso and alternative brewing methods, coffee cannot be roasted in the same way. It is because acids dissolve in water first, then light components, and at the very end, heavy ones. If the coffee is roasted for an alternative and brewed in espresso, it will have an unpleasant and pungent acidity in its taste. Because of the difference in the ratio of coffee and water, this effect will significantly increase. And if you roast coffee for espresso, and prepare it with an alternative method, the coffee will be too bitter.

That’s why coffee for espresso needs to be roasted longer. Especially during the second half of the roasting process (from 175 °C to 200 °C), so it will be darker and less acidic.

How is roast color controlled

To be sure that the coffee roast is right, the color of the coffee is measured with laser colorimeters after each roast. They allow you to determine the color of coffee according to the ColorTrack scale.

This is how it happens: after each coffee roast, the color of beans and ground coffee is measured. And then roasters write down the values to compare them with the results of the next roasts. To do this, they use professional colorimeters, which control coffee roasting.
To exclude the influence of ambient light, coffee is put into special cells which slide under the colorimeter laser
The higher the colorimeter value, the darker the coffee is roasted. Colorimeter for ground coffee typically values from 45 to 70 on the ColorTrack scale.
The correct degree of roast is always a very fine line. This is the line between fully revealing coffee and not getting the negative aspects of roasting: ash shades and viscosity. And this line is very easy to miss, because in the final stage of roasting every second counts and matters. That is why it is extremely important to carefully determine its color.

What is development time and how it influences coffee color

During coffee roast process, the pressure inside each cell increases tenfold. Evaporating moisture and carbon dioxide, formed from ongoing reactions, try to get out of the grain, but partially rest against the cell walls. The pressure builds up gradually, and as a result, the grain cracks with a characteristic jerky sound, similar to the preparation of popcorn. This moment is called "crack".

Crack usually starts in many grains at the same time. The time from the start of the "crack" to the discharge of coffee is called the development time. During this stage, all processes proceed very quickly due to high temperatures. To make coffee flavor to fully develop, the development time should be 15-20% of the total roast time. 15% for a filter and 20% for an espresso.

During coffee roast, there are two cracks – the first and second. The first occurs at temperatures up to 200 °C, mainly due to evaporating moisture. The second usually occurs after 220 °C, due to the burning of sugars and cell walls. Coffee roasted to the second crack is very dark coffee with oil coming out on the surface.

Coffee from Mr. Viet is made of carefully selected and expertly roasted coffee beans in Vietnam, Dalat region. We supply high quality freshly roasted coffee directly from Vietnamese farmers. Mr. Viet provides a wide range of flavors – from authentic Vietnamese traditional blends to selected Arabica beans. Follow us to learn more about our coffee beans and other products!

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