What factors in roasting affect the flavour of the coffee?

Before it’s roasted, the untrained eye might struggle to tell what a coffee bean is. With their green colour, grassy aroma and without the trademark crack down the centre (which only appears after roasting), green coffee beans need to be carefully roasted to bring out their natural flavours, aromas and acidity. And sometimes, to mask some of those qualities.

So, what factors in roasting affect the flavour of your finished cup of coffee?

Roast degree

Roast degree is all about the colour and relies on the roaster’s expertise to determine the best roast level for each individual coffee. Different coffee beans have different natural characteristics based on how and where they’re grown, and how the coffee cherries are processed after picking, and which characteristics you want to emphasise, draw out or hide will determine the best roast profile.

For more acidity, a light roast works better, and also brings out more citrus flavours and clean notes with no flavour added by the roasting process. A light roast extracts very little natural oil from the beans, so you’ll usually get a thinner, more tea-like mouthfeel. Light roasts can also be higher in caffeine, as the caffeine doesn’t have time to break down as it would in a darker roast.

Medium roasts are many roasters’ go-to, as they produce a little more oil and richer flavours, for a more all-round traditional coffee flavour and slightly heavier body, which also makes them good for multiple brewing methods.

Dark roasted coffees tend to be more bitter and have more of the deep flavours you’d generally associate with coffee, with added smokiness added in the roast. Dark roasts tends to have fewer fruity flavours as the higher the roast, the more of the organic compound that produces them is broken down. The amount of sulphuric compounds increases however, which produces more burnt flavours. If done well, dark roasts can be delicious, but many roasters take it too far, giving dark roast coffee an unnecessarily bad name.

Roasting time

While roast degree has the most impact on the flavour profile of your coffee, how much time it’s roasted for also plays a part. A fast roast will bring out more of the flavours and aromas you’re looking for, but it’s also easy to burn the beans and bring out bitter, rubbery flavours.

A fast roast will bring out a broader range of flavours, and increase the amount of aroma compounds. But a fast roast won’t remove some characteristics, like high acidity, which needs a slower roast to allow the natural acids to break down. So, if you’re making an espresso blend with high acidity beans, you’ll want to roast them more slowly to get the flavour profile you need.

Roasting method

 Consistency is key in roasting, and while many experts will roast using a thermometer, a clock and their eyes alone, we use state-of-the-art automated roasting machines to ensure every roast tastes consistently good from one bag of coffee to the next.

Ready to explore different roasts and find your new favourite? Experiment with our single origin coffees and house blends.