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How to know if your coffee was badly roasted

Whose fault is it when the coffee tastes bad? The roaster or the barista? This is a common question I come across whenever I am troubleshooting coffee. Was it poorly extracted or just a bad roast to begin with?

The answer? It’s always the barista’s fault.
Because I am the roaster and I can never be wrong. Just kidding.

Here’s how you can tell when the roast needs improving:

When the acidity is unbalanced

A well roasted coffee should present a balanced / palatable acidity. This can vary widely depending on your preference.

The easiest way to determine whether the coffee’s acidity is well managed is to test it along the extraction curve.

As you extract more from the coffee, the acidity should progress from sour to crisp and balanced to muted and bitter.

If increasing extraction (grinding finer) results in the acidity going from sour to slightly balanced then back to sour again, then it is highly likely that the coffee is too light and insufficiently developed for the current brewing method.


When flavour is not well-developed

Flavour is the one aspect of coffee that is majorly determined by the coffee and roast, not extraction.

Although you can alter perceptions slightly at different brew strengths, the main underlying flavour categories such as nutty, fruity, floral, chocolatey can’t be influenced through extractions.

Flavours like mango etc. come from the coffee when it is well roasted to showcase the inherent flavours of the coffee. You cannot alter a mango flavour to taste like hazelnuts through extraction.

A low-extraction will only present weaker flavours or even generic coffee flavours.

If you have obvious flavour defects such as charred/burnt or grassy/unripe fruits/vegetal notes, those are signs that the roast needs amendment. 

When the coffee tastes salty

Saltiness in coffee can be attributed to both extraction and roast faults. Severe under-extraction can create saltiness in some coffees. However, note the word "severe".

This means in most cases where extraction is in a reasonably standard range and there is no channelling, you should not experience saltiness in coffee. If you do, chances are the roast needs fixing. Saltiness is generally attributed to an under-developed roast.


What a barista can do

In most instances, I find that it is possible to brew a decent cup even with coffees that are not perfectly roasted (they rarely are).

A barista should learn how to deal with all the imperfections of a roast. But more importantly, they must also communicate with their roaster when they have difficulties achieving the desired cup profile.

As a roaster, we must chuck our egos at the door and troubleshoot the coffee without any bias. This is much easier said than done.

Many times our cognitive biases are unconscious and very powerful. The key is approaching the situation as an opportunity to pinpoint areas for improving and creating a better end product rather than a criticism of our work.

To do this, roasters need to have a strong grasp of extraction and brewing coffees in order to guide and help baristas achieve the desired cup profile. If they do not have a good understanding of these fundamentals, how can they possibly distinguish between the results of their roast vs extraction faults?

If you want to learn more about perfecting your craft in coffee roasting, we’ve got the perfect tool here: The Ultimate Coffee Roasting course. Learn from roasting champions and practice with professionals at our Co-roasting Space.

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  • Doing a roast defect kit
    By : Pradyut Moona On 01/21/2021

    You know, a roast defect kit might be a good idea, go from underdeveloped, to good roast, to overdeveloped

    Replied by : Kenneth Ong On 01/22/2021 Thanks Pradyut, that is indeed in the works!