A coffee defect is a flaw or variation in the taste, aroma or appearance of coffee that makes the end result undesirable or undrinkable. There are many different types of defects in coffee, which can be caused by various factors such as pest infestation, poor processing, or insufficient storage.

Some of the most common coffee defects are:

  • Mould: Mould can occur due to insufficient drying or storage of coffee beans. Mouldy coffee has an unpleasant smell and taste and can even be harmful to health.

  • Fermentation: Coffee that is fermented for too long during the processing process can have an unpleasant taste and smell reminiscent of sour milk.

  • Oxidation: Coffee that is exposed to air for too long can oxidise and develop a rancid taste.

  • Impurities: Foreign bodies such as twigs, stones or soil can remain in the coffee beans and lead to an undesirable taste during roasting.

Coffee impurities can have a significant impact on the quality and taste of the coffee and are an important issue in the coffee business. Coffee producers and roasters work hard to minimise coffee defects and ensure that only high quality coffee reaches the market.

The higher the quality of a coffee, the less likely it is to have defects such as quakers, stones or the like. Nevertheless, coffee is a natural product and in some cases a small stone can end up in a coffee bag. That's why you should always take a close look at the beans when you put your coffee in the grinder. After all, you are the last person to check the beans before you drink your cup of coffee.